Study on coordinated reactive power control strategies for power plant auxiliary system energy efficiency and reliability improvement

From efficiency and reliability standpoints, there are three major issues in coal-fired power plant auxiliary systems: high in-house load, low power factor, and weak disturbance-ride-through capability. This paper presents a cost-effective solution to solve these problems. The proposed solution consists of Variable Frequency Drives (VFDs) with Active Rectifier Units (ARUs), mechanically switched shunt capacitor banks, and coordinated reactive power control strategies implemented in the power plant Distributed Control System (DCS). In this paper, the design principles of the proposed solution will be introduced. Coordinated control strategies of the ARUs and capacitors for which implement the steady-state power factor control and dynamic voltage support under disturbances will be described. The overall potential benefits resulting from the proposed solution will be discussed and demonstrated with example studies corresponding to a 300MW coal-fired power plant.