Research On Control Strategy Of Bidirectional Isolated AC-DC Matrix Converter

Bidirectional isolated AC-DC matrix converter(IAMC)is a topology of a two-stage power conversion structure with a small number of conversion stages,high transmission efficiency,and adjustable input current and power factor on the sinusoidal network,No need for large-capacity energy storage elements,energy can flow in both directions and a series of advantages.As a result,the IAMC has received widespread attention in areas such as offshore power generation,battery energy storage systems,electric vehicle charging,and DC microgrids.Based on the two-level topology of IAMC,this paper analyzes its traditional control method and proposes a new control method.This article first explains the IAMC topology and development process,and introduces the existing modulation strategies and control strategies of the IAMC.Then,the mathematical models of three-phase stationary abc,two-phase stationary ??,and two-phase rotating dq in the three coordinate systems of the IAMC grid are established.This article describes in detail the coordinated modulation strategy adopted by the IAMC.This modulation strategy can achieve IAMC network-side power factor adjustment and network-side input current sine.Then,in this paper,the power transmission relation at both ends of the IAMC under the coordinated modulation strategy is derived.Based on this,the traditional grid-side current indirect control and grid-side current direct control strategies are introduced and their advantages and disadvantages are analyzed.These two control strategies only directly control the DC-side or grid-side currents,and the currents on both sides are directly controlled.Direct control cannot be performed at the same time,which affects the control performance of the system.In view of this,this paper proposes a new IAMC control strategy.This method decomposes the control tasks.The H-bridge converter takes the control of the output DC current and the active power of the system as its main tasks.The active power of the IAMC is controlled by phase-shifted angle closed-loop control.Perform direct control to achieve high-performance control of DC-side current and voltage;while the three-phase-single-phase matrix converter aims to achieve high-precision control of the power factor on the grid side,and directly control the power factor on the grid side;the proposed control The strategy can guarantee the good performance of the control system.The above three control strategies are all based on PI controllers,which have the problem of slow dynamic response.To this end,the above control strategies are improved and a direct current control strategy under fast dynamic response is proposed.The IAMC network side is adopted under this control strategy.For direct power control,a fast dynamic method is used on the DC side.The four control strategies are compared and simulated under MATLAB simulation platform,and the correctness and superiority of the proposed control strategy are obtained.Finally,in order to further verify the correctness of the proposed control strategy,a closed-loop experimental platform for IAMC was set up,and the hardware components and software programs required for the experiment were designed.According to the experimental waveform results,the correctness and feasibility of the direct current control strategy proposed in this paper can be obtained.