ETA-based optimization scheme of WADC with consideration of time-varying delays

Abstract

With the development of the Wide-Area Measurement System (WAMS), researchers has proposed different kinds of Wide-Area Damping Controller (WADC) to suppress inter-area power oscillations. However time delays in WAMS communication networks have made it less effective to improve dynamic stability of large-scale power system. Traditional methods such as modal analysis and simulation cannot study the time delay impacts on the dynamic characters theoretically and obtain boundary conditions of stability for the optimization of damping controllers. To solve these problems, this paper studies the influence of time delays on the inter-area dynamic characters using two-machine Electric Torque Analysis (ETA) method. The mathematical relationships between the time delay, electric torque coefficients, and damping ratio of a power system installed with a WADC are explored. The stability criteria of inter-area mode and the delay margin are studied. An optimization scheme of WADC is proposed to implement fast online damping control considering time-varying delays. This method is verified in a four-generator-two-machine benchmark installed with a SVC-based WADC. Simulation results show the proposed scheme can improve the robustness of WADC against time delays and has advantages over traditional methods.