Research On Model Predictive Control Of Three-Phase Voltage Source PWM Converter Under Harmonic Grid Voltage Conditions

In recent years,clean energy has been greatly developed.The pulse-width modulation(PWM)converter is an important part of the renewable power generation system,whose control performance has a significant effect on the overall performance of the generation system.The research on the harmonic current suppression strategy of the PWM converter under harmonic grid voltage conditions is very important to improve the power quality of the renewable power generation system.Although the traditional vector control can restrain the harmonic current,the constraints of the control performance will lead that the switching frequency of the PWM converter can not be reduced effectively.Model predictive control(MPC)is a new control strategy in recent years.So far,a lot of research literature shows that MPC has good control performance.The multiple targets can be considered in the MPC strategy at the same time and some nonlinear constraints can also be taken into account.If the switching frequency of the PWM converter is taken as an optimization objective,the switching loss of the power device will be reduced remarkably.Therefore,in this paper,the MPC of the PWM converter under the condition of harmonic grid voltage is studied in depth.Firstly,this paper studies the operation principle of the three-phase voltage source PWM converter,and establishes the mathematical model of the PWM converter which is suitable for harmonic grid voltage conditions.On this basis,the working principle and realization method of the traditional voltage-oriented vector control strategy are introduced,and the suppression of the harmonic current in the grid side is realized by using the vector control.Secondly,the working principle and realization method of the MPC are a nalyzed.A mathematical model for the MPC strategy is established and the control strategy is studied which uses the model predictive control to suppress the harmonic current in grid side.In addition,by establishing the appropriate objective function,the switching state of the power device of the PWM converter is considered into the objective function to reduce the switching frequency of the power device.As a result,the loss and heat can be reduced,and improve the comprehensive performance of the PWM converter.Thirdly,based on the MATLAB/Simulink simulation platform and the actual parameters of the experiment system,the simulation models based on the voltage-oriented vector control and model predictive control are respectively established.At the same time,a comprehensive comparison of the performance of the two control strategies is taken by the simulation.Finally,the experiment platform of the three-phase voltage source PWM converter is built,and the control program of the two control strategies is coded.The vector control and MPC strategy are respectively used to suppress the harmonic current in the grid side.The dynamic performance,static performance and switching frequency characteristics are compared.The correctness and feasibility of the proposed control strategy is verified by the experiments.In this paper,the MPC method is utilized to achieve the suppression of the harmonic current of the grid-connected PWM converter.Compared with the traditional vector control,the control strategy proposed in this paper has a comparable control effect.Meanwhile,the switching frequency and losses of the power devices can be reduced effectively,which significantly improve the efficiency of the PWM converter.