An Improved Control for DC-Link Fluctuation during Voltage Dip based on DFIG

The main purpose of this work is to limit the DC-link voltage fluctuation in doubly fed induction generator (DFIG) based wind turbine system to enhance low voltage ride through capability. Grid-side and rotor-side converters control has been addressed to avoid disconnection of turbine during fault conditions but these works, thoughts, often ignore dc-bus voltage ripples limitation during voltage dips, and fault ride through of DFIG may not be satisfactory without minimizing the DC-link voltage fluctuations within their acceptable ranges. In this work an improved control strategy to limit the DC-link voltage fluctuation under normal and fault conditions is implemented. A modified control scheme has been applied to the direct current loop of the grid-side controller. If the grid filter active current setting during the voltage dip is determined, the sum of instantaneous powers of the grid and the grid filter is nearly equal to the instantaneous output rotor power, the DC-link voltage will not change significantly and will remain nearly constant. Simulations performed by Matlab software demonstrate the performances of the proposed method in limiting DC-bus voltage fluctuation during severe voltage dip.