Toward PMU-based robust automatic voltage control (AVC) and automatic flow control (AFC)

This paper is motivated by the need to automate adjustments of deviations in key output variables from their scheduled values. In particular, it is important to maintain load voltages within their pre-specified limits in response to many disturbances, for example load power factor deviations. Similarly, it is important to regulate real power line flows to within their pre-specified limits as disturbances around scheduled real power generation dispatch take place. Such automation is a feasible goal since the PMUs could provide accurate and fast sensing of key output variables of interest. Given the number of PMUs, the selection of best locations of PMUs and the control design based on these measurements becomes an engineering design problem. In this paper we provide a problem formulation for a robust Automated Voltage Control (AVC) and Automated Flow Control (AFC) design based on selecting the best locations for placing the PMUs. The AVC and AFC designs are illustrated using a small 5-bus example first. This is followed by illustrating potential performance of such design on an equivalent NPCC 36-bus system. The results indicate that the (N-1) reliability criteria can be met by combining the economic dispatch for scheduling resources given demand forecast, and by relying on an automated feedback to ensure that voltage and line flow deviations remain within the pre-specified limits in between scheduling intervals. This is done without having to know the exact location and magnitude of disturbances.