Modeling and dynamic simulations of new rotary frequency converter which consists of doubly-fed machine and induction machine

The doubly-fed (or adjustable speed) pumped storage generating systems which have been newly developed with recent progress of power electronic technology as its setting can contribute not only to power system frequency control at night, but also to improvement of power system stability. In this paper, as an application of doubly-fed machine technologies of large capacity, a new rotary frequency converter is proposed that consists of MG set of a doubly-fed machine and an induction machine. Compared with a conventional rotary frequency converter that consists of a couple of synchronous machines, the new doubly-fed rotary frequency converter can control power transfer actively. The mathematical models of the proposed new converter and basic considerations for their fundamental control strategy based on the models are described, and the results of dynamic simulations for investigating the characteristics of control and operation of the converter in power system are presented.