Abstract：For the photovoltaic grid-connected inverter, the z-domain model under digital control is established firstly. Then through the frequency characteristics of the z-domain open-loop transfer function, the conditions of -180° crossing in different ranges of resonance angle frequency are determined. Meanwhile, combined with Nyquist criterion, the stability conditions of grid-connected inverter in different ranges of resonance angle frequency are given. Accordingly, the optimized design idea and method of photovoltaic grid-connected inverter are put forward, which can resist the wide range changes of grid equivalent impedance. Finally, the theoretical analysis is verified by the simulation and experiment.
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2018, Vol. 33 
