Photovoltaic low-voltage ride-through control strategy based on flexible power point tracking

Abstract

To solve the direct current (DC) bus overvoltage problem existing in low voltage ride through (LVRT) control of the photovoltaic (PV) grid-connected systems and improve the fault recovery capacity of the grid-connected system,a cost-effective LVRT control strategy based on flexible power point tracking (FPPT) is proposed in this paper. To begin with,the graphical approximation method is used to quickly estimate the operating voltage of the power curtailment point,and the position of the PV reference operating point during the fault process is deduced,based on which the rapid active power curtailment control strategy is proposed. Subsequently,the voltage against current curve of PV is fitted to estimate the PV short-circuit current and the voltage of the maximum power point is calculated by using the Lambert-W function,based on which the fast recovery control for faults is proposed. Finally,simulations and experiments are analyzed by Matlab and hardware-in-the-loop testing platform,respectively. The results prove that the proposed control strategy has good fault ride-through capability and fault recovery effect,which contributes to promote the application of grid-connected PV power generation technology.

Keywords

• grid-connected photovoltaic system;flexible power point tracking;separation of positive and negative sequence components;photovoltaic inverter;low voltage ride through;hardware in the loop