Non-linear Optimization Approach to Determine Parameters of Small Salient-pole Synchronous Machines from the Short-circuit Test

Abstract

The sudden three-phase short-circuit test is commonly used to derive synchronous machine parameters and has been standardized by the IEEE/IEC. However, because they ignore the quadrature axis and use an envelope-tracing technique, the standard methods are inconvenient in determining the parameters of small salient-pole synchronous machines, which have strong second harmonic short-circuit current and short time constants. This article presents an alternative procedure to determine equivalent circuit parameters of small salient-pole synchronous machines from the conventional short-circuit test. The machine steady-state parameters are determined by the standard methods, while the other parameters are estimated from the machine transient short-circuit currents using a non-linear optimization approach. The parameters of the direct- and quadrature-axes are both obtained with a single test. A new state-space linear model and a transient saturation model of synchronous machines in phase quantities are developed to predict the short-circuit test. The method is successfully applied for the parameter estimation of a synchronous motor/generator of 208 V, 1.5 kVA, and 60 Hz. The estimated parameters are validated under load as well as saturation conditions.