Transient Control Research Of Virtual Synchronous Generator Based On Power Angle Stability Optimization Strategy

In view of the worsening of the current energy crisis,the state vigorously develops new energy generation technology.Distributed generation technology has developed rapidly.However,compared with synchronous generators system,the stability of distributed power system needs to be supported by the power grid,but it cannot provide strong support for the power grid.Hence,Virtual Synchronous Generator(VSG)technology emerged,combining the flexibility of power electronics and synchronous generator operation characteristics,can achieve the friendly grid connection of distributed power supply.However,when it is faced with complex transient conditions,its stability will face severe challenges.Therefore,in order to further improve the study of VSG,this paper mainly studies the transient control of VSG under fault interference and small signal interference,and the main contents are as follows:Firstly,the control mechanism of VSG is briefly described and its mathematical model is established.By simulating the operating characteristics of synchronous generator,the active frequency loop and reactive voltage loop are designed to increase the inertia and damping of the system.Finally,the transient response of VSG under fault interference and small signal interference is studied,and the running performance of VSG under transient condition is simulated by Matlab/Simulink software to verify the working characteristics of VSG.Secondly,in view of the voltage drop and current impact that VSG faces under fault conditions,a power angle control based VSG fault crossing control strategy is proposed.The causes of power angle instability and current shock under VSG control are analyzed.The active power command is used in the active power loop to adjust and control the steady-state power angle term of the unbalanced power of VSG under the fault,and then the dynamic power angle term of the unbalanced power is compensated by the power compensation control.The reactive voltage command control is combined with the current loop and virtual impedance to effectively suppress the current shock,achieve overcurrent protection,and provide reactive power support to compensate the system.Then,the model is optimized and the adaptive control strategy of moment of inertia and damping coefficient is proposed in view of the given active power mutation and network frequency fluctuation faced by VSG under small signal interference.However,the contradiction between moment of inertia,damping coefficient and frequency response speed still exists in VSG.By exploring the relationship between virtual impedance and frequency during the transient state,VSG transient control strategy based on parameter adaptive is proposed.The frequency fluctuation of VSG can be suppressed during the transient state and the frequency response speed of the system can be improved.Finally,an experimental platform based on VSG control algorithm is built to test VSG under resistive load,load mutation and given active power mutation,it is used to verify the correctness and effectiveness of VSG control algorithm.