Modelling of electrical power systems

The work described in this thesis concerns the time-domain simulation of various items of plant for a limited power system.· Initially, an isolated 3-phase synchronous generator is considered, with the generator equations expressed in the phase reference frame since this copes easily with both balanced and unbalanced fault and load switching conditions. Various fault and load switching conditions are investigated, with theoretical results for a 3-phase short circuit being compared with corresponding results obtained using a classical dq model. The single generator model is then extended to a multi-generator power system, comprising 2, 3 or 4 generators connected in parallel and supplying a common bus bar. A method based on Kron's diakoptic approach is used, whereby the network is torn into sub-networks, which are solved separately, and are then re-connected to form the complete system. Comparison between this approach and results obtained from a conventional mesh analysis of the system indicates a considerable saving in the computer run-time required for a diakoptic solution. Finally, mathematical models are developed for both uncontrolled and controlled bridge converters using tensor methods to define the circuit equations as the circuit topology changes. A model for a separately-excited DC motor supplied from a fullwave. 3-phase thyristor bridge is described and theoretical waveforms are compared with those obtained on a small laboratory-scale machine. Speed control is incorporated in the system and the theoretical performance is investigated.