An efficient method of simulating stiffly connected power systems with stator and network transients included
Abstract
Transient stability programs are widely used to study the slower electromechanical phenomena of large-scale interconnected power systems. In virtually all of these programs, the electric transients associated with the machine stator windings and with the transmission network are neglected. This approximation decreases substantially the computational requirements when calculating the dominant electromechanical system response following major network disturbances. However, the response predicted by these reduced-order simulations is only an approximation to the actual system response. Moreover, these simulations cannot be used to directly study unbalanced operating conditions or the valve-by-valve operation of static power converters. In this research, a method has been developed for simulating interconnected power systems with the stator and network transients included. This method is applicable to stiffly connected power systems in which the tie-lines interconnecting the system components are electrically short (i.e. the tie-line charging capacitance can be neglected). It is based on the reformulation of the standard synchronous and induction machine models to include the stator currents as state variables. These models are then interconnected to create a composite state model of the system. To insure that the resulting composite model is in minimal state form, an algorithm has been derived that may be used to identify independent stationary-circuit currents. These currents are included in the list of state variables. Simulations of an example system have shown that the computation time associated with this method is comparable with that of a transient stability program. However, this method more accurately predicts the actual system response. Since the stator and network transients are retained in this method, unbalanced operating conditions can be simulated. Models of unbalanced faults and the sequential opening of a circuit breaker have been derived. These models have been included in an example system and representative simulation results are given. Finally, a model of a static power converter which is suitable for simulating the valve-by-valve operation of the converter has been derived.
Degree
Ph.D.
Advisors
Wasynczuk, Purdue University.
Subject Area
Engineering|Electrical engineering
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