Comparative study of three control strategies for the synchronous salient poles and wound rotor machine in automotive applications with on board energy

The DC machine is currently used for the propulsion of city cars and its advantages are well known. Nevertheless, its commutators bring some problems that can be avoided with AC machines. The considered application imposes some new constraints in comparison with classic field oriented control. To avoid a gear box, the machine needs to work in a wide speed range, so with varying flux level. Energy consumption becomes of prime importance with regard to the torque constant time. The synchronous salient poles and wound rotor machine, by its three control parameters, is well suited to this application. The simultaneous control of the amplitude and the “position” of the stator current vector and the field current may allow energetic optimization. This paper proposes to compare three control laws: maximum efficiency; maximum of the product (efficiency*power factor); and working at maximum power factor. This comparison uses precise simulation taking account of iron losses and limitations due to the low voltage supply (batteries) in transient as well as in steady state operation. The results of the simulations are validated on a microcomputer control system (OS9 68000) which has been designed for a 1 kW motor