Research On Model Predictive Control Strategy Of Three-phase Voltage Source PWM Rectifier

Three-phase voltage-source PWM rectifiers are widely used in the field of power electronics because of their ability to achieve bidirectional energy flow,four-quadrant operation and controllable output voltage.Model Predictive Control(MPC)has received a lot of attention from academia because of its intuitive concept,easy modeling,no need for precise mathematical models and no need for complex control parameter design.In this paper,a model predictive control strategy for a three-phase voltage-source PWM rectifier is studied and analyzed.Firstly,the main circuit topology of the three-phase voltage-source PWM rectifier and its operating principle are introduced,and the mathematical model of the rectifier based on the three-phase stationary coordinate system,two-phase stationary coordinate system and two-phase rotating coordinate system is analyzed.The principle and implementation process of space vector modulation are also introduced in detail.Then,the principle of finite control set model predictive control(FCS-MPC)is analytically introduced,and the discrete model of rectifier power variation with the same sampling time interval can be obtained by discretizing the rectifier continuous time model.By using the finite rectifier switching state,the optimal switching state can be predicted based on the set cost function based on the target active power and reactive power,and the optimal switching state can be predicted by traversing the switching state of the next cycle at each sampling period.However,this method has the problems of low control accuracy,high requirement for system sampling frequency,and irregular system switching frequency.To address these problems,a space vector modulation model predictive control strategy(SVM-MPC)is introduced,which achieves fixed switching frequency control by combining model predictive control with space vector modulation,but the method has the problem of large system inertia.This paper proposes an optimized switching sequence model predictive control strategy(OSS-MPC)based on multi-vector synthesis,which reduces the system computation by introducing voltage sector judgment through the optimization of finite control set while ensuring the system control accuracy;then,based on multi-vector synthesis,the optimal vector sequence combination of adjacent sampling periods is selected based on the principle of minimum switching times to achieve The fixed switching frequency control reduces the current harmonics and improves the control accuracy.Through simulation analysis,the feasibility and improvement effect of the proposed control strategy are verified.Finally,by building an experimental platform of three-phase voltage-source PWM rectifier,the above three control strategies are further verified and analyzed.The results show that the proposed optimal switching sequence model prediction control strategy has the advantages of improving network-side current harmonic distribution and enhancing control accuracy.