Stability Strategy of Parallel Grid-connected Inverter System Based on Active Impedance Reconstruction Device

To improve the stability among distributed grid-connected parallel inverters and the ability to resist the interference from power grid, firstly, a generalized impedance model was proposed to characterize the stability of grid-connected multi parallel inverter system. Secondly, an active impedance reconfiguration strategy was put forward to increase the output impedance of the inverter. Thirdly, the complicated transfer function matrix was decomposed into output impedance matrix of the inverter and the impedance matrix of power grid by the generalized impedance model, and the higher inverter output impedance was derived theoretically to enhance the stability of the inverter system and its ability to resist the interference from power grid. To verify the correctness of the proposed method, a parallel inverter system composed by sixteen single-phase inverters was utilized to the simulation, and two parallel grid-connected inverter platforms were constructed for the experiment. Both results from simulation and experiments show that using the proposed method the stability of parallel grid-connected inverter system can be effectively enhanced.