Control method of photovoltaic grid-connected inverter under three-phase voltage unbalanced dips

To meet the requirements to low voltage ride-through (LVRT) capability of photovoltaic grid-connected inverter under three-phase voltage unbalanced dips, this paper proposes a current positive sequence synchronous rotational coordinate independent control method. In the strategy, the positive and negative sequence component is controlled independently. So that the negative sequence current and the grid current harmonics can be retrained. So the photovoltaic grid-connected inverter can work well at LVRT situation, and shall not affect the power quality of power grid. The positive and negative sequence component detection of the grid voltage are studied in detail and the pro and con of two detection methods are analyzed and one of them is selected and verified. The LVRT method proposed has passed the no voltage ride-through certification, which verifies the effectiveness of the proposed technical solution.