Research On VSG Control Based On LCL Grid-connected Inverter

In order to cope with the increasingly harsh natural environment and the rapid consumption of non-renewable energy,research on renewable energy power generation technology has become a solution.However,with the continuous improvement of the penetration rate of renewable energy power generation in the existing power system,the power grid began to show the characteristics of low damping and low inertia,which affected the stability of the power system.For this reason,the control strategy of virtual synchronous generator based on LCL grid-connected inverter is proposed in this paper.This paper introduces and analyzes the resonant peak of LCL filter.A single current loop suppression scheme on the side of inverter is proposed,which can effectively suppress the resonant peak.Through the analysis of double-loop control,it can be seen that the amplitude and frequency characteristics of the low-frequency section of the voltage loop are negative,which can effectively suppress the low-order harmonics brought to the junction current when the voltage quality of the network side is poor.The parameters of LCL filter were designed and verified,and the PI parameters of current loop and voltage loop were adjusted and simulated.By discussing the principle of virtual synchronous generator and different control methods,the model and specific control parameters of virtual synchronous generator are determined.An improved adaptive control strategy of the moment of inertia is proposed in view of the adverse effect of the three-phase inverter in the grid-connected state on the inverter when it is subjected to too large impact.This plan through the analysis of the small signal model of virtual synchronous generator parameters adjusting range,according to the virtual synchronous generator power Angle curve to determine the parameter adaptive dynamic adjustment process,at the same time to make the inverter can be smooth and off-grid pre synchronization control strategy is put forward.Simulation verification is carried out for all kinds of theoretical analysis.Finally,the experimental platform of three phase grid-connected inverter is designed and constructed.Verified by debugging,this paper adopted the inverter side of the single current loop scheme can effectively inhibit LCL resonance peak,the proposed control strategy of synchronous generator are simulated by the virtual synchronous generator external characteristic,moment of inertia of improved adaptive control strategy can get good dynamic response when power change.