Applying a STATCOM for stability improvement to an existing wind farm with fixed-speed induction generators

Wind farms are becoming important distributed renewable energy resources. However, voltage stability issues with wind farms employing fixed-speed induction generators may require such systems to be augmented with dynamic compensation devices, such as STATCOM units. In preparation for deployment of a 10 MVA STATCOM at an existing wind farm in the Bonneville Power Administration (BPA) system, the STATCOM controller is to be tested through hardware-in-the-loop simulation with a real-time digital simulator, which will model both the BPA system and wind farm with high fidelity, transient models. This paper presents groundwork conducted in preparation for the dynamic testing of the controller, including studies of the stability improvement facilitated by the introduction of the STATCOM into the BPA system. The enhancement of voltage stability and induction generator stability by the STATCOM is studied analytically by power-voltage and torque-slip relationships of a simple wind power system, as well as through simulation studies with the real-time simulation to be used for testing of the controller. Simulation results from both approaches are compared and illustrate the potential benefit of the STATCOM in preventing voltage collapse caused by serious network changes, such as opening a line, as well as improvement of the Fault Ride Through capability of the wind power system.