Research On Control System Of Three-phase Isolated AC/DC Converter

Isolated AC / DC converter has many advantages such as power conversion,high efficiency,small size,high power density and being able to act as load or power supply according to control needs.Because the current stress of the topology affects the performance of the system,a control strategy to reduce the current stress is proposed to improve the reliability of the system and reduce the state loss.Firstly,this paper introduces the circuit structure of isolated AC / DC converter in detail,then analyzes its bipolar current spatial vector modulation strategy and several control strategies,the switching states of 3-1 matrix converter and H-bridge is also analyzed,and the synchronous control method between the matrix converter and h-bridge is given.Commutation strategy of matrix converter and soft switching condition is discussed.Then conventional fixed shift phase angle direct current control,fixed modulation coefficient direct current control and fixed modulation coefficient model predictive control are analyzed in this paper.Because the conventional control methods use constant shift phase angle or constant modulation coefficient,it cannot obtain minimum peak current of inductor.A control algorithm based on coordinated control of modulation coefficient and shift phase angle with minimum peak current is deduced to reduce the current stress of isolated AC / DC converters,then reduce the channel loss,and increase efficiency of steady performance of converter.Based on the minimum algorithm,this paper proposed the PI control method with minimum peak value of inductor current and the model predictive control method with minimum peak value of inductor current.In order to prove that the proposed control strategy to reduce the current stress can achieve the theoretical goal,the MATLAB platform is used to build simulation and comparative verification,the results show that the current stress is lower than the constant modulation coefficient PI and model prediction control strategy.Finally,the experimental platform is constructed and the control strategy is proved to have the advantages of reducing the current stress and fast dynamic performance by comparing the control with the control with the model.