Control And Stability Analysis Of Inverter Interfaced Distributed Generator Based On Virtual Synchronous Generator

The inverter interfaced distributed generator(IIDG)is the main form of the grid-connected distributed power supply.Its control is precise,and its response is fast.However,due to the lack of inertia,its dynamic regulation ability is insufficient in the face of external frequency disturbance.With the gradual increase in the penetration rate of distributed generation,the influence of this kind of deficiency on the stable operation of the distribution network becomes more and more serious when the system is disturbed.To solve this problem,this paper analyzes the dynamic characteristics of grid connected VSG-IIDG.This paper puts forward a dual-adaptive inertia frequency control strategy,which can adjust the virtual inertia adaptively,improve the dynamic regulation characteristics and operation stability of the inverter distributed power supply when it is disturbed.At the same time,the stability mechanism of grid-connect VSG-IIDG is analyzed.Combining the theory of Popov stability and Lyapunov theory,this paper constructs the Lyapunov function,establishes the inequality of the VSG stability region,which can reflect the disturbance tolerance of the system and is an essential basis for optimizing control parameters.Finally,considering the influence of the current limiting element on the stability of VSG,this paper analyzes the instability type of VSG when the current limit unit is saturated by using the equivalent area rule.The analysis shows: The fixed virtual inertia introduces trades-off between the frequency regulation and power regulation,and the overshoot and responding speed.The proposed dual-adaptivity inertia control strategy can address the problem.The large-signal stability domain of a VSG increases with light load,short line and small virtual inertia.The current saturation of the current limit unit makes the VSG more likely to become unstable.However,instability is not a necessary result because the system may recuperate if desaturation happens.