Efficient Explicit Representation of AC Machines Main Flux Saturation in State-Variable-Based Transient Simulation Packages

Inclusion of magnetic saturation in low-order qd models of induction and synchronous machines improves the accuracy of system studies. Over the years, numerous explicit and implicit methods of representing magnetic saturation have been proposed in the literature, some of which find their use in commonly used transient simulation packages. This paper presents a straightforward and improved flux correction method of modeling saturation explicitly in classical qd state variable ac machine models. The approach requires limited additional information and avoids the need for a dynamic inductance, which is present in many other approaches. The method is first developed for induction machines and then extended to salient-pole synchronous machines as a more general case. Computer studies demonstrate the accuracy of the proposed method for predicting the dynamic and steady-state cross-saturation phenomena, as well as its computational advantages.