Research on the Control Strategy of Photovoltaic Storage Microgrid and Off-Grid

With the increasing severity of global warming and energy depletion, the photovoltaic storage microgrid system has gradually become a research hotspot at home and abroad. Photovoltaic storage microgrids can supply the power of photovoltaic distributed energy resources to AC loads or connect excess power to the public grid. However, the connection of large-scale distributed power generation into the large power grid will lead to the reduction of system inertia, and the system will be unstable when the load fluctuates, which will affect the safe operation of the power grid. Virtual Synchronous Generator (VSG) has a certain virtual inertia due to the characteristics of simulated synchronous generators, and has certain anti-interference ability compared with traditional grid-connected control strategies. Therefore, it is of great significance to study the control strategy of VSG grid-connected inverter. In order to solve the problems of current impulse and voltage oscillation during the grid connection of VSG inverter, this paper adopts a phase-locked loop pre-synchronous control strategy, which aims to reduce the impact of inverter grid connection on the grid and maintain the stable operation of the system, Establish a mathematical model of photovoltaic and energy storage to analyze the influence of light intensity and temperature on the output of photovoltaic cells; Due to the uncertainty and randomness of photovoltaic power generation, the Maximum Power Point Tracking (MPPT) algorithm is used to make the photovoltaic output always be at the maximum power point. The influence of charging or discharging of the energy storage system on the DC bus voltage when the photovoltaic output changes, and then the constant voltage control strategy of the DC bus is proposed.