For the parallel system of two grid-connected inverters, the effect of each inverter on the grid-connected current is analyzed by using the superposition theorem, and the grid-connected current is decomposed. Besides, the mechanism of resonance generated by the interaction current and the common current is studied, and the resonance frequency point characteristics of parallel systems with multiple grid-connected inverters of the same and different capacities are compared and analyzed. Moreover, based on the resonant frequency point generated by the interactive current in the parallel system, a digital notch filter is designed and introduced into the traditional capacitive current feedback active damping control to realize the static-free control of the fundamental signal, which meets grid-connected requirements of such systems. Furthermore, the models of parallel systems of inverters with the same and different capacities are built. The simulation results verify the correctness and effectiveness of the proposed strategy.
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