Computer methods for transient stability analysis of isolated power generation systems with special reference to prime mover and induction motor modelling
This thesis aims to establish computer methods for the transient stability analysis of electric power systems which operate isolated from the large interconnected system. A typical isolated system is characterized by a compact network in which the size of the load is relatively large when compared to the total, installed generation capacity. The stability problems are thus more severe for this system than for the grid-type system. This results in the need for more accurate representations for the system components in the computer studies. This work considers particularly the prime mover and the induction motor modelling. The accurate modelling for turbo-charged diesel engines and single shaft gas turbines is considered first due to the significative presence of these types of prime movers in the isolated systems. The quasi-steady approach is adopted in the development of these models. The induction motor modelling is then dealt with and an accurate model which accounts for the deep-bar effects and includes the stator transients is presented. In addition, this work also investigates the possibility of substituting all these detailed models by simple, reduced models in the computer simulations since the latter pose less problem in assembling the necessary data than the former ones. Furthermore, some theoretical aspects for the representation of synchronous machines, automatic voltage regulators and transformers are included in the thesis. Some insight on the numerical integration method used in the stability program - the Trapezoidal implicit - is also given in the text with the advantages and disadvantages being stated. Several studies are shown in the thesis which aim firstly to compare the various models for prime mover and induction motor representations and secondly to test the complete simulation package when dealing with stability analyses of typical isolated systems.