Stability Analysis Of Photovoltaic And Energy Storage Microgrid System Based On Port Impedance Characteristics

This article aims to use microgrids in remote areas as the research background,using renewable energy sources such as solar energy to replace traditional power sources,and combining energy storage devices for power supply.In the microgrid system in this article,the photovoltaic link uses a current control inverter,and the energy storage link uses a droop control inverter.Combining the photovoltaic link and the energy storage link can achieve complementary solar storage,peak shaving and valley filling.For the parallel system of droop control inverter and current control inverter,the coupling and interaction between the inverters will affect the anti-disturbance performance of the system,thereby affecting the stability of the system.For the research on the stability of the parallel system,this topic chooses the dq axis linear modeling method in the impedance analysis method.First,model the impedance of the inverter.For the droop control inverter,this paper establishes the inverter output impedance model from the perspectives of open loop,current inner loop,voltage and current double loop,and droop control outer loop.Open loop,current loop and current control inverter are established.The impedance model of the phase-locked loop.Because the droop loop of the droop control inverter will cause the system frequency to change,and the phase-locked loop will introduce the frequency change into the current control inverter.For the full inverter system including droop control inverter and current control inverter,an impedance model with frequency state variables is established to analyze the stability of the system.Finally,the impedance model of the inverter was tested and compared with the theoretical model to verify the accuracy of the impedance model.Secondly,the stability of the entire inverter parallel system is analyzed.According to the model,the control block diagrams of two droop control inverter parallel systems and two droop control inverters in parallel with multiple current control inverter systems are established in turn and a "source-load division" of the system has been established.Applying the established output impedance models to draw back ratio matrix Nyquist diagrams.According to the Generalized Nyquist Criterion(GNC),the influence of the droop coefficient on the stability of the droop control inverter parallel system and the effect of increased photovoltaic capacity on system stability in a droop control inverter in parallel with multiple current control inverter systems are analyzed.Then the simulation verification is carried out by building a MATLAB/Simulink simulation model corresponding to the working conditions.Finally,a hardware-in-the-loop test platform based on RTDS was built,and hardware-in-the-loop principles and system design were introduced.In the meantime,the potential stability problems of the multi-inverter parallel system are verified.