Research On Inverter Control Strategy Based On Virtual Synchronous Generator

With the increasing penetration of new energy,the moment of inertia and damping of power system decrease,which in turn threatens the frequency stability of the system.In the current inverter control strategy,virtual synchronous generator(VSG),control is the preferred method to solve this problem.In this paper,starting with the basic principle of virtual synchronous generator the structure diagram of control system is obtained.Then,the transfer function between electromagnetic power and mechanical power is derived,and the relationship between natural oscillation angular frequency and damping ratio and moment of inertia and damping,and the influence of moment of inertia and damping on frequency stability are obtained.By analyzing the power angle characteristic curve and swing curve,the adaptive control strategy of moment of inertia and damping is obtained when the system is subjected to small disturbance.Based on the above analysis,this paper puts forward the technological innovation:an adaptive control strategy of virtual synchronous generator based on improved multi-objective particle swarm optimization(improved multi-objective PSO)algorithm with physical process.This method gives attention to both static and dynamic performance of the system,and when faced with small disturbance,it can adjust the inertia and damping in a planned way and reduce the search range of inertia,thus reducing the frequency deviation and speeding up the end of the transition process.Although VSG can enhance the frequency stability of the system,other parameters need to be controlled by other parts.Double closed-loop control system can control the output voltage or current of inverter and reduce harmonic distortion rate.However,there are some problems in the PI parameter tuning of double closed-loop control,such as inapplicability,complex tuning process and heavy workload.Therefore,a new PI parameter tuning method is proposed in this paper.Based on the traditional typical system configuration method,the PI parameter tuning process of the current inner loop is improved,which solves the problem that the original method is not applicable when the cut-off frequency of the current loop is less than 3 times the resonant angular frequency of the LC filter.And through Matlab drawing to verify the rationality of the control method,and in the Simulink simulation model to simulate 5 groups of PI parameters.The phenomenon of integral saturation is analyzed theoretically,and the solutions are put forward.Finally,the virtual impedance control parameters are designed,and the simulink simulation models in isolated island mode and grid-connected mode are obtained.Furthermore,the validity of the adaptive control strategy of virtual synchronous generator based on improved multi-objective particle swarm optimization algorithm is verified by Simulink simulation,and compared with the other two methods.