Low Voltage Ride Through(LVRT) control strategy of grid-connected variable speed Wind Turbine Generator System

Abstract

In this paper, a Low Voltage Ride Through (LVRT) control strategy for variable speed full scale Wind Turbine Generator System (WTGS) is proposed. Grid-connected wind power system should satisfy LVRT requirement when grid fault occur, and the variable speed full scale WTGS has advantage of satisfying LVRT compared with the fixed speed WTGS. The proposed LVRT control strategy satisfies not only LVRT requirement but also stabilizing a DC link voltage regardless of reduced DC link capacitance. During the grid faults, especially three phase to ground fault, the grid side converter cannot control the DC link voltage because it is impossible to control grid side power. In this situation, the DC link voltage can be controlled by the generator side inverter using the proposed DC link voltage control scheme. The proposed control scheme can keep the power balance between grid and generator side power in any case of grid fault condition for LVRT. The compliance to Grid Codes has been evaluated by computer simulations. Though the experimental results, it is verified that the proposed method has satisfied the LVRT requirements and DC link voltage control specification simultaneously.