Maximum Torque Per Ampere Angle Detection for Interior Permanent Magnet Synchronous Machines based on Signal Injection

Maximum torque per ampere (MTPA) control is designed to identify the ideal current angle for interior permanent magnet synchronous machines (IPMSMs), aiming to minimize current consumption while achieving the required torque. This paper introduces an innovative MTPA control strategy for IPMSM utilizing gradient descent algorithm and signal injection. The approach involves injecting small current harmonics into the machine to search for the MTPA angle. Derived from the torque equation specific to the IPMSM, a fundamental relationship is established between the induced current harmonic and the speed harmonic of the machine. This relationship reveals that the first-order induced speed harmonic emerges solely when a disparity arises between the machine parameters employed in MTPA control and the real machine parameters. Consequently, the investigation of speed harmonics is employed to identify and adjust the MTPA angle by minimizing the magnitude of the speed harmonic through the application of the gradient descent algorithm. The proposed approach doesn't necessitate knowledge of machine parameters for MTPA angle calculation, ensuring a robust MTPA control across varying loading and speed conditions. To validate its efficacy, extensive simulations were conducted employing a nonlinear PMSM model derived from finite element analysis (FEA).