Control Of Frequency And Voltage Of Micro- Grid Based On Virtual Synchronous Generator

The penetration of distributed power source is increasing in recent years,and its impact on main gird catches more and more attention.Because that distributed power source lacks of moment of inertia as the synchronous generator,the frequency and voltage stability of micro-grid is becoming a crucial problem.Virtual Synchronous Generator(VSG)technology provides an ideal solution for the above problem.The basic idea of VSG method is to mimic the machinery characteristic and voltage characteristic of synchronous generator by using energy storage system and proper control algorithm,which provides a virtual “inertia” and “damping” to the inverter,thus gives the inverter frequency and voltage modulation characteristics similar to the synchronous generator.Based on traditional VSG algorithm,a modification of damping coefficient is proposed to achieve self-adapted regulation according to the variation of loads,the ability of restraining frequency fluctuation is improved while the transient process is not significantly increased,and its effectiveness of frequency and voltage control is verified by simulation.To solve the problem of weak robustness of PI control,a predictive control method is introduced.A state observer is designed to estimate disturbances,a direct power predictive control theory was proposed,and the final direct power predictive control based on VSG module is built.The effectiveness of proposed model is verified by simulation,and the results show that robustness of micro-grid system is improved under the condition of model parameter perturbation by conducting proposed algorithm.