Control Study on Starting of BDFM

The brushless doubly fed machine (BDFM) is attractive for variable speed drive (VSD) applications as its use can reduce the cost of the associated power electronics. Using a simple combination of a rectifier and inverter is attractive but this restricts the speed range to natural speed and above if the machine is to be operated efficiently. However, by appropriate control of the inverter switches, the BDFM can be started in cascade mode followed by a transition to the normal synchronous mode. This paper describes the control issues involved in successful synchronization and gives results which show the practicality of this method of starting a BDFM