A low cost AC speed drive for low voltage high current induction machines

In this article, the authors present an AC speed drive carrying out a low voltage and high current induction machine (IM). The electric traction application is for an industrial vehicle. This embedded autonomous system has to be very compact and low cost product, needing simple maintenance. It has to guarantee the operation security and the best dynamic and static performances. In this study, the authors chose the direct field oriented control (DFOC) to assure the required performances constraint, i.e. the constant torque operation for the lower rotation speed and the power constant operation for the over rotation speed conditions. This low cost electric propulsion system imposes the reduction of the sensor number to be used. So, the flux sensor necessary to the DFOC strategy, will be replaced by a full order rotor flux deterministic observer and the DC-link current measurement allows to eliminate the Hall effect AC current sensors. In this way, the stator currents are indirectly estimated. The authors validate control strategy, proposed for this embedded system, using the quasi-experimental method. They verify different steady and transient state operations, according to the required vehicle trajectory, by the precise Saber simulation software.