A systematic method for the determination of the parameters of synchronous machines from the results of frequency response tests

This paper deals with the analysis of the frequency responses of the d and q axis impedances of synchronous machines. Numerical curve-fitting techniques have normally been used to find the best set of time constants to fit the frequency response data, but limitations or constraints are introduced with these techniques. The process to be described here is based on characteristic features of the equivalent circuits which overcome the need to make the assumptions inherent in a numerical approach. The extraction process is demonstrated using an equivalent circuit chosen to produce a frequency response similar to that for the direct axis of a production machine. This enables the intrinsic advantages of the proposed process for extraction of the time constants to be demonstrated which then leads directly to a unique set of equivalent circuit parameters.