Design of wide-area damping controllers using the block relative gain

A novel technique to determine the best pairing of inputs and outputs for the design of wide-area damping controllers (WADCs) is proposed. The method extends the conventional use of the relative gain array (RGA) for interacting control systems, to the block relative gain (BRG) to analyze interactions among multi-input multi-output (MIMO) controllers. First, geometric measures of controllability and observability are used to screen the most effective stabilizing signals for partially centralized control of large interconnected power systems. Then, the BRG analysis is used to quantify the potential for adverse interactions between a given set of controllers or subsystems. This gives candidate sets for supplementary controllers which are solved using linear matrix inequality (LMI) techniques and are evaluated in closed-loop mode to detect and quantify process interactions. In general, this approach also allows better coordination of control capabilities and the use of interaction measures to help in the choice of control location and structure. The effectiveness of the proposed control scheme on system behavior is tested on a realistic 5-area model of the Mexican interconnected power system.