MTPA Speed Control for IPMSM Drives Without Current Sensing

This paper introduces a current sensorless speed control method for interior permanent magnet synchronous motors (IPMSMs) to track the maximum torque per ampere (MTPA) trajectory. Unlike traditional cascaded control structures, current measurements and inner regulation loops are eliminated. Instead, the MTPA is attained by directly adjusting the voltage vector amplitude and angle. An analytical formulation based on the motor voltage model is developed to extract the optimal voltage amplitude to run the motor within the MTPA operating points, disregarding any control law approximation or lookup tables-based numerical solutions. As a result of excluding current measurements and regulation loops, a one-speed controller is required. This leads to a significant reduction in control system complexity. Moreover, the simple structure of the control system highly qualifies it for cost-effective implementation of IPMSM applications. The validity of the designed control method is confirmed experimentally using a
$5 Hp$
IPMSM. The experimentally obtained results are compared to the conventional field-oriented MTPA (FOC) to highlight the effectiveness of the suggested control system considering different operating conditions. Additionally, the MTPA trajectory tracking accuracy is quantitatively assessed using two performance metrics.