Dynamic modelling of the brushless doubly fed machine

A coupled‐circuit model for the brushless doubly fed machine (BDFM) has been developed. The transformation of the model into the d – q axis form, ultimately in a synchronous reference frame in which machine currents and voltages have constant values in the steady state, has been carried out. A model‐reduction technique is presented, which gives a concise representation of the ‘nested‐loop’ rotor design using a single d – q pair. These models have been experimentally verified and give a convenient and accurate way of calculating the dynamic behaviour of a BDFM. The ability to represent the BDFM with a single d – q pair considerably simplifies the design of suitable controllers.