Multi-Functional PV Inverter With Low Voltage Ride-Through and Constant Power Output

Renewable photovoltaic (PV) energy is a primary contributor to sustainable power generationin microgrids. However, PV grid-tied generators remain functional as long as the grid voltage and the inputPV source remain normal. Abnormal conditions like transient grid sags or solar irradiation flickering canmake the grid-tied inverter go offline. Simultaneous shut down of PV generators residing in the distributiongrid may lead to an overall grid instability or outage. Therefore, PV generators must be equipped with fault-ride-through mechanisms in order to remain connected and operational during faults. This paper presentsa PV-inverter with low-voltage-ride-through (LVRT) and low-irradiation (LR) compensation to avoid gridflickers. The single-phase inverter rides through the voltage sags while injecting reactive power into the grid.The proposed control strategy ensures a steady DC-link voltage and remains connected to the grid duringAC-side low voltage and DC-side low-irradiation faults. Unlike other PV inverters, the controller maintainsthe maximum-power-point-tracking (MPPT) in all conditions. LVRT, constant power output, and robustMPPT are the noticeable features of the proposed system. Frequency analysis, simulations, and a laboratoryprototype validate the proposed control strategy.