A new two-stage framework for voltage stability enhancement incorporating preventive and corrective control actions

Abstract

Summary Nowadays voltage stability is an important concern in power system operation due to many blackouts caused by voltage collapse. This paper presents a new two-stage framework for voltage stability enhancement that in the first stage a preventive control action is applied to increase the voltage stability margin of the system under normal condition. In addition, in the second stage an optimal load shedding scheme as one of the most effective tools to save system stability against severe contingencies is implemented. To do this, a new special protection system design based on definition of a multi-objective function containing the objectives of voltage stability margin, deviation of voltage limits, branches' overload, and load shed amounts is proposed. A theta gravitational search algorithm is also suggested to solve the multi-objective non-linear optimization problem to determine the optimum amounts of load cut as well as the other objective functions. Furthermore, for avoiding either excessive load shedding or voltage collapse, both voltage threshold and critical time of load shedding implementation are determined by dynamic simulations. Azarbayejan area of Iran's power system in 2012 peak load time is applied as a test case of the presented framework. Effectiveness of the proposed approach is illustrated by comparing its simulation results with the results of the current load shedding scheme and two other optimization approaches. Copyright © 2014 John Wiley & Sons, Ltd.