Abstract
Grid-connected group-series photovoltaic cluster inverter system will cause resonance, which will adversely affect the system. To suppress grid-connected resonance, the mathematical model, resonance mechanism and resonance characteristics of the cluster inverters are analyzed, and a global resonance suppression strategy based on hybrid damping is proposed. In the current loop of the inverter, capacitive current feedback and parallel voltage proportional feed-forward are introduced as active dampers to reduce the harmonics of the parallel current. On this basis, RLC type second-order resonance suppression circuit is added as passive damping to suppress system resonance, so that the output current of the inverters can meet the grid-connected conditions when the cluster is connected to the grid. The simulation and experimental results show that the total harmonic distortion of the grid-connected current decreases from 10.54% to 1.97% after three series photovoltaic cluster inverters adopt this strategy, which effectively suppresses the grid-connected resonance.