Research On Control Strategy Of Grid Connected Inverter In Microgrid Based On FPGA For Virtual Synchronous Generator

The grid-connected inverter is an important device for connecting the microgrid and the power grid.The control strategy and the quality of the control system hardware are two key factors that affect the performance of the inverter and the stability of the system.Traditional inverters based on vector control strategies are decoupled from power control and frequency.After a large number of such inverters are connected to the grid,the damping of the system will be weakened,thus jeopardizing the stable operation of the power system.Aiming at the problems existing in traditional inverters,this paper studies the control strategy of virtual synchronous generators to solve the inertia and damping problems of inverters.An inverter hardware design based on FPGA(Field-Programmable Gate Array)is proposed to improve the real-time and control performance of the system.Firstly,the principle of virtual synchronous generator control strategy is deeply studied.Based on the control theory of synchronous generator,the virtual governor and virtual excitation regulator are designed.Compared with the traditional control strategy,the control strategy not only has many advantages,but also makes the external performance of the inverter exhibit similar inertia and damping effects of the synchronous generator,and improves the ability of the power grid to receive distributed power.Then the hardware topology of the inverter is analyzed in detail,and the hardware circuit design of the acquisition circuit,the drive circuit and the protection circuit is completed around the FPGA.And under limited resources,using FPGA to complete the program of signal acquisition calculation,pulse width modulation and virtual synchronous generator control algorithm,provides a feasible technical solution for inverter hardware design.Finally,the experiment is compared with the traditional droop control strategy on the FPGA-based virtual synchronous generator platform.The experimental research is carried out under the conditions of island voltage step,load switching and grid-connected off-grid.The experimental results show that the inverter of the virtual synchronous generator based on FPGA not only has the similar external characteristics of synchronous generator,but also has good control performance and dynamic response capability,which improves the real-time performance and stability of the system.