Performance capability analysis of the brushless doubly-fed machine as a wind generator

This paper introduces capability curves to aid in the design of brushless doubly-fed induction machines (BDFMs) as wind generators as well as motors. The capability curve graphically portrays the limits of torque, efficiency, and power factor that can be obtained at a given speed and control winding voltage. The torque limit predicted from the torque capability curve is shown to be near the actual measured value of maximum torque capability. It is noted that the predicted torque limit is optimistic when compared to test data; consequently, designers should use an appropriate safety margin in practical designs. In addition, the steady state model of the BDFM is further validated with laboratory measurements. Basic design guidelines are given along with a graph showing the preferred regions of operation for the BDFM