Control Strategies for Robust Low-Voltage Ride-Through Operation of Grid-Tied PV Inverters

This paper investigates the low-voltage ride-through (LVRT) operation of a grid-tied photovoltaic inverter system. To prevent over-rating operations, the conventional constant peak current strategy is usually implemented to limit the peak current amplitude considering the injected reactive current. However, this can lead to a dc-link energy imbalance due to the maximum-power-point tracking function. A short-term overshoot of the dc-link voltage can occur after grid voltage recovery. Abnormal oscillations can occur due to the nonlinear characteristics of the demand reactive current specified in grid codes. Moreover, mismatching injections of the reactive power can also occur due to the inaccurate voltage sag detections. To cope with the aforementioned issues, control strategies are proposed to guarantee robust LVRT operations. The proposed control methods are validated in simulations under different scenarios.