Robust MTPA Control for Steady-State Operation of Low-Cost IPMSM Drives

The efficient control of interior permanent magnet synchronous motors (IPMSM) requires implementation of maximum torque per ampere (MTPA) control. However, MTPA control requires knowledge of motor parameters to evaluate the
d
- and
q
-axis current trajectories. This article proposes a robust self-tuning maximum torque per ampere control algorithm for IPMSM drives. This algorithm is designed to operate in conjunction with conventional control schemes, where the output of the speed controller is the commanded quadrature current and direct current is calculated using an MTPA equation. In contrast to the conventional approach, the proposed algorithm does not make use of any equations and motor parameters. It continuously varies the current phase, trying to minimize the magnitude of the stator current vector, at the given load torque. These makes the algorithm insensitive to motor parameters variation, due to heating or steel saturation, which is extremely important for systems that prioritize reliability and efficiency.