Research On Inverter Control Strategy Of Microgrid System Based On Virtual Synchronous Generator

With the gradual scale and widening of new energy power generation,the penetration of distributed energy systems into the grid has been intensified.Due to the random,intermittent,and unpredictable characteristics of new energy power generation,and the low inertia and underdamping characteristics of traditional power electronic inverters,which will lead to a decrease in the stable operation and control capabilities of the power system,and pose new challenges to the output quality of the power grid.By introducing VSG technology into the power electronic inverter,the inverter can simulate the inertia and damping characteristics of SG,to improve the adjustment ability of the grid system when large-scale distributed energy is connected to the grid.Based on this background,this article further discusses the research on the stability control strategy of the inverter of the microgrid system based on the VSG on the basis of previous work.The main contents include the following:Firstly,the structure and characteristics of the VSG system are analyzed.According to the different mathematical models of VSG that have been proposed by related researchers,The state space equations based on angle,frequency and torque(power)are determined,By comparing and analyzing two commonly used VSG models.At the same time,the space model of the battery energy storage system is determined.Secondly,based on the microgrid system of the VSG,a projection adaptive terminal sliding mode backstepping control strategy is proposed to achieve the purpose of the inverter participating in the system inertia adjustment and improve the stability of the system.Combining the projection adaptive control in the backstepping control,the system parameters that are difficult to be directly obtained in the VSG can be automatically tracked by the system in an adaptive manner to obtain the most appropriate value.By applying terminal sliding mode control in the state equation based on system angle,frequency and torque error,the robustness of system can be improved.The final simulation results show that the controller can realize the stability adjustment of the system and achieve better control goals.Then,considering that the terminal sliding mode control method requires high switching frequency in practical applications,which is likely to cause severe chattering of the system,a adaptive projection operator strategy based on prescribed performance function is proposed.By introducing the prescribed performance function to perform error conversion on the corresponding sliding mode surface,the bounded control of the sliding mode surface can be realized and the dynamic response capability of the system can be improved.The simulation results show that the prescribed performance control can control the corresponding sliding mode surface in any small area and meet the corresponding convergence speed.Finally,considering that the application of distributed energy is becoming more and more widespread,electric vehicles are becoming more and more popular.When the power supply of the community grid fails,a certain number of electric vehicles can serve as short-term power supply equipment.Since the electric energy state between electric vehicles cannot be guaranteed to be consistent in real time,in order to ensure the power distribution and operational stability of the system,a VSG-based electric vehicles So C consistency distributed collaborative adaptive command filtering backstepping control strategy is adopted.Due to the adjustment of some sampling parameters,the mathematical model of the system is rederived;the information interaction algorithm based on multi-agents is used to realize the power distribution strategy due to the inconsistent energy storage state of electric vehicles;in order to realize the tracking control of the system angle,frequency and power deviation and the adjustment of the corresponding control parameters,a projection adaptive command filter sliding mode control strategy is adopted for the state equation of the VSG.The final simulation results show that the control strategy can better achieve the control goal on the basis of ensuring the stability of the system.