A hybrid on-line slow voltage control scheme for large power systems

This paper proposes a hybrid on-line slow voltage control scheme to closely monitor and control the transmission grid steady state voltages of large power systems. The control scheme is meant to be used to coordinate control actions of generators and discrete control devices in those power systems with large amount of generation resources. The control scheme has three operation phases where the optimization problems are formulated as continuous or discrete problems, depending on the nature of the control devices. Under normal operating conditions such as morning load pickups, the controller will act in the way similar to that of AGC, trying to adjust generator reactive outputs to maintain the desired voltage profile. The discrete control devices are treated as supplemental reactive power to generator reactive reserves, which need to be kept at certain level such that there could be enough fast reactive power support in case of emergency. Simulation results on small and large scale power systems (IEEE 30 & WECC) indicate that the proposed control scheme is effective and suitable for on-line implementation in large-scale power systems.