Low voltage ride through control strategy for high-power grid-connected photovoltaic inverter

This paper presents a low voltage ride through (LVRT) control strategy for high-power grid-connected photovoltaic (PV) inverter, which can assure the PV inverter operates under grid faults with sinusoidal output currents. The control strategy of PV inverter is made up of inner current loops and outer voltage loop in a cascade structure under normal working conditions. The outer loop regulates the voltage on dc-link capacitance to the maximum power point of PV arrays, and the inner current loops are composed of four closed loops for positive sequence and negative sequence in synchronous reference frame. If the low voltage fault signal has been detected, the control system should shift to single loops control strategy for low voltage ride through. Finally, a laboratory prototype of 150 kW PV inverter with LCL filter has been implemented to test the theoretical analysis. The feasibility and effectiveness of the proposed LVRT control strategy have been verified by simulation and experimental results.