Wide area dynamic monitoring and stability controls

Abstract

This paper presents a new approach for wide area dynamic monitoring of the system with many possible applications. One such application is discussed to provide real time stability controls. The new approach utilizes a substation based dynamic state estimation. The substation based dynamic state estimation uses data from relays, PMUs, meters, FDRs etc in the substation only thus avoiding all issues associated with transmission of data and associated time latencies. The substation based dynamic state estimator provides accurate representation of the dynamic state of the system. The dynamic state estimator runs at rates comparable to the suggested rates in the synchrophasors standard C37.118. Presently it has been implemented to execute 10 times per second thus providing the dynamic state of the substation 10 times per second. The results of the substation based dynamic state estimator are transmitted to a central location for monitoring the dynamic state of the system. A major advantage is the fact that only the dynamic state of the substation is transmitted instead of the raw PMU data that typical wide area monitoring implementations use. Note that the data describing the dynamic state is much less that the raw data of the PMUs. This fact facilitates the speedier transmission of the data in addition to the advantage of a more accurate dynamic state as opposed to the raw data. This infrastructure can be used for a number of applications. The paper focuses on transient stability monitoring, identification of out of step conditions and control. We propose an approach that is based on accurate evaluation of the system energy function (Lyapunov indirect method) and extraction of stability properties from the energy function. Specifically, we provide a methodology for determining the required data accuracy for the reliable real time estimation of the energy function. When the data meet these requirements, the estimated energy function can be visualized and animated providing a powerful visual tool for observing the transient stability or instability of the system. The infrastructure of the substation based dynamic state estimator provides the required accuracy and the ability to predict instabilities before they occur.