Field oriented control of IPM drives for optimal constant power operation

Interior permanent magnet (IPM) drives are particularly adapted to flux-weakening, then to constant power operation over a wide speed range. Most of the Space-Vector strategies for IPM drives are based on the control of the current vector. Flux-weakening is obtained by setting the (d, q) current synchronous components according to the magnetic model of the motor. In case of variable dc-link, this strategy necessarily requires an additional voltage loop. The control of the flux vector, in a field-oriented frame, is proposed, in order to make the constant voltage operation easier in the the flux weakening range. A control algorithm, based on stator field-orientation, is described and tested on an IPM drive designed for EV traction. The full exploitation of the constant power range is obtained, also with a spread on the dc-link voltage. Discrete-time simulation and experimental results are presented.