Coordinated voltage control scheme for transmission system considering objectives and constraints of network and control devices

Abstract

Need for sufficient reactive power reserve for fast reaction against large disturbances necessitates developing an integrated and coordinated voltage control scheme including controlled and mechanically switched control devices. This paper proposes a day-ahead optimal voltage control scheme for transmission system considering static var compensators (SVCs), capacitor banks, load tap changers(LTCs) transformers and synchronous machines. The scheme is based on defining an optimization problem which includes two objective functions for reactive power reserve and voltage regulation precision of SVCs, two objective functions related to number of capacitors switching and LTCs tap changing, and two objective functions for improving the network performance. The multi-objective optimization problem is solved subject to a complete set of constraints related to the network and voltage control devices. The solution algorithm of the proposed problem is based on defining a single objective function by applying appropriate weighting coefficients to the normalized indices. Performance of the proposed scheme is investigated on IEEE 30-bus system through various studies. Particularly, the effectiveness of the scheme is demonstrated to realize the objectives for conditions where the load profiles at transmission buses are considerably modified due to structuring changes in the downstream networks.