Research On Energy Storage Emergency Active And Reactive Power Control Strategy Based On Virtual Synchronous Generator

As the proportion of power electronic devices in the power system gradually increases.voltage source converters(VSCs)using conventional grid-following control(GFL)cannot actively provide inertia and damping for the power grid,posing serious challenges to the safety and stability of the power grid.In order to solve this problem,scholars have proposed the concept of Virtual Synchronous Generator(VSG)control,which adjusts the voltage and frequency of the power grid by simulating the rotor motion equation,primary frequency regulation control,and excitation regulator of the synchronous generator.However,due to its operational characteristics similar to synchronous generators,VSG also face stability issues.In addition,due to the limitations of power electronic devices,VSG also faces overcurrent issues.Therefore,based on the mathematical model of VSG,this article proposes a design criterion for inertia and damping parameters and two improved control strategies,which improve the reliability of VSG operation in power systems and the transient voltage stability of multi-feed DC systems.The main content of this article is as follows:Firstly,a mathematical model was established for analyzing VSG.Based on the mathematical model of VSG,an analytical expression for the variation of VSG output power over time is derived when the reference value of VSG active power and the grid frequency are disturbed.Based on the derived expression,the influence of inertia and damping parameters on the dynamic characteristics of VSG output power was analyzed.To ensure the safe and stable operation of VSG,a design criterion for inertia damping parameters is proposed by comprehensively considering the limit requirements of the state of charge of energy storage,the maximum active power limit requirements of VSG,and the system stability limit requirements,laying the foundation for the improvement of VSG control strategy.Secondly,in order to ensure the safe and stable operation of VSG during large disturbances and improve the power supply capacity during voltage dips,an emergency control strategy considering VSG current limitation and transient angle stability is proposed based on the large signal mathematical models of VSG in normal and fault states.This method divides the operating area of VSG into non-emergency area and emergency area.If the operating point of VSG is located in the non-emergency area after a fault,only the active power reference value of VSG is changed to avoid current exceeding the limit and transient power angle instability;If the operating point of VSG is located in the emergency area,changing the VSG active power reference value and inputting virtual impedance can avoid current exceeding the limit and transient power angle instability.Finally,in the multi-feed DC system,the effects of three traditional reactive power control strategies of VSG on the transient voltage of converter station are compared and analyzed.On the basis of using constant voltage control in the VSG reactive power loop,considering the output current limitation of VSG and the improvement of system transient voltage stability,an improved reactive power control strategy is proposed,which optimizes the control effect of VSG.