Volt/VAR control for wind generation

Wind generating facilities often require significant reactive power support to maintain voltage and power factor within operating limits prescribed by the transmission grid entity. Many installations include multiple stages of switched capacitor and reactor banks for this purpose. Coordinated control of these capacitor and reactor banks, which are often connected to the point of interconnection via multiple step-up transformers, requires a centralized control system. This paper discusses a reactive power control system that utilizes a central automation controller to regulate both power factor and voltage at the point of utility interconnection. This controller includes the capabilities of a complete communications processor to exchange voltage, power flow, and status information along with control commands to microprocessor-based relays throughout the system. It also includes a powerful IEC 61131-3-compliant soft programmable logic controller (PLC) logic engine to execute the control algorithms. The system is easily adaptable and scalable to nearly any configuration. The challenge when controlling both power factor and voltage is to prevent hunting due to conflicts between the two control requirements. An adaptive algorithm is utilized to deal with this challenge. The controller also includes a sophisticated sequencing algorithm to ensure that both reactors and capacitors are not in service at the same time, to optimize power factor through multiple step-up transformers to reduce losses, and to even out switching operations between reactive banks.