Research On Control Strategy Of High Frequency Link Matrix Converter System Based On Optimal Current Stress

Facing the increasingly severe problem of resource shortage,energy storage technology has begun to play an important role,and electric vehicles as mobile distributed energy storage,have ushered in a period of rapid development.V2 G technology to realize vehicle network interaction has become a research hotspot of scholars at home and abroad.In order to ensure safe and stable energy interaction,bidirectional battery chargers has very important practical significance and application value.High frequency link matrix converter(HFLMC)is a promising choice for connecting DC and AC systems.It has the characteristics of bidirectional power flow,electrical isolation,sinusoidal current on the grid side,adjustable power factor,and high power density.Therefore,this paper mainly studies the system control strategy of HFLMC,from the perspective of optimizing current stress and improving grid-connected power quality,so as to better realize the high-performance energy transmission between electric vehicles and the power grid.Firstly,the topological structure and working principle of HFLMC are introduced.Aiming at the low reliability problems of traditional bipolar current space vector modulation strategy(BC-SVM)such as commutation failure,the modulation principle of nine-stage B-C-SVM strategy and the synthesis sequence of the vector are described,and the expression of duty cycle is derived.At the same time,according to the principle of coordinated phase shift,the HFLMC modulation strategy is designed based on nine-stage B-C-SVM which is coordinated with phase shift modulation.On this basis,the variation trend of peak value of inductance current under different working conditions is analyzed for the traditional inter-bridge phase shift and in-bridge phase shift modulation methods,and the modulation strategy of in-bridge phase shift has less inductance current stress in a certain voltage range.The simulation results demonstrate the effectiveness of the designed nine-stage B-C-SVM strategy with bridge internal phase shift in reducing current stress and improving system reliability.Secondly,according to the necessary conditions of safe operation of matrix converter,the implementation process and commutation sequence of two-step commutation strategy are described and designed.Compared with the four-step commutation strategy,the two-step commutation strategy has fewer switching times and shorter commutation time,so as to ensure sufficient driving signal to complete the commutation,improve the reliability of commutation.And then to solve the problem of system oscillation caused by LC filter on the grid side,an active damping control strategy is designed.By injecting the damping signal into the output reference current,the harmonic content at the resonant point and high frequency can be effectively suppressed,and the current quality on the grid side can be improved.In addition,the power transmission and the power factor Angle on the grid side can be controlled by controlling the current on the grid side and the current on the DC side.It has good dynamic and steady performance.Finally,the experimental prototype of HFLMC was built based on STM32F407ZGT6+EPM570T100C5N as the core controller.The modulation,commutation and grid-connection control strategies were verified experimentally.The results show that the designed system control strategy is effective and the theoretical analysis is correct.