Power System Security Restoration by Secondary Control

The paper develops a co-ordinated control scheme based on linear programming (LP) for the secondary control in a power system where it is required to restore system security in relation to voltages and power flows, and, simultaneously, minimize the network loss, following a system disturbance or contingency. The secondary control scheme proposed is more general than the classical secondary voltage control where only voltages are considered. The scheme automatically adjusts the reference settings of the power system controllers to achieve the objectives specified in the secondary control. The algorithm is derived on the basis of the linearized power system model the parameters of which are determined online using the information obtained from the phasor measurement units and/or state estimation. The LP-based scheme is suitable for online application in secondary control. Representative results based on a test power system with FACTS devices and subject to disturbance/contingency are included in the paper.