Research On Control Strategy Of Bidirectional DC/AC Converter In Hybrid Microgrid

The bidirectional DC/AC converter control strategy studied in this paper is derived from the research of Sino-British cooperative zero-carbon building hybrid power supply system.In this research project,the AC/DC hybrid power supply system is adopted,the rated voltage of the DC bus is 400 V,and the AC bus voltage is AC220 V for the home user.Compared with the traditional distribution network,the AC/DC hybrid microgrid interacts with multiple micro-sources in the micro-grid,and at the same time has low inertia characteristics,which is more prone to oscillation instability.The bidirectional DC/AC converter is an important device for connecting the AC sub-microgrid and the DC sub-microgrid.Its control strategy is an important factor affecting the stability of the AC-DC hybrid microgrid.A good control strategy for the AC/DC hybrid microgrid is stable.It is of great significance.This paper analyzes the topology and basic working principle of the bidirectional DC/AC converter,and determines the topology of the full bridge with LC filter.In the rectification mode,the bidirectional DC/AC converter can be equivalent to the PFC circuit.Due to the high requirements on the inductance and DC side capacitance in the PFC circuit,the inductance and DC side capacitance parameters are designed according to the requirements of the PFC circuit,and then the inductance is used.Based on the parameters,the size of the filter capacitor required by the LC filter is calculated,and the rationality of the parameter is verified by the Bode diagram.In this paper,the working mode of the bidirectional DC/AC converter is analyzed.In order to reduce the switching frequency of the bidirectional DC/AC converter operating mode,a three-stage droop control is adopted.In order to conveniently calculate the reference value of the bidirectional DC/AC converter transmission power,the method of unitizing the bus voltage sampling value is adopted to make the AC side and the DC side uniform,and the AC and DC sides can adopt the same droop coefficient,which simplifies calculation.The AC/DC hybrid microgrid is more susceptible to instability than the larger grid.To improve the robustness of the microgrid system,a fuzzy PI controller is introduced and the bidirectional DC/AC converter control strategy is designed based on this.At the end of the paper,according to the design parameters,the main circuit device of the bidirectional DC/AC converter is selected,and the corresponding control circuit is designed.In order to verify the feasibility of the control strategy used in this paper,a simulation model was built on Matlab/simulink platform.Compared with the control system using traditional PI controller,the fuzzy PI-based bidirectional DC/AC converter control strategy was used in DC.Hybrid microgrid systems have better robustness in the case of side power abrupt changes.