Research On Power Angel Strategy Of Virtual Synchronous Generator Based On Flexible Inertia Adjustment

With the increasing demand for energy,the popularization and application of distributed photovoltaic(DPV)has become an important solution to solve the energy crisis.However,the randomness of DPV output and the inherent characteristics of grid connected equipment lead to the lack of inertia support.The control strategy of virtual synchronous generator(VSG)is designed to improve the stability of DPV grid connected operation.In order to improve the transient power angle stability of VSG,an inertia adaptive control strategy based on power angle is proposed by using the flexible and adjustable control parameters of VSG.Firstly,the working principle of SG unit is analyzed,and the equivalent SG mathematical model of grid connected inverter is constructed which proved that the DPV connected by inverter has the ability to simulate the operation characteristics of SG.Based on the simplified model of SG unit and its control objectives,the overall control strategy of VSG considering the power coupling effect is built.The difference of control effect caused by different following frequency of power frequency controller is analyzed in detail and the realization of excitation controller in parallel and off grid operation provides a reliable theoretical basis for the subsequent optimization strategy.Secondly,the adaptive virtual inertia control strategy is proposed to optimize the power angle and the transient angle stability is analyzed.The definition of DPV virtual power angle is analyzed.Based on the analysis method of SG unit power angle stability,the power angle characteristic curve of DPV under normal operation and current output saturation is established.The transient power angle expression of DPV controlled by VSG is calculated,and the influencing factors of power angle variation are analyzed.According to the power angle characteristic curve,the optimization scheme is obtained.The virtual inertia is selected as the control parameter to improve the stability of power angle,and the value scheme of power angle virtual inertia is proposed,and the parameters of the scheme are optimized.Finally,the DPV simulation model based on VSG control is established to verify the effectiveness of the control strategy proposed in different operation states of DPV,and analyze the control effect of different adaptive inertia value schemes,which provides guidance for the control scheme under different operating conditions of the system.