Unified Compensation Strategy For AC/DC Bus Voltage Of Hybrid Microgrid Based On Interface Converter

AC/DC hybrid microgrid has become the future development trend of microgrid because it can effectively combine the advantages of AC microgrid and DC microgrid.As a bridge connecting AC and DC buses in hybrid microgrid,bi-directional interface converter controls the energy exchange between AC and DC subnets and plays a decisive role in maintaining the stable operation of AC/DC hybrid microgrid.Aiming at the instantaneous power ripple of bi-directional interface converter caused by unbalanced AC voltage in hybrid microgrid and the double frequency ripple of DC voltage caused by single-phase AC load merging into DC microgrid,a bi-directional interface converter with unified compensation of AC and DC bus voltage and its control strategy are proposed.By introducing a step-down fluctuating power compensation circuit into the DC side of bi-directional interface converter to absorb the double frequency fluctuating power on both sides of AC and DC,and using the power margin of interface converter to compensate the AC unbalanced voltage,the unified management of voltage quality on both sides of AC and DC bus interface converter is realized.Firstly,according to the second harmonic power transmission characteristics of AC/DC hybrid microgrid under unbalanced conditions,a unified AC/DC bus voltage compensation strategy based on interface converter is designed.When the interface converter uses its own power margin to compensate the AC unbalanced voltage,it can absorb the fluctuating power on both sides of AC and DC by controlling the compensation circuit,so as to stabilize the DC pulsating voltage and achieve the purpose of unified compensation of AC and DC bus voltage.Secondly,aiming at the proposed unified compensation strategy of AC/DC bus voltage of the interface converter,the frequency domain mathematical model of the interface converter system is established,the stability of the closed-loop control system is analyzed by Bode diagram,the key control parameters of the system are designed according to the stability analysis results,and the capacitance of the compensation circuit is quantitatively analyzed.Thirdly,based on the MATLAB/Simulink simulation platform,the simulation model of AC/DC hybrid microgrid and interface converter with compensation circuit is built.Based on the simulation model,a series of steady-state simulation and transient simulation are carried out.By comparing the simulation results,it is proved that the proposed control strategy can realize the unified compensation of AC/DC bus voltage compared with the traditional bidirectional interface converter,It has good steady-state performance and dynamic response.Finally,based on d SPACE 1006 hardware in the loop simulation platform,the experimental circuit of the interface converter system is built.By comparing the simulation and experimental waveforms,the effectiveness of the proposed unified compensation strategy for AC and DC bus voltage of the interface converter is proved again,as well as the superiority over the traditional control method.