Chuanping Wu

Power Electronic Hybrid System for Load Balancing Compensation and Frequency-Selective Harmonic Suppression

The proposed power electronic hybrid system which consists of a thyristor-controlled reactor (TCR) and a resonant-impedance-type hybrid active power filter (RITHAPF) is used for compensating reactive power and harmonic current. From the point of the nature of load balancing compensation, the calculation of balancing controlled susceptance based on voltage vector transformation is proposed for the TCR to exactly compensate negative-sequence current caused by asymmetrical loads in industrial field. Because the impedance of a filter inductor, a matching transformer, and passive power filters according to the harmonic current is inductive, the phase of the RITHAPF compensating current through them would be shifted. A π-aimed Smith predictor is established based on the fact that there is a π delay between the compensating current and the sum of harmonic currents of loads and the TCR. In terms of the proposed predictor and generalized integrators, a frequency-selective predictive current controller is designed for perfectly eliminating the impact of phase shift on the RITHAPF filtering performance. The simulation and industrial application results validate the theoretical analysis.

A Negative Sequence Compensation Method Based on a Two-Phase Three-Wire Converter for a High-Speed Railway Traction Power Supply System

This paper presents a negative sequence compensation system based on a novel two-phase three-wire converter to eliminate a negative sequence current for the high-speed railway traction power system with a three-phase V/V traction transformer. In this compensation system, the proposed two-phase three-wire converter is fed by two single-phase power sources formed with two step-down transformers connecting to the two feeder sections. The proposed converter contains three switch legs, one of which is connected to the common ground wire of two single-phase voltages. Hence, a switch leg is saved compared with two conventional single-phase converters, and the ratings of the power switches are not increased. In order to enhance the dynamic and steady-state performances of the compensation system, a compound control method composed of hysteresis control and dividing frequency control is presented. Simulation and experimental results are presented to demonstrate that the proposed compensator and its control strategy are very effective.

A Simplified Power Conditioner Based on Half-Bridge Converter for High-Speed Railway System

With the rapid development of high-speed and high-power railway system in China, power quality such as the negative sequence current and harmonic current caused by electric locomotives becomes more and more critical. This paper proposes a half-bridge-converter-based railway static power conditioner (RPC) (HBRPC) which consists of two half-bridge converters connected by two capacitors in series. Compared with the traditional RPC, the HBRPC requires only a pair of power switch legs and two capacitors. Under the premise of accomplishing the same function of RPC, the proposed conditioner can reduce half of the power switches, which can make it with lower cost and hardware complexity. A double-loop control is proposed for HBRPC to keep the dc-link voltage stable and achieve the dynamic tracking of the current reference signals, while a balanced voltage control is proposed to eliminate the error of two capacitor voltages and maintain the normal operation of HBRPC. Finally, simulation and experiment results have verified the proposed structure and its control method effectively.

Railway Static Power Conditioners for High-speed Train Traction Power Supply Systems Using Three-phase V/V Transformers

In order to eliminate the negative-sequence and harmonic currents in the high-speed train traction systems with three-phase V/V transformers, a compensation strategy based on the railway static power conditioners (RPC) is proposed in this paper. An RPC contains two converters that are connected back to back by sharing the same dc link. In this paper, the structure and principle to compensate negative-sequence currents for the RPC with a three-phase V/V transformer are explained, and a strategy to provide the compensation references for negative-sequence and harmonic currents is proposed. Also, a method to separate active current, reactive current, and harmonic current references from the total negative-sequence and harmonic current references is given. Moreover, a controller is proposed to maintain the dc-link voltage and to compensate the negative-sequence and harmonic currents. Simulation and experimental results are provided to demonstrate that the proposed strategy is very effective.

A Dual-Loop Control Strategy of Railway Static Power Regulator Under V/V Electric Traction System

For power quality in V/V traction system of the 350-km/h high-speed railway, a kind of railway static power conditioner (RPC) is discussed, which is used to carry out the comprehensive compensation of negative sequence and harmonic currents in the traction substation. In order to improve the control effect and performance of RPC, a dual-loop control strategy is constructed for RPC. Taking into account the disturbance and variation of electrified railway environment, a recursive proportional-integral control based on fuzzy algorithm is adopted to realize a fast and smooth tracking to the reference current. An energy-balance control is proposed to suppress the fluctuation of dc-link voltage and maintain the stability of RPC, which is an accurate and adaptive feedback control based on corresponding parameters. Finally, the correctness of the analysis proposed in this paper has been confirmed by the simulation and experiment results.

A Dynamic Hybrid Var Compensator and a Two-Level Collaborative Optimization Compensation Method

In this paper, a dynamic hybrid var compensator (HVC) for distribution grid is proposed. The system is based on a combination of a small-capacity distribution static compensator (DSTATCOM) and multigroup large-capacity thyristor switched capacitor (TSC). The DSTATCOM is the continuous subsystem of HVC, and the TSCs are the discrete subsystem of HVC. A new hybrid control method based on expert decision has been proposed to make sure that the HVC has good performance. A two-level collaborative optimization arithmetic, which is used to decide the optimal capacity of each HVC, has been proposed in this paper. A dynamic energy-saving system based on HVCs has been developed for a melt factory in southern China; application results show that compared to traditional reactive power compensation systems, the proposed system can effectively correct power factor, support supply voltage, mitigate voltage flicker, and obtain good effect for energy saving with low cost.

A research of microgrid energy supply and filtering system based on inverter multiplexing

Most micro sources need to use the inverter system to connect the grid. Because the microsources are intermittent and easily affected by the adverse weather, also the reason of getting the maximum power output, the capacity of inverter system is larger enough than need and its utilization rate is not high. Microgrid power quality is a new emerging area of research and drawing more attention. Based on the same main circuit configuration of gird-connected inverter of microsource and active power filter, a feasibility study for inverter multiplexing is put forward. An energy supply and filtering composite system based on gird-connected generation and active power filter and its uniform control method is presented. The generator can work as gird-connected inverter and active power filter simultaneously, which exerts the advantage of distributed generation, and improves the power quality. Theoretic analysis, simulation and experiment proved the feasibility of this scheme.

Development and Application of the Two-Phase Orthogonal Power Supply for Electromagnetic Stirring

This paper presents a three-leg voltage-source inverter topology for two-phase orthogonal power supply used for driving electromagnetic stirring. Compared with the conventional two two-leg inverter, the three-leg structure reduced the loss of power module and switching. The improved structure has an inductor in series between two-phase orthogonal power supply and the common phase of electromagnetic stirring, which make it possible to apply deadbeat current control method to two-phase orthogonal power supply, thus the controller design is simplified, the current adjustment speed is enhanced, and the current waveform is improved. A control strategy with reactive power compensation is proposed for enhancing the utilization rate of a three-phase pulsewidth modulation (PWM) rectifier in two-phase power supply, which makes it possible that the three-phase PWM rectifier not only operating rectification status but also operating reactive power compensation status. Hence, the reactive compensation cost of enterprises will be decreased. At last, simulation and industrial application results are provided to verify the effectiveness of the proposed topology and control strategy.

Integrated mathematical model and closed loop control characteristic analysis of hybrid active power filter

An integrated mathematical model of voltage source inverter (VSI) under two types of closed loop control methods is proposed based on the analysis of operating principle of Hybrid Active Power Filter (HAPF). Then the integrated mathematical model of HAPF is presented based on the integrated model of voltage type inverter. Furthermore, the closed loop control characteristics of HAPF are discussed. Simulation and experiment results have confirmed the validity of the closed loop control characteristics analysis of HAPF.