Dynamic control of brushless doubly-fed machines

This thesis presents the development of dynamic control strategies for the brushless doubly-fed machine (BDFM). A simple open-loop scalar controller is first investigated and its response is found to be oscillatory. Basing the speed feedback signal, an improved closed loop scalar control algorithm is designed. Steady state performance is controlled by the magnitude of the BDFM control winding current. Simulation and experimental results demonstrate that the closed loop algorithm has a slow response and is suitable for low performance drive applications. A model reference adaptive control algorithm is investigated in simulation, attempting to improve the BDFM dynamic response and assure its robustness against system parameter variations.; Further investigations reveal that the field orientation principle for conventional induction machines can be adapted for the BDFM. This enables the design of a rotor flux oriented control algorithm, based on a newly established synchronous reference frame model. Simulation results illustrated the algorithm's fast dynamic response and robustness against parameter variations.; The verification of various control algorithms is carried out on a laboratory system consisting of an experimental BDFM, a power converter and associated control hardware. An Intel 80196Kr microprocessor is used to implement inverter switching and current regulation for the BDFM control winding. The rotor flux oriented control algorithm is implemented using an Intel 80968KB floating joint microprocessor, achieving a control bandwidth in the kHz-order.; Evaluation of a BDFM synchronous angle shows its significance in control design, and it is incorporated into the later control algorithm development in order to eliminate electric torque estimation. This simplifies control algorithm design and is verified experimentally. Consequently, the control algorithm for the BDFM can approach the simplicity of equivalent induction machine control techniques.