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Journal articles on the topic 'Linear voltage stabilizer'
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1
Titovskii, S. N., T. S. Titovskaia, N. V. Titovskaia, and Z. E. Shaporova. "Digital contour of linear control in the pulse voltage stabilizer." IOP Conference Series: Materials Science and Engineering 537 (June 18, 2019): 062033. http://dx.doi.org/10.1088/1757-899x/537/6/062033.
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Harb, A. M., and M. S. Widyan. "Controlling Chaos and Bifurcation of Subsynchronous Resonance in Power System." Nonlinear Analysis: Modelling and Control 7, no. 2 (December 5, 2002): 15–36. http://dx.doi.org/10.15388/na.2002.7.2.15191.
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Linear and nonlinear state feedback controllers are proposed to control the bifurcation of a new phenomenon in power system, this phenomenon of electro-mechanical interaction between the series resonant circuits and torsional mechanical frequencies of the turbine generator sections, which known as Subsynchronous Resonance (SSR). The first system of the IEEE second benchmark model is considered. The dynamics of the two axes damper windings, Automatic Voltage Regulator (AVR) and Power System Stabilizer (PSS) are included. The linear controller gives better initial disturbance response than that of the nonlinear, but in a small narrow region of compensation factors. The nonlinear controller not only can be easily implemented, but also it stabilizes the operating point for all values of the bifurcation parameter.
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Titovskii, S. N., N. V. Titovskaia, and T. S. Titovskaya. "Influence of the digital data representation error in the linear control contour of a pulse voltage stabilizer." Journal of Physics: Conference Series 1399 (December 2019): 022051. http://dx.doi.org/10.1088/1742-6596/1399/2/022051.
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Usmanov, E. G., A. N. Rasulov, M. K. Bobojanov, and R. Ch Karimov. "Non-contact voltage relay for switching windings of a boost transformer." E3S Web of Conferences 139 (2019): 01079. http://dx.doi.org/10.1051/e3sconf/201913901079.
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In power supply systems the change in the magnitude of the voltage degrades the operation of electrical appliances right up to their failure. The proposed scheme of a contactless voltage relay based on a contactless voltage relay with switching the windings of a booster step-up transformer with a time delay allows switching the windings of a magnetizing booster transformer with a voltage change at the consumer terminals. Analytical studies of a non-autonomous non-linear dynamic circuit, which is the basis of the proposed device based on the classical method of solving a differential equation, which determines the nature of the voltage change for controlling thruster switches. The change of energy parameters of the proposed stabilizer depending on the voltage is given. The article considers the principle of operation of the proposed scheme of a contactless switching device based on a contactless voltage relay that switches the windings of a booster step-up transformer. An analytical study of a non-autonomous nonlinear dynamic circuit, which is the basis of the proposed device and the characteristics uc = f t required for switching the thruster is presented.
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Qian, Jing, Yun Zeng, Li Xiang Zhang, and Tian Mao Xu. "Analysis on Equivalence between Transfer Function and Equivalent Circuit Simulation in General Hamiltonian Modeling." Applied Mechanics and Materials 204-208 (October 2012): 4896–99. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.4896.
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Take generator system included AVR (automatic voltage regulator) and PSS (power system stabilizer) as an example, Using the time simulation method, Study the equivalence between the transfer function model and the equivalent circuit simulation, and establish the corresponding relations between the circuit structures, internal parameters and transfer function parameters, based on the energy of equivalent circuit, the Hamiltonian function of transfer function is derived indirectly, and the Hamiltonian model is established. The study in this paper provides a new way to establish generalized Hamiltonian model for linear system based on transfer function.
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Mahoney, Patrick P., John P. Guzowski, Steven J. Ray, and Gary M. Hieftje. "Electrospray Ionization Time-Of-Flight Mass Spectrometer for Elemental Analysis." Applied Spectroscopy 51, no. 10 (October 1997): 1464–70. http://dx.doi.org/10.1366/0003702971939235.
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Electrospray ionization (ESI) has been combined with a time-of-flight (TOF) mass spectrometer for elemental analysis. With the use of a heated-capillary interface, the instrument is shown to be stable to within 5% relative standard deviation (RSD) over a 60-min period. The ratio between the isotopes of rubidium is measured with a precision of 0.4% RSD for a 1-min integration time. With the addition of a supporting electrolyte as a spray stabilizer and internal standard, the dynamic range is linear over at least three orders of magnitude. The extent of solvent-cluster fragmentation is found to be governed primarily by the voltage differential between the capillary and skimmer and, to a lesser extent, by the capillary temperature. The capillary voltage also affects the distribution of species among the parent and its fragment ions for ferrocene and tetraethyllead. Under “mild” interface conditions, a resolving power of 1400 is achieved for an organolead complex. A spectrum for a larger molecule, polypropylene glycol, is presented to show the versatility of the ESI-TOF instrument for both atomic and molecular analysis.
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Anarkooli, M. Yousefi, and H. Afrakhteh. "Improvement Model Damping Low Frequency Oscillations Presence UPFC by Cuckoo Optimization Algorithm." Indonesian Journal of Electrical Engineering and Computer Science 3, no. 1 (July 1, 2016): 67. http://dx.doi.org/10.11591/ijeecs.v3.i1.pp67-79.
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<p>Low frequency oscillation (LFO) is a negative phenomenon repeated for the power system increases the risk of instability. In recent years, power systems stabilizer (PSS) for damping low frequency oscillations is used. With FACTS devices such as integrated power flow controller (UPFC) can control power flow and transient stability increase. So, UPFC low frequency oscillation damping can be used instead of PSS. UPFC through direct control voltage and low frequency oscillation damping can be improved. In this study, a single linear model of synchronous machine connected to an infinite bus Heffron-Philips in the presence of UPFC to improve low frequency oscillation damping is used. The selection of the output feedback parameters for the UPFC controllers is converted to an optimization problem which is solved by cuckoo optimization algorithm (COA). COA, as a new evolutionary optimization algorithm, is used in multiple applications. This optimization algorithm has a strong ability to find the most optimistic results for dynamic stability improvement. The controller UPFC and damping in MATLAB software environment is designed and simulated. The simulation was performed for a variety of loads and for various loads and more effective UPFC controller electromechanical oscillation damping compared to other algorithm types is shown.</p>
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Зольников, Владимир, Vladimir Zolnikov, А. Яньков, A. Yankov, К. Чубур, K. Chubur, А. Кулай, et al. "INVESTIGATION OF LINEAR VOLTAGE STABILIZERS FOR RESISTANCE TO SPECIAL FACTORS." Modeling of systems and processes 12, no. 3 (December 1, 2019): 48–53. http://dx.doi.org/10.12737/2219-0767-2019-12-3-48-53.
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The paper deals with the issues of resistance of linear voltage stabilizers to the influence of special factors. The conducted researches are described, electric schemes at measurement of output voltage and current of chips are resulted. The calculated estimates of the resistance of linear voltage stabilizers to the influence of various special factors are also considered
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Chen, Yi, Bu Han Zhang, Cheng Xiong Mao, and Xiao Kang Dai. "VRB/EDLC Hybrid Storage System with PID Controller Based on BP Neural Network." Advanced Materials Research 724-725 (August 2013): 855–61. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.855.
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In order to stabilize fluctuations caused by intermittent energy and complement different storage elements advantages, we designed a hybrid energy storage combining VRB pack with EDLC bank. This hybrid energy storage device has two DC/DC convertors; DC/DC(A) controls VRB pack's power and DC/DC(B) stabilizes the voltage on DC bus. By doing this, it is easy to make power schedule for VRB according to renewable energy forecast and SOC of battery, while EDCL bank stabilizes the short-time power fluctuation, most of which result from forecasting error. To achieve the above goals, self-adaptive PID controller based on BP neuron network is applied in DCDC(B), for switching-mode convertor is strongly non-linear system and traditional PID controller is not suitable to the case of large changed load. Simulations in Matlab Simulink are presented to testify the novel control method and show this hybrid energy storage device can work efficiently.
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Bityukov, V. K., A. A. Ivanov, N. G. Mikhnevich, and V. A. Petrov. "Measurement of the Fluctuation Rejection Ratio by Linear Voltage Stabilizers." Measurement Techniques 59, no. 11 (February 2017): 1210–16. http://dx.doi.org/10.1007/s11018-017-1117-3.
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Hossain, Jahangir, Apel Mahmud, Naruttam K. Roy, and Hemanshu R. Pota. "Enhancement of Transient Stability Limit and Voltage Regulation with Dynamic Loads Using Robust Excitation Control." International Journal of Emerging Electric Power Systems 14, no. 6 (October 23, 2013): 561–70. http://dx.doi.org/10.1515/ijeeps-2013-0037.
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Abstract In stressed power systems with large induction machine component, there exist undamped electromechanical modes and unstable monotonic voltage modes. This article proposes a sequential design of an excitation controller and a power system stabiliser (PSS) to stabilise the system. The operating region, with induction machines in stressed power systems, is often not captured using a linearisation around an operating point, and to alleviate this situation a robust controller is designed which guarantees stable operation in a large region of operation. A minimax linear quadratic Gaussian design is used for the design of the supplementary control to automatic voltage regulators, and a classical PSS structure is used to damp electromechanical oscillations. The novelty of this work is in proposing a method to capture the unmodelled nonlinear dynamics as uncertainty in the design of the robust controller. Tight bounds on the uncertainty are obtained using this method which enables high-performance controllers. An IEEE benchmark test system has been used to demonstrate the performance of the designed controller.
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Nasir, M. N. M., Awang Jusoh, and Alias Khamis. "DC Bus Instability Driving by Photovoltaic Source with Constant Power Load." Applied Mechanics and Materials 313-314 (March 2013): 853–57. http://dx.doi.org/10.4028/www.scientific.net/amm.313-314.853.
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This study presented the DC bus instability in distributed power system driving by Photovoltaic (PV) source with constant power load (CPL). The aim of this study is to investigate the effect of PV source towards the performances of DC bus voltage stability using constant power load. The system first was tested using linear DC supply as voltage source and CPL was modeled and connected to the voltage source through LC filter network. A passive damping circuit was chosen to stabilize the DC bus instability. The system was repeated using PV source. PV array was modeled based on the parameters obtained from a commercial PV data sheet. A circuitry simulation was performed under the similar design excluding the DC source in order to investigate DC bus instability. Results showed that the stability of DC bus become unstable when using linear DC voltage supply and slightly affected when using PV source. The instability phenomenon due to the negative incremental impedance of a constant power load can be overcome by using damping technique. For linear DC voltage source, DC bus voltage system tends to oscillate. However, with PV source which is actually a current source input seems not much affecting the DC bus voltage stability.
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Kobayashi, Kenkichiro, Hiroki Kobayashi, Yasumasa Tomita, Yasuhisa Maeda, and Yosiumi Khono. "Preparation of N-Doped ZnO Films by MOCVD." Key Engineering Materials 421-422 (December 2009): 123–26. http://dx.doi.org/10.4028/www.scientific.net/kem.421-422.123.
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Crystalline ZnO films were grown on Y-stabilized ZrO2 substrates heated at 300 - 600 °C in NH3 atmosphere. It is clarified from Fourier transform infrared measurements that N-doped ZnO films grown at 350 and 400 °C contain N-C and Zn-H bonds. In the devices of n-type ZnO/N-doped ZnO/Au, a good rectification characteristic is attained for an N-doped ZnO film deposited at 300°C, whereas a linear current vs. voltage characteristic is seen for a film deposited at 500 °C.
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Singh, S. N., and P. R. Bandyopadhyay. "Linear Feedback Control of Boundary Layer Using Electromagnetic Microtiles." Journal of Fluids Engineering 119, no. 4 (December 1, 1997): 852–58. http://dx.doi.org/10.1115/1.2819508.
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This paper presents a system-theory approach to control of a two-dimensional turbulent flow of saltwater on a flat plate using Lorentz forces produced by microtiles of small magnets and electrodes. Beginning with the two-dimensional Navier-Stokes equations of motion, a finite, dimensional, linear state variable, approximate model is obtained using Galerkin’s procedure. Based on this model, linear feedback control laws are obtained to achieve stabilization of the perturbed flow to the base flow. It is shown that spatially distributed longitudinal or surface-normal forces stabilize the flow perturbations. However, for lower wave numbers, longitudinal forces are more effective because surface-normal forces require larger electrode voltages for the same response characteristics. Simulation results are presented to show how stabilization is accomplished in the closed-loop system.
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Elahinia, M., J. Koo, M. Ahmadian, and C. Woolsey. "Backstepping Control of a Shape Memory Alloy Actuated Robotic Arm." Journal of Vibration and Control 11, no. 3 (March 2005): 407–29. http://dx.doi.org/10.1177/1077546305051201.
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This paper investigates a nonlinear controller designed to stabilize a single-degree-of-freedom rotary shape memory alloy (SMA) actuated robotic arm. To this end, a bias-type robotic arm was built using 150 pm Flexinol SMA wire. This robot is designed to lift and position lightweight objects. Upon complete phase transformation, the SMA wire actuates the robot to rotate up to 1350. A linear spring is used to extend the wire to its original length because the SMA wire can only apply force in one direction. To measure the angular position of the robotic arm, an optical rotary encoder was used. To stabilize the robot, a model-based controller was developed. The controller incorporates the SMA actuated robot model with nonlinear control techniques. The model consists of three parts: the dynamics/kinematics of the arm, the thermoruechanical behavior of SMA wire, and the heat transfer model of the wire. The model-based backstepping controller determines the applied voltage to the SMA wire for positioning the arm at the desired angle by first calculating the wire's stress to stabilize the arm. The voltage to the SMA wire is then calculated based on the desired stress and the SMA's thermomechanical and heat transfer models. A series of simulations were performed to investigate stabilizing performance of the controller. Moreover, other issues such as robustness of the control design was evaluated. The results show that the control algorithms is able to globally and asymptotically stabilize the robot. The results further indicate that the sliding mode control has better robustness properties.
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Kamal, Elkhatib, Magdy Koutb, Abdul Azim Sobaih, and Sahar Kaddah. "Maximum Power Control of Hybrid Wind-Diesel-Storage System." Advances in Fuzzy Systems 2008 (2008): 1–9. http://dx.doi.org/10.1155/2008/963710.
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Extraction of maximum wind power of variable speed wind turbines in hybrid wind-diesel-storage system (HWDSS) is considered due to economical purposes. The proposed control algorithm utilizes extended fuzzy-linear matrix equalities (FLMEs) systems design of stabilizing fuzzy controllers for nonlinear systems described by Takagi-Sugeno (TS) fuzzy models. The algorithm maximizes the power coefficient for a fixed pitch. Moreover, it reduces the voltage ripple and stabilizes the system over a wide range of wind speed variations. The control scheme is tested for different profiles of wind speed pattern and provides satisfactory results.
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SU, HSIAO WEI, and YICHUANG SUN. "HIGH-FREQUENCY LINEAR MULTIPLE-OUTPUT CMOS TRANSCONDUCTANCE AMPLIFIER FOR CURRENT-MODE FILTERS." Journal of Circuits, Systems and Computers 15, no. 05 (October 2006): 701–17. http://dx.doi.org/10.1142/s0218126606003325.
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A high-frequency highly linear tunable CMOS multiple-output operational transconductance amplifier (MO-OTA) for fully balanced current-mode OTA and capacitor (OTA-C) filters is presented. The MO-OTA is based on the cross-coupled pairs at the input and provides two pairs of differential outputs. A simple common-mode feedback (CMFB) circuit to stabilize the DC output levels of the MO-OTA is also proposed and two such CMFB circuits are used by the MO-OTA. The proposed MO-OTA is suitable for relatively low voltage (2.5 V) applications as its circuit has only two MOS transistors between the supply and ground rails. Simulated in a TSMC 0.25 μm CMOS process using PSpice, the MO-OTA has at least ± 0.3 V linear differential input signal swing with a single 2.5 V power supply and operates up to 1 GHz frequency. The MO-OTA has a THD less than -46 dB for a differential input voltage of 0.9 Vp-p at 10 MHz, dynamic range (DR) at THD = -46 dB is over 50 dB, and power consumption (with the common-mode feedback circuit) is below 8 mW for the whole tuning range. A fully balanced multiple loop feedback current-mode OTA-C filter example using the proposed MO-OTA is presented. This example also shows that the current-mode follow-the-leader-feedback (FLF) structure can achieve good performances for OTA-C filter design.
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A. Okou, Francis, Ouassima Akhrif, Louis A. Dessaint, and Derrick Bouchard. "A Decentralized Multivariable Robust Adaptive Voltage and Speed Regulator for Large-Scale Power Systems." International Journal of Emerging Electric Power Systems 14, no. 1 (May 30, 2013): 41–56. http://dx.doi.org/10.1515/ijeeps-2012-0042.
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Abstract This papter introduces a decentralized multivariable robust adaptive voltage and frequency regulator to ensure the stability of large-scale interconnnected generators. Interconnection parameters (i.e. load, line and transormer parameters) are assumed to be unknown. The proposed design approach requires the reformulation of conventiaonal power system models into a multivariable model with generator terminal voltages as state variables, and excitation and turbine valve inputs as control signals. This model, while suitable for the application of modern control methods, introduces problems with regards to current design techniques for large-scale systems. Interconnection terms, which are treated as perturbations, do not meet the common matching condition assumption. A new adaptive method for a certain class of large-scale systems is therefore introduces that does not require the matching condition. The proposed controller consists of nonlinear inputs that cancel some nonlinearities of the model. Auxiliary controls with linear and nonlinear components are used to stabilize the system. They compensate unknown parametes of the model by updating both the nonlinear component gains and excitation parameters. The adaptation algorithms involve the sigma-modification approach for auxiliary control gains, and the projection approach for excitation parameters to prevent estimation drift. The computation of the matrix-gain of the controller linear component requires the resolution of an algebraic Riccati equation and helps to solve the perturbation-mismatching problem. A realistic power system is used to assess the proposed controller performance. The results show that both stability and transient performance are considerably improved following a severe contingency.
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Chraygane, M., N. El Ghazal, M. Fadel, B. Bahani, A. Belhaiba, M. Ferfra, and M. Bassoui. "Improved modeling of new three-phase high voltage transformer with magnetic shunts." Archives of Electrical Engineering 64, no. 1 (March 1, 2015): 157–72. http://dx.doi.org/10.1515/aee-2015-0014.
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Abstract This original paper deals with a new approach for the study of behavior in nonlinear regime of a new three-phase high voltage power supply for magnetrons, used for the microwave generators in industrial applications. The design of this system is composed of a new three-phase leakage flux transformer supplying by phase a cell, composed of a capacitor and a diode, which multiplies the voltage and stabilizes the current. Each cell. in turn, supplies a single magnetron. An equivalent model of this transformer is developed taking into account the saturation phenomenon and the stabilization process of each magnetron. Each inductance of the model is characterized by a non linear relation between flux and current. This model was tested by EMTP software near the nominal state. The theoretical results were compared to experimental measurements with a good agreement. Relative to the current device, the new systemprovides gains of size, volume, cost of implementation and maintenance which make it more economical.
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P, Thirumalini, R. Arulmozhiyal, and M. Murali. "A Cascade Multilevel Z-Source Inverter for Photovoltaic System." TELKOMNIKA Indonesian Journal of Electrical Engineering 16, no. 3 (December 1, 2015): 473. http://dx.doi.org/10.11591/tijee.v16i3.1637.
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This paper describes a multilevel Z-source inverter for solar photovoltaic applications. The conventional power conversion topology performs either buck or boost the input voltage for non linear load depending upon duty ratio and modulation index in a multiple stage conversion with the help of impedance source passive network (L and C), which is usually known as Z-Source, which couples the n level source with input to the power source and increase the power efficiency. The multilevel z network capabilities of inverter are operated in the shoot through state of duty cycle and it acts as a filter to reduces the level of harmonics, stabilize power factor and to increase the output AC voltage range of inverter. To overcome further harmonics, multilevel level operation z source inverter compensates the fundamental level of harmonic in renewable. Proposed work as a whole involves the simulation part to design multilevel inverter. The output of the simulation is obtained by Simulink model using MATLAB.
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Martinez, Eduardo. "Static Properties and Current-Driven Dynamics of Domain Walls in Perpendicular Magnetocrystalline Anisotropy Nanostrips with Rectangular Cross-Section." Advances in Condensed Matter Physics 2012 (2012): 1–21. http://dx.doi.org/10.1155/2012/954196.
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The current-induced domain wall motion along thin ferromagnetic strips with high perpendicular magnetocrystalline anisotropy is studied by means of full micromagnetic simulations and the extended one-dimensional model, taking into account thermal effects and edge roughness. A slow creep regime, where the motion is controlled by wall pinning and thermal activation, and a flow regime with linear variation of the DW velocity, are observed. In asymmetric stacks, where the Rashba spin-orbit field stabilizes the domain wall against turbulent transformations, the steady linear regime is extended to higher currents, leading to higher velocities than in single-layer or symmetric stacks. The pinning and depinning at and from a local constriction were also studied. The results indicate that engineering pinning sites in these strips provide an efficient pathway to achieve both high stability against thermal fluctuations and low-current depinning avoiding Joule heating. Finally, the current-driven dynamics of a pinned domain wall is examined, and both the direct and the alternating contributions to the induced voltage signal induced are characterized. It was confirmed that the direct contribution to the voltage signal can be linearly enhanced with the number of pinned walls, an observation which could be useful to develop domain-wall-based nano-oscillators.
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Huo, Mingying, He Liao, Yanfang Liu, and Naiming Qi. "The Coupled Orbit-Attitude Dynamics and Control of Electric Sail in Displaced Solar Orbits." International Journal of Aerospace Engineering 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/3812397.
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Displaced solar orbits for spacecraft propelled by electric sails are investigated. Since the propulsive thrust is induced by the sail attitude, the orbital and attitude dynamics of electric-sail-based spacecraft are coupled and required to be investigated together. However, the coupled dynamics and control of electric sails have not been discussed in most published literatures. In this paper, the equilibrium point of the coupled dynamical system in displaced orbit is obtained, and its stability is analyzed through a linearization. The results of stability analysis show that only some of the orbits are marginally stable. For unstable displaced orbits, linear quadratic regulator is employed to control the coupled attitude-orbit system. Numerical simulations show that the proposed strategy can control the coupled system and a small torque can stabilize both the attitude and orbit. In order to generate the control force and torque, the voltage distribution problem is studied in an optimal framework. The numerical results show that the control force and torque of electric sail can be realized by adjusting the voltage distribution of charged tethers.
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Afzal, Muhammad Moin, Muhammad Adil Khan, Muhammad Arshad Shehzad Hassan, Abdul Wadood, Waqar Uddin, S. Hussain, and Sang Bong Rhee. "A Comparative Study of Supercapacitor-Based STATCOM in a Grid-Connected Photovoltaic System for Regulating Power Quality Issues." Sustainability 12, no. 17 (August 21, 2020): 6781. http://dx.doi.org/10.3390/su12176781.
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Renewable energy resources (RERs) play a vital role in reducing greenhouse gases, as well as balancing the power generation demand in daily life. Due to the high penetration of RERs and non-linear loads into utility power systems, various power quality issues arise, i.e., voltage drop, harmonic distortion, reactive power demand, etc. In order to handle these power quality issues, there is a need for smart flexible alternating current transmission system (FACTS) devices. In this paper, a super capacitor energy storage system (SCESS)-based static synchronous compensator (STATCOM) is designed in order for the grid-connected photovoltaic (PV) system to overcome the abovementioned power quality issues. A voltage controller and a d-q axis controller are used for the efficient performance of the STATCOM. In order to show the superiority of the supercapacitor, a detailed comparison is made between a battery energy storage system (BESS)-based STATCOM and a SCESS-based STATCOM. Four scenarios are studied to evaluate the performance of the proposed STATCOM design. The proposed SCESS-based STATCOM not only boosts the voltage but also stabilizes it from 368 V to 385 V (Ph-Phrms). The simulated results have confirmed that the proposed design is not only superior to a BESS-based STATCOM but also has the capability to overcome the power quality issues as well.
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Chaudhary, Rekha, Arun Kumar Singh, and Saligram Agrawal. "A Novel Approach to PID Controller Design for Improvement of Transient Stability and Voltage Regulation of Nonlinear Power System." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 5 (October 1, 2016): 2225. http://dx.doi.org/10.11591/ijece.v6i5.10818.
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<p>In this paper, a novel design method for determining the optimal PID controller parameters for non-linear power system using the particle swarm optimization (PSO) algorithm is presented. The direct feedback linearization (DFL) technique is used to linearize the nonlinear system for computing the PID (DFL-PID) controller parameters. By taking an example of single machine infinite bus (SMIB) power system it has been shown that PSO based PID controller stabilizes the system and restores the pre-fault system performance after fault is cleared and line is restored. The performance of this controlled system is compared with the performance of DFL-state feedback controlled power system. It has been shown that the performance of DFL-PID controlled system is superior compared to DFL-state feedback controlled system. For simulation MATLAB 7 software is used. </p>
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Chaudhary, Rekha, Arun Kumar Singh, and Saligram Agrawal. "A Novel Approach to PID Controller Design for Improvement of Transient Stability and Voltage Regulation of Nonlinear Power System." International Journal of Electrical and Computer Engineering (IJECE) 6, no. 5 (October 1, 2016): 2225. http://dx.doi.org/10.11591/ijece.v6i5.pp2225-2238.
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<p>In this paper, a novel design method for determining the optimal PID controller parameters for non-linear power system using the particle swarm optimization (PSO) algorithm is presented. The direct feedback linearization (DFL) technique is used to linearize the nonlinear system for computing the PID (DFL-PID) controller parameters. By taking an example of single machine infinite bus (SMIB) power system it has been shown that PSO based PID controller stabilizes the system and restores the pre-fault system performance after fault is cleared and line is restored. The performance of this controlled system is compared with the performance of DFL-state feedback controlled power system. It has been shown that the performance of DFL-PID controlled system is superior compared to DFL-state feedback controlled system. For simulation MATLAB 7 software is used. </p>
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An, Ke, and Kenneth L. Reifsnider. "A Multiphysics Modeling Study of (Pr0.7Sr0.3)MnO3±δ∕8mol% Yttria-Stabilized Zirconia Composite Cathodes for Solid Oxide Fuel Cells." Journal of Fuel Cell Science and Technology 2, no. 1 (October 25, 2004): 45–51. http://dx.doi.org/10.1115/1.1842782.
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Solid oxide fuel cells (SOFCs) are expected to be a future power source. Simulation analyses of SOFCs can help to understand well the interactive functions among the multiphysics phenomena in the SOFC system. A three-dimensional multiphysics finite-element model was used to simulate the performance of a half-cell SOFC with (Pr0.7Sr0.3)MnO3±δ∕8mol% yttria-stabilized zirconia (8YSZ) composite cathode on one side of the 8YSZ electrolyte before and after aging. Multiphysics phenomena in the SOFC were considered in the modeling. The current/voltage curves simulated matched the experimental data before and after aging. The average current density was found to have a linear relationship to the logarithm of the effective exchange current density. The effect of the effective ionic conductivity of the composite cathode was more apparent for small total effective ionic conductivity values than for large ones.
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Lan, Tian Syung, Kuei Shu Hsu, Tung Te Chu, Long Jyi Yeh, and Ming Guo Her. "Electronic Circuit Simulation and Digital PC-Based Implementation of Dynamic MRR Optimization." Materials Science Forum 505-507 (January 2006): 493–98. http://dx.doi.org/10.4028/www.scientific.net/msf.505-507.493.
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Dynamic MRR (material removal rate) modeling is constructed and optimum solution through Calculus of Variations in maximize the machining profit of an individual cutting tool under fixed tool life is introduced. The mathematical model is formulated by reverse experiments on an ECOCA PC-3807 CNC lathe, and the electronic circuit is developed using linear regression technique for virtual machining. The inaccuracy between actual and simulated voltage is assured to be within 2%. By introducing a real-world CNC (computerized numerical control) machining case from AirTAC into the virtual system, the simulated cutting forces are shown to promise the feasible applicability of the optimum MRR control. Additionally, the implementation of dynamic solution is experimentally performed on a proposed digital PC-based lathe system. The surface roughness of all machined work-pieces is found to not only stabilize as the tool consumed, but also accomplish the recognized standard for finish turning.
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Hamilton, Sarah J., David Isaacson, Ville Kolehmainen, Peter A. Muller, Jussi Toivainen, and Patrick F. Bray. "3D Electrical Impedance Tomography reconstructions from simulated electrode data using direct inversion $ \mathbf{t}^{\rm{{\textbf{exp}}}} $ and Calderón methods." Inverse Problems & Imaging 15, no. 5 (2021): 1135. http://dx.doi.org/10.3934/ipi.2021032.
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<p style='text-indent:20px;'>The first numerical implementation of a <inline-formula><tex-math id="M2">\begin{document}$ \mathbf{t}^{\rm{{\textbf{exp}}}} $\end{document}</tex-math></inline-formula> method in 3D using simulated electrode data is presented. Results are compared to Calderón's method as well as more common TV and smoothness regularization-based methods. The <inline-formula><tex-math id="M3">\begin{document}$ \mathbf{t}^{\rm{{\textbf{exp}}}} $\end{document}</tex-math></inline-formula> method for EIT is based on tailor-made non-linear Fourier transforms involving the measured current and voltage data. Low-pass filtering in the non-linear Fourier domain is used to stabilize the reconstruction process. In 2D, <inline-formula><tex-math id="M4">\begin{document}$ \mathbf{t}^{\rm{{\textbf{exp}}}} $\end{document}</tex-math></inline-formula> methods have shown great promise for providing robust real-time absolute and time-difference conductivity reconstructions but have yet to be used on practical electrode data in 3D, until now. Results are presented for simulated data for conductivity and permittivity with disjoint non-radially symmetric targets on spherical domains and noisy voltage data. The 3D <inline-formula><tex-math id="M5">\begin{document}$ \mathbf{t}^{\rm{{\textbf{exp}}}} $\end{document}</tex-math></inline-formula> and Calderón methods are demonstrated to provide comparable quality to their 2D counterparts and hold promise for real-time reconstructions due to their fast, non-optimized, computational cost.</p>
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Elnady, A., and M. AlShabi. "Operation of Parallel Inverters in Microgrid Using New Adaptive PI Controllers Based on Least Mean Fourth Technique." Mathematical Problems in Engineering 2019 (June 19, 2019): 1–19. http://dx.doi.org/10.1155/2019/4854803.
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This paper shows the operation of the microgrid using a new adaptive PI controller based operational (control) scheme. The core of the proposed control scheme is the suggested adaptive PI controller. The parameters of the PI controller are adaptively tuned using a variable step-size least mean fourth algorithm with no need for any system model to operate this adaptive controller. The main merit of the proposed scheme is that it stabilizes the magnitude and frequency of the voltage at any loading condition such as variable balanced loads, variable unbalanced loads, and nonlinear loads. The proposed scheme has a simple structure and accurate performance. In addition, the structure of proposed scheme provides a seamless transition toward any loss or reconnection of any inverter in the microgrid. Furthermore, the suggested operational scheme is flexible enough to enable the microgrid to be operative in a grid-connected mode and to transfer from the voltage control mode to power control mode with a smooth transitional procedure. To validate the meritorious performance of the suggested scheme, its performance is compared to similar schemes based on a linear controller (regular PI controller), single-neuron PI controller (adaptive PI controller), recursive least square-support vector machine based PI controller (another adaptive PI controller), and nonlinear controller (sliding mode controller) for different operations of the microgrid.
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KISLOV, V. V., Yu V. GULYAEV, V. V. KOLESOV, I. V. TARANOV, S. P. GUBIN, G. B. KHOMUTOV, E. S. SOLDATOV, I. A. MAXIMOV, and L. SAMUELSON. "ELECTRONICS OF MOLECULAR NANOCLUSTERS." International Journal of Nanoscience 03, no. 01n02 (February 2004): 137–47. http://dx.doi.org/10.1142/s0219581x04001912.
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The molecular nanoclusters proved to be very promising objects for applications in electronics not only because they have absolutely identical chemical structure and allow for bottom to top approach in constructing new electronic devices, but also for the possibility to design and create great variety of such clusters with specific properties. The formation and deposition of mixed Langmuir monolayers composed of inert amphiphile molecular matrix and guest ligand-stabilized metal-core nanoclusters are described. This approach allowed to obtain the ordered stable reproducible planar monolayer and multilayer nanocluster nanostructures on solid substrates. The use of novel polymeric Langmuir monolayers formed by amphiphilic polyelectrolytes and nanoclusters resulted in fabrication of ultimately thin monomolecular nanoscale-ordered stable planar polymeric nanocomposite films. The morphology and electron transport in fabricated nanostructures were studied experimentally using AFM and STM. The effects of single electron tunneling at room temperature through molecular cluster object containing finite number of localized states were theoretically investigated taking into account electron–electron Coulomb interaction. It is shown that tunnel current-bias voltage characteristic of such tunnel junction is characterized by a number of staircase steps equal to the number of cluster's eigenlevels, however the fronts of each steps are asymptotically linear with finite inclination. The analytically obtained current–voltage characteristics are in agreement with experimental results for electron tunneling through molecular nanoclusters at room temperatures.
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Turowski, Bartłomiej, and Katarzyna Agnieszka Rutkowska. "Fabrication of the liquid crystalline periodic waveguiding structures by means of the photo-polymerization process." Photonics Letters of Poland 9, no. 3 (September 30, 2017): 82. http://dx.doi.org/10.4302/plp.v9i3.770.
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Photonic structures in a form of the waveguide channels, with periodic spatial changes in refractive index in the wavelength scale, are typically manufactured based on well-developed silica and gallium arsenide technology [1], as well as with use of the high-precision lithography. The main disadvantage related to practical application of such devices is that their optical properties cannot be altered after fabrication. Due to this fact, liquid crystalline periodic waveguiding structures, manufactured with use of the photo-polymerization process, have been proposed in this work. Importantly, propagational characteristic of such photonic structures can be easily adjusted during fabrication procedure, and then may be also dynamically tuned by e.g. applied external voltage, as presented in this communication. Full Text: PDF ReferencesM.J. Ablowitz, Z.H. Musslimani, "Discrete spatial solitons in a diffraction-managed nonlinear waveguide array: a unified approach", Physica D: Nonlinear Phenomena 184(1), 276 (2003). CrossRef L. Vicari, Optical applications of liquid crystals, CRC press, 2016. CrossRef J. Yan, S.-T. Wu, "Effect of Polymer Concentration and Composition on Blue Phase Liquid Crystals", J. Display Technol. 7, 9 (2011). CrossRef J. Schirmer et al., "Birefringence and Refractive Indices Dispersion of Different Liquid Crystalline Structures", Mol. Cryst. Liquid Cryst. 307, 17 (1997). CrossRef D. Xu et al., "Blue phase liquid crystals stabilized by linear photo-polymerization", Appl. Phys. Lett. 105, 8 (2014). CrossRef I. Dierking et al., "Stabilising liquid crystalline Blue Phases", Soft Matter 8, 4355 (2012). CrossRef K. Kang, L.C. Chien, S. Sprunt, "Polymer-stabilized cholesteric liquid crystal microgratings: a comparison of polymer network formation and electro-optic properties for mesogenic and non-mesogenic monomers", Liquid Crystals 29, 9 (2002). CrossRef K.A. Rutkowska, M. Chychłowski, U.A. Laudyn, "Polymer-stabilized periodic waveguiding structures in liquid crystalline materials", Proc. SPIE 10325 (2017). CrossRef
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Moon, Gitae, Wonjun Jang, Intae Son, Hyun Cho, Yong Park, and Jun Lee. "Fabrication of New Liquid Crystal Device Using Layer-by-Layer Thin Film Process." Processes 6, no. 8 (August 1, 2018): 108. http://dx.doi.org/10.3390/pr6080108.
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Indium tin oxide (ITO) transparent electrodes are troubled with high cost and poor mechanical stability. In this study, layer-by-layer (LBL)-processed thin films with single-walled carbon nanotubes (SWNTs) exhibited high transparency and electrical conductivity as a candidate for ITO replacement. The repetitive deposition of polycations and stabilized SWNTs with a negative surfactant exhibits sufficiently linear film growth and high optoelectronic performance to be used as transparent electrodes for vertically aligned (VA) liquid crystal display (LCD) cells. The LC molecules were uniformly aligned on the all of the prepared LBL electrodes. VA LCD cells with SWNT LBL electrodes exhibited voltage-transmittance (V-T) characteristics similar to those with the conventional ITO electrodes. Although the response speeds were slower than the LCD cell with the ITO electrode, as the SWNT layers increased, the display performance was closer to the LCD cells with conventional ITO electrode. This work demonstrated the good optoelectronic performance and alignment compatibility with LC molecules of the SWNT LBL assemblies, which are potential alternatives to ITO films as transparent electrodes for LCDs.
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Zheng, Jie, and Fred J. Sigworth. "Intermediate Conductances during Deactivation of Heteromultimeric Shaker Potassium Channels." Journal of General Physiology 112, no. 4 (October 1, 1998): 457–74. http://dx.doi.org/10.1085/jgp.112.4.457.
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A previous study of the T442S mutant Shaker channel revealed activation-coupled subconductance levels that apparently represent kinetic intermediates in channel activation (Zheng, J., and F.J. Sigworth. 1997. J. Gen. Physiol. 110:101–117). We have now extended the study to heteromultimeric channels consisting of various numbers of mutant subunits as well as channels without mutant subunits, all in the background of a chimeric Shaker channel having increased conductance. It has been found that activation-coupled sublevels exist in all these channel types, and are traversed in at least 80% of all deactivation time courses. In symmetric K+ solutions, the currents in the two sublevels have a linear voltage dependence, being 23–44% and 54–70% of the fully open conductance. Sublevels in different channel types share similar voltage dependence of the mean lifetime and similar ion selectivity properties. However, the mean lifetime of each current level depends approximately geometrically on the number of mutant subunits in the channel, becoming shorter in channels having fewer mutant subunits. Each mutant subunit appears to stabilize all of the conducting states by ∼0.5 kcal/mol. Consistent with previous results in the mutant channel, sublevels in channels with two or no mutant subunits also showed ion selectivities that differ from that of the fully open level, having relatively higher K+ than Rb+ conductances. A model is presented in which Shaker channels have two coupled activation gates, one associated with the selectivity filter and a second associated with the S6 helix bundle.
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Denisov, А., Y. Denisov, and O. Bursala. "THE STABILIZATION ACCURACY OF THE PHASE POSITION OF THE WORKING BODY OF THE ROBOTICS COMPLEX." Наукові праці Державного науково-дослідного інституту випробувань і сертифікації озброєння та військової техніки, no. 3 (May 28, 2020): 20–28. http://dx.doi.org/10.37701/dndivsovt.3.2020.03.
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To stabilize the phase position of the working body of the robotics complex a single-circuit precision electric drive system was developed based on the principle of phase-locked loop. The direct-driven electric drive is made on the basis of brushless direct current motor, which is switched to synchronous mode with minimal discrepancy between the phases of the reference signals and the pulse speed sensor. The phase error signal is fed to the input of the PID controller, which controls the pulse width modulation of the impulses controlling the operation of the power transistors of the autonomous voltage inverter. In a static mode, the control system of the autonomous voltage inverter implements a sinusoidal law of the pulse width modulation of the output pulses. The PID controller and the control system of the autonomous voltage inverter are programmatically implemented on the basis of the controller.
In the process of analysing of the stabilization accuracy, the synchronous motor is represented by a second-order linear link, which establishes a relation between the phase deviations of the motor rotor and the stator magnetic field. The autonomous voltage inverter is represented by a zero-order hold whose coefficient of amplification on amplitude is found by the results of the approximation of its output voltage using the Walsh-Fourier series.
The analysis of the phase stabilization process is performed on the basis of the state variables method taking into account the perturbations at the moment of load using the program which implements the recurrent procedure.
The settings of the PID controller are determined by the variation results when the moment of load changes. Their initial values are determined as a result of optimizing the system in terms of operation speed considering the condition of finite duration processes. It is assumed that there is no moment of load perturbation.
The procedure for setting the PID controller parameters to the optimal operation speed mode can also be performed on the basis of neural networks.
As a result of the calculations, it was found that with an increase of the load moment by 5%, the maximum deviation of the rotor phase was 0.22 us and 0.03 us of minimum deviation respectively.
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Srisuai, N., N. Chattrapiban, and W. Rakreungdet. "The Effects of Temperature, Injection Current and Optical Feedback on the Frequency Stabilization of External Cavity Diode Laser." Advanced Materials Research 979 (June 2014): 459–62. http://dx.doi.org/10.4028/www.scientific.net/amr.979.459.
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A frequency-stabilized diode laser is widely used for applications in laser cooling and high-resolution spectroscopy. In this work, the 780-nm external cavity diode laser was constructed and subsequently frequency-controlled by three parameters, i.e., temperature, injection current and optical feedback. The laser frequency was measured with respect to the 5S1/2 → 5P3/2 (D2-lines) transition of Rubidium, while the laser mode was characterized by a Fabry-Perot interferometer. The laser temperature was passively controlled to a single value between 20 ̊C and 25 ̊C while the injection current was investigated in combination with course and fine adjustments of optical feedback. Only data relevant to a single-mode laser operation was collected. It was found that as the current increased, the laser frequency shifted linearly with slopes approximately 0.5-0.8 GHz/mA. Optical feedback from the external cavity was tuned by the voltage applied to the piezoelectric transducer, yielding a linear frequency response of approximately 0.2 GHz/V. The measured parameters were rearranged to represent the island of stability of the laser, suggesting suitable conditions that yielded single-mode operation, at a desirable laser frequency. The results were important for a design of an active feedback, in order to further reduce the frequency linewidth and intensity noise of the laser.
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Le, T. T., and J. U. Jeon. "Stability analysis of a time-optimally controlled electrostatic suspension system and suspension experiments in a vacuum." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 225, no. 1 (June 20, 2010): 88–100. http://dx.doi.org/10.1243/09544062jmes1925.
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Electrostatic suspension permits conductive, semiconductive, and dielectric materials to be supported without mechanical contact, in contrast to electromagnetic levitation by which only ferromagnetic materials can be levitated. To expand applications of electrostatic suspension systems, a low-cost electrostatic suspension system using a time optimal bang—bang control scheme where linear analogue high-voltage amplifiers that are costly and bulky are not employed has already been implemented. In this article, a time optimal bang—bang control scheme is used to stabilize the system like the previous work. First, the process to find the recoverable set for all the states in which a time optimal bang—bang control exists is described in detail. Then, the switching criterion for the suspension system is derived by using a backward integration technique and the system stability is theoretically investigated using Lyapunov's function as well. To experimentally verify the system stability in vacuum, suspension experiments are carried out with 3.5 in aluminium discs in a vacuum environment. Experiments in the atmosphere are also conducted for comparison with the results in the vacuum. The experimental results show that an aluminium disc has been stably suspended at a reference gap length of 300 μm in a vacuum environment.
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Bimarta, Rizka, Thuy Vi Tran, and Kyeong-Hwa Kim. "Frequency-Adaptive Current Controller Design Based on LQR State Feedback Control for a Grid-Connected Inverter under Distorted Grid." Energies 11, no. 10 (October 8, 2018): 2674. http://dx.doi.org/10.3390/en11102674.
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This paper proposes a frequency-adaptive current control design for a grid-connected inverter with an inductive–capacitive–inductive (LCL) filter to overcome the issues relating to both the harmonic distortion and frequency variation in the grid voltage. The current control scheme consists of full-state feedback control to stabilize the system and integral control terms to track the reference in the presence of disturbance and uncertainty. In addition, the current controller is augmented with resonant control terms to mitigate the harmonic component. The control scheme is implemented in the synchronous reference frame (SRF) to effectively compensate two harmonic orders at the same time by using only one resonant term. Moreover, to tackle the frequency variation issue in grid voltage, the frequency information which is extracted from the phase-locked loop (PLL) block is processed by a moving average filter (MAF) for the purpose of eliminating the frequency fluctuation caused by the harmonically distorted grid voltage. The filtered frequency information is employed to synthesize the resonant controller, even in the environment of frequency variation. To implement full-state feedback control for a grid-connected inverter with an LCL filter, all the state variables should be available. However, the increase in number of sensing devices leads to the rise of cost and complexity for hardware implementation. To overcome this challenge, a discrete-time full-state current observer is introduced to estimate all the system states. When the grid frequency is subject to variation, the discrete-time implementation of the observer in the SRF requires an online discretization process because the system matrix in the SRF includes frequency information. This results in a heavy computational burden for the controller. To resolve such a difficulty, a discrete-time observer in the stationary reference frame is employed in the proposed scheme. In the stationary frame, the discretization of the system model can be accomplished with a simple offline method even in the presence of frequency variation since the system matrix does not include the frequency. To select desirable gains for the full-state feedback controller and full-state observer, an optimal linear quadratic control approach is applied. To validate the practical effectiveness of the proposed frequency-adaptive control, simulation and experimental results are presented.
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Rösch, Tobias, Peter Treffinger, and Barbara Koch. "Remuneration of Distribution Grids for Enhanced Regenerative Electricity Deployment—An Analysis and Model for the Analysis of Grid Structures in Southern Germany Using Linear Programming." Energies 13, no. 20 (October 15, 2020): 5385. http://dx.doi.org/10.3390/en13205385.
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Ecological concerns on the climatic effects of the emissions from electricity production stipulate the remuneration of electricity grids to accept growing amounts of intermittent regenerative electricity feed-in from wind and solar power. Germany’s eager political target to double regenerative electricity production by 2030 puts pressure on grid operators to adapt and restructure their transmission and distribution grids. The ability of local distribution grids to operate autonomous of transmission grid supply is essential to stabilize electricity supply at the level of German federal states. Although congestion management and collaboration at the distribution system operator (DSO) level are promising approaches, relatively few studies address this issue. This study presents a methodology to assess the electric energy balance for the low-voltage grids in the German federal state of Baden-Württemberg, assuming the typical load curves and the interchange potential among local distribution grids by means of linear programming of the supply function and for typical seasonal electricity demands. The model can make a statement about the performance and development requirements for grid architecture for scenarios in 2035 and 2050 when regenerative energies will—according to present legislation—account for more than half of Germany’s electricity supply. The study details the amendment to Baden-Württemberg’s electricity grid required to fit the system to the requirements of regenerative electricity production. The suggested model for grid analysis can be used in further German regions and internationally to systematically remunerate electricity grids for the acceptance of larger amounts of regenerative electricity inflows. This empirical study closes the research gap of assessing the interchange potential among DSO and considers usual power loads and simultaneously usual electricity inflows.
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Oliveira, Ricardo Vasques de, Rodrigo Andrade Ramos, and Newton Geraldo Bretas. "Calculation of parameter ranges for robust gain tuning of power system controllers." Sba: Controle & Automação Sociedade Brasileira de Automatica 23, no. 3 (June 2012): 331–45. http://dx.doi.org/10.1590/s0103-17592012000300007.
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This work proposes a computational tool to assist power system engineers in the field tuning of power system stabilizers (PSSs) and Automatic Voltage Regulators (AVRs). The outcome of this tool is a range of gain values for theses controllers within which there is a theoretical guarantee of stability for the closed-loop system. This range is given as a set of limit values for the static gains of the controllers of interest, in such a way that the engineer responsible for the field tuning of PSSs and/or AVRs can be confident with respect to system stability when adjusting the corresponding static gains within this range. This feature of the proposed tool is highly desirable from a practical viewpoint, since the PSS and AVR commissioning stage always involve some readjustment of the controller gains to account for the differences between the nominal model and the actual behavior of the system. By capturing these differences as uncertainties in the model, this computational tool is able to guarantee stability for the whole uncertain model using an approach based on linear matrix inequalities. It is also important to remark that the tool proposed in this paper can also be applied to other types of parameters of either PSSs or Power Oscillation Dampers, as well as other types of controllers (such as speed governors, for example). To show its effectiveness, applications of the proposed tool to two benchmarks for small signal stability studies are presented at the end of this paper.
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Sathishkumar, D., and C. Karthikeyan. "Adaptive power management strategy-based optimization and estimation of a renewable energy storage system in stand-alone microgrid with machine learning and data monitoring." International Journal of Wavelets, Multiresolution and Information Processing 18, no. 01 (September 4, 2019): 1941023. http://dx.doi.org/10.1142/s0219691319410236.
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This work is carried out with the optimum design of a stand-alone hybrid energy storage system (HESS) based on solar, wind and super capacitor (SC) with battery storage system which is effectively optimized in the grid power system. The distribution of the power source is mainly considered on the Hybrid renewable energy power sources. This discourse presents an adaptive power optimizing the three-phase inverter and grid-connected hybrid renewable energy resources efficiently. In this analysis, the similar parameters are taken for the compensation such as voltage fluctuation, harmonics and Frequency imbalance by implementing Adaptive Power Management Strategy (APMS) and the obtained issues are synchronized by inverter control. All these comparative activities of the inverter are done either discretely or combined to stabilize the unbalanced impacts of a wide range of adjusted, uneven, power loss at the circulation level. A battery and SC energy management are essential for maintaining the energy sustainability in renewable energy system. Combination of solar and wind with the battery and SC is used to test the proposed stand-alone grid management. The proposed hybrid power system is designed to work under classical-based energy management and this performance is monitored with the help of the Internet of Things (IoT) and machine learning based on Polynomial Linear Regression Algorithm. The focus of the suggested HESS is reduced by the loss in stand-alone grid system with an economic performances.
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FAHEY, PATRICK K., and DWIGHT A. BURKHARDT. "Effects of light adaptation on contrast processing in bipolar cells in the retina." Visual Neuroscience 18, no. 4 (July 2001): 581–97. http://dx.doi.org/10.1017/s0952523801184087.
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Effects of light adaptation on contrast processing in the outer retina were investigated over nearly four decades of background illumination by analyzing the intracellular responses of 111 bipolar cells, 66 horizontal cells, and 22 cone photoreceptors in the superfused eyecup of the tiger salamander (Ambystoma tigrinum). Light adaptation had striking and similar effects on the average contrast responses of the hyperpolarizing (Bh) and depolarizing (Bd) classes of bipolar cells: Over the lower two decades of background illumination, the contrast gain increased 7-fold to reach values as high as 20–30, the dynamic range and the half-maximum contrast decreased by about 60%, the total voltage range increased some 40%, and contrast dominance changed from highly positive to more balanced. At higher levels of background, most aspects of the contrast response stabilized and Weber's Law then held closely. In this background range, the contrast gain of bipolar cells was amplified some 20× relative to that of cones whereas the corresponding amplification in horizontal cells was about 6×. Differences in the growth of contrast gain with the intensity of the background illumination for cones versus bipolar cells suggest that there are at least two adaptation-dependent mechanisms regulating contrast gain. One is evident in the cone photoresponse such that an approximately linear relation holds between the steady-state hyperpolarization and contrast gain. The other arises between the voltage responses of the cones and bipolar cells. It could be presynaptic (modulation of cone transmitter release by horizontal cell feedback or other mechanisms) and/or postsynaptic, that is, intrinsic to bipolar cells. Contrast gain grew with the background intensity by a larger factor in horizontal than in bipolar cells. This provides a basis for the widely held view that light adaptation increases the strength of surround antagonism in bipolar cells. On average, the effects of light adaptation and most quantitative indices of contrast processing were remarkably similar for Bd and Bh cells, implying that both classes of bipolar cells, despite possible differences in underlying mechanisms, are about equally capable of encoding all primary aspects of contrast at all levels of light adaptation.
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Wilson, Charles J., Angela Weyrick, David Terman, Nicholas E. Hallworth, and Mark D. Bevan. "A Model of Reverse Spike Frequency Adaptation and Repetitive Firing of Subthalamic Nucleus Neurons." Journal of Neurophysiology 91, no. 5 (May 2004): 1963–80. http://dx.doi.org/10.1152/jn.00924.2003.
Full textAbstract:
Subthalamic nucleus neurons exhibit reverse spike-frequency adaptation. This occurs only at firing rates of 20–50 spikes/s and higher. Over this same frequency range, there is an increase in the steady-state frequency–intensity ( F– I) curve's slope (the secondary range). Specific blockade of high-voltage activated calcium currents reduced the F– I curve slope and reverse adaptation. Blockade of calcium-dependent potassium current enhanced secondary range firing. A simple model that exhibited these properties used spike-triggered conductances similar to those in subthalamic neurons. It showed: 1) Nonaccumulating spike afterhyperpolarizations produce positively accelerating F– I curves and spike-frequency adaptation that is complete after the second spike. 2) Combinations of accumulating aftercurrents result in a linear F– I curve, whose slope depends on the relative contributions of inward and outward currents. Spike-frequency adaptation can be gradual. 3) With both accumulating and nonaccumulating aftercurrents, primary and secondary ranges will be present in the F– I curve. The slope of the primary range is determined by the nonaccumulating conductance; the accumulating conductances govern the secondary range. The transition is determined by the relative strengths of accumulating and nonaccumulating currents. 4) Spike-threshold accommodation contributes to the secondary range, reducing its slope at high firing rates. Threshold accommodation can stabilize firing when inward aftercurrents exceed outward ones. 5) Steady-state reverse adaptation results when accumulated inward aftercurrents exceed outward ones. This requires spike-threshold accommodation. Transient speedup arises when inward currents are smaller than outward ones at steady state, but accumulate more rapidly. 6) The same mechanisms alter firing in response to irregular patterns of synaptic conductances, as cell excitability fluctuates with changes in firing rate.
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MÄHLMANN, STEFAN, and DEMETRIOS T. PAPAGEORGIOU. "Interfacial instability in electrified plane Couette flow." Journal of Fluid Mechanics 666 (January 6, 2011): 155–88. http://dx.doi.org/10.1017/s0022112010004155.
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The dynamics of a plane interface separating two sheared, density and viscosity matched fluids in the vertical gap between parallel plate electrodes are studied computationally. A Couette profile is imposed onto the fluids by moving the rigid plates at equal speeds in opposite directions. In addition, a vertical electric field is applied to the shear flow by impressing a constant voltage difference on the electrodes. The stability of the initially flat interface is a very subtle balance between surface tension, inertia, viscosity and electric field effects. Under unstable conditions, the potential difference in the fluid results in an electrostatic pressure that amplifies disturbance waves on the two-fluid interface at characteristic wave lengths. Various mechanisms determining the growth rate of the most unstable mode are addressed in a systematic parameter study. The applied methodology involves a combination of numerical simulation and analytical work. Linear stability theory is employed to identify unstable parametric conditions of the perturbed Couette flow. Particular attention is given to the effect of the applied electric field on the instability of the perturbed two-fluid interface. The normal mode analyses are followed up by numerical simulations. The applied method relies on solving the governing equations for the fluid mechanics and the electrostatics in a one-fluid approximation by using a finite-volume technique combined with explicit tracking of the evolving interface. The numerical results confirm those of linear theory and, furthermore, reveal a rich array of dynamical behaviour. The elementary fluid instabilities are finger-like structures of interpenetrating fluids. For weakly unstable situations a single fingering instability emerges on the interface. Increasing the growth rates causes the finger to form a drop-like tip region connected by a long thinning fluids neck. Even more striking fluid motion occurs at higher values of the electric field parameter for which multiple fluid branches develop on the interface. For a pair of perfect dielectrics the vertical electric field was found to enhance interfacial motion irrespective of the permittivity ratio, while in leaky dielectrics the electric field can either stabilize or destabilize the interface, depending on the conductivity and permittivity ratio between the fluids.
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Nguyen, T. D., A. I. Zanko, D. A. Golosov, S. M. Zavadski, S. N. Melnikov, V. V. Kolos, and N. К. Тоlochko. "Formation and investigation of characteristics of thermoresistive structures based on vanadium oxide films." Doklady BGUIR 19, no. 4 (July 1, 2021): 85–93. http://dx.doi.org/10.35596/1729-7648-2021-19-4-85-93.
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The processes of reactive magnetron sputtering of a V target in Ar/O2 gas mixture are investigated. It was found that when using a pulsed current for sputtering and a pressure in the chamber less than 0.06 Pa, the intensities of the emission lines of vanadium at 437.922 nm, argon at 750.386 nm, and oxygen at 777.417 nm with a change in the oxygen concentration in Ar/O2 gas mixtures (ГO2) have no hysteresis and unambiguously depend on the parameters of the sputtering process, which makes it possible to stabilize the process without using feedback systems. By monitoring the sputtering process by optical emission spectroscopy and depositing films on a rotating substrate of diameter 100 mm, vanadium oxide (VOx) films with nonuniformity thickness less than ±2.4 % and surface resistance less than ±2.5 % were obtained. Studies by transmission line method of the influence of the parameters of the reactive magnetron sputtering and subsequent annealing at O2 pressure of 0.04 Pa on the characteristics of thermoresistive structures based on VOx films showed that when the contacts are deposited without ion cleaning, the current-voltage characteristics (IV) and the dependence of the resistance on the length of resistors R(L) are nonlinear, which indicates the presence of a potential barrier in the contacts. Preliminary ion cleaning can significantly improve the linearity of the IV characteristic. The most linear IV characteristics were obtained for Ti contacts. However, the specific contact resistance of the VOx/Ti contact increases with an increase in the oxidation state of the VOx films and reaches ρc = 0.1 Ohm·m2 at the specific resistance of vanadium oxide ρ = 0.1 Ohm·m. The analysis of the dependences of the temperature coefficient of resistance (TCR) and ρ of VOx films on the annealing temperature showed that, upon annealing, ρ and TCR slightly decrease, i. e. there occurs a partial deoxidation of the films. However, unlike annealing at atmospheric pressure, there are no temperature regions at which a sharp decrease in the resistivity and TCR occurs.
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Yadav, D. K. "A Unique Concept of Limited Grid Capacity and Voltage-Frequency Control of an RES Based Rural Electrification System." International Journal of Emerging Electric Power Systems 19, no. 5 (August 17, 2018). http://dx.doi.org/10.1515/ijeeps-2018-0026.
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Abstract This paper presents dynamic performance analysis of a PV-biogas-biodiesel-grid based hybrid power system designed for rural electrification. The linear small signal model of the system using power balance equations is developed and small step change in solar incident power and active and reactive load demand of the system are applied. The objective of this work is to control the system voltage (magnitude and angle), frequency and to operate the grid for controlled supply. The voltage source inverter (VSI) used for photovoltaic (PV) system provides active and reactive support and controlled to maintain system voltage and frequency constant. The biogas and bio-diesel engine are equipped with electronic governor control, uses synchronous generator (SG) with automatic voltage regulator (AVR). The variation in load demand is balanced by the biogas, bio-diesel generator and by PV system keeping grid supply constant. The system is simulated in MATLAB and the performance is analyzed for variable loads and input solar power. The PI controllers are applied and their gains are optimized using ISE method. The state variables are plotted and their oscillations are stabilized within few seconds. The system voltage, frequency and grid are controlled effectively.
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"Optimal Tuning of Linear Quadratic Regulator Controller Using Ant Colony Optimization Algorithm for Position Control of a Permanent Magnet DC Motor." Iraqi Journal of Computer, Communication, Control and System Engineering, July 31, 2020, 29–41. http://dx.doi.org/10.33103/uot.ijccce.20.3.3.
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This paper presents the design of an optimal Linear Quadratic Regulator (LQR) controller using Ant Colony Optimization (ACO) and particle swarm optimization (PSO) methods for position control of a permanent magnet DC (PMDC) motor. In this work, Ant Colony control and particle swarm control algorithms have been utilized to set the optimal elements of the weighting matrices subjected to a proposed cost function. The proposed cost function is a combination of the quadratic performance index and integral square error. The proposed design can overcome the difficulty in setting the weighting matrices with the suitable elements. The simulation results using (Matlab Package) show that the optimal LQR controller using ACO algorithm can give excellent performance in terms of obtaining smooth and unsaturated state voltage control action that will stabilize the DC motor system performance and minimize the position tracking error of the system output. In addition, the rising time and settling time is decreased in comparison with the LQR based PSO controller performance.
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Goughari, Rohollah Sadeghi, Mehdi Jafari Shahbazzadeh, and Mahdieh Eslami. "Investigation of the Behavior of Output Variables for Arbitrary Inputs to high Voltage Direct Current Power System Modeling Using Lyapunov Function Nonlinear Control Model." Recent Advances in Electrical & Electronic Engineering (Formerly Recent Patents on Electrical & Electronic Engineering) 13 (August 21, 2020). http://dx.doi.org/10.2174/2352096513999200821124317.
Full textAbstract:
Background: Until now, a variety of proportional integral controllers and local controllers and predictive controller models have been used to stabilize VSC-HVDC transmission lines. One of the disadvantages of a linear model predictive control is that it is difficult and time consuming to adjust it for times when the disturbance entering the system is sudden. the goal is to monitor and take appropriate action to balance power and eliminate voltage or current that has exceeded the allowable limit. Methods: The way it works is that first, the DC current and the measured voltage of converter power source (VSC) is supplied based on various factors, and then the converters slowly begin to track the desired reference value, and this continues until the power sources adjusted according to current and voltage limits. Results: To achieve this goal, this paper examines recent articles on the modeling of VSC-HVDC power transmission systems and a comprehensive model has been chosen that has not been published for several months since its publication. Next, to control the se-lected model, the combined control strategy of nonlinear predictive based on the Lyapunov function is used to ensure the stability of the system. Conclusion: The results of the implementation of this control strategy on the HVDC power transmission system model in MATLAB soft-ware express the ability of this controller to track the reference input values.
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Pati, Avadh, and Richa Negi. "An anti-windup control strategy to actuator saturating input voltage for active magnetic bearing system." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 35, no. 3 (March 17, 2016). http://dx.doi.org/10.1108/compel-04-2015-0167.
Full textAbstract:
Purpose The active magnetic bearing is highly nonlinear and unstable system. In general most of physical systems, conventional PID control strategies are employed for their stable operation but the dynamics of the system are influenced by input voltage saturation that degrades the performance of the system. The conventional PID control scheme does not work properly alone. In such a situation, PID faces windup phenomenon that leads to instability in the system. To overcome this problem, an anti-windup control scheme leads to stable and smooth operation of active magnetic bearing system. Design/methodology/approach The proposed anti-windup control strategy is based on dynamic output feedback that is applied on linearized active magnetic bearing (AMB) system to stabilize and avoid the input voltage saturation effect in the actuator. Findings An anti-windup controller is designed for active magnetic bearing system in presence of input voltage saturation. The stability of AMB system with anti-windup controller is derived in sense of Lyapunov and expressed as linear matrix inequality problem for AMB system and the designed anti-windup controller also enlarges the region of attraction of considered AMB system. Originality/value T-S fuzzy technique is used for obtaining local linear model of nonlinear active magnetic bearing system for easy and simple implementation of anti-windup control scheme. In proposed methodology the region of attraction for anti-windup compensator is also discussed. The effectiveness of proposed method is verified by the numerical simulation results for considered active magnetic bearing system and domain of attraction or stability region of closed loop AMB system are also calculated using Eigen Value Optimization technique for both the cases such as with and without anti-windup controller. The comparative result and the contribution of proposed control strategy are also discussed.