Distributed Automatic Voltage Control framework for large-scale wind integration in China

Three critical cascading faults with nearly 2000 WTGs (Wind Turbine Generator) tripped took place in China on early 2011, from which the reactive power and voltage control issues for large wind farms are spotlighted. Some key factors inducing the cascading trip are surveyed by this paper firstly, including WTGs voltage distribution, dynamic reactive power reserves and coordination of tight-coupled wind farms. Rather than only focusing on the PCC (Point of Common Coupling) voltage, AVC (Automatic Voltage Control) in a wind farm is actually a network-based control considering voltage distribution and drop on the radial feeders. A hierarchical control AVC (Automatic Voltage Control) framework considering wind farms integration is presented and the detailed functions are introduced, involving network model, state estimation, 3-D visualization based monitoring, power flow & sensitivity calculation, security assessment & early warning and control strategy decision. Such an AVC system has been applied into several wind farms, one of which is selected as an example to introduce the configuration and deployment details. The distributed AVC system is also a mini-EMS (Energy Management System) prototype for large wind farms.