Research And Development Of Single-phase PWM Rectifier Based On Fixed Frequency Predictive Control

In recent years,the application of clean energy has become a hot topic for researchers and engineers.The charging system of electric vehicles,cascaded battery energy storage systems,photovoltaic or wind power generation system are developing rapidly,and the power converter plays a vital role.The single-phase PWM rectifier has the advantages of bidirectional energy transmission,high power factor,low harmonic content of grid-side current,and adjustable output voltage.It is a bridge connecting the power grid and the load,and plays the role of energy conversion.The control performance of the single-phase PWM rectifier is largely affected by the control strategy.Model predictive control has the advantages of simple control,and multivariable control.However,traditional model predictive control adopts single vector control,which has disadvantages such as unstable switching frequency,low switching frequency,and large harmonic current on the grid side.Based on the traditional finite-control-set model predictive control(FCS-MPC),this paper proposes a model predictive current control(MPCC)scheme with fixed switching frequency and dead-time compensation.The switching frequency can be fixed by using an effective switching state and two zero switching states.The current prediction equation is derived based on the optimal action time of the effective switching state.The optimal action time of the effective vector is obtained by deriving the objective function,which is established based on minimizing the current error.Then,in order to improve the prediction model and suppress the dead-time effect,the influence of dead-time on the effective switching state and zero switching state is analyzed,and the current prediction equation is revised to complete the dead-time compensation.The simulation results show that the current of the traditional finite set model predictive control contains a large number of low-frequency harmonics,and the current obtained by the model-predictive current control scheme proposed in this paper contains highfrequency harmonic currents as the main component,and the current total harmonic distortion rate is also greatly reduced.The simulation results also show that adding the dead-time will cause the current waveform distortion and increase the total current distortion rate.However,after adopting the dead-time compensation scheme proposed in this paper,the dead-time effect is effectively suppressed and the total current distortion rate is also reduced.Finally,a lowpower experimental platform for single-phase PWM rectifiers is built.According to the experimental results,the conclusion can be drawn: Compared with PI control scheme,FCS-MPC,and model predictive direct power control(MP-DPC),the MPCC scheme proposed in this paper can get the lowest current total harmonic distortion rate.In addition,compared with the PI control scheme,it has the advantage of fewer adjustment parameters.Compared with the MP-DPC,it has the advantages of simple program and short running time.And the dead-time compensation scheme can also effectively suppress the deadtime effect and reduce the distortion of the current waveform.This paper is supported by the Guangdong Key Laboratory of Clean Energy Technology,the State and Local Joint Engineering Laboratory of Wind Power Control and Grid Connection Technology.