Research On Control Strategy Of Isolated AC-DC Matrix Converter

Due to bidirectional power flow,sinusoidal input current,adjustable power factor,less-power-conversion stages,avoidable large DC-link capacitors and high power density,the isolated AC-DC matrix converter(IAMC)is employed by energy storage,wind power generation,DC microgrids and V2 G.The three-phase to single-phase matrix converter(3-1MC)requires an LC filter to remove the high-order harmonics of current in the AC side.However,the LC filter decreases the AC power factor.Then,we improve the control strategy to promote the performance of the IAMC with LC filter.The main works and contributions are given as follows:First,we describe the modulation strategy which includes the bipolar current space vector modulation in 3-1MC and the phase-shifting control in H-bridge converter.According to the equivalent circuit of the AC side filter,we build the AC side mathematical models of three coordinate systems.On basis of this mathematical model,we obtain the relationship between the AC side power factor angle and the input power factor angle,and quantitatively analyze the influence of the main circuit parameters in AC side power factor.Second,a hybrid control strategy with virtual capacitance and virtual resistance is proposed to decrease the AC side power factor and suppress the resonance spikes.Under different load conditions,the virtual capacitor current compensate the phase difference between the grid-side voltage and current,so that IAMC can work under grid-side unit power factor or maximum achievable power factor(MAPF).Active damping control with virtual resistance increase the damping ratio of the LC filter and suppress resonance spikes.Besides,an input shaping strategy is introduced to reduce the grid-side current oscillation during the transient process.The closed-loop IAMC simulation model is built by MATLAB and the results validity the superiority of the proposed control.Finally,an experimental platform is built to verify the effectiveness of the proposed control further.We select suit parameters for hardware circuit related components and develop software programs for DSP and CPLD microchip.The experimental results are consistent with the theoretical analysis and verify the correctness of the proposed control.