Dissertations / Theses on the topic 'Single phase single-stage'

The main objective of the project is to develop a Photovoltaic (PV) system using three phase Pulse Width Modulation (PWM) converter as the interfacing component in Power factory. Already existing model in Power factory tool uses static generator as the interfacing converter. Moreover the control technique implemented within the PV model is very basic. Aworking model is already available in PSCAD simulation tool using PWM converter but it is a very detailed one in terms of modeling which results in longer simulation time. Through this project a new PV model is developed in Power factory, an improved version of existing PSCAD and Power factory models. Then a comparison study is carried out between the PSCAD and the new Power factory model in order to validate the created model’s functionality. Several case studies with the DC and AC side disturbances are performed to analyze the behavior of two models. The new PV model is found to function very similar to that of the existing PSCAD model, thus proving its credibility. Further improvements and additional functions are also included in the new Power factory model which makes it a better choice to carry out grid studies than the existing model in PSCAD.

In order to extract the maximum amount of power from the PV modules and convert it into an appropriate form for grid integration, a power electronics interface is needed. This thesis focuses on analysis and modeling of the single-phase two-stage inverter for grid-connected PV application with special attention given to the harmonic issues. A DC/DC battery-integrated boost converter can serve as the front end in a two-stage PV inverter configuration. A steady-state analysis for this new type of converter is carried out. An application of this converter in distributed Maximum Power Point Tracking (MPPT) architecture is proposed and compared with the conventional boost converter. By adding energy storage devices, it has the potential to compensate for the intermittent attribute of the PV generators. It also yields a more stabilized DC-link voltage in the distributed MPPT application. This thesis also analyzes the harmonic distortions generated from a PV inverter, which mainly relate to the DC/AC stage of the PV inverter. The field measurements are carried out at the CSIRO micro-grid. The high total harmonic distortion phenomenon is found when the PV inverters operate at light load condition. The conventional model of a PV inverter does not contain any harmonic information. A linear model for the PV inverter is modified to analyze the harmonic formation process. The causes of harmonics are summarized for the PV inverter operating at different power levels. The constant DC-link voltage assumption is not necessarily true for the two-stage PV inverter. The model of the grid-connected PV inverter with feedback control becomes time-varying with consideration for the DC-link voltage ripple. A series of odd harmonics is identified to be caused by this double-line frequency DC-link voltage ripple. The transfer function cannot be derived for this model. It is a challenge to calculate the exact harmonic amplitudes. The closed-form solution for this time-varying model is derived based on an idea which is similar to the harmonic balance method. A guideline is provided to select the minimum size of capacitor for the DC-link without sacrificing the power quality. Simulation and experimental results are provided to verify the aforementioned analysis results. In addition, some suggestions for future work are given.

The generic concept of quasi-single-stage (QSS) power conversion topology for ac-dc rectification and dc-ac inversion is proposed. The topology is reached by direct cascading and synchronized switching of two variety of buck or two variety of boost switching networks. The family of QSS power converters feature single-stage power processing without a dc-link low-pass filter, a unidirectional pulsating dc-link voltage, soft-switching capability with minimal extra commutation circuitry, simple PWM control, and high efficiency and reliability. A new soft-switched single-phase QSS bi-directional inverter/rectifier (charger) topology is derived based on the QSS power conversion concept. A simple active voltage clamp branch is used to clamp the otherwise high transient voltage on the current-fed ac side, and at the same time, to achieve zero-voltage-switching (ZVS) for the switches in the output side bridge. Seamless four-quadrant operation in the inverter mode, and rectifier operation with unity power factor in the charger (rectifier) mode are realized with the proposed uni-polar center-aligned PWM scheme. Single-stage power conversion, standard half-bridge connection of devices, soft-switching for all the power devices, low conduction loss, simple center-aligned PWM control, and high reliability and efficiency are among its salient features. Experimental results on a 3 kVA bi-directional inverter/rectifier prototype validate the reliable operation of the circuit. Other single-phase and three-phase QSS bi-directional inverters/rectifiers can be easily derived as topological extensions of the basic QSS bi-directional inverter/rectifier. A new QSS isolated three-phase zero-voltage/zero-current-switching (ZVZCS) buck PWM rectifier for high-power off-line applications is also proposed. It consists of a three-phase buck bridge switching under zero current and a phase-shift-controlled full-bridge with ZVZCS, while no intermediate dc-link is involved. Input power and displacement factor control, input current shaping, tight output voltage regulation, high-frequency transformer isolation, and soft-switching for all the power devices are realized in a unified single stage. Because of ZVZCS and single-stage power conversion, it can operate at high switching frequency while maintaining reliable operation and achieving higher efficiency than standard two-stage approaches. A family of isolated ZVZCS buck rectifiers are obtained by incorporating various ZVZCS schemes for full-bridge dc-dc converters into the basic QSS isolated buck rectifier topology. Experimental and simulation results substantiate the reliable operation and high efficiency of selected topologies. The concept of charge control (or instantaneous average current control) of three-phase buck PWM rectifiers is introduced. It controls precisely the average input phase currents to track the input phase voltages by sensing and integrating only the dc rail current, realizes six-step PWM, and features simple implementation, fast dynamic response, excellent noise immunity, and is easy to realize with analog circuitry or to integrate. One particular merit of the scheme is its capability to correct any duty-cycle distortion incurred on only one of the two active duty-cycles which often happens in the soft-switched buck rectifiers, another merit is the smooth transition of the input currents between the 60o sectors. Simulation and preliminary experimental results show that smooth operations and high quality sinusoidal input currents in the full line cycle are achieved with the control scheme.<br>Ph. D.

A pesquisa desenvolve o projeto e a implementaÃÃo de um microinversor monofÃsico de estÃgio Ãnico obtido da derivaÃÃo de quatro conversores flybacks CC-CC operando no modo descontÃnuo e associado em mÃdulos paralelos. Este arranjo reduz o volume dos magnÃticos, diminui os esforÃos de correntes nos primÃrios dos transformadores, bem como minimiza as oscilaÃÃes no mÃdulo fotovoltaico. Em meio as principais propriedades do microinversor flyback (MIF) desta pesquisa, as chaves dos primÃrios atuam com comutaÃÃo SPWM em alta frequÃncia e defasadas em cento e oitenta graus, enquanto as chaves dos secundÃrios sÃo comandadas por PWMâs complementares. Para validar a pesquisa serà desenvolvido um protÃtipo que efetuarà o processamento de energia interligando um painel fotovoltaico com 200 W de potÃncia, em cargas resistivas com caracterÃsticas senoidais. O sistema proposto està fundamentado na configuraÃÃo mÃdulo inversor integrado (MIC), que por sua vez, possui menores perdas nos semicondutores e elementos magnÃticos da topologia, quando comparado aos complexos sistemas fotovoltaicos centralizados. Dentre as aplicaÃÃes do microinversor flyback encontram-se: abastecimento de sistemas remotos, alimentaÃÃo de aparelhos eletroeletrÃnicos, pequenas estaÃÃes de bombeamentos de Ãgua, conexÃes a rede elÃtrica, entre outros. Apesar da baixa potÃncia, o microinversor apresenta caracterÃsticas elÃtricas essenciais a inserÃÃo na matriz energÃtica, tais como: isolaÃÃo entre a fonte e a carga, formas de ondas de tensÃes e correntes na saÃda com pequenas distorÃÃes e na frequÃncia da rede. Os resultados obtidos em laboratÃrio revelam que o microinversor flyback operando em malha aberta obtÃm rendimentos prÃximos a 90%, sendo entregue à carga cerca de 180 W. Sendo assim, a facilidade na construÃÃo, a utilizaÃÃo de poucos componentes e os resultados coletados experimentalmente habilitam o microinversor flyback a realizar a conversÃo CC-CA de sistemas fotovoltaicos de pequenas potÃncias conectados em cargas lineares monofÃsicas com caracterÃsticas senoidais ou interligados à rede elÃtrica.<br>The study proposes the design and implementation of a single phase inverter of single stage obtained the derivation of four flybacks converters CC - CC operating in discontinuous mode and associated in parallel modules. This arrangement reduces the amount of magnetic and decreases current efforts in primary transformers and minimizes fluctuations i n photovoltaic module. Among the main properties of micro inverter flyback (MIF) this research, the primary keys work with SPWM switching at high frequency and lagged in one hundred and eighty degrees, while the secondary keys are controlled by PWM's compl ementary. To validate the research, we will develop a prototype that will effect the processing power connecting a photovoltaic panel with 200W power in resistive loads with senoidais characteristics. The proposed system is based on the configuration of th e integrated module drive (MIC), which, in turn, has lower losses in the semi - conductors and magnetic elements of the topology, when compared to complex centralized photovoltaic systems. Among the applications of micro inverter flyback are: supply of remote systems, power electronics devices, small water pumping stations, connections to the grid, among others. Despite the low power, micro inverter has electrical characteristics essential for the insertion in the energy matrix, such as: insulation betwe en the source and the load, types of voltages and currents waves in output with little distortion and frequency of the network. The results obtained in the laboratory show that the micro inverter flyback operating in open loop gets yields close to 90% bein g delivered to the load about 180W. Thus, the ease of construction, the use of fewer components and results collected experimentally enable the micro inverter flyback to perform the CC - CA conversion of photovoltaic systems of small powers connected in sing le - phase linear loads with senoidais characteristics or interconnected to the electric grid

Master of Science<br>Department of Electrical and Computer Engineering<br>Behrooz Mirafzal<br>In this thesis, a modified version of the phasor pulse width modulation (PPWM) switching method for use in a single-stage three-phase boost inverter is presented. Because of the required narrow pulses in the PPWM method and limitations in controller resolution, e.g. dSPACE, the desired switching pattern for a boost inverter requires a costly processor. A low resolution processor can cause pulse dropping which results in some asymmetric conditions in output waveforms of the boost inverter and therefore, an increase in the THD of the output waveform. In order to solve this problem, a new switching pattern is developed which guarantees symmetric conditions in the switching pattern by discretizing the switching pattern in every switching cycle. This switching pattern has been applied to a boost inverter model developed by SimPowerSystems toolbox of MATLAB/Simulink. The model has been simulated in a wide range of input DC voltage and load. Moreover, a laboratory-scaled three-phase boost inverter has been designed, built, and tested using an identical switching pattern in the same input voltage and load range. Both simulation and experimental results confirm the effectiveness of the new switching pattern.

碩士<br>國立虎尾科技大學<br>電機工程研究所<br>100<br>This thesis proposes a novel single-stage single-phase AC to three-phase AC converter. Based on a zero vector technique, the proposed converter combines a single-phase full-bridge with three-phase full-bridge to form a single-stage circuit structure. The converter has unity power factor and sinusoidal input current in input side. Adjustable amplitude and frequency of three-phase current source are in output side. The proposed converter consists of eight power switches, one capacitor, one boost inductor and three output inductors. It’s worth mentioning that ten switches of the traditional converter can reduce to eight, and this can reduce cost and improve efficiency obviously. Besides, general solution of the switching duty ratio is obtained by using the state space averaging technique. Furthermore, employing the three-phase dead-band control can decrease the ratio of 1/3 times switching number. Consequently, this reduce the switching loss, and improves efficiency of the converter. In the control circuit, both VisSim simulation and DSP TMS320F2812 are employed to finish digital control for power factor correction of the input side and feedback control of the output side. Finally, some experiment results are presented to verify the feasibility of the proposed converter.

碩士<br>國立清華大學<br>電機工程學系<br>90<br>Inverters are widely used in various applications. However, traditional inverter configuration basically belongs to a step/down topology. In other words, the maximum peak voltage of the output AC voltage is limited to the input DC voltage. Hence, in case a higher output voltage is needed, it is necessary to either cascade one more stage of step/up CD converter or add an step/up transformer. This will, of course, result in larger size, lower efficiency and higher cost. In view of there, it is the main objection of this thesis to develop a single stage step up/down inverter without using an extra transformer. Basically, the contributions of this thesis may be summarized as follows. First, a novel single stage step up/down inverter without using a transformer is proposed to extend operation range of the output AC voltage. In fact, due to the four-quadrant operation capability of the proposed inverter, the new inverter can also be operated as an AC to DC converter. Second, mathematical model of the proposed inverter is also derived for feedback controller design and implementation. Third, in order to achieve a better performance, a closed loop controller is also presented to satisfy the desired specification. Finally, a hardware prototype of the proposed inverter is constructed to verify the feasibility of the proposed inverter.

博士<br>國立交通大學<br>電機與控制工程系所<br>93<br>This dissertation presents a new input current shaper (ICS) for single-phase single-stage AC/DC converters with harmonic current correction and fast output voltage regulation. The proposed ICS are applied in flyback structure, forward structure, and bridge structure with the function of harmonic current correction. All the circuits are analyzed in steady state consideration. The study contains operation principle analysis, critical parameters analysis, design procedure. Finally, simulations and experiment results are shown for verifications. In the proposed AC/DC converters, an extra winding wound in the transformer provides two key advantages: (i) The size of the bulk inductor used in the conventional boost-based PFC cell can be significantly reduced in the proposed converters. In same output power application, the main transformer should has similar size but the boost inductor in prior single-stage PFC converter will be up to 1.7Lm or 1.4mH, and the inductor L1 in the proposed circuit can be down to 0.1Lm or 30μH. (ii) The voltage across bulk capacitor can be held under 450V by tuning the transformer windings ratio even though the converter operates in a wide range of input voltages (90V~265V/ac). Similar technique has been reported in recent years, but complex control circuit is needed to achieve high power factor or still use a bulk inductor in the boost-cell in the front stage of the converter. In a competitive market of switching power supply, the main consideration includes a simple, reliable, and cost-effective. Therefore, there is an improved opportunity in those presented solutions. These new converters comply with IEC 61000-3-2 class D from the load range up to 600W, and can achieve fast output voltage regulation. The proposed circuit has a simple, reliable, and cost-effective structure. The switching frequency is fixed in the proposed converters, which benefits the design of transformer and EMI filter. The proposed solution employs conventional controller, UC3842 or TL494, to implement the circuits and the solution can comply with the agent’s standards.

碩士<br>國立臺北科技大學<br>車輛工程系<br>107<br>This paper proposed a new single-phase three-wire single-stage inverter for the residential low-voltage power distribution. The proposed system structure integrates with an energy storage device, the active electronic switches, and a multi-port high-frequency transformer, for single-phase three-wire output loads. With the newly topology characteristic, the proposed inverter has the better system reliability, capability of single-stage power conversion for high-efficiency conversion, wide input voltage operation and the electrical isolation with safety satisfied. The content of the thesis includes the circuit operation principle, the small-signal model and the control loop analyzes, and pulse-width modulation techniques. Finally, a 1000W prototype has been built to verify the simulation and theoretical analysis results, for proving the system feasibility. The highest efficiency of 84% of the proposed inverter under 500W is achieved, compared with the buck/boost and boost/buck hybrid inverter types, the increased conversion efficiency is about 5%. The voltage gain is higher than semi-two-stage, boost, boost/buck hybrid, and boost/half-bridge hybrid inverter types are 3.2 times, 4 times, 1.9 times and 1.3 times.

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>101<br>This thesis presents a single-stage three-phase CCM wind-power converter. In order to achieve both maximum-power-point-tracking (MPPT) and three-phase power-factor-correction (PFC) mechanisms, two stages are employed in the conventional wind energy conversion system (WECS). However, the two-stage system results in some drawbacks, including larger volume, more components, higher circuit cost, more complicated control scheme and lower system efficiency. Therefore, the proposed converter of this thesis is developed to avoid these problems and increase the electromechanical conversion efficiency of the wind turbine generator (WTG), the MPPT and three-phase PFC mechanisms are employed simultaneously. In the proposed circuit, a three-phase PFC converter and an average-current-mode control (ACMC) scheme are utilized to improve the power factor of the converter for the WEC. Besides, according to the characteristics of the WTG, the output voltage, current, and power of the WTG can be operated at MPP for each wind speed by using the ACMC scheme and subtracting amplifier. In this thesis, a wind turbine emulator (WTE) is used as the AC source for the proposed circuit with the emulated wind speed ranging from 5m/s to 9m/s. The lowest and highest powers at MPP of the WTE are 185W and 1079W, respectively. Finally, a prototype circuit of the single-stage three-phase CCM wind-power converter is built to verify the performances using MPPT and three-phase PFC mechanisms.

In this thesis, a new approach for single-stage power factor correction converters is proposed to increase their power ratings to be in the multiple kilowatts levels. The proposed techniques are based on the utilization of modified three-level resonant converter topologies. These topologies provide low component stresses, high frequency operation, zero voltage switching, applicability under a wide range of input and output conditions as well as added control flexibility. The proposed control algorithms are based on a combination of variable frequency and asymmetrical pulse width modulation control or variable frequency and phase shift modulation control. In either case, the variable frequency control is used to tightly regulate the output voltage, whereas, pulse width or phase shift modulation is used to regulate the dc-bus voltage as well as the input power factor. New converter topologies, their operation and steady state and dynamic analyses are presented in details. A modelling approach based on average multiple frequency methods is also proposed. This approach leads to the development of a full order state space model with the two control variables explicitly separated allowing a better controller design. The model can be used either at high level of detail expressing the non-linearities of the system or it can readily be simplified to a linear decoupled model for approximate solutions. Finally, a discrete time controller for the proposed converters, which is suitable for FPGA implementation, is presented. Analytical, simulation and experimental results are provided to verify the proposed concepts.<br>Thesis (Ph.D, Electrical & Computer Engineering) -- Queen's University, 2008-01-30 14:28:15.725

In this work, a photovoltaic system was designed that supplies a single phase standalone load at 230V, 50Hz. As PV is the only source of power and due to intermittency of solar radiation, a battery storage was added to ride through the periods of insufficient power generation by the solar arrays. Lead acid battery was chosen due to its low cost per capacity. Also, the issue of maintaining power balance at all times is very much essential and this problem has been handled in this project in a diligent manner. For interfacing the battery to the photovoltaic system, a bidirectional DC-DC converter has been used. Maximum Power Point tracking is accomplished by a Boost converter, which also does the work of stepping up the voltage from the array into the range suitable for inverter. As the power produced by the PV array flows through the boost converter and inverter before reaching the load, it is called a two stage system. The energy balance has been accomplished without using communication infrastructure, that is all the power electronic interfaces are controlled by three independent loops. A means of knowing the exact average value of the pulsating DC bus voltage without approximations and complex computations has been demonstrated. This enables the control loops to eliminate the effect of pulsating DC bus voltage, caused by the single phase inverter, on the battery. This ensures that the battery current does not suffer from direction reversal at double the AC line frequency, especially when the PV power and load power are close enough, which is quite common in a PV system. This prevents rapid deterioration of battery lifetime. Also, the system has been simulated in MATLAB/SIMULAINK and simulation results shows the working of Photovoltaic System.

This thesis proposes a three-level DC-to-DC converter with capacitive output filter and its extension to single-phase, single-stage, three-level AC-to-DC converter with capacitive output filter. The AC-to-DC converter integrates a three-level boost converter operating in discontinuous conduction mode (DCM) and a three-level half-bridge DC-to-DC converter with capacitive output filter. The steady-state operation of the DC-to-DC converter and AC-to-DC converter with capacitive output filter are studied with phase-shifted gating scheme. The three-level topology reduces the voltage rating of the switches to half of the input voltage. Soft-switching is achieved for switches at different load and input voltage conditions. Boost section of the AC-to-DC converter achieves automatic power factor correction (PFC). At reduced load and higher input voltage conditions, the line current Total Harmonic Distortion (THD) increases with phase-shifted gating scheme. The THD has been reduced by using a complementary PWM gating control in the AC-to-DC converter.

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>91<br>The study and implementation of a DSP-based digital controller for the single-stage three-phase photovoltaic（PV） energy conversion system is proposed in this thesis. The proposed maximum power point tracking strategy allows PV energy conversion system to track the maximum power point rapidly and smoothly. The proposed PV energy conversion system acts as a solar generator on sunny days and as an active power filter under low insolation conditions. In addition, the proposed controller performs maximum power point tracking and also provides power to utility with unity power factor. Moreover, the current controller with single loop is simple and easy to design, as compared with the conventional double loop controller. Finally, experimental results demonstrate the desired performance of the proposed technique.

碩士<br>國立聯合大學<br>電機工程學系碩士班<br>104<br>Large and medium wind power generation system is mainly setup in a centralized manner. On the contrary, small wind power system suits for distributed applications to support the stand-alone system such as home, traffic instrument, street light and remote telecommunication system. This thesis presents a wind charger that employs the single-stage isolated three-phase bridge PFC topology based on the SEPIC converter. Fixed frequency and high PF control technique is presented for controlling the output current of the generator. It simplifies the complexity of the control circuit, reduce the generator current distortion and thus the noise and vibration. This thesis also presents a fast maximum power point tracking (MPPT) method based on generator speed control to cope with the fast wind speed variation. The MPPT also combines with a battery three-stage charging strategy that can shift the operating point to reduce the braking resistor requirement and extend the life cycle of the battery. The charger is fully digital control implemented with TI F28335 DSP IC. A 700W prototype circuit is designed and implemented. The effectiveness is confirmed with some simulation and experimental results.

碩士<br>國立成功大學<br>電機工程學系碩博士班<br>96<br>In this thesis, a single-stage high power factor three-phase AC-DC converter is proposed. The proposed converter is composed of a three phase AC-DC buck/boost converter integrated with a DC-DC buck-boost converter. The front semi-stage circuit is used for power factor correction and the rear semi-stage circuit is used for DC-DC conversion. The proposed converter can achieve unity power factor with a simple control and structure. The operation principles and characteristics of the proposed converter are discussed. Finally, the single-stage power supply of 500W is performed with a line input voltage of 200 Vrms 10% and DC output 48V/500W is performed in the laboratory to verify the feasibility of the proposed converter.

碩士<br>國立勤益科技大學<br>電機工程系<br>107<br>The main purpose of this thesis is to propose a three phase Multi-input Single-stage Grid-tied inverter (MSG-inverter) which can be used in distributed photovoltaic power generation systems (PVPGS). The proposed inverter is composed of micro dc-dc buck-boost converters (BBCs) and a dc-ac unfolder. Each micro BBC is connected to a single photovoltaic module (PV) in a PVPGS. The micro BBCs are connected to the central dc-ac unfolder through a dc bus. The micro BBCs are operating in discontinuous conduction mode (DCM). The pulsating dc current reduces stress and losses in the dc bus. Each micro BBC is equipped with a simple maximum power point tracker (MPPT) designed specifically to achieve maximum energy transfer. Each micro BBC is equipped with an interleaving power control scheme which is controlled using a signal from a phase lock loop (PLL). The architecture and control scheme of the proposed three phase MSG-inverter achieves a distributed MPPT (DMPPT) control and distributed power control of the PV array in distributed PVPGS. Finally some computer simulations results are presented to verify the performance of the proposed MSG-inverter.

This thesis focuses on the boost converter and single phase VSI used with photovoltaic electricity generating systems in grid tied applications.A simple power control method is proposed.The control of time variant systems is more complicated compared to time invariant systems. However, by using suitable transformation techniques, time-variant systems (often vary sinusoidally with time) become time-invariant at the fundamental frequency, and are hence much easier to deal with. The direct application of transformation theory in single phase power systems is not possible without modification,and the d-q components would not be time-invariant in situations where harmonics, resonances or unbalance of system is present. The main objective is to address,the problems found with single-phase designs based on hysteresis controller in terms of cost, efficiency,power management and power quality. So a reliable single-phase inverter controller design based on voltage oriented control, with the implementation of direct quadrature reference frame has been proposed.As the first step the photovoltaic module is analyzed using SIMULINK software. By using MPPT extraction of maximum possible power from the PV can be done and feed this power to the inverter via boost converter, in which required magnitude of voltage can be acquired in steps. The second step, is the modelling of the single-phase inverter control using synchronous rotating frame. A mathematical analysis is conducted to determine the mechanism of the coupling that exists between the voltage phase and amplitude terms. The line frequency components of the feedback signals are transformed to time-invariant components, thus eliminating the ripple and reducing the computational burden associated with the controller stage.The inverter is control by bipolar sinusoidal pulse width modulation (SPWM) technique. Grid and VSI synchronization by SOGI-PLL is presented.By using SOGI generation of fictitious phase is presented. By park transform two-axis stationary (αβ) is converted into rotary (dq) frame. Finally, PI-controller based active and reactive power controller is implemented and the results areobtained using MATLAB/ SIMULINK.

碩士<br>國立臺北科技大學<br>電機工程系研究所<br>100<br>This paper presents a new electrolytic capacitor-less and single-stage controlled three-phase battery charger with electrical isolation to provide wide-range output voltage for EV applications. To achieve this, a three-phase rectifier cascaded by a current-feed isolated buck-boost converter is proposed to yield DC voltage output and eliminate the bulk electrolytic capacitor installed behind the rectifier. Therefore, the lifetime of charger can be dramatically extended. Duo to without bulk electrolytic capacitor, there exists large ripple voltage at the output of three-phase rectifier. A design procedure of the controller with high rejection for voltage disturbance is developed to mitigate the current and voltage ripples for charging battery. Besides, the power factor compared to traditional rectifier is improved by the proposed single-stage topology simultaneously. Due to ZVS in light load and single stage switching architecture for the proposed charger, the efficiency is increased. Experimental results derived from the DSP-based controlled charger will be presented. The charger rating is 4 kW and output voltage is from 50V to 400V. It will be shown that the output current and voltage ripple is reduced significantly without any electrolytic capacitors in the proposed charger. It will also be demonstrated that the efficiency is nearly 96% and the power factor is also improved at rated load compared that for rectifier. These experimental results therefore confirm the superb performance of the proposed topology and control techniques.

In this paper, we present the results of the design and fabrication of a 12 channel nano-membrane-based optical phased array that allows for large angle beam steering operating at wavelength=1.55µm. Our device is fabricated on silicon-on-insulator using standard CMOS process. By implementing unequally spaced waveguide array elements, we can relax the half-wavelength spacing requirement for large angle beam steering, thereby avoiding the optical coupling between adjacent waveguides and reducing the side-lobe-level of the array radiation pattern. 1D beam steering of tranverse-electric polarized single mode light is designed to be achieved thermo-optically through the use of thin film metal phase shifters.<br>text