Predictive Control Of Single Phase Voltage Source PWM Rectifier

In the traction drive system,single-phase PWM rectifier needs to realize voltage stable output of intermediate dc link,and ensure the stability of net side power factor.When the train is running in the traction condition,ensure that the voltage and current phase of the network side are the same.When the train is running in the braking condition,the phase of voltage and current at the network side is guaranteed to be opposite,and the bidirectional flow of electric energy can be realized.Therefore,the selection of PWM rectifier control strategy has an important impact on improving the power factor of the grid,reducing the harmonic current on the net side,and stabilizing the output of dc-link voltage.In this paper,two kinds of PWM rectifier topologies(single-phase two-level topology and single-phase three-level topology)for emu are taken as examples.Firstly,the operating principle of single phase PWM rectifier in four quadrant is analyzed,and the corresponding mathematical model is established by analyzing the working state of the two topologies.Secondly,based on the finite set model predictive control,the discrete model of two kinds of rectifier topologies is established,and the cost function selection scheme is given.In order to improve the inaccuracy of the system prediction due to the control delay in the single step predictive control,a delay compensation strategy is added based on the traditional finite set model predictive control.The simulation shows that the delay compensation strategy can ensure the operation of the system unit power factor,and the power fluctuation is small and the current harmonic content is low.To solve the problem of too much calculation in the online optimization process of the system,this paper proposes a method to simplify the optimization process of cost function.The simulation waveform shows that both voltage and power pulsation are significantly reduced,and the current THD is lower.In addition,regarding the neutral voltage imbalance imbalance in single-phase three-level PWM rectifier,the cause of the problem is discussed in the paper,and the cost function in the control algorithm is to establish a link to join the corresponding improvement strategy.The simulation shows that the voltage amplitudes of the two supporting capacitors can be kept equal,with a little fluctuation range is smaller.This article in view of the single phase two level/three-level PWM rectifier simulation model is established,based on Matlab/Simulink simulation platform,the traditional finite set of mentioned model predictive control,optimization and simplify the cost function of the time delay compensation process improvement strategy for validation.The simulation result proves the control strategy and improve the correctness of the algorithm.