Two stabilising control strategies for the brushless doubly-fed machine (BDFM)

The BDFM shows economic promise as a variable speed drive. One practical obstacle to commercial exploitation is the presence of operating speeds at which BDFM synchronous action cannot be maintained under open loop conditions. Two control strategies are proposed: feedback linearisation and control winding phase angle control which will enable BDFM synchronous action to be attained over the necessary operating speeds. This paper explains the theory of the two strategies, then suggests controllers for a specific BDFM. Finally the proposed control systems are tested by simulation and experiment. Both controllers successfully stabilised the BDFM. Whilst the feedback linearisation strategy gave superior performance in simulation, the difficulties of implementing it could limit its practical application.