High Power Factor Operation Research Articles

Power converter for battery charger of electric vehicle with controllable charging current

Research on electric vehicle chargers primarily focuses on improving charging technology to enhance the convenience, quality, efficiency, and affordability of charging electric vehicles. This paper discusses a different AC-DC power converter topology proposed as a potential candidate for electric vehicle battery charger. Using the proposed converter circuit, the charging process of electric vehicle battery can be simply adjusted to meet the battery requirement, and even for increasing the charging speed while avoiding overcharging of battery. During the charging process, if the voltage of battery approaches to the targeted battery voltage level, the charging current can be reduced gradually to zero. Hence it will prevent the battery from overcharging condition. Moreover, the ability of working at high power factor operation, low distortion of alternating current (AC) input current, and low direct current (DC) output current ripple are other features of the proposed charger circuits. Some test results of the proposed power converter were presented. The test results revealed potential features of the converter for battery charger of electric vehicle with power factor 0.9996, total harmonic distortion (THD) of AC current 2.73%, and low charging current ripple, i.e. 3.91%. Therefore, it minimizes the negative effects caused by ripples of charging current especially for lithium-ion batteries widely used in electric vehicles.

Cascaded Multilevel Rectifiers for Open-End Winding PMSM

This article proposes three-phase cascaded multilevel rectifiers for wind energy conversion system applications. These configurations operate as machine-side converters and play an essential role in the integration of wind power generation units. The proposed rectifiers are connected to a permanent magnet synchronous machine by an open-end winding arrangement, making the ac–dc conversion of the power delivered with high-power factor operation. Their structures are composed of a combination of a converter based on Vienna rectifiers and one H-bridge per phase with a floating capacitor. Compared with the conventional configurations, the proposed ones provide sinusoidal currents with lower harmonic distortion using, proportionally, a fewer number of controlled switches. Furthermore, they can operate with a lower switch blocking voltage. These features make them attractive options for industrial applications due to their good performance, providing an interesting cost–benefit. The system model, pulsewidth modulation technique, capacitor voltage balancing, and control strategy are detailed. Computer simulations and experimental tests are provided in order to validate their feasibility.

A Hybrid Modulation Featuring Two-Phase Clamped Discontinuous PWM and Zero Voltage Switching for 99% Efficient DC-Type EV Charger

Two-stage AC-DC converters are considered as a prominent solution for DC-type electric vehicle (EV) chargers. However, this kind of architecture suffers from high switching losses with large heatsink and DC-link capacitor volume. To relieve this issue, this paper presents a new hybrid modulation for DC-type EV chargers, where a two-phase clamped discontinuous pulse-width-modulation (DPWM) in the front-end circuit is cooperated with the variable frequency triangular-current-mode (TCM) zero voltage switching (ZVS) or its simplified implementation, i.e., boundary-ZVS (B-ZVS) strategy, in the back-end circuit. The former can stop the switching actions in the front-end stage during two-thirds of the grid period, while the AC currents are at their highest values, which can yield to the best switching loss reduction and deliver high power factor operation. Besides, TCM-ZVS or B-ZVS modulations can achieve ZVS turn-on action for all semiconductors during all operating range in the DC-DC stage to further reduce the power losses on the semiconductors. With such characteristics, the proposed strategies can reduce the switching losses of the system to the best extent, and thus allow an enhancement of the system power density by improving the power conversion efficiency. The proposed strategy is described, analyzed, validated, and benchmarked in a 5 kW SMD SiC MOSFET-based two-stage AC-DC converter. A 99% power efficiency can be achieved with the solution implementing the TCM-ZVS strategy at an output voltage of 400 V and rated power.

Generalised model predictive control scheme for three‐level converter under unbalanced grid voltage considering full power factor operation

With the increase of grid-connected renewable power generation units, the three-level converter (TLC) is widely utilized. However, when unbalanced grid voltage occurs, the converter should provide a certain of reactive power to satisfy the grid code, which decreases the power factor and degrades neutral-point (NP) voltage balance. The existing model predictive control methods for NP voltage balance in TLC mainly focus on high power factor operation, which are not applicable to low power factor operation. To solve this problem, this study proposes a generalized model predictive control (GMPC) scheme for the TLC. By analyzing the influence of P-type and N-type small vectors on NP voltage, it is indicated that the charging and discharging operation of the dc-link capacitors are determined by the grid currents directions with the defined small vectors. Since the directions of grid currents are changed with different power factors, the effect of one small vector on NP voltage is change. In the proposed GMPC scheme, the direction of grid currents and the capacitor voltage difference are simultaneously used to select the appropriate small vector to mitigate the NP voltage unbalance effectively in the full power factor range. The validity is verified by simulation and experimental results.

Control of Three Phase to High Frequency Single Phase Matrix Converter Capable of High Power Factor Operation and Soft Switching

Control of Three Phase to High Frequency Single Phase Matrix Converter Capable of High Power Factor Operation and Soft Switching

Research on power supply of booster based on PWM rectifier

The magnet power supply system of HEPS mainly includes the linear magnet power supply, the booster power supply, the transportation line magnet power supply and the storage ring magnet power supply. According to the physical design requirements, the output current of the booster magnet power supply is a current with a DC bias period of 1 Hz, and the waveform can be a sine wave or a trapezoidal wave (Jiang et al. Sci Sin Phys Mech Astron 44(10):1075–1094, 2014). The dipole magnet of the booster should be powered in series, the inductance value is relatively large (about 160 mH), and the power of the power supply reaches several hundred kilowatts. The three-phase PWM rectifier controls the orderly turn-on of power electronic devices and takes the input voltage phase of the power grid as the command current phase to make the input current waveform follow the power grid voltage, so as to achieve the purpose of improving the power factor. In this paper, the PWM rectifier is modeled and simulated, and based on the simulation, an experimental prototype is built. The experimental results of the power supply prototype of the PWM rectifier show that the PWM rectifier can achieve high power factor operation on the grid side (Akagi and Sato, in: Control and performance of a flywheel energy storage system based on a doubly-fed induction generator–motor for power conditioning, 1999). The PWM rectifier can be used in the power supply of the booster and has a very good application prospect.

Grid Synchronization and Islanding Detection Methods for Single-Stage Photovoltaic Systems

Synchronization and islanding detection represent some of the main issues for grid-connected photovoltaic systems (PVSs). The synchronization technique allows to achieve PVS high power factor operation and it provides grid voltage monitoring. The islanding detection control function ensures safe operation of the PVS. Focusing on low-power single-stage PVSs, in this study the most adopted and the highest performance synchronization and islanding detection methods are discussed. The role of the synchronization system is fundamental to detect the grid conditions, for the islanding detection purpose, and to manage the reconnection to the grid after a PVS trip. Hence a combined review is advantageous.

A High-Power-Factor Dimmable LED Driver with Integrated Boost Converter and Half-Bridge-Topology Converter

This paper proposes a dimmable light-emitting diode (LED) driver featuring a high power factor and zero-voltage switching on (ZVS). The circuit is obtained by integrating a boost converter and a dc-dc converter with half-bridge topology. The high power factor is achieved by operating the boost converter in discontinuous current mode (DCM). The LEDs are dimmed by the control scheme of asymmetrical pulse-width modulation (ASPWM). The developed circuit eliminates the inherited dc-offset current of the transformer in a conventional asymmetrical half-bridge converter by introducing a balance capacitor. Both active switches can operate at ZVS by freewheeling the boost inductor current and the transformer magnetizing current to discharge the energy stored in their parasitic capacitance. The circuit operation is analyzed in detailed, and mathematical equations are derived. Finally, a 115-W prototype circuit for driving high brightness LEDs was built and tested. The experimental results verify the feasibility of the proposed LED driver with satisfactory performance. It can achieve a high power factor and ZVS operation.

Experimental verification of a linear AC LED driver with a light flicker compensating circuit and high power factor operation by modulating the current regulator

AbstractThis article proposes a linear PFC regulator with a light flicker compensating circuit for LED lighting applications. The proposed circuit is small in size because it includes no reactors or electrolytic capacitors. The light flicker compensating circuit, which is connected in parallel to the LED string, consists of four ceramic capacitors and diodes. These capacitors are operated in series in the charge state and in parallel in the discharge state by using a diode network circuit. Therefore, an external controller and large capacitors are not required. The proposed circuit is experimentally validated using a 9 W prototype. From the experimental results, it is found that the power fluctuation of the LED string is less than the JIS and JLMA limitations, and the power factor is 0.95. In addition, the power loss is analyzed at an efficiency of 89.4% for the prototype circuit. Also, by modulating the current regulator, sinusoidal input current can be achieved. The second proposed circuit is experimentally validated using a 7.5 W prototype, and the power factor and input current distortion are found to be 0.999 and 2.1%, respectively.

Experimental Verification of a Linear AC LED Driver with a Light Flicker Compensating Circuit and High Power Factor Operation by Modulating the Current Regulator

Experimental Verification of a Linear AC LED Driver with a Light Flicker Compensating Circuit and High Power Factor Operation by Modulating the Current Regulator

Independent active–reactive power control scheme for NSC-drive operated at constant frequency

ABSTRACTThis paper presents a new control scheme for the ac-dc-ac nine-switch converter (NSC) with induction motor operated at constant frequency. The NSC at constant frequency operates optimally and its application for induction motor drive with re-active power compensation is proposed. In industries for various applications, induction motors are operated at constant frequency but at different loading conditions. These motors are operated at lagging power factor. The power distribution company demands high power factor operation and it gives benefits to consumer on operating a system closer to unity. In this paper, a control scheme is proposed to operate NSC drive at unity as well as at leading power factor with sinusoidal input current. The independent active–reactive power control technique is developed. The input–output active power relation is developed such that with the change in load, output active power matches input active power without affecting dc-link voltage. This results in faster dynamic response as compared to conventional dc-link balancing control techniques. With the proposed control scheme, the NSC is operated at desired leading power factor to compensate reactive power at point of common coupling. The simulation and experimental results show the feasibility of the proposed control scheme.

A Modified Neutral Point Balancing Space Vector Modulation for Three-Level Neutral Point Clamped Converters in High-Speed Drives

This paper describes a high-performance neutral point voltage balancing technique for a neutral point clamped (NPC) converter. Conventional neutral point voltage balancing methods do not function well under low power factor, low pulse ratio, and near-unity modulation index operation conditions. These conditions are essentially dominant operation conditions for aircraft starter/generator systems. This paper introduces an alternative space vector modulation technique for three-level NPC converters in an aircraft starter generator system. The selection of voltage space vectors is optimized for high modulation index and low power factor operation. Disturbances caused by a low pulse ratio are also compensated. The proposed method maintains neutral point voltage balance and ripple minimization over the full range of operating conditions. This paper also provides a detailed analysis of the sources of neutral point voltage imbalances and ripples in high-speed drives with deep flux weakening. Simulation results obtained from a Simulink/PLECS model and experimental results obtained from a 45 kVA, 32 krpm aircraft starter generator test rig prove that the proposed method eliminates the neutral point voltage imbalance and significantly reduces the neutral point voltage ripple.

Implementation of Closed-Loop Control of NSC-Drive with Reactive Power Compensation

This paper presents a closed-loop control scheme of the AC–DC–AC nine switch converter (NSC) with induction motor operated under dynamic loading conditions. In industries, induction motors are widely used which are operated at lagging power factor and different loading conditions. The electrical distribution company demands high power factor operation, and it gives benefits to the consumer on operating a system closer to unity. The scope of this paper is to control active and reactive power flow between NSC-drive and utility within NSC converter operating constraints. The control scheme is developed such that the active power required for the induction motor is directly transferred from the utility without affecting DC-link voltage. Also, the NSC with induction motor is used to operate at unity power factor and even at leading power factor. On operating NSC at desired leading power factor, the required reactive power at the point of common coupling can be compensated. The proposed control algorithm is implemented in MATLAB software as well as in the hardware. The 5 KVA prototype of NSC is developed in the laboratory. Software and hardware results confirmed the practicability of the proposed control technique.

A Maximum Current Control Method for Three-Phase PWM Rectifier for the ITER In-Vessel Vertical Stability Coil Power Supply

The required peak current and peak voltage of ITER in-vessel vertical stability (VS) coil power supply are up to 80 kA and 2.4 kV, so VS coil power supply needs a pulse width modulation (PWM) rectifier to achieve high power factor operation under the highly transient power demand of the value of 144 MW. A new maximum current control method for three-phase voltage source PWM rectifier based on its mathematical model in $d$ – $q$ frame and improved by dual-closed-loop control method has been presented. This control method meets the fast power charging demand and the dc-side voltage stabilization demand of power supply, and achieves a unity or high power factor operation; its controller is easier to be designed and implemented than dual-closed-loop control at charging mode. The advantages and feasibility of this control method have been verified by simulation and experiment.

Reactive Power Compensation Using Induction Motor Driven by Nine Switch AC-DC-AC Converter

Induction motors (IM) used for various industrial applications operate with lagging power factor. Electrical distribution agency insists high power factor operation and it gives incentives on operating a system closer to unity. This paper presents a novel reactive power compensation using IM driven by nine switch ac–dc–ac converter for a high power factor operation at the point of common coupling (PCC). The nine switch converter (NSC) with leading power factor operation delivers reactive power to the PCC. Thus, reactive power required for another load at PCC is compensated. Modified sinusoidal pulse width modulation is developed for NSC to operate the active front end rectifier and an inverter simultaneously to feed three-phase IM. A closed loop proportional integral control technique is developed to achieve desired VAR compensation. As per the required VAR compensation, front end rectifier voltage is modified. This is achieved by phase shifting of front end rectifier modulation reference by an angle $\delta$ with respect to utility phase voltage. The PCC phase voltage is continuously sensed to track instantaneous phase angle $\theta$ using synchronous reference frame phase lock loop. The analysis of VAR compensator is presented in the d-q reference frame. The proposed system is simulated in MATLAB for VAR compensation at PCC with 5.4 hp induction motor drive to test the performance of VAR control loop. To validate the feasibility of the proposed system an experimental prototype is developed with 1 hp induction motor drive. Gate pulses are generated using digital signal controller dsPIC33EP256MU810. The simulation and experimental results proved the feasibility of the proposed VAR compensation system.

An Extinction Angle Control of Three Phase Induction Motor Drive for High Power Factor Operation

An Extinction Angle Control of Three Phase Induction Motor Drive for High Power Factor Operation

Type-2 Fuzzy Logic Predictive Control of a Grid Connected Wind Power Systems with Integrated Active Power Filter Capabilities

This paper proposes a real-time implementation of an optimal operation of a double stage grid connected wind power system incorporating an active power filter (APF). The system is used to supply the nonlinear loads with harmonics and reactive power compensation. On the generator side, a new adaptive neuro fuzzy inference system (ANFIS) based maximum power point tracking (MPPT) control is proposed to track the maximum wind power point regardless of wind speed fluctuations. Whereas on the grid side, a modified predictive current control (PCC) algorithm is used to control the APF, and allow to ensure both compensating harmonic currents and injecting the generated power into the grid. Also a type 2 fuzzy logic controller is used to control the DC-link capacitor in order to improve the dynamic response of the APF, and to ensure a well-smoothed DC-Link capacitor voltage. The gained benefits from these proposed control algorithms are the main contribution in this work. The proposed control scheme is implemented on a small-scale wind energy conversion system (WECS) controlled by a dSPACE 1104 card. Experimental results show that the proposed T2FLC maintains the DC-Link capacitor voltage within the limit for injecting the power into the grid. In addition, the PCC of the APF guarantees a flexible settlement of real power exchanges from the WECS to the grid with a high power factor operation.

Direct Power Control Strategy of PWM Rectifier Based on Improved Virtual Flux-Linkage Observer

In order to achieve the low cost and high performance control of three-phase PWM rectifier, a direct power control (DPC) strategy based on a new-style virtual flux-linkage observer is proposed. The model of three-phase PWM rectifier and the principle of virtual flux-linkage vector control are introduced firstly. Then, in order to avoid the effect of integral initial value and cumulative deviation, three first-order low-pass filters are cascaded to replace the pure integral link; an improved virtual flux-linkage observer of three-phase power grid is presented. From the observed virtual flux-linkage, the voltage and instantaneous power of three-phase power grid are online estimated. On this basis, the power grid voltage sensorless direct power control system of three-phase PWM rectifier is designed. Simulation results have shown that, both in the rectifying state and in the inverting state, the power grid side current and the DC side voltage of three-phase PWM rectifier all can be effectively controlled; the high power factor operation of three-phase PWM rectifier is realized.

Buck converter‐based power supply design for low power light emitting diode lamp lighting

This study deals with the analysis and implementation of an HPF (high power factor) single-stage, single switch buck converter-based power supply design for an LED (light emitting diode) lamp load of 13 W operated at the universal ac mains. In general purpose lighting applications, a buck converter is a good candidate for power factor correction with low component count and reduced cost. In low-power lighting, it is a tough task to control the THD i (total harmonic distortion) of ac mains current under the limits of strict international standards such as IEC-61000-3-2 with universal ac mains for class D equipments. In the proposed optocouplerless topology, HPF operation at input ac mains is achieved by operating the buck ac-dc converter in continuous conduction mode. The design, modelling and simulation of the proposed topology are executed using MATLAB-Simulink and sim-power system toolboxes. A prototype of the power supply for LED lamp is developed for multiple LEDs connected in series configuration. The efficiency of the proposed LED lamp driver is observed as 83.76% at rated voltage of 220 V and the THD of ac mains current less than 17.27% for a wide range of voltages of 90-270 V.

HARMONICS REDUCTION IN FRONT END RECTIFER OF UNINTERRUPTIBLE POWER SUPPLIES WITH ACTIVE CURRENT INJECTION

Harmonics are the by-products of modern electronics devices so it is necessary to mitigate the harmoni cs and offer techniques to mitigation of harmonics. It is greatly hampered by a three phase rectifier use d as a front-end ac-to-dc converter in many systems. High power factor is achieved by injecting high-frequenc y currents into the three-phase rectifier. This study presents the high power factor operation of the co nverter with reduced total harmonic distortion up to 47.06% . The power quality up gradation is due to highfrequency current injection, at the input of the fr ont-end rectifier. Sinusoidal PWM technique is used for controlling the output voltage. DSP is used for gen erating the desired gate pulses. The converter has high efficiency, low EMI emissions, high power packing density and suitable for UPS system.