CASED: A simulation package designed for variable speed drives

Abstract

In recent years there has been an increase in the types and usage of AC variable speed drives. However, as the complexity of these systems has increased, so has the occurrence of problems which are often caused by the interaction of the various drive components. The authors have developed CASED which allows users to simulate complete drive systems. An overview is given of the types of models used for the converter and the motor, from which it is seen that three special features are required. Firstly the models are modular in nature, hence the simulator must be able to link the various models. Secondly a combination of discrete and continuous time simulation is required to model the converters, and lastly there may occasionally be a need for specialised stiff differential equation (DE) solvers. It is shown that by choosing the correct DE solver the simulation time can be decreased by more than one hundred fold. CASED has shown itself to be a specialised and powerful tool in variable speed drive analysis.