Linear over-modulation strategy for current control in photovoltaic inverter

Photovoltaic (PV) inverters autonomously adjust their DC-link voltages to maximize power generation. Around sunrise or sunset, a PV inverter may operate at much lower DC-link voltage than the nominal level due to the low irradiance. The inverter would be under over-modulation if the DC-link voltage is relatively low to the grid voltage at the point of common coupling. In this paper, a series of implementation schemes are proposed to keep the current regulation under over-modulation. After the proposed method is detailed, its fundamental operations are verified by a small-scale prototype inverter and further evaluated by the 250 kW PV inverter installed at a proving ground.