A Generalised Ward Equivalent for Security Analysis

A generalised Ward-type external-system equivalent for static security analysis is presented. The well-known standard and extended Ward equivalents can be obtained by simplifying this generalised Ward equivalent. Special attention is given to the representation of external generating units with primary voltage regulation. The equivalent requires no real-time measurement data or base-case state of the external system. The magnitude of the information exchange depends on the number of boundary nodes. The new equivalent is verified and compared to other Ward equivalents by simulation on a 65-bus test system.