Time-domain equivalencing of external networks for power system switching transients simulation

The main contribution of the work presented in this dissertation is the development of a generalized theory for (direct) time domain modeling of frequency dependent equivalent(s) which is applicable to both single-port and multi-port external systems. A unique feature of the developed technique applied to the multi-port case is that it explicitly parameterizes the travel (time) delay between ports separated by transmission lines, thus decoupling the model of the equivalent connected at one port from that at another port. This renders the equivalent's model analogous to the discrete-time frequency dependent transmission line model currently used in any EMTP.;The dissertation first introduces the nature of the problem and the adopted research methodology by delineating the problem formulation and the objectives of the research. This is followed by an extensive and critical review of the various types of equivalencing techniques used and/or proposed until now and examines the issues favoring or limiting the application of each.;Against this backdrop, the proposed theory for obtaining time domain equivalents is described. The equivalencing technique is first developed for single-port single-phase external systems and then extended to balanced three-phase systems. Next, the basic ideas and concepts of single-port equivalencing are extended to the more general case of multi-port equivalents. In particular, the most common case of two-port equivalents is described in detail for single-phase systems and balanced three-phase systems. Finally, the procedure to integrate the time domain equivalent model(s) in the solution technique of EMTP is provided.;The proposed modeling technique is then applied to obtain single and two-port equivalents for a test system, which are validated by simulating two types of switching events. First, the frequency response of the admittances characterizing the external system(s) are plotted within the bandwidth selected for equivalencing to illustrate the frequency dependence of the required equivalents. Then the models for the time domain equivalents are obtained and their stability is investigated. Next, the simulation results of line energization and fault (short-circuit) transients studies by using the equivalents are validated by comparison with those from EMTP simulation using full representation of the external system. Finally, the performance of the developed equivalents is compared with that of existing reduced-order, frequency dependent network equivalents.;The dissertation concludes with a review of the salient features of the research work and indicates the areas requiring further investigation and research effort.