A comprehensive LVRT strategy of two-stage photovoltaic systems under balanced and unbalanced faults

The increase in penetration of photovoltaic (PV) systems into utility grid poses great challenges in terms of system stability, thus, force several countries to update their grid codes to accommodate the low voltage ride-through (LVRT) capability of PV systems to stay connected to the grid and supply the reactive current to support grid voltage during grid faults. In line with this, a comprehensive LVRT strategy is proposed in this paper for grid-connected PV systems under balanced and unbalanced grid faults. The proposed strategy includes the power references calculation method to meet the requirements of grid codes, the active power reduction method to avoid the overvoltage of the dc-link, the peak current limiting method to avoid the overcurrent of the inverter, and three current reference generators implemented by the proposed current reference formulations to ensure the reliable operation of PV systems under different grid faults. The effectiveness of the proposed strategy has been verified in MATLAB/SIMULINK simulation platform and the results show that the proposed LVRT strategy has good performance under different grid faults.