Coordinating Control of Static VAR Compensators and Synchronous Generators Based on Selected Remote Measurements

The wide-area coordinating control concept has gained rapid interest in power system control. It now offers substantial potential and great challenge to the power industry. This article proposes a new control design method based on wide-area measurements to coordinate generator excitations and static VAR compensator auxiliary controls. A state space model of a multi-machine power system that includes a static VAR compensator is derived first. This model clearly shows the interactions between a static VAR compensator and generator variables. Next, remote measurements are used to generate coordinating signals for the static VAR compensator controller and the generator excitations. Two different control strategies are proposed. The first controller decouples the system dynamics by compensating the interaction terms between the static VAR compensator and generator variables. The second controller utilizes the relative gain array concept to evaluate the interactions. Only signals that contribute to the strongest interactions are used by the controller to reduce the interactions between the system components considerably. The second controller with a reduced set of measurements is compared to the first controller with full measurements. Results show that performances of both controllers are very similar. They provide significant additional damping for both local and inter-area oscillations. Communication time-delay effects are also considered in this study.