Journal articles: 'Zero sequence current compensation'

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Montoya-Mira, Rafael, Pedro A. Blasco, José M. Diez, Rafael Montoya, and Miguel J. Reig. "Unbalanced and Reactive Currents Compensation in Three-Phase Four-Wire Sinusoidal Power Systems." Applied Sciences 10, no. 5 (March 4, 2020): 1764. http://dx.doi.org/10.3390/app10051764.

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In an unbalanced linear three-phase electrical system, there are inefficient powers that increase the apparent power supplied by the network, line losses, machine malfunctions, etc. These inefficiencies are mainly due to the use of unbalanced loads. Unlike a three-wire unbalanced system, a four-wire system has zero sequence currents that circulate through the neutral wire and can be compensated by means of compensation equipment, which prevents it from being delivered by the network. To design a compensator that works with unbalanced voltages, it is necessary to consider the interactions between it and the other compensators used to compensate for negative-sequence currents and positive-sequence reactive currents. In this paper, through passive compensation, a new method is proposed to develop the zero sequence current compensation equipment. The method does not require iteration algorithms and is valid for unbalanced voltages. In addition, the interactions between all compensators are analyzed, and the necessary modifications in the calculations are proposed to obtain a total compensation. To facilitate the application of the method and demonstrate its validity, a case study is developed from a three-phase linear four-wire system with unbalanced voltages and loads. The results obtained are compared with other compensation methods that also use passive elements.

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Han, Zhao, Xiaoli Wang, Baochen Jiang, and Jingru Chen. "A Control Strategy for Suppressing Zero-Sequence Circulating Current in Paralleled Three-Phase Voltage-Source PWM Converters." Applied Sciences 10, no. 5 (March 2, 2020): 1703. http://dx.doi.org/10.3390/app10051703.

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In microgrids, paralleled converters can increase the system capacity and conversion efficiency but also generate zero-sequence circulating current, which will distort the AC-side current and increase power losses. Studies have shown that, for two paralleled three-phase voltage-source pulse width modulation (PWM) converters with common DC bus controlled by space vector PWM, the zero-sequence circulating current is mainly related to the difference of the zero-sequence duty ratio between the converters. Therefore, based on the traditional control ideal of zero-vector action time adjustment, this paper proposes a zero-sequence circulating current suppression strategy using proportional–integral quasi-resonant control and feedforward compensation control. Firstly, the dual-loop decoupled control was utilized in a single converter. Then, in order to reduce the amplitude and main harmonic components of the circulating current, a zero-vector duty ratio adjusting factor was initially generated by a proportional–integral quasi-resonant controller. Finally, to eliminate the difference of zero-sequence duty ratio between the converters, the adjusting factor was corrected by a feedforward compensation link. The simulation mode of Matlab/Simulink was constructed for the paralleled converters based on the proposed control strategy. The results verify that this strategy can effectively suppress the zero-sequence circulating current and improve power quality.

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Zhou, Jun, and Ke Zheng Cao. "Locating Method of Single-Phase Grounding Fault in Small Current Grounding System Based on Distribution Automation." Applied Mechanics and Materials 321-324 (June 2013): 1423–28. http://dx.doi.org/10.4028/www.scientific.net/amm.321-324.1423.

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In case of the arc suppression coil for neutral point grounding of small current grounding system, when single-phase grounding fault occurs, due to the arc suppression coil for fault line of the compensation effect of the zero sequence current, the fault features is not obvious, it can't implement the fault line selection and fault point location. This paper puts forward a method of change fault lines zero sequence current shortly, namely a resistance inductance (RL) series branch parallel in arc suppression coil, the series branch acts on the system shortly and changes arc suppression coil compensation degree temporarily in single-phase grounding fault. The change of zero sequence residual current only appears the loop from the neutral point to the fault point via the fault line, using FTU (feeder terminal units) on lines monitor the change of zero sequence current on each nodes for fault regional location. And prove this theory the feasibility of the by using MATLAB software of system modeling simulation method.

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Jun, Zhou, Cao Ke-Zheng, and Zheng Hong-Xia. "The Study of Fault Location Method Based on FTU Feeder Automation Technology." Open Electrical & Electronic Engineering Journal 7, no. 1 (December 13, 2013): 143–48. http://dx.doi.org/10.2174/1874129001307010143.

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With the development of power distribution automation system, feeder automation technology in the small current grounding system single-phase grounding fault location plays an important role. In the neutral arc suppression coil grounding system, because of the compensation effect of arc suppression coil, the system fault feature is not obvious. This paper puts forward a method of RL series branch parallel in arc suppression coil, when system single-phase grounding fault occurs, the series branch switch gets closed and acts on the neutral, that changes the compensation degree of arc suppression coil to zero sequence current in fault line, the change of zero sequence residual current being the biggest in the fault section from neutral to fault point. FTU is used to monitor the change in each fault line for fault regional location.

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Tian, Shu, Jin Peng He, and Yu Zheng. "The Research Based on Zero Sequence Energy to the Line Selection in Distribution Network." Advanced Materials Research 614-615 (December 2012): 846–49. http://dx.doi.org/10.4028/www.scientific.net/amr.614-615.846.

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When single phase-to-ground fault happened in power network with arc suppression coil grounded, capacitor current through fault point is compensated and reduced by installing arc suppression coil. Zero-sequence current’s amplitude and phase of fault lines and sound lines are so similar that it increases the difficulty of selecting the fault line. But the resistance component of zero sequence current has no relationship with the arc extinguishing coil compensation, absolute value of resistance component to the fault lines show the maximum, and zero sequence current’s polarity of fault lines is contrary to sound lines. In this paper, because of the characteristic of resistance component, a method is put forward based on zero sequence energy to the line selection in distribution network, it import auto-reclosing techniques into the line selection. The principle is verified by MATLAB simulator. It has high accuracy to select the fault line with this method.

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Kai, Takaaki, Mitsuhiro Furuse, Takayuki Matsuda, Motonobu Yoshikawa, and Hidehiko Matsusaki. "The improvement of zero-phase-sequence circulating current compensation scheme for balance ground relaying." IEEJ Transactions on Power and Energy 109, no. 3 (1989): 111–18. http://dx.doi.org/10.1541/ieejpes1972.109.111.

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Geng, Jun Mei, and Chun Guang Li. "Leakage Failure and Principle of Underground Low Voltage Grid." Applied Mechanics and Materials 214 (November 2012): 254–58. http://dx.doi.org/10.4028/www.scientific.net/amm.214.254.

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To describe the leakage protection of underground low voltage grid are based on zero-sequence voltage and zero sequence power direction of the current leakage protection and earth leakage protection based on the additional DC power supply two kinds. The paper gives the theoretical analysis of these two kinds of leakage, and unified the three-phase neutral point grounding system and by arc suppression coil grounding the under compensation leakage detection program, that provides a new approach for underground leakage detection.

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Naderipour, Amirreza, Zulkurnain Abdul-Malek, Mohammad Reza Miveh, Mohammad Jafar Hadidian Moghaddam, Akhtar Kalam, and Foad H. Gandoman. "A Harmonic Compensation Strategy in a Grid-Connected Photovoltaic System Using Zero-Sequence Control." Energies 11, no. 10 (October 1, 2018): 2629. http://dx.doi.org/10.3390/en11102629.

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Mitigation of harmonics for a grid-connected inverter is an important element to stabilize the control and the quality of current injected into the grid. This paper deals with the control method of a three-phase Grid-Connected Inverter (GCI) Photovoltaic (PV) system, which is based on the zero-sequence current adjuster. The proposed method is capable of removing the harmonic current and voltage without using any active and passive filters and without the knowledge of the microgrid topology and also impedances of distribution bands and loading conditions. This concept is adopted for the control of a Distributed Generator (DG) in the form of grid-connected inverter. The proposed control can be applied to the grid connected inverter of the PV. The fast dynamic response, simple design, stability, and fast transient response are the new main features of the proposed design. This paper also analyzes the circuit configuration effects on the grid connected inverter capability. The proposed control is used to demonstrate the improved stability and performance.

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Feng, Guoli, Zhihao Ye, Yihui Xia, Heng Nian, Liming Huang, and Zerun Wang. "High Frequency Resonance Suppression Strategy of Three-Phase Four-Wire Split Capacitor Inverter Connected to Parallel Compensation Grid." Energies 15, no. 4 (February 17, 2022): 1486. http://dx.doi.org/10.3390/en15041486.

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With the continuous penetration and development of renewable energy power generation, the distributed grid and the microgrid are becoming increasingly important in modern power systems. In distribution networks and the microgrid, the grid impedance is comparatively large and cannot be ignored. Usually, the parallel compensation is used to improve the grid quality. In the grid with parallel compensation, the large phase angle difference between the impedance of the grid-connected inverter and the impedance of the grid at amplitude intersection will result in high frequency resonance (HFR). Because the inverter shows filter characteristics due to limited bandwidth of the controller, the parallel compensation grid, respectively, performs as the capacitance characteristic and inductance characteristic in different high frequency range. Compared with the three-phase, three-wire system, an additional zero-sequence path exists in the three-phase four-wire split capacitor inverter (TFSCI) system, so that the existing high frequency resonance suppression methods will be not effective. Since the zero-sequence component is neglected, HFR will also occur, in addition to the positive-sequence component and the negative-sequence component. Therefore, in order to suppress the high frequency resonance caused by positive-sequence, negative-sequence and zero-sequence components, an impedance reshaping strategy based on current feedback is proposed in this paper. This proposed method can reshape the amplitude and phase of the inverter impedance in a high frequency range without affecting the performance of the fundamental frequency control and ensure that the inverter contains a sufficient phase margin. Additionally, the proposed method can reshape the impedance of TFSCI within a wide frequency range, which makes it able to cope with the challenge of the parallel compensation degree change. Theoretical analysis and experiments verify the availability of the proposed control strategy.

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Zhu, Yixin, Tao Wang, Liansong Xiong, Gaofeng Zhang, and Xin Qian. "Parallel Control Method Based on the Consensus Algorithm for the Non-Isolated AC/DC Charging Module." Energies 11, no. 10 (October 19, 2018): 2828. http://dx.doi.org/10.3390/en11102828.

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A high-power charging station for electric vehicles usually adopts a parallel structure of multiple power modules. However, due to the parameter differences among power modules, a parallel system always has circulating current issues. This paper takes a non-isolated AC/DC charging module as the research object and proposes a current sharing control strategy for multiple power modules based on the consensus algorithm. By constructing a sparse communication network with the CAN (Controller Area Network) protocol and exchanging current information, accurate current sharing among power modules is realized. Firstly, the zero-sequence circulating current issue is analyzed through a parallel model of the three-phase rectifier, with an improved circulating current restraint strategy proposed based on the zero-sequence voltage compensation. Then, the principle of the consensus algorithm is explained, which is applied to the current sharing control of multiple power modules. Finally, the proposal is tested by the designed simulation and experimental cases. From the obtained results, it can be seen that the proposed control strategy can effectively realize accurate current sharing among multiple power modules and well restrain the zero-sequence circulating current at the input side.

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Najafi, Foad, Mohsen Hamzeh, and Matthias Fripp. "Unbalanced Current Sharing Control in Islanded Low Voltage Microgrids." Energies 11, no. 10 (October 16, 2018): 2776. http://dx.doi.org/10.3390/en11102776.

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This paper reports a new control strategy to improve sharing of unbalanced currents in islanded LV microgrids. This technique provides fast and effective sharing of positive-, negative- and zero-sequence currents, and is the first example of zero-sequence current sharing in the literature. The controllers are designed in the stationary frame. The control structure consists of four loops: (1) the current controller; (2) the voltage controller; (3) the droop controller and the (4) negative and zero sequence current controllers. The output current is considered unknown for the controller and is added to the control system as a disturbance. The proposed controller features a high gain in fundamental and harmonic frequencies, hence a good voltage quality is obtained in the presence of unbalanced and nonlinear loads. To this aim, a proportional-resonant (PR) controller is adopted as the current controller. By using a multi-resonant controller as current controller, a unified control structure is obtained which is suitable for both grid-connected and islanded modes. The voltage controller is designed using a resonant controller so that the voltage can have low VUF and THD in the presence of unbalanced and nonlinear loads. Furthermore, in this paper, the droop method is applied to the control structure to share real and reactive powers. Simulation studies show that the conventional droop method cannot share the oscillatory part of the output power that is due to the presence of unbalanced loads in the microgrid. This paper relies on using zero and negative sequence virtual impedance controller to share the oscillatory part of output power. By using zero-sequence virtual impedance controller (ZSVIC) and negative-sequence virtual impedance controller (NSVIC), the zero and negative sequence currents in the microgrid are controlled and shared effectively. By compensating zero- and negative-sequence currents locally, the flow of these currents in the microgrid is minimized, and the overall power quality of the islanded LV microgrid is improved.

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Lu, Daorong, Chenxing Sha, Yu Yu, Xiang Li, Haibing Hu, and Yan Xing. "Flexible Nonsinusoidal Zero Sequence Voltage Injection Method to Extend Negative Sequence Current Compensation Range for Star-Connected CHB STATCOM." IEEE Transactions on Power Electronics 36, no. 10 (October 2021): 11357–71. http://dx.doi.org/10.1109/tpel.2021.3071458.

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13

Yun, Wei Jun, Gang Yao, Li Dan Zhou, Chen Chen, and Jun Min Pan. "A Novel Control Strategy for Three-Phase Four-Wire STATCOM." Advanced Materials Research 516-517 (May 2012): 1722–27. http://dx.doi.org/10.4028/www.scientific.net/amr.516-517.1722.

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Nowadays Static Synchronous Compensator (STATCOM) has gradually become one of the representative techniques in the field of dynamic reactive power compensation in the power distribution system. This paper analyzed the topology and the voltage imbalance problem of the up and down capacitors on DC side of the three-phase four-wire STATCOM. In allusion to the imbalance problem of neutral point, a novel control strategy based on the control of zero-sequence current was proposed. By the triple close-loop control strategy, the STATCOM can achieve great control accuracy and dynamic performance. Simulation result proves that the proposed control method is effective.

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Sołjan, Zbigniew, Grzegorz Hołdyński, and Maciej Zajkowski. "CPC-Based Minimizing of Balancing Compensators in Four-Wire Nonsinusoidal Asymmetrical Systems." Energies 14, no. 7 (March 24, 2021): 1815. http://dx.doi.org/10.3390/en14071815.

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The article presents the possibility of using the currents’ physical components (CPC) theory to generate the reference current of the active power filter (APF). The solution proposed by the authors is based on the cooperation of minimizing balancing compensators (MBC), which, due to their use in 4-wire systems, have been divided into two structures. The first compensator, which purpose is to minimize and balance the reactive current and the unbalanced current of the zero sequence, is built in the star system (STAR-MBC). The purpose of the second compensator, which operation occurs in the delta system (DELTA-MBC), is to minimize and balance the other two components, i.e., the unbalanced current of the negative sequence and the unbalanced current of the positive sequence. The two structures cooperating with each other significantly reduce the currents associated with the reactive elements, i.e., reactive current, and the unbalanced current. As mentioned, these currents are reduced but not compensated to zero or to the reference value. In order for the compensation and balancing to bring the preferable effect, an APF system should be included, which will cooperate with MBC compensators. This solution is presented in this publication. The control of the active part of the hybrid active power filter (HAPF), which was presented in the paper, consists of the reflection of the waveform of the nonsinusoidal active current. In this approach, no current shift in relation to voltage is obtained, but the waveforms of these quantities remain distorted. The reactive current is compensated and the unbalanced currents are balanced. The second definition of generating a reference current can also be used. Through this approach, the active current with a sinusoidal waveform is achieved. The second approach allows for an additional reduction of the three-phase RMS value of the load’s current. In both of these approaches, the active currents flowing through the lines will reflect the amplitude and phase asymmetry that is present in the supply voltage. The APF system will follow the changes in power or load conditions and generate the correct value for the reference current. The calculations presented in the article, as well as the current and voltage waveforms, were created as a result of the constructed mathematical models, which were used for theoretical illustrations. Calculations and waveforms were generated based on a script written in Matlab.

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Chernyshov, Maxim, Valery Dovgun, Sergei Temerbaev, and Zumeyra Shakurova. "Hybrid power quality conditioner for three-phase four-wire power systems." E3S Web of Conferences 178 (2020): 01009. http://dx.doi.org/10.1051/e3sconf/202017801009.

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The article considers a hybrid power quality conditioner (HQPC) for 3-phase 4-wire systems with a distributed modular structure. Some conditioner modules provide compensation for the component currents and voltages that form the negative and zero sequence systems. The open structure of the HQPC, consisting of independent modules, allows compensating for distortions of currents and voltages of the 3-phase network caused by the nonlinear nature and asymmetry of single-phase loads. The compensation characteristics of the proposed conditioner were researched using a model developed in the MatLab environment. The simulation showed that the proposed conditioner can ensure normalization of power quality in 3-phase 4-wire system at various modes of network operation.

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Ding, Wenlong, Chenghui Zhang, Feng Gao, Bin Duan, and Han Qiu. "A Zero-Sequence Component Injection Modulation Method With Compensation for Current Harmonic Mitigation of a Vienna Rectifier." IEEE Transactions on Power Electronics 34, no. 1 (January 2019): 801–14. http://dx.doi.org/10.1109/tpel.2018.2812810.

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Chebabhi, Ali, Mohammed-Karim Fellah, Mohamed-Fouad Benkhoris, and Abdelhalim Kessal. "Sliding mode controller for four leg shunt active power filter to eliminating zero sequence current, compensating harmonics and reactive power with fixed switching frequency." Serbian Journal of Electrical Engineering 12, no. 2 (2015): 205–18. http://dx.doi.org/10.2298/sjee1502205c.

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In this paper, the four leg inverter controlled by the three dimensional space vector modulation (3D SVM) is used as the shunt active power filter (SAPF) for compensating the three phase four wire electrical network, by using the four leg inverter with 3D SVM advantages to eliminated zero sequence current, fixed switching frequency of inverter switches, and reduced switching losses. This four leg inverter is employed as shunt active power filter to minimizing harmonic currents, reducing magnitude of neutral wire current, eliminating zero sequence current caused by nonlinear single phase loads and compensating reactive power, and a nonlinear sliding mode control technique (SMC) is proposed for harmonic currents and DC bus voltage control to improve the performances of the three phase four wire four leg shunt active power filter based on Synchronous Reference Frame (SRF) theory in the dq0 axes, and to decoupling the four leg SAPF mathematical model.

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Fujun, Ma, Luo An, Xiong Qiaopo, He Zhixing, and Xu Qianming. "Derivation of zero‐sequence circulating current and the compensation of delta‐connected static var generators for unbalanced load." IET Power Electronics 9, no. 3 (March 2016): 576–88. http://dx.doi.org/10.1049/iet-pel.2014.0682.

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Li, Yongshen, Chengning Zhang, Xueping Li, Ying Zhou, and Shuo Zhang. "An Improved Model-Free Predictive Current Control Scheme for Open-Winding PMSM with Common DC Bus." Journal of Physics: Conference Series 2224, no. 1 (April 1, 2022): 012113. http://dx.doi.org/10.1088/1742-6596/2224/1/012113.

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Abstract To improve the parameter robustness of the open-winding permanent magnet synchronous motor (OW-PMSM), this paper proposes an improved model-free predictive current control (MFPCC) method. First, the first-order ultra-local model of OW-PMSM is established, which does not contain any motor parameter. Secondly, a sliding mode observer (SMO) is introduced into the model to estimate the current in d-q-0 axis. Then, to suppress the torque ripple generated by the zero-sequence current (ZSC), the central hexagonal modulation strategy and the q-axis current injection method are combined, and the compensation current that needs to be injected into the q-axis is calculated according to the estimated value of ZSC. Finally, after considering the one-step delay, the voltage reference at the next instant is calculated based on the estimated values of d-q axis current and compensation current. Simulation and experimental results indicate that the proposed method can improve the parameter robustness of OW-PMSM, and the performance of current and torque has been improved under various parameter mismatch conditions.

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Panigrahi, Swetapadma, and Amarnath Thakur. "A Novel Approach for grid integration of Cascaded H-bridge Multilevel Inverter Under Partial Shading Condition." International Journal of Power Electronics and Drive Systems (IJPEDS) 9, no. 3 (September 1, 2018): 1330. http://dx.doi.org/10.11591/ijpeds.v9.i3.pp1330-1337.

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<p>A modular cascaded H-bridge PV inverter system is presented in this paper. The modular structure of PV inverter helps in obtaining the maximum output power of PV system along with increase the overall efficiency of the whole system. Moreover to utilize the system up to the best a distributed MPPT controller is attached with each PV panel. As partial shading causes power imbalance at the converter output that leads to imbalance grid current, a control technique called the modulation compensation is adopted in such a way that if three phase unbalanced voltage varies directly according to unbalanced power, the injected zero sequence voltage components make the grid current balanced.</p>

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Wu, Zhihong, Weisong Gu, Yuan Zhu, and Ke Lu. "Current Control Methods for an Asymmetric Six-Phase Permanent Magnet Synchronous Motor." Electronics 9, no. 1 (January 16, 2020): 172. http://dx.doi.org/10.3390/electronics9010172.

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Via the vector space decomposition (VSD) transformation, the currents in an asymmetric six-phase permanent magnet synchronous motor (ASP_PMSM) can be decoupled into three orthogonal subspaces. Control of α–β currents in α–β subspace is important for torque regulation, while control of x-y currents in x-y subspace can suppress the harmonics due to the dead time of converters and other nonlinear factors. The zero-sequence components in O1-O2 subspace are 0 due to isolated neutral points. In α–β subspace, a state observer is constructed by introducing the error variable between the real current and the internal model current based on the internal model control method, which can improve the current control performance compared to the traditional internal model control method. In x–y subspace, in order to suppress the current harmonics, an adaptive-linear-neuron (ADALINE)-based control algorithm is employed to generate the compensation voltage, which is self-tuned by minimizing the estimated current distortion through the least mean square (LMS) algorithm. The modulation technique to implement the four-dimensional current control based on the three-phase SVPWM is given. The experimental results validate the robustness and effectiveness of the proposed control method.

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Peñalvo-López, Elisa, Vicente León-Martínez, Joaquín Montañana-Romeu, and Javier Cárcel-Carrasco. "Passive Reactive Power Compensators for Improving the Sustainability of Three-Phase, Four-Wire Sinusoidal Systems Supplied by Unbalanced Voltages." Sustainability 13, no. 20 (October 9, 2021): 11134. http://dx.doi.org/10.3390/su132011134.

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Compensation of reactive power is necessary in power systems due to economical, energetic, and environmental reasons. Reactive power increases energy power losses and carbon dioxide emissions in distribution lines and power transformers. However, capacitor banks used in most industrial applications do not significantly reduce energy losses in lines and transformers when supply voltages and loads are unbalanced and therefore do not fully improve the sustainability of distribution networks. This fact is explained in this paper using positive-, negative-, and zero-sequence reactive power components in three-phase, four-wire sinusoidal power systems supplied with unbalanced voltages. Likewise, several devices have also been developed for the compensation of the total reactive power and, specifically, for each of its components in these power systems. Comparing the effectiveness of these reactive compensators and other well-known passive compensators as capacitor banks on the sustainability improvement of the electrical installation of an actual industry, reductions between 20% and 100% in energy losses and carbon dioxide emissions, caused by circulation of reactive currents in transformer and lines, can be expected depending on the type of compensator used.

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Sekhar Mishra, Chandra, Ranjan Kumar Jena, and Soumya Ranjan Nayak. "PQ improvement of Micro-Grid by Using DG and Power Quality Conditioner with BESS." International Journal of Engineering & Technology 7, no. 2.32 (May 31, 2018): 245. http://dx.doi.org/10.14419/ijet.v7i2.32.15577.

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DG Grid interfaced system has been focused through this paper. The objective is to improve power quality of the grid, which was polluted by various means. The improvement of power quality of the micro grid includes uses of a specially designed DG, BESS and Power Quality conditioner. The system consists of a two-stage power conversion. Solar PV supplies power for both DC and AC loads. Manufacturer datasheet is used for modeling the PV panel. In order to keep the BUS voltage stable a BESS is joined to DC BUS through power electronic converter, which is used to absorb the excess power whenever production is high and deliver power to the load on low production. The system continues to supply the local loads, incase of grid discontinuity. Thus it eliminates threats of islanding. This paper also focuses on control and stability of DC bus voltage and energy management scheme. The project uses Matlab/Simulink platform for efficient verification. For power quality improvement of Micro Grid it uses 3leg inverter, which is coupled with SPV and MPPT with Battery storage, which is used as compensator for the whole system. For prevention to reduce voltage current and power flow between DG and Grid, it is necessary to have an optimum control. Through the adjustment of power circulation between shunt paired DG ensures current voltage and power on micro grid. +ve, -ve and Zero sequence components of currents and voltage can be adjusted by the suggested methodology in Grid tied DG system. The said PQC have multiple uses. Firstly as a power converter and secondly as a shunt APF for harmonic compensation on voltage, current and power (both active and reactive) for both balanced and unbalanced loads in the Grid tied DG system. It also cares for the neutral conductor. Either individually or in grid connected mode all the above objectives can be achieved. For the entire Grid, it is realized that after compensation three phase four wired un-balance loads looks as balanced linear resistive load for the Grid. All these task significantly replicated on MATLAB/Simulink. After compensation the total harmonic distortion on input voltage and current reduced drastically. IEEE519 in the range of 5% suitably accepts it.

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Wang, Songda, Danyang Bao, Gustavo Gontijo, Sanjay Chaudhary, and Remus Teodorescu. "Modeling and Mitigation Control of the Submodule-Capacitor Voltage Ripple of a Modular Multilevel Converter under Unbalanced Grid Conditions." Energies 14, no. 3 (January 28, 2021): 651. http://dx.doi.org/10.3390/en14030651.

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A modular multilevel converter’s (MMC’s) submodule (SM)-capacitor voltage will increase under unbalanced grid conditions. Depending on the imbalance level, the voltage ripple can be considerably high, and it can exceed the pre-defined safe limits. If this occurs, the converter will trip, which can lead to serious stability problems for the grid. This paper first proposes an analytical solution for deriving the three-phase imbalanced SM ripple of an MMC under an unbalanced grid. With this analytical tool, the imbalance mechanism of the SM voltage ripple can be easily understood. What is more, the symmetrical component method is first applied to analyze the three-phase SM capacitor ripple, and the positive-/negative-/zero-sequence components of the three-phase SM voltage ripple are easily identified by the proposed analytical method. Then, based on this powerful analytical tool, the proper circulating-current profile to be injected can be obtained, allowing for the right compensation of the voltage ripple. Based on this approach, two new voltage ripple compensation methods are proposed in this paper. Simulations were carried out to validate the analytical description of the submodule-capacitor voltage ripple proposed in this paper. Moreover, simulation and experimental results are provided to validate the new compensation techniques introduced in this paper.

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Lee, Seung-Yong, and Jae-Jung Jung. "The Circulating Current Reduction Control Method for Asynchronous Carrier Phases of Parallel Connected Inverters." Energies 15, no. 5 (March 7, 2022): 1949. http://dx.doi.org/10.3390/en15051949.

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Parallel operation of inverters is one of the most effective and representative ways to increase system capacity. However, zero-sequence circulating currents occur due to the practical deviations of components constituting individual inverters in case of parallel connected inverters in which a common direct current (DC) or alternating current (AC) bus is shared. In particular, circulating currents of the high-frequency component as well as those of the low-frequency component are generated due to the asynchronization of the carriers of individual inverters. In order to suppress the circulating currents as such, the phases of the carriers should be shifted as much as the phase errors between the carriers to compensate for the phase errors. A difficulty in this phase compensation control is that when there are several pulse-width modulation (PWM) carriers, it is impossible to identify the phase of each carrier. In this paper, to overcome the problem, a method to specify the position of one of the many carriers and control the carriers and compensate for phase errors based on the relevant phase was proposed. In addition, this paper includes the analysis of circulating currents generated in the case of carrier phase errors and proposes a method to identify carrier phase errors and compensate for the relevant errors. The proposed method was verified through simulations and experiments.

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Bhattar, Chandrakant L., and Vilas N. Ghate. "A New Control Algorithm for Three-Phase, Four-Wire Unified Power Quality Conditioner (UPQC) in Distributing Systems." Advanced Materials Research 433-440 (January 2012): 6731–36. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.6731.

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This paper presents the new control algorithm for three-phase, four-wire distributing system using unified power quality conditioner (UPQC). The UPQC, a combination of series and shunt active filter (AF) with common dc link, is one of the best solution towards the compensation of voltage sag, swell problems and also compensate voltage flicker/imbalance, reactive power, negative sequence current and maintain zero voltage regulation (ZVR) at the point of common coupling (PCC) on distribution system. The series AF is seen by using a three-phase, three leg voltage source inverter (VSI) and the shunt AF is of a three-phase, four leg voltage source inverter (VSI). The proposed model of the UPQC is developed in the MATLAB/SIMULINK environment and the simulation results prove the power quality improvement in the system.

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Sharma, Rashmi, and Vijay H. Makwana. "An advanced LVRT controlled DSCC-STATCOM for reactive power compensation." International Journal of Power Electronics and Drive Systems (IJPEDS) 14, no. 1 (March 1, 2023): 294. http://dx.doi.org/10.11591/ijpeds.v14.i1.pp294-303.

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<span lang="EN-US">This article focuses on the control of STATCOM for the improvement of reactive power compensation during grid faults and unbalanced load. The problem encountered with convectional voltage source converter based STATCOM for reactive power management and capacitor voltage balancing during grid faults are analyzed and its operational limitations are studied. To remove the above problems, an adaptive low voltage ride through control technique based modular double star cascaded converter (DSCC) STATCOM is proposed. In this dynamic control, the positive reactive currents and negative reactive currents are separately controlled for reactive power management and a zero (Vo) sequence voltage is inserted for the management of active power. This advanced control method effectively balances the submodule capacitor voltage within its prescribed limits by managing the equal distribution of active power between converter legs and provides dynamic reactive power management during grid faults. The effectiveness of the DSCC-STATCOM, with proposed control method is verified using MATLAB/Simulink software-based simulations under single line to ground fault and unbalanced load.</span>

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Zhang, Jingwei, Zhongfeng Pan, Xiaolong Liang, Keqiang Wang, Gang Liu, Li Ning, Xiaoning Tang, and Pengyang Zhao. "Fault transient feature extraction method of 66kV transmission line based on improved wavelet threshold and CEEMDAN-FME." Journal of Physics: Conference Series 2422, no. 1 (January 1, 2023): 012020. http://dx.doi.org/10.1088/1742-6596/2422/1/012020.

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Abstract In the 66kV transmission line, the compensation effect of the arc suppression coil, so the amplitude of fault zero sequence current is weak after the occurrence of single-phase grounding responsibility. The fault characteristics are not obvious, and there is environmental noise interference during fault signal acquisition, which further increases the difficulty of ground fault feature extraction. To solve the above problems, a fault transient feature extraction method of 66kV transmission line is proposed, based on improved wavelet threshold and Complete Ensemble Empirical Mode Decomposition with adaptive noise (CEEMDAN) - Fuzzy measure entropy (FME). The characteristics of single-phase grounding transient fault in small current grounding system are analyzed. The transient fault signal was preprocessed by an improved wavelet threshold method, and the transient fault characteristics were extracted accurately by CEEMDAN-FME processing. The proposed method has good anti-noise performance through the simulation comparison and verification of denoising processing and transient feature extraction by MATLAB. It can effectively extract fault features when the interference degree is significant.

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Syvokobylenko, V. F., and V. A. Lysenko. "APPLICATION OF WAVELET TRANSFORM FOR PHASE-TO-GROUND FAULT PROTECTION IN MEDIUM VOLTAGE ELECTRICAL NETWORKS." Tekhnichna Elektrodynamika 2021, no. 4 (June 17, 2021): 55–62. http://dx.doi.org/10.15407/techned2021.04.055.

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For electrical networks with voltage of 6-35 kV with a compensated, isolated or resistor-grounded neutral, a phase-to-ground protection has been developed, in which, based on the results of the time-frequency wavelet transform of zero-sequence currents, voltages and their derivatives, using the obtained analytical expression, the total reactive power wavelet for different frequencies is determined. It is shown that at the initial moment of a phase-to-ground fault on the damaged feeder the power is always positive, and on the undamaged feeder it is negative, regardless of the operating mode of the neutral. Wavelet transform coefficients are found by convolution of discrete values of measured signals with sine-cosine signals of the Morlet mother function. The time-reversed sequence of these signals is obtained using a matrix for which the rules for its formation are stated. An excess of the zero phase sequence voltage amplitude of the set value is used as a starting protection element. With the help of a mathematical model of the network, studies of the behavior of protection in case of blind and arc phase-to-ground faults at various degrees of compensation of capacitive currents, at various voltage values at the moment of the short circuit have been carried out. In all modes, a reliable protection operation is obtained, the sensitivity of which is an order of magnitude higher than the protection based on Fourier transforms. Positive results of testing a protection sample implemented on a microprocessor-based element base at a laboratory stand are obtained. References 20, figures 7, tables 2.

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Ravi Teja, S., and Md Enamullah. "DC capacitor voltage stabilization for five-level NPC inverter based STATCOM under DC offset in load." International Journal of Engineering & Technology 7, no. 1.8 (February 9, 2018): 148. http://dx.doi.org/10.14419/ijet.v7i1.8.11537.

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DC voltage regulation of compensator plays a significant role in tracking performance of STATCOM. It is a common practice to employ voltage source inverter with split – capacitor topology for shunt compensator in three phase four wire systems. However, drift in each capacitor voltage is observed with the presence of dc component in zero sequence current although STATCOM control unit regulates total dc voltage, which results in poor tracking of reference current by the compensator. An external voltage balancing circuit is identified to be a good solution to overcome this problem. This paper proposes an improved controller for external voltage balancing circuit to restore the dc capacitors voltage. The effectiveness of the proposed control of external voltage balancing circuit is verified by simulation results showing restoration of capacitors voltage drift and there by the restoration of tracking performance of the compensator.

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He, Feng, Xuran Hu, and Decai Zhang. "Ground fault location research based on multidimensional scaling and density clustering algorithm." Journal of Physics: Conference Series 2306, no. 1 (November 1, 2022): 012009. http://dx.doi.org/10.1088/1742-6596/2306/1/012009.

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Abstract When a single line-to-ground fault occurs in a current distribution network containing distributed power sources, fault location is primarily performed by current-based directional protection. This implies using the switching information at the nodes; however, this does not sufficiently maximize the fault information. To address these issues, a single-phase grounding fault location methodology is planned for distribution networks supported by a combination of three-dimensional scaling (MDS) and density-based spatial clustering of applications with noise (DBSCAN). First, the network description matrix is made to support the network topology. Second, the zero-sequence and negative-sequence currents collected at the terminals square measure pre-processed to obtain two-dimensional fault data feature vectors. Third, the fault feature vectors square measure is subjected to DBSCAN bunch analysis to obtain the fault zones of the distribution network, thus compensating for the disadvantage that DBSCAN cannot efficiently replicate high-dimensional knowledge. The simulation results reveal that the planned methodology is not tormented by fault location, fault resistance, fault angle, or line sort; therefore, the fault location results in a correct square measure and might effectively utilize the fault data.

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Mishra, Praveen Kumar, and Anamika Yadav. "Combined DFT and Fuzzy Based Faulty Phase Selection and Classification in a Series Compensated Transmission Line." Modelling and Simulation in Engineering 2019 (February 3, 2019): 1–18. http://dx.doi.org/10.1155/2019/3467050.

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The conventional distance protection scheme malfunctions sometimes in case of a fixed series capacitor compensated transmission line due to the change in relaying impedance of the protected line during faulty conditions. In order to mitigate this problem, a combined discrete Fourier transform and fuzzy (CDFTF) based algorithm has been proposed in this paper. This method has been tested on a 400 km, 735 kV series compensated transmission line network and WSCC 3-machine 9-bus system for all fault types using MATLAB/Simulink and PSCAD platforms, respectively. A fixed series capacitor is located at the middle of the protected line. The fundamental components of phase currents, phase voltages, and zero-sequence current are fed as inputs to the proposed scheme. The fault detection, faulty phase selection, and fault classification are achieved within 1/2–1 cycle of power frequency. The proposed CDFTF-based scheme is less complex and is better than other data mining techniques which require huge training and testing time. Test results corroborate the proposed scheme reliability with wide variations in fault location, fault resistance, fault inception angle, evolving faults, compensation level, and heavy load interconnection. The results discussed in this work indicate that the proposed technique is resilient to wide variations in fault and system conditions.

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De Kooning, Jeroen D. M., Dimitar Bozalakov, and Lieven Vandevelde. "Discrete Time Domain Modeling and Control of a Grid-Connected Four-Wire Split-Link Converter." Electronics 10, no. 4 (February 21, 2021): 506. http://dx.doi.org/10.3390/electronics10040506.

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Distributed generation (DG) allows the production of renewable energy where it is consumed, avoiding transport losses. It is envisioned that future DG units will become more intelligent, not just injecting power into the grid but also actively improving the power quality by means of active power filtering techniques. In this manner, voltage and current harmonics, voltage unbalance or over-voltages can be mitigated. To achieve such a smart DG unit, an appropriate multi-functional converter topology is required, with full control over the currents exchanged with the grid, including the neutral-wire current. For this purpose, this article studies the three-phase four-wire split-link converter. A known problem of the split-link converter is voltage unbalance of the bus capacitors. This mid-point can be balanced either by injecting additional zero-sequence currents into the grid, which return through the neutral wire, or by injecting a compensating current into the mid-point with an additional half-bridge chopper. For both methods, this article presents a discrete time domain model to allow controller design and implementation in digital control. Both techniques are validated and compared by means of simulation results and experiments on a test setup.

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Grabchuk, B. L., and Yu F. Romaniuk. "ANALYSIS OF ENERGY FLOWS IN POWER SUPPLY SYSTEMS WITH NON-LINEAR LOAD." METHODS AND DEVICES OF QUALITY CONTROL, no. 1(42) (June 27, 2019): 56–64. http://dx.doi.org/10.31471/1993-9981-2019-1(42)-56-64.

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The problem of the non-sinusoidal modes analysis of the power supply system with non-linear elements and their influence on the efficiency of the power transmission are considered. It is carried out numerical analysis of electric energy flows for three phase power supply system with sinusoidal electromotive force source, linear active load and non-linear elements (diodes). Power transfer is considered as distribution of the primary power flow from source. The part of this flow is converted by non-linear elements and return into the network like secondary power stream of zero sequence and high harmonics which is consumed by resistance elements and causes additional power losses. As a result transporting efficiency and power factor are reduced and energy quality becomes worse. In order to improve the quality of electricity, it is proposed to normalize the relative value of the reactive power of distortion for non-linear electric collectors and to oblige manufacturers of electrical products to complete them with filters of higher harmonics. With the purpose of correct selection of the type and power of compensating devices and monitoring the parameters of the electric network mode, it is proposed to expand the functionality of electronic meters by dividing the reactive power into two components - shear power and distortion power, and for the objective analysis of energy flows, it is proposed to standardize the reactive power of distortion. It is shown that in such system current in neutral line increases due to overlaying of zero sequence harmonics currents. This should be taking into account during neutral line cross-section choice and power losses calculation.

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Buraimoh, Elutunji, Innocent E. Davidson, and Fernando Martinez-Rodrigo. "Fault Ride-Through Enhancement of Grid Supporting Inverter-Based Microgrid Using Delayed Signal Cancellation Algorithm Secondary Control." Energies 12, no. 20 (October 21, 2019): 3994. http://dx.doi.org/10.3390/en12203994.

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The growing level of grid-connected renewable energy sources in the form of microgrids has made it highly imperative for grid-connected microgrids to contribute to the overall system stability. Consequently, secondary services which include the fault ride-through (FRT) capability are expected to be possessed characteristics by inverter-based microgrids. This enhances the stable operation of the main grid and sustained microgrid grid interconnection during grid faults in conformity with the emerging national grid codes. This paper proposes an effective FRT secondary control strategy to coordinate power injection during balanced and unbalanced fault conditions. This complements the primary control to form a two-layer hierarchical control structure in the microgrids. The primary level is comprised of voltage/power and current inner loops fed by a droop control. The droop control coordinates grid power-sharing amongst the voltage source inverters. When a fault occurs, the participating inverters operate to support the grid voltage, by injecting supplementary reactive power based on their droop gains. Similarly, under unbalanced voltage condition due to asymmetrical faults in the grid, the proposed secondary control ensures the positive sequence component compensation and negative and zero sequence components clearance using a delayed signal cancellation (DSC) algorithm and power electronic switched series impedance placed in-between the point of common coupling (PCC) and the main grid. While ensuring that FRT ancillary service is rendered to the main utility, the strategy proposed ensures relatively interrupted quality power is supplied to the microgrid load. Consequently, this strategy ensures the microgrid ride-through the voltage sag and supports the grid utility voltage during the period of the main utility grid fault. Results of the study are presented and discussed.

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Xu, Hao, Chaoyong YIN, Guoqin DONG, Shannuo WANG, Liqiang XU, Fan OUYANG, and Weijun ZHU. "Optimization of zero-sequence voltage compensation for zero-sequence directional elements." Electric Power Systems Research 197 (August 2021): 107300. http://dx.doi.org/10.1016/j.epsr.2021.107300.

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Mikheev, Georgi M., and Ayrat G. Ziganshin. "THE ABILITY OF MODERN TECHNOLOGIES TO INFLUENCE THE NEUTRAL MODE OF ELECTRIC GRIDS." Vestnik Chuvashskogo universiteta, no. 3 (September 29, 2021): 103–12. http://dx.doi.org/10.47026/1810-1909-2021-3-103-112.

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In this article, we consider the modes of neutrals of 0,38 to 750 kV networks. In any network with different voltage classes, the neutral point of a power transformer winding can operate both in isolated and deaf earthed mode. However, the choice of this mode depends on economic feasibility. The paper presents arguments and advantages of application of system with isolated and compensated neutral of networks with voltage classes 6–35 kV. For networks of these voltage classes various options of connecting arc suppression reactors with step and smooth regulation, as well as low and high impedance resistors in the neutral point of neutralizing transformer or zero sequence filter are considered. On the example of operation of electric networks of the Republic of Chuvashia for many decades it is emphasized that compensation of capacitive currents with arc suppression reactors is an effective and reliable way to protect not only substation electrical equipment from overvoltage, but also to ensure electrical safety of people and animals, as well as reinforced concrete towers from destruction. It is noted that the 6–35 kV networks in the future can be made with deaf earthed neutral. However, this will be possible under the condition that self-supporting insulated wires will be installed on overhead transmission lines instead of bare wires, and cross-linked polyethylene cables will be used on cable lines. It is emphasized that the introduction of work under voltage in 6-35 kV networks and digitalization of substations with the widespread introduction of microprocessor technology will accelerate the transition from a system with insulated (or compensated) neutral to a deaf earthed system. Nevertheless, the decision to switch from the insulated neutral system to a deaf earthed system will remain the prerogative of the design organization based on the specifics of the electrical equipment and the sphere of industrial activity.

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Zhou, Xue Song, Wei Liu, and You Jie Ma. "Detecting Method for Harmonic and Fundamental Negative Sequence and Zero Sequence Currents in Unbalanced Three-Phase Four-Wire Circuits." Advanced Materials Research 1092-1093 (March 2015): 254–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1092-1093.254.

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Shunt Active Power Filter (SAPF) is a new device for compensating harmonic currents in power system [1]. For unbalanced three-phase four-wire circuits, it need detect the total of harmonic and fundamental negative sequence and zero sequence currents at the same time. Base on traditional method of ip-iq, a detecting method which is suitable for unbalanced three-phase four-wire is proposed and analyzed by mathematical reasoning. At last, correctness of the result is verified by simulation.

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Sonoda, Toshikatsu, Ryuzo Ueda, and Toshihiko Ohtsu. "Detection of Zero-Sequence Current and its Current Sensor." IEEJ Transactions on Industry Applications 113, no. 2 (1993): 179–88. http://dx.doi.org/10.1541/ieejias.113.179.

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Tsimtsios, Aristotelis M., and Vassilis C. Nikolaidis. "Setting Zero-Sequence Compensation Factor in Distance Relays Protecting Distribution Systems." IEEE Transactions on Power Delivery 33, no. 3 (June 2018): 1236–46. http://dx.doi.org/10.1109/tpwrd.2017.2762465.

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Seyedi, Heresh, Peyman Soleiman Nezhad, and Saeed Teimourzadeh. "Adaptive zero sequence compensation algorithm for double-circuit transmission line protection." IET Generation, Transmission & Distribution 8, no. 6 (June 1, 2014): 1107–16. http://dx.doi.org/10.1049/iet-gtd.2013.0538.

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Lv, Kangfei, Xinwei Dong, and Cong Zhu. "Research on Fault-Tolerant Operation Strategy of Permanent Magnet Synchronous Motor with Common DC Bus Open Winding Phase-Breaking Fault." Energies 15, no. 8 (April 15, 2022): 2927. http://dx.doi.org/10.3390/en15082927.

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In some key areas, fault-tolerant control is usually needed in order to enable the motor to operate continuously in fault mode. Given that it is difficult to detect the zero-sequence current of the open winding permanent magnet synchronous motor after the phase break fault occurs, the traditional zero-sequence current suppression strategy is no longer applicable after the phase break fault occurs. Therefore, a zero-sequence current suppression strategy for a common DC bus under a phase break fault is proposed in this paper. By establishing the mathematical model between the current component in the synchronous coordinate system and the current component and the zero-sequence current in the static coordinate system, the relationship between the non-fault phase current and the zero-sequence current in the open phase fault is analyzed. A method of suppressing the zero-sequence current by using proportional integral double resonance in a zero-sequence current control loop is proposed. In addition, according to the large number of calculations in traditional space vector modulation (SVPWM)—such as sector judgment and coordinate transformation—a decoupling modulation algorithm is proposed to modulate the reference voltage vector. Finally, the experimental platform for the common DC bus open winding permanent magnet synchronous motor is built, and the zero-sequence current suppression method for the common DC bus OW-PMSM under phase break fault is verified experimentally.

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Shogenov, Yu Kh, and A. Kh Shogenov. "Drying Induction Motor Windings with Zero-Sequence Current." Russian Electrical Engineering 92, no. 4 (April 2021): 217–20. http://dx.doi.org/10.3103/s1068371221040064.

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Valle, G., M. Dell’Omodarme, P. G. Prada Moroni, and S. Degl’Innocenti. "Relevance of the small frequency separation for asteroseismic stellar age, mass, and radius." Astronomy & Astrophysics 635 (March 2020): A77. http://dx.doi.org/10.1051/0004-6361/201936353.

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Aims. We performed a theoretical analysis aimed at quantifying the relevance of the small frequency separation δν in determining stellar ages, masses, and radii. We aimed to establish a minimum uncertainty on these quantities for low-mass stars across different evolutionary stages of the main sequence and to evaluate the biases that come from some systematic differences between the stellar model grid adopted for the recovery and the observed stars. Methods. We adopted the Stellar CharactEristics Pisa Estimation gRid (SCEPtER) pipeline for low-mass stars, [0.7, 1.05] M⊙, from the zero-age main sequence (ZAMS) to the central hydrogen depletion. For each model in the grid, we computed oscillation frequencies. Synthetic stars were generated and reconstructed based on different assumptions about the relative precision in the δν parameter (namely 5% and 2%). The quantification of the systematic errors arising from a possible mismatch between synthetic stars and the recovery grid was performed by generating stars from synthetic grids of stellar models with different initial helium abundance and microscopic diffusion efficiency. The results obtained without δν as an observable are included for comparison. Results. The investigation highlighted and confirmed the improvement in the age estimates when δν is available, which has already been reported in the literature. While the biases were negligible, the statistical error affecting age estimates was strongly dependent on the stellar evolutionary phase. The error is at its maximum at ZAMS and it decreases to about 11% and 6% (δν known at 5% and 2% level, respectively) when stars reach the 30% of their evolutionary MS lifetime. The usefulness of small frequency separation in improving age estimates vanishes in the last 20% of the MS. The availability of δν in the fit for mass and radius estimates provided an effect that was nearly identical to its effect on age, assuming an observational uncertainty of 5%. As a departure, with respect to age estimates, no benefit was detected for mass and radius determinations from a reduction of the observational error in δν to 2%. The age variability attributed to differences in the initial helium abundance resulted in negligible results owing to compensation effects that have already been discussed in previous works. On the other hand, the current uncertainty in the initial helium abundance leads to a greater bias (2% and 1% level) in mass and radius estimates whenever δν is in the observational pool. This result, together with the presence of further unexplored uncertainty sources, suggest that precision in the derived stellar quantities below these thresholds may possibly be overoptimistic. The impact of microscopic diffusion was investigated by adopting a grid of models for the recovery which totally neglected the process. The availability of the small frequency separation resulted in biases lower than 5% and 2% for observational errors of 5% and 2%, respectively. The estimates of mass and radius showed again a greater distortion when δν is included among the observables. These biases are at the level of 1%, confirming that threshold as a minimum realistic uncertainty on the derived stellar quantities. Finally, we compared the estimates by the SCEPtER pipeline for 13 Kepler asteroseismic LEGACY sample stars with those given by six different pipelines from literature. This procedure demonstrated a fair agreement for the results. The comparison suggests that a realistic approach to the determination of the error on the estimated parameters consists of approximately doubling the error in the recovered stellar characteristics from a single pipeline. Overall, on the LEGACY sample data, we obtained a multi-pipeline precision of about 4.4%, 1.7%, and 11% on the estimated masses, radii, and ages, respectively.

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Zheng, Tao, Xinhui Yang, Xingchao Guo, Xingguo Wang, and Chengqi Zhang. "Zero-Sequence Differential Current Protection Scheme for Converter Transformer Based on Waveform Correlation Analysis." Energies 13, no. 7 (April 9, 2020): 1814. http://dx.doi.org/10.3390/en13071814.

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Through the analysis of the recovery inrush current generated by the external fault removal of the converter transformer, it is pointed out that the zero-sequence current caused by the recovery inrush may result in the saturation of the neutral current transformer (CT), whose measurement distortion contributes to the mis-operation of zero-sequence differential current protection. In this paper, a new scheme of zero-sequence differential current protection based on waveform correlation is proposed. By analyzing the characteristics of zero-sequence current under internal fault, external fault and external fault removal, the waveform correlation of the zero-sequence current measured at the terminal of the transformer and the zero-sequence current measured at the neutral point of the transformer is used for identification. The polarity of the CT is selected to guarantee the zero-sequence currents at the terminal and neutral point of the transformer exhibit a "ride through" characteristic under external fault, then the waveform similarity is high, and the correlation coefficient is positive. On the other hand, when internal fault occurs, zero-sequence current waveforms on both sides differ from each other largely, and the correlation coefficient is negative. Through a large number of simulations verified by PSCAD/EMTDC, this criterion can accurately identify internal and external faults, exempt from effects of the recovery inrush. Moreover, it presents certain ability for CT anti-saturation.

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Chen, Ying, and Xiang Jie Chen. "Current Detection Simulate for STATCOM Dynamic Compensation System." Key Engineering Materials 439-440 (June 2010): 378–83. http://dx.doi.org/10.4028/www.scientific.net/kem.439-440.378.

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In view of low-pressure area for dynamic reactive power compensation device application present situation, a more advanced static reactive power compensation techniques was proposed that is STATCOM (Static Synchronous Compensator-STATCOM) which based on the modern power electronic technology, and it applied to the low-voltage dynamic reactive power compensation area, developed a new and more advanced low-voltage dynamic reactive power compensation device. In this paper, STATCOM compensation system simulation model was established in MATLAB6.5, futher to study its real-time compensation. Theory analyze and simulation results indicate that compare with static capacitor compensation，dynamic compensation achieved zero phase angle between power source current and voltage on rating frequency，demand for power supply rating power is reduced and power transmission performance is ensured.

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Chen, Saixuan, Minzhou Luo, Guanwu Jiang, and Omar Abdelaziz. "Collaborative robot zero moment control for direct teaching based on self-measured gravity and friction." International Journal of Advanced Robotic Systems 15, no. 6 (November 1, 2018): 172988141880871. http://dx.doi.org/10.1177/1729881418808711.

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The focus of this study is a moment compensation control algorithm driven by a direct current servo motor. Zero moment robot teaching is achieved with a joint moment compensation algorithm. The moment equilibrium equation is derived based on moment compensation. The current signal detected by a Hall effect sensor is multiplied by a torque constant to estimate the torque value of the robot joint. The compensation current is obtained through parameter identification to overcome gravitational and friction torques. The two variables of speed and position are separately controlled, allowing the compensation current of Coulomb friction and viscous friction force to be separated from the compensation current of friction torque. This study presents the system research, design, and development of a high-precision position control theory of a robot zero moment teaching control method. A collaborative robot is used as the test and verification platform to confirm the feasibility and effectiveness of the proposed theoretical method and implementation technology.

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Takemoto, Kazuo, and Tokio Gotoh. "Phenomena of current zero miss on cable compensation reactor circuit." IEEJ Transactions on Power and Energy 109, no. 7 (1989): 330–36. http://dx.doi.org/10.1541/ieejpes1972.109.330.

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O A., Ezechukwu. "INSTABILITY PROBLEM OF CONVENTIONAL TRANSFORMER DIFFERENTIAL PROTECTION-APPLICATION OF ZERO SEQUENCE CURRENT TRAP." INTERNATIONAL JOURNAL OF COMPUTERS & TECHNOLOGY 10, no. 4 (August 5, 2013): 1563–68. http://dx.doi.org/10.24297/ijct.v10i4.3257.

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Zero sequence component of current usually causes instability of the differential protection. It enters circuits through earthed terminals. The traditional way of solving the problem in differential schemes is by connecting the interposing current transformers (ICTs) in delta since there is no path for zero sequence component of current in delta. This paper suggests another way of dealing with the problem. A zero sequence trap is modeled to pass the zero sequence current through an output logic which ensures that operation of the relay is enabled only when there is a real differential fault.

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Guo, Qiang, Zhiping Dong, Heping Liu, and Xiaoyao You. "Nonlinear Characteristics Compensation of Inverter for Low-Voltage Delta-Connected Induction Motor." Energies 13, no. 3 (January 28, 2020): 590. http://dx.doi.org/10.3390/en13030590.

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This paper proposes a scheme that can compensate for the nonlinear characteristics of voltage source inverters (VSIs) for low-voltage delta-connected induction motors (IMs). Due to the nonlinearity introduced by the dead-time, the on/off delay, and the voltage drop across the power device, the output voltage of VSIs is seriously distorted, causing distortion in the phase current of the IM, which will lead to output torque ripple. However, the existing compensation methods for three-phase VSIs are derived from star-connected loads, or ignore the conducting properties of power devices. Moreover, the current polarity detection near the current zero is quite complex. In this paper, by taking such nonlinear characteristics into consideration, especially the conducting property of metal-oxide-semiconductor field effect transistors (MOSFETs), an output voltage model of VSIs for low-voltage delta-connected induction motors is presented. After that, in view of the difficulty in detecting the line current polarity near the current zero which might lead to the wrong compensation, an advancing current crossing zero (ACCZ) compensation is proposed. Subsequently, a compensation scheme which combines the compensation based on the VSI output voltage model and ACCZ compensation is proposed. Finally, the proposed compensation scheme is implemented based on a digital signal processor (DSP) drive system. The experimental results show that the proposed scheme has better performance than the common method in terms of suppressing the effect of the nonlinear characteristics of VSI, which demonstrates that the proposed compensation scheme is feasible and effective for the compensation of the nonlinear characteristics of VSI for low-voltage delta-connected IMs.

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Journal articles on the topic 'Zero sequence current compensation'

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