A comparison of local vs. sensory, input-driven, wide area reactive power control

In the evolution of wide area measurement systems (WAMS) to wide area control systems (WACS), several subsystems can be considered. One such subsystem to be considered under WACS is shunt capacitor switching strategies to provide reactive power support. Many shunt capacitors are operated using local voltage control, but WACS controlled shunt capacitors are operated remotely using a system wide strategy. A WACS control of capacitor switching is proposed based on indices that assess bus voltage magnitude and complex line flows. The switching scheme which produces operationally acceptable bus voltage magnitudes or line power flows, or a combination of the two phenomena, is used for global control of reactive power support. The differences between WACS and local control are illustrated utilizing the IEEE 57 bus system as a test bed. A strategy based on the grouping of capacitors for WACS control is illustrated and compared to local control. Results show that WACS has better results when the number of bus voltage magnitudes out of range and total system losses are considered as assessment measures of control effectiveness.