High-voltage ride through strategy for DFIG-based wind farms under bipolar blocking of HVDC system

Excessive reactive power generated by the filter and compensation devices of rectifier station will flow into the AC system when DC bipolar block occurs, which brings a high voltage threat to doubly-fed induction generator (DFIG)-based wind farms at the sending-end. This paper proposes a nonlinear robust tracking control (RTC) strategy to enhance the high-voltage ride through (HVRT) capability of DFIG-based wind farms. In the proposed strategy, the nonlinear characteristics of wind farms and the disturbance attenuation requirements during DC bipolar block is fully considered. The RTC problem is formulated with control objective of absorbing the reactive power injected into the AC system, and state-dependent Riccati equation (SDRE) technique is adopted to obtain an approximate solution. Case studies are performed on MATLAB/Simulink, the results illustrate the proposed HVRT control strategy has a better transient performance of suppressing overvoltage under Bipolar Blocking of HVDC System.