Maximum Torque-per-Amp Control for Traction IM Drives: Theory and Experimental Results

Abstract

-A novel maximum torque per Ampere (MTPA) controller for induction motor (IM) drives is presented. It is shown to be highly suited to applications that do not demand an extremely fast dynamic response, for example electric vehicle drives. The proposed MTPA field oriented controller guarantees asymptotic torque (speed) tracking of smooth reference trajectories and maximises the torque per Ampere ratio when the developed torque is constant or slow varying. An outputfeedback linearizing concept is employed for the design of torque and flux subsystems to compensate for the torque-dependent flux variations required to satisfy the MTPA condition. As a first step, a linear approximation of the IM magnetic system is considered. Then, based on a standard saturated IM model, the nonlinear static MTPA relationships for the rotor flux are derived as a function of the desired torque, and a modified torque-flux controller for the saturated machine is developed. The flux reference calculation method to achieve simultaneously an asymptotic field orientation, torque-flux decoupling and MTPA optimization in steady state is proposed. The method guarantees singularity-free operation and can be used as means to improve stator current transients. Experimental tests prove the accuracy of the control over a full torque range and show successful compensation of the magnetizing inductance variations caused by saturation. The proposed MTPA control algorithm also demonstrates a decoupling of the torque (speed) and flux dynamics to ensure asymptotic torque tracking. In addition, a higher torque per Ampere ratio is achieved together with an improved efficiency of electromechanical energy conversion.

Online maximum torque per ampere control for induction motor drives considering iron loss using input–output feedback linearisation

“…In the rotor FOC, the torque equation is given by (13). From (7) and writing i md in terms of i iq , we have…”

“…It should be noted that since the iron loss effect is not considered, the proposed control strategy is different from efficiency optimisation. In [7], the MTPA strategy is realised in the steady‐state operation. In the proposed strategy, which is also based on a search algorithm, the saturation effect is taken into account.…”

Losses Minimization Control for an Integrated Multidrive Topology Devoted to Hybrid Electric Vehicles

“…In (31), the flux current component i ds is assumed to be established at priori, according to an efficiency optimization current profile linking the two projections of the stator current vector on the qd reference frame synchronous to the rotor flux position [32], [33], [39]- [41]. The latter shall be selected in accordance with the induction motor (IM) characteristics.…”

Analysis and Implementation of Constrained MTPA Criterion for Induction Machine Drives

“…Reference [21] applies model predictive control to the field weakening control, which enhances the robustness of the system. In [22], MTPA is utilized to compute excitation current and torque current references for induction machines, but this paper can not extend MTPA to field weakening mode. In [23], the MTPA control based on the measured current-torque curve is proposed, which does not depend on the parameters of induction machines and improve the robustness of the system.…”