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The deployment of electric vehicles (EVs) protects the environment by reducing carbon emissions. Since plugged-in EVs require energy from the power grid to charge their batteries, the charger component is inevitable. With the appropriate control, additional functions can be achieved with the existing charger’s converter topology. This paper discussed the implementation of a new control strategy in a three-phase off-board EV charger, which provided grid voltage regulation while charging the vehicle. The vehicle charging control (P-control) and grid voltage regulation control (V-control) were implemented in the back-end DC/DC converter and front-end AC/DC converter of the charger, respectively. The proposed P-control utilized the constant current/reduced constant current charging approach to rapidly charge the battery while alleviating battery deterioration. Meanwhile, the proposed V-control had the capability to regulate the grid voltage and DC-link voltage during the EV charging process. Besides the PSCAD/EMTDC simulation, experimental testing was performed on a 2 kVA laboratory EV charger to validate the control performance. While complying with the harmonic standards, the experimental results showed that the charger prototype effectively regulated the grid voltage to the pre-charge voltage while maintaining the DC-link voltage at 150 V during various charging currents of up to 5 A.

This paper presents a voltage-controlled distribution static synchronous compensator (DSTATCOM)-based voltage regulator for low-voltage distribution grids. The voltage regulator is designed to temporarily meet the grid code, postponing unplanned investments while a definitive solution could be planned to solve regulation issues. The power stage is composed of a three-phase four-wire voltage-source inverter and a second-order low-pass filter. The control strategy has three output voltage loops with active damping and two dc bus voltage loops. In addition, two loops are included to the proposed control strategy: the concept of minimum power point tracking (mPPT) and the frequency loop. The mPPT allows the voltage regulator to operate at the minimum power point, avoiding the circulation of unnecessary reactive compensation. The frequency loop allows the voltage regulator to be independent of the grid voltage information, especially the grid angle, using only the information available at the point-of-common coupling. Experimental results show the regulation capacity, the features of the mPPT algorithm for linear and nonlinear loads, and the frequency stability.

In this letter, the five-level packed U-cell (PUC5) inverter is reconfigured with two identical dc links operating as an active power filter (APF). Generally, the peak voltage of an APF should be greater than the ac voltage at the point-of-common coupling (PCC) to ensure the boost operation of the converter in order to inject harmonic current into the system effectively; therefore, full compensation can be obtained. The proposed modified PUC5 (MPUC5) converter has two equally regulated separated dc links, which can operate at no load condition useful for APF application. Those divided dc terminals amplitudes are added at the input of the MPUC5 converter to generate a boosted voltage that is higher than the PCC voltage. Consequently, the reduced dc-links voltages are achieved since they do not individually need to be higher than the PCC voltage due to the mentioned fact that their summation has to be higher than PCC voltage. The voltage balancing unit is integrated into the modulation technique to be decoupled from the APF controller. The proposed APF is practically tested to validate its good dynamic performance in harmonic elimination, ac-side power factor correction, reactive power compensation, and power quality improvement.

Wireless power transmission (WPT) based on near-field inductive coupling principle is a promising solution to the power supply issue of a freely moving capsule robot (CR) that employs dc motors as actuators. However, the limited inductive power can cause a voltage drop when dc motors start or stall, because short-time peak power is required. To handle the voltage drop issue, we propose the use of a novel power management circuit (PMC) that consists of four successively connected segments of a full-bridge rectifier for ac–dc conversion, a buck dc–dc converter for highly efficient voltage reduction, a power buffer for power storage and short-time power supply, and a low drop-out (LDO) regulator for voltage stabilization. The power buffer is implemented with a super-capacitor array (SCA) that employs the output voltage of the dc–dc converter as its charging voltage. To analyze and optimize the PMC containing the SCA (PMC-SCA), a model is built based on deducing the input resistance relations between each pair of adjacent segments, and its correctness is then validated experimentally. A comparison between the PMC-SCA and the traditional PMC (a rectifier + a regulator) is also conducted, and the former shows superiorities in both reducing voltage drop and improving safety related to temperature rise of onboard receiving coil (RC). Finally, a primary PMC-SCA prototype measuring $\Phi $ 13 mm $ \times $ 4 mm is integrated to an inchworm-like CR for effectiveness validation; the CR working voltage is measured to be higher than 3 V at all times, which ensures the proper functioning of the CR.

This paper presents a study of proposed approach founded on series active power filter based on photovoltaic array (PV-SAPF) which is controlled by classical PI using pulse width modulation inverter (PWM). The proposed system is connected to grid system to feed linear and nonlinear loads to handle deep sags, swells voltage, voltage distortion and power factor crushing caused by any electrical perturbation. In the other hand, the excess of the energy is injected into the mains when the network is not affected and after compensation. To prove the effectiveness of the planned system, the PV-SAPF is carried out using MATLAB / Simulink environment. The results Simulations results proved the ability and the efficiency of the proposed system in mitigation the harmonic voltage distortion, correction the voltage sag and swell, power factor improvment and power quality enhancement.

This paper compares different methods for voltage-dip characterization. Those methods are based on earlier proposed algorithms for extracting three-phase characteristics (dip type, characteristic voltage, and so-called “PN factor”). The difference between the 12 methods being studied in this paper is in the way in which the time variation of those characteristics is treated to result in single-event characteristics. The methods are applied to 259 measured voltage dips, and the performance of the different methods is compared. It is found that small differences in the method can result in big differences in results. From the comparison, two methods are selected and recommended for inclusion in international standards.

Varactors are often used in phase-locked-loop (PLL) circuits for dynamic frequency control. However, the voltage and current ratings of varactors are too low to be used in most power electronic circuits. This paper proposes a transistor-controlled variable capacitor (TCVC), which functions similar to varactors in that its equivalent capacitance can be controlled by a dc voltage. However, TCVC can handle high voltages and currents so that it can be used in dc-ac power converters of wireless power transfer (WPT) systems such as an autonomous push-pull resonant converter to adjust its zero voltage switching (ZVS) frequency so that the operating frequency of the system can be stabilized to simplify the circuit and EMI filter design particularly for WPT systems with multiple power pickups while maintaining soft-switching operation of the converter against magnetic coupling and load variations. The relationship between the equivalent capacitance of the TCVC and the dc control voltage is developed by theoretical analysis and verified by experimental results. A prototype circuit is built with a PLL controller to demonstrate that the soft-switching condition of the converter is maintained when the operating frequency is locked in at 1.65 MHz under load and magnetic coupling variations.

A novel voltage-doubling circuit with parallel-resonant dc–dc converter is proposed. The converter consists of full-bridge inverter, resonant tank, high-frequency high-voltage transformer, and voltage-doubling circuit. In the high-voltage applications, low-output voltage ripple has been given much attention. The output voltage step-up ratio is increased by two parts. One is a high-frequency high-voltage transformer and the other is a voltage-doubling circuit. The novel voltage-doubling circuit can not only reach a higher output voltage but also reduce output ripple to a lower level than the conventional one. Therefore, while maintaining the same output voltage, the transformer's turn ratio can be reduced compared with the conventional voltage-doubling circuit. The output power can be adjusted by the phase-shift control technique. In addition, combining this technique with the parallel resonant tank can make all the switches achieve zero voltage turn on (ZVS). The operating principles, steady-state analysis, and the parameter designs are discussed in this paper. Finally, a prototype circuit with 400-V input voltage, 40-kV output voltage, and 300-W output power is developed in the laboratory to verify the performance of the proposed converter.

To enhance the power quality in the medium/high-voltage distribution power systems, a single-phase unified power quality conditioner (UPQC) based on the modular multilevel matrix converter (M3C) is presented in this paper. The M3C-UPQC is comprised of four identical multilevel converter arms and associated filtering inductors. According to the established equivalent circuit of M3C-UPQC, its operation principle and power balance of each arm are analyzed theoretically, and the parameters’ design for the arm inductance as well as submodule capacitance is studied. Then, an integrated control method for M3C-UPQC in which the dc circulating current is used to balance the instantaneous active power of each arm is proposed to prevent the capacitor voltages from divergence inter- and intra-arms, so as to achieve voltages balance of M3C-UPQC. Finally, the effectiveness of the proposed control method is verified by a prototype rated at 8 kVA.

This paper presents the flexible dc capacitor voltages balancing control method for star-connected cascaded H-bridge converters. In this paper, the power flows are analyzed by investigating all the converter's control freedoms. Based on the analyses, users can accomplish the dc capacitor voltage balancing with both negative-sequence current and zero-sequence voltage. These two kinds of control options are further integrated together with the defined weighting factor $K$ . The low-voltage ride-through operation of a proposed control method is also discussed in this paper. The control method is verified with a 220-V 1-kVA static synchronous compensators based on the star-connected cascaded H-bridge converters, and the experimental test results show that all the dc voltages are well regulated at the commanded value with different weighting factor $K$ .

A novel integrated implementation of a high step-down multiphase buck for low voltage power supply is presented. The design and test chip measurements of a 10.8,16V to 0.65,2V, 2A, 10MHz, 25.6mW/mm2, four-phases single-chip solution are presented with considerations on architecture, passive components, problems related to high frequency integration and relative improvements on power density. The experimental results confirm the theoretical predictions by simulations and are compared with respect to previous discrete implementations and integrated topologies focusing on high step-down conversion and output power. So-called "high step-down multiphase buck" topologies present advantages in terms of extended duty cycle, reduced passive components' size and reduced switches' breakdown voltages. However, these topologies require a more complex gate drive structure for their high side switches which are working each on a different voltage domain. A novel drive architecture that eliminates the need of any external auxiliary voltage source, being directly supplied on fractions of the input voltage, is proposed. This architecture provides also a recycling of the gate charge at the turn-off of the switches. Another problem addressed is the start up of the converter, which requires a proper pre-charging of the topology's flying capacitors. Power stage measured waveforms show the correct start-up and steady-state operation of the proposed converter design.

Submodule (SM) capacitor is a key component in a modular multilevel converter (MMC), the selection of which must consider the component’s specifications and the requirements of the targeted converter application. This paper focuses on the capacitor selection for MMCs in applications including high-voltage direct current (HVDC) transmission and static VAr compensation using metalized polypropylene film (MPPF) capacitors. The dominant ageing mechanisms of the MPPF capacitors are reviewed to define their operational limits. A straightforward computational procedure and a set of curves are presented to assist the capacitor selection, taking into account criteria in the aspects of maximum capacitor voltage, capacitor voltage ripple, SM voltage capability, and capacitor ripple current stress. Simulation shows the validity of the method and demonstrates its use in design examples.

This paper presents a new dual-switch control structure for an ac/dc noninverting cascaded buck–boost power factor correction converter. The proposed converter operates at a discontinuous capacitor voltage mode providing an inherent high-power factor and a zero voltage turn-off switching. Additionally, the proposed control structure enables for a nondistorted sinusoidal current for a wide range of output voltage levels. Unlike the conventional methods, a mode detector is not required and consequently there is no hard transition between buck and boost modes. Although both converter switches are controlled, only one feedback control loop is required to obtain the desired power flow at a unity power factor. The principle of operation, theoretical analysis, simulation, and experimental results of a 1.6-kW prototype grid-connected converter are presented. The results confirmed the validity of the proposed system under various operating conditions.

The active power filter designed to compensate inactive power components. Aim: The aim of the study is to assess the quality of the three-phase active power filter in the distortion of the mains voltage supply, which is caused by the influence of non-linear loads, and then comparing the two active filtering algorithms - Fryze power theory and p-q theory of instant power. Materials and Methods: Reviewed a three-phase active power filter connected in parallel to the mains via inductance. To study the modes of filter with non-linear loads with non-sinusoidal voltage programmed in Matlab/Simulink the model of electricity system is implemented. As the algorithm of implementation for determining of inactive components of power the Fryze theory and p-q theory were considered. Results: Obtained a time diagrams of network current after compensation when applying the theory of Fryze and p-q theory. Built the graphs of efficiency of reactive power compensation, fall of coefficient of network current distortion and errors of active power under the changing of firing angle of thyristor converter.

Voltage security is extensively concerned with the development of power systems, especially in multi-infeed high-voltage DC systems. For predicting voltage stability robustness of a power system, various voltage stability assessments have been proposed to search for weak buses and areas. However, these assessments are only related to network topology, time-consuming, or suitable only for high-voltage DC voltage stability analysis. Therefore, the extended voltage sensitivity factor, an improved voltage stability assessment that considers voltage/power characteristics of dynamic reactive power sources, is proposed and formulated based on a matrix elimination method in this article. Sensitivities of high-voltage DC and dynamic reactive power sources, are derived in detail. And a generalized algorithm of the extended voltage sensitivity factor is proposed for all buses in different grid scales with rapid solution. Afterward, some examples are illustrated and analyzed at different conditions that are r...

The capacitor voltage imbalance is a critical issue of five-level diode-clamped converters (5L-DCC). To address this issue, an inner-hexagon-vector-decomposition-based space-vector modulation (VDSVM-H1) approach is provided in the literature, which obtains the capacitor voltage balancing with high modulation index and high power factor, but renders some drawbacks. To overcome these shortcomings, a novel capacitor voltage balancing method is proposed here. First, the previous VDSVM-H1 approach is modified by introducing six new vector sequences to each triangle and applying a new vector selection rule such that the converter will not violate the 5L-DCC switching mechanism in all operating conditions. Second, the variation of the line-to-line voltage output in one sampling period is restricted to one- or two-level in the optimized region, instead of the three-level in the previous VDSVM-H1 approach, which means less harmonics generating in the ac-side outputs. Finally, the simulation and experimental results show that the proposed method can improve the VDSVM-H1 with convincing results.

This study proposes a single-phase multi-level AC–DC power conversion interface that is composed of a power factor correction stage and a buck power conversion stage. The power factor correction stage is configured using two power factor correctors (PFCs) connected in cascade. Only the power electronic switch in one of the PFCs is switched in high-frequency pulse-width modulation to generate a five-level voltage at the input AC terminals of the power factor correction stage. The input current of the power factor correction stage is controlled to be sinusoidal and in phase with the utility voltage. Accordingly, the voltage stress and switching loss are improved because the change in voltage in each switching operation is reduced. The filter inductance and the electromagnetic interference are also reduced. The buck power conversion stage integrates a buck power converter and a forward power converter that combines the output voltages of the two PFCs in a stable DC voltage that supplies the load. The controllers for the buck power converter and the forward power converter are integrated to simplify the controller for the buck power conversion stage. A hardware prototype is developed to verify the performance of the proposed single-phase AC–DC power conversion interface.

This paper proposes about a powerful control mechanism of UPQC (Unified Power Quality Conditioner) work on voltage source inverter which can effectively compensate source current harmonics and also mitigate all voltage collapse such as dip, swell, voltage unbalances and harmonics. The consolidation of series and parallel active power filters sharing mutual DC bus capacitor forms UPQC. PI (Proportional Integral) controller is mainly used in order to maintain continual DC voltage along with the hysteresis current controller. The parallel and series power filters were designed using 3-phase voltage source inverter. The reference signals for shunt and series active power filters were obtained by Synchronous Reference Frame (SRF) theory and Power Reactive (PQ) theory respectively. By using these theories, reference signals were obtained which was fed to the controllers for generating switching pulses for parallel and series active filters. The UPQC dynamic performance is obtained through testing terms like the compensation of voltage, current harmonics and all voltage distortion associated with 3-phase 3-wire power system which is simulated using MATLAB-Simulink software.

To achieve the maximum current rising rate, second-generation Experimental Advanced Superconducting Tokamak (EAST) plasma vertical displacement active feedback power supply applies voltage control mode while retaining the first-generation current tracking mode. When the power supply outputs high voltage, the accompanied frequent over-current protection will return the power to DC side, which leads to over-voltage protection, so the current limiting protection is applied. Experimental results prove that the voltage mode can greatly improve the ability to suppress vertical unstable displacement of plasma.

The power supply system in KSTAR neutral beam injector consists of low voltage and high current DC power supplies for plasma generator of ion source and high voltage and high current DC power supply for accelerator grid system. The arc discharge is initiated by an arc power supply supplying the arc voltage between the chamber wall and 12 filaments which are heated by individual filament power supply. The negative output of arc power supply is common to each positive output of 12 filament power supplies. To interrupt the arc discharging for the fault condition of the arc current unbalance, DCCT current monitor is placed at the positive output cable of the filament power supply. The plasma grid (G1) power supply has the maximum capability of 120 kV/70 A which consists of low voltage regulator with IGBT-switched chopper array system for the voltage control in unit of 600 V and the high voltage rectified transformers to supply DC voltage of 20 kV, 30 kV, and 50 kV. The output voltage of the G1 power supply is also connected to the input of the voltage divider system which supplies the gradient voltage to the gradient grid (G2) in the range of 80–90% of G1 voltage by changing tap of winding resistors in unit of 1%. The charged G1 voltage is turned on and off by the high voltage switch (HVS) system consisting of MOSFET fast semiconductor switches which can immediately be opened less than 1 μs when the ion source grid breakdown occurs. The decelerating grid (G3) power supply is inverter system using capacitor-charge power supply to supply maximum −5 kV/5 A. The important component in power supply system is the surge absorber near the ion source to limit the arc energy deposited to accelerator grid. This paper presents configuration and features of power supply system, main controller, and interlock system of KSTAR NBI.

In this paper, a modified Sheppard–Taylor converter operating in continuous inductor current mode and discontinuous capacitor voltage mode (CICM/DCVM) is studied and implemented. The operation sequences are described and the averaged model of the converter over a switching cycle is developed. With the obtained, the dc characteristics of the converter were derived, and design criteria for components selection to ensure DCVM operation were reported. The converter is then used for power factor correction in a single-phase rectifier with a front-end diode-bridge. This mode of operation provides the converter some desirable features: zero-voltage turnoff switching and natural purely resistive behavior at low dc output voltage level. This can be achieved by simply using an open-loop control, which offers better reliability than the CICM/CCVM previously reported in the literature, where feedback control is required. The theoretical study of the converter is presented and validated through experimental measurements carried out on a 500 W laboratory prototype. It is shown that this rectifier exhibits an input power factor higher than 99.7% and a source current distortion lower than 6% at small output voltage level.

A new soft switching converter is presented for medium power applications. Two full-bridge converters are connected in series at high voltage side in order to limit the voltage stress of power switches at Vin/2. Therefore, power metal–oxide–semiconductor field-effect transistors (MOSFETs) with 600 V voltage rating can be adopted for 1200 V input voltage applications. In order to balance two input split capacitor voltages in every switching cycle, two flying capacitors are connected on the AC side of two full-bridge converters. Phase-shift pulse-width modulation (PS-PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active MOSFETs can be turned on under zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. Two full-bridge converters are used in the proposed circuit to share load current and reduce the current stress of passive and active components. ...

The neutral beam injection generate ultra-high temperature energy in the tokamak of nuclear fusion. The neutral beam injection make up arc power supply, filament power supply and acceleration & deceleration power supply. The arc power supply has characteristics of low voltage and high current. Arc power supply generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The proposed buck converter used parallel switch because it can be increased capacity and decrease conduction loss. When an arc generated, the neutral beam injection chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus the proposed converter should be designed for the characteristics of low voltage and high current. Also, the arc power supply should be guaranteed for system stability. The proposed parallel buck converter enables the system stability of the divided low output voltage and high current. The proposed converter with constant output be the most important design of the output inductor. In this paper, designed arc power supply verified operation of system and stability through simulation and prototype. After it is applied to the 288(kW) arc power supply for neutral beam injection.

Reactive power control by loads is one of the methods to control voltage in distribution lines. The authors improved reactive power control method by use of power factor correction converters which are often used in loads. The method modifies input current reference by multiplying sawtooth wave and controls reactive power by changing slope of sawtooth wave. It was confirmed that the method can control distribution line voltage. Three types of voltage control methods were introduced to decide reactive power controlled by proposed method. Voltage control ability, stability were evaluated and compared by simulations. It was confirmed that all voltage control methods can control distribution voltage. One method was not stable in some conditions, other methods were stable in the conditions of the simulations. The proposed methods have a possibility to be introduced to loads and to reduce additional cost to install reactive power control equipment.

Power factor displacement and voltage fluctuation might produce due to high reactive power consumption of loads or long distribution lines. These power quality problems need more consideration in islanded microgrids (MGs) due to operating in low voltage grid with the absence of main grid. In this line, a novel control strategy for static synchronous compensator (STATCOM) is proposed in this paper to integrally correct power factor and mitigate voltage fluctuation in permissible ranges. In the previous approaches, auxiliary devices are used to compensate a certain point while, depending on load condition and distribution lines lengths, power quality of the other points except of the considered point might need compensation rather. In a different approach, the proposed strategy considers all the DGs buses for power factor correction and all the points of common coupling (PCCs) for voltage regulation. To this aim, communication network is applied. The proposed method is evaluated by MATLAB/Simulink.

High-altitude wind power (HAWP) generating system uses dc-dc converter to transform the dc link voltage to an optimal medium voltage dc for efficient transmission to ground-based station. This paper presents a comparative study of current-fed and voltage-fed (VF) isolated dc-dc converters for HAWP application. VF converters (VFCs) with inductive and capacitive filters are compared with current-fed converters for a 100-kW rated power. The power electronic converters used maintain zero-voltage switching on the primary side switches to reduce switching losses. The current and voltage ratings of the components used are provided to realize higher power-to-weight (P/W) ratio. Losses and P/W ratio are assessed using the components' datasheets and compared with evaluate the converters that exhibit higher P/W ratio and efficiency. It is observed that VFC with capacitive filter exhibits higher P/W ratio and efficiency. Small signal modeling of VFC with capacitive filter is carried out to obtain the state-space model. Transmission voltage is controlled at optimal value using voltage control loop for efficient power transmission. Simulation studies of VFC with capacitive filters are carried out to verify the steady state analysis and performance using the software PSIM-9 at 100-kW power level that converts 600-8000 V. A 1-kW scaled down laboratory prototype is designed, built, and tested using modular devices and accessed to validate the performance. It yields an efficiency of 94.2% at full load converting a ten-times scaled down voltage of 60-800 V.

This paper presents a new transformerless single-stage single-switch (S4) converter which integrates a buck-type power factor correction cell with a buck-type dc-dc output cell in a special way. The proposed converter preserves the advantages of existing transformerless S4 converters, such as the low voltage stress across the dc-link capacitor, low current stress of the switch, and high step-down input-to-output voltage. Moreover, the proposed converter provides a new attractive feature, i.e., its input power factor always keeps constant even when the line- and load-conditions vary. These characteristics make the proposed converter cost-efficient, easy-to-design, and suitable for the low-power and nonisolated applications. The principle and analysis of the proposed converter are presented in this paper, and a design example is also given to show the validity of analysis.

This paper presents a fully integrated energy harvester that maintains >35% end-to-end efficiency when harvesting from a 0.84 mm 2 solar cell in low light condition of 260 lux, converting 7 nW input power from 250 mV to 4 V. Newly proposed self-oscillating switched-capacitor (SC) DC-DC voltage doublers are cascaded to form a complete harvester, with configurable overall conversion ratio from 9× to 23×. In each voltage doubler, the oscillator is completely internalized within the SC network, eliminating clock generation and level shifting power overheads. A single doubler has >70% measured efficiency across 1 nA to 0.35 mA output current ( >10 5 range) with low idle power consumption of 170 pW. In the harvester, each doubler has independent frequency modulation to maintain its optimum conversion efficiency, enabling optimization of harvester overall conversion efficiency. A leakage-based delay element provides energy-efficient frequency control over a wide range, enabling low idle power consumption and a wide load range with optimum conversion efficiency. The harvester delivers 5 nW-5 μW output power with >40% efficiency and has an idle power consumption 3 nW, in test chip fabricated in 0.18 μm CMOS technology.

In this article, an analytical and delay-less model for the unified power quality conditioner is proposed to improve electrical power quality in power systems. The designed model includes a shunt active filter, series active filter, and common DC link, which is capable of improving power quality parameters in different conditions. The proposed control is based on a combination of the rotating reference frame theory and least mean square method that (1) can enhance power quality, including reduction of the voltage and current harmonics, voltage flicker, and reactive power of system, and (2) has no delay in the reference current generation. The DC link is also designed in a manner that capacitor voltage has a stabilized voltage in all instants. In addition, fundamental frequency estimation is employed to control frequency changes in the control system. For testing the proposed method in the worst conditions, the electric arc furnace load based on an actual stochastic arc that can generate almost all...

This paper presents a high-power dual-module parallel charging system which consists of a power converter and digital control software. The power converter consists of an active power factor correction (APFC) circuit and a resonant voltage fed full-bridge converter (RVFFBC). The APFC circuit is used for AC/ DC conversion and power factor correction for improved power quality. The RVFFBC is used to provide stable power for charging the battery by converting the high voltage of the power stage to a lower value. The system software was designed by combining the power control loop into a voltage and current loop to achieve current sharing of the dual-module charging system and to overcome the effect of differences in hardware components. Finally, this paper demonstrates the implementation of a high-power dual-module charging system with a widely varying AC input voltage ranging from 85 ~ 265 Vac. Experimental results verified that the maximum power factor of the system and the Total Harmonic Distortion (THD) were 0.99 and 2.8% respectively. The proposed charging system possesses very high expansibility. The parallel dual-module output DC current of the system is 70 A and the total output power is 4 kW.

The paper deals with an indirect current controlled shunt active power filter (APF) for improving power quality by reactive power compensation and harmonic filtering. The proposed APF is based on a voltage source inverter (VSI). The VSI is controlled by two loops, the voltage control loop and the current control loop. The voltage control loop regulates the DC link capacitor voltage and the current control loop uses hysteresis band control to shape the source current such that it is in-phase with and of the same shape as the input voltage. The major advantage of the proposed APF is that the reference current for power quality improvement is generated from the DC link capacitor voltage. The proposed scheme has been verified through simulation and experimental investigations.

This paper presents a brushless dc (BLDC) motor drive with power factor correction (PFC) for low-power applications. In this work, the speed of the BLDC motor is controlled by adjusting the dc link voltage of the voltage source inverter (VSI) feeding a BLDC motor. Therefore, VSI is used for achieving only an electronic commutation of the BLDC motor and operates in a low frequency switching for reduced switching losses. A PFC-based isolated zeta converter operating in discontinuous conduction mode (DCM) is used for controlling the dc link voltage of the VSI with inherent PFC at ac mains using single voltage sensor. The proposed drive is implemented to achieve a unity power factor at ac mains for a wide range of speed control and supply voltage fluctuations. An improved power quality is achieved with power quality indices within limits of IEC 61000-3-2 standard.

This paper presents a new control technique to regulate the capacitor voltage in cascaded multilevel inverters. Without requiring transformers, the scheme proposed here allows the use of a single dc power source with the remaining n − 1 dc sources being capacitors, which can achieve an effective role on harmonic elimination while generating the ideal output voltage. This paper focuses mainly to achieve an effective capacitor voltage regulation, and the effect of power factor on capacitor voltage regulation with the Phase shift modulation. The main advantages of this paper are to eliminate the harmonics, high-quality output power due to its high number of output levels. It shows hope to reduce the voltage ripple of the capacitors, which leads to higher power conversion efficiency with equal power distribution, reduces the initial cost, and complexity hence it is apt for industrial applications. Simulation work is done using the MATLAB software and experimental results have been presented to validate the theory.

Conventional dynamic voltage restorers (DVRs) install parallel battery and capacitor sets at the DC bus to supply the required power for voltage sag compensation. However, the reactive power output of a DVR may increase the ripple voltage at the inner DC bus, possibly resulting in a higher operating temperature of the battery and thus decreased battery life. This paper proposes a DVR system that uses a cascade power module to effectively compensate voltage sag. By separating the active and reactive compensation powers, the proposed DVR provides a lower ripple DC link for extending battery life and offers a flexible way to design the capacitor bank. To confirm the effectiveness of the proposed design, theoretical analysis and experimental validation were conducted under various scenarios. Test results confirm the feasibility and practicality of the proposed method.

This paper proposes a new solar power generation system, which is composed of a dc/dc power converter and a new seven-level inverter. The dc/dc power converter integrates a dc-dc boost converter and a transformer to convert the output voltage of the solar cell array into two independent voltage sources with multiple relationships. This new seven-level inverter is configured using a capacitor selection circuit and a full-bridge power converter, connected in cascade. The capacitor selection circuit converts the two output voltage sources of dc-dc power converter into a three-level dc voltage, and the full-bridge power converter further converts this three-level dc voltage into a seven-level ac voltage. In this way, the proposed solar power generation system generates a sinusoidal output current that is in phase with the utility voltage and is fed into the utility. The salient features of the proposed seven-level inverter are that only six power electronic switches are used, and only one power electronic switch is switched at high frequency at any time. A prototype is developed and tested to verify the performance of this proposed solar power generation system.

Full-bridge single-stage (FBSS) ac-dc converters allow to regulate both the output voltage and the input current that achieves a near sinusoidal waveform using only the four bridge transistors. Independent of this feature, these converters still need to be optimized in order to become an interesting and attractive solution for modern switch mode power supplies with power factor corrector (PFC) function. One of the most important improvements needed is the downsizing of the dc bus capacitor C b with the inherent cost reduction. However, this action introduces complex issues in the regulation of the input current and it is also responsible for the generation of high output voltage ripple. The new contribution of this paper consists in the introduction of a set of power circuit optimizations and control techniques in a FBSS PFC converter that solves the referred issues in order to enable the reduction of the dc bus capacitor's size and cost. These procedures are based in the use of a free wheeling circuit that improves the light load operation and in the application of one shot nonlinear modulator, in order reduce the output voltage ripple even when the dc bus ripple is high. The possibility of using, in the proposed topology, a reduced ratio capacitance/watt lower than the typical values used in commercial applications (0.7-0.5 μF/W for 385-450 V, respectively), while maintaining the accurate input current regulation, is also theoretically proved. The developed concepts, solutions and design criteria are detailed described in the paper. The correspondent theoretical study is verified trough experimental results token in an optimized FBSS topology prototype.

This paper proposes an isolated quasi-switched-capacitor (QSC) dc/dc converter to serve as an auxiliary power supply in electric and hybrid electric vehicles, managing a bidirectional power flow between the high-voltage (HV) battery and the low-voltage dc bus. A QSC dc/ac circuit with a 3:1 voltage step-down ratio is proposed to serve as the front-stage circuit of the converter. Based on it, an isolated QSC dc/dc converter is proposed with a synchronous-rectifier, current-doubler post-stage circuit. Compared with existing full-bridge, half-bridge, and three-level converters, the features of the proposed converter include: 1) the voltage stresses on HV-side switches are reduced to two-third of the HV-dc-bus voltage; 2) the voltage stress on transformer is reduced to one-third of the HV-dc-bus voltage; 3) the transformer turns ratio is reduced; 4) it has soft-switching capability and high efficiency; and 5) bidirectional power-flow and simple control can be implemented. The operation principles, soft-switching analysis, and simulation results are presented. Wide Bandgap devices are selected for the proposed converter to shrink the size of passive components, provide high efficiency, and decrease the cooling requirement. Guidelines are given to estimate the key circuit parameters, including the capacitance of the switched capacitors, the transformer dc-bias flux density, and the average currents of the post-stage inductors. Experiment results provided from a 1-kW prototype built with SiC MOSFETs on the HV-side validate the feasibility and superior performance of the proposed converter.

A laboratory-scale passive hybrid power system for transportation applications is constructed and tested in this study. The hybrid power system consists of a fuel cell stack connected with a diode, a lithium-ion battery pack connected with a DC/DC power converter and another diode. The power converter is employed to regulate the output voltage of the battery pack. The dynamic responses of current and voltage of the stack to the start-up and acceleration of the load are experimentally investigated at two different selected output voltages of the DC/DC converter in the battery line. The power sharing of each power source and efficiency are also analyzed and discussed. Experimental results show that the battery can compensate for the shortage of supplied power for the load demand during the start-up and acceleration. The lowest operating voltage of the fuel cell stack is limited by the regulated output voltage of the DC/DC converter. The major power loss in the hybrid power system is attributed to the diodes. The power train efficiency can be improved by lowering the ratio of forward voltage drop of the diode to the operating voltage of the fuel cell stack.

This study proposes a voltage and reactive coordinative control strategy with distributed generator (DG) in a distribution power system. The aim is to determine the optimum dispatch schedules for an on-load tap changer (OLTC), distributed generator settings and all shunt capacitor switching on the load and DG generation profile in a day. The proposed method minimizes the real power losses and improves the voltage profile using squared deviations of bus voltages. The results indicate that the proposed method reduces the real losses and voltage fluctuations and improve receiving power factor. This paper proposes coordinated voltage and reactive power control methods that adjust optimal control values of capacitor banks, OLTC, and the AVR of DGs by using a voltage sensitivity factor (VSF) and dynamic programming (DP) with branch-and-bound (B&B) method. To avoid the computational burden, we try to limit the possible states to 24 stages by using a flexible searching space at each stage. Finally, we will show the effectiveness of the proposed method by using operational cost of real power losses and voltage deviation factor as evaluation index for a whole day in a power system with distributed generators.

This paper presents a three-phase transformerless structure of modular multilevel converters based on cascaded pulsewidth-modulated chopper cells in medium-voltage D-STATCOM application. It is suggested for installation on unbalanced medium-voltage power-supply systems to achieve higher performance in improving power quality. This paper proposes a new control strategy based on power-flow analysis with a focus on dc capacitor voltage control that is insulated from the source voltage fault. This control strategy enables the D-STATCOM system to compensate unbalanced nonlinear load even under asymmetrical grid fault conditions and it has no limitations on the cascaded number. Experimental results obtained from a 60-V 3-kVA downscaled prototype verify that this D-STATCOM system performs satisfactory, not only compensating for unbalanced nonlinear load but also keeping the capacitor voltages maintained at the given value even in unbalanced power systems.

In this study an adaptive control is designed for a three-phase voltage source converter (VSC) acting as a static synchronous compensator to provide power factor compensation. The proposed method relies on an approximate third-order nonlinear model of the VSC that accounts for uncertainty in three system parameters. The design ensures asymptotic tracking of q-axis current and dc-voltage reference trajectories. Simulation and experimental results verify the performance of the controller relative to an established vector control method.

DC-bus voltage is affected by fluctuations of load and grid impact, threating the safe operation of the system. According to the instantaneous active power balance, a power feedforward control strategy was proposed to reduce the DC voltage fluctuations. In this strategy, the load active power was directly fed-forward to the grid-side given instantaneous active power node through a constructed load state feedforward channel, which avoided the slower process of indirect power adjustment through outer voltage loop. So, the system response speed was greatly accelerated, the DC-bus voltage fluctuation was inhibited effectively, and the dynamic performance of the system had improved. Test results demonstrate the effectiveness of the proposed strategy.

Capacitor charging power supply (CCPS) is a developed technology that utilizes resonant converters topology for high power applications. This paper proposes new a capacitor charging power supply using leg-rotation control method within a phase-shifted PWM full-bridge dc/dc converter. The capacitor charging power supply was connected in series to increase output voltage. Also, the proposed system is designed with soft switching techniques in order to achieve high efficiency, and a leg-rotation control method was used to reduce the heat generated from the IGBTs. The operation of the converter and design methodology will be described. A simplified model of a high-voltage high-frequency transformer is given and the structure is designed to decrease high-voltage stress. The validity of the proposed system is then verified by experimental results. The performance test of the capacitor charging power supply was carried out with a 2 μF capacitive load with a 20 kV output voltage.

Electronic devices such as SMPS, UPS, rectifier and electronic ballast primarily require DC power supply. Electronic switching devices draw highly distorted input current (spikes with respect to the line voltage) for a short duration, due to their non-linear nature. This results in interference with other electrical equipment, increase in Total Harmonic Distortion (THD) and poor Power Factor (PF), which further results in poor output voltage regulation. Power factor correction (PFC) circuits are being increasingly used to mitigate the problems associated with poor power factor. This paper discusses an Active Power Factor Correction (APFC) technique using voltage feed forward and voltage feedback loop. It is based upon current wave shaping technique to get the source current in phase with the input voltage. Current wave shaping is achieved by implementing voltage control loop and current control loop. This paper explains the development of boost converter as a power factor correction controller, operating in continuous conduction mode (CCM). The boost converter is also designed to regulate the output voltage. The prototype of boost active PFC has been developed for single-phase rectifier, supplying load of 80W at 400V DC. Analysis has been carried out for different load conditions which prove that the PF can be improved from 0.6 to 0.98∼0.99 with THD reduction.

Uninterruptable power supplies (UPS) units are basically used in almost all military applications with preferred voltages of 36V DC and 48V DC. In such applications, Float Cum Boost Charger (FCBC) is most commonly used power supply module. Normally, the output voltage obtained from FCBC was used to drive the ULSB MK-II devices which operates on 48V DC. In the present work, the FCBC module has been modified to drive ULSB MK-III devices resulting in better line and load regulation, power factor, efficiency, ripple voltage (lower). FCBC is basically a UPS for delivering regulated output voltage of 48V DC at 4Amps when loaded fully. Alternatively, a battery backup is also provided wherein, the battery is charged when AC mains is present. Even when the 230V AC power supply is OFF, charged battery backup of 24V, 6Amps is sufficient to deliver the required output voltage. The change over from AC supply mode to BATTERY mode is automatically done under the power failure conditions. Therefore, this work is of great interest especially for military applications due to desired outputs.

A new approach of power factor correction technique is reclaimed in this paper. In power systems, the power factor correction usually consists of branching capacitive loads to the power line in order to reduce the reactive power generated from inductive loads. The determination of the capacitance value depends on different parameters such as the voltage, current, frequency and the phase angle between the voltage and current. Thus, lots of measurements and calculations are required to branch the best capacitor value and reduce the power loss. The majority of industrial correctors use trial and error techniques or are limited to few steps of power correction. The system proposed in this paper uses a simple algorithm with fewer mathematical operations to determine the best capacitance value which can be selected among 256 different choices. The system engages the required capacitance in one shot in order to expand the lifetime of the switching relays and capacitors.

In this paper, a grid-connected battery charger is developed. The developed battery charger is composed of a power factor corrector and a buck converter. The power factor corrector control the input current to be sinusoidal and in phase with utility voltage to perform unity power factor. The buck power converter is step-down the output power of power factor corrector to charge the battery set in constant current or constant voltage. The power factor corrector contains a rectifier, a boost converter and a switched-capacitor circuit. The switching capacitors circuit is applied to be the output of the boost converter and the input of the buck converter. Controlling the switched-capacitor circuit, the output voltage of boost converter is divided into two levels according to the utility voltage such that step-up voltage gain can be reduced when the utility voltage is small. In addition, the switched-capacitor circuit can reduce the step-down voltage ratio of the buck converter. Accordingly, the efficiency of the grid-connected battery charger is advanced. A prototype is developed and tested to verify the performance of the proposed grid-connected battery charger.

This paper is focused on a single phase shunt active filter based on detection of harmonic voltages at the point of installation; the mission of the active filter is to eliminate these harmonic voltages implementing a repetitive-based control. The active filter is a single-phase voltage-controlled voltage source inverter controlled so to generate a harmonic voltage in phase with the one detected at the point of installation. The proposed repetitive-based control regulates the power at the fundamental frequency so to maintaining the dc voltage of the capacitor placed on the dc side of the filter close to a reference; such an issue is faced implementing the self-charging functionality or supplying real power to the grid when the active filter is a distributed generation solution. Numerical results are provided so to demonstrate the effectiveness and the feasibility of the proposed repetitive-based control in compensating harmonic voltages in an electrical power distribution system.

The power of photovoltaic (PV) system is greatly influenced by the natural environment factors, contributing to poor power supply reliability and voltage quality, while energy storage system can solve this problem effectively. Hybrid energy storage system combines the characteristics of the battery with larger capacity, medium power and fewer charge/ discharge times and the super capacitor with the characteristics of larger power density, smaller capacity and long cycling life, realizing complementary advantages of battery and super capacitor in operation. The storage system is controlled by power electrical converters to charge or discharge in harmony, which guarantees the quality of the PV energy, improves the overall performance of the energy storage system, extends the operation life of the energy storage system and reduces the costs of PV power. The paper adopts double BUCK- BOOST DC/DC converters to form a power bi-directional power transmission control circuit of hybrid energy storage system. The circuit controls the charging and discharging operation of battery and super capacitor orderly, and realizes the high-quality control of DC bus voltage of PV system.

Electric power systems will need to accommodate large amounts of renewables and a growing number of DC loads with reduced costs and losses. Medium-voltage DC distribution lines can play a key role. Moreover, a higher availability and reliability of the power supply can be achieved with energy storage systems (ESSs). In this paper, a hybrid configuration merging both concepts is evaluated. A medium-voltage DC distribution system with an integrated ESS has been proposed, modelled, and simulated. Voltage source converters have been used for the AC/DC conversions. The ESS is connected to the DC bus through a dual active bridge enabling bidirectional power flow while covering a large voltage gap. The controllers for all converters and a supervisory control scheme have been implemented. Simulations show the capability of the hybrid configuration to fulfill variable grid demand regardless of the wind power generation, thus transforming a fluctuating source into a dispatchable supply.