Voltage stress minimization by optimal reactive power control

TL;DR

This paper proposes an optimization-based method to enhance power system stability by optimally controlling reactive power injections, ensuring voltage levels within bounds and increasing the distance from voltage collapse, with efficient convex solutions and distributed algorithms.

Contribution

It introduces a convex optimization framework for reactive power control that maximizes voltage stability margin and includes a distributed algorithm for real-time implementation.

Findings

Convex reformulation enables efficient computation of optimal reactive injections.

The method increases the voltage stability margin in the IEEE30 bus network.

A distributed feedback controller can implement the optimization in real-time.

Abstract

A standard operational requirement in power systems is that the voltage magnitudes lie within prespecified bounds. Conventional engineering wisdom suggests that such a tightly-regulated profile, imposed for system design purposes and good operation of the network, should also guarantee a secure system, operating far from static bifurcation instabilities such as voltage collapse. In general however, these two objectives are distinct and must be separately enforced. We formulate an optimization problem which maximizes the distance to voltage collapse through injections of reactive power, subject to power flow and operational voltage constraints. By exploiting a linear approximation of the power flow equations we arrive at a convex reformulation which can be efficiently solved for the optimal injections. We also address the planning problem of allocating the resources by recasting our problem in a sparsity-promoting framework that allows us to choose a desired trade-off between optimality of injections and the number of required actuators. Finally, we present a distributed algorithm to solve the optimization problem, showing that it can be implemented on-line as a feedback controller. We illustrate the performance of our results with the IEEE30 bus network.