Implementation of a novel and versatile initial rotor position estimation method on surface-mounted permanent magnet syn
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Indian Academy of Sciences Sadhana(0123456789().,-volV)F T3](0123456789().,-volV)
Implementation of a novel and versatile initial rotor position estimation method on surface-mounted permanent magnet synchronous motor prototype at zero speed SOURABH PAITANDI* and MAINAK SENGUPTA Department of Electrical Engineering, Indian Institute of Engineering Science and Technology, Shibpur 711103, India e-mail: [email protected]; [email protected] MS received 17 January 2020; revised 13 August 2020; accepted 16 September 2020 Abstract. This paper presents a novel initial rotor position estimation method for a surface-mounted permanent magnet synchronous motor (SPMSM) using its inherent magnetic features. Here, the initial rotor position has been estimated utilising the variation in phase inductances arising out of the unavoidable but very small saliency occurring either out of magnetic saturation of the machine or the magnet shape. Detailed investigations have been carried out to enumerate the actual magnitude of the inductances of the SPMSM with distributed armature winding and the dynamic saturation status with armature current variation. Here, 3-phase balanced voltage of higher frequency (150 Hz) is applied to the motor terminals for a short period of time (for 300 ms) and the corresponding phase currents are indirectly used to determine the rotor position. Innovative signal processing steps have been used to distinguish small differences in the 3-phase currents caused by the small differences in the phase inductances. The position is determined from the relative values of different phase currents using a novel approach. This still leads to two diametrically opposite (electrical phase) solutions for the instantaneous rotor position. To eliminate this ambiguity, two alternative methods (for pole identification) have been proposed. Extensive co-simulations of finite-element method (FEM)-based electromagnetic simulation and system simulation (for logic implementation) have been conducted. The estimation methods have been validated experimentally on a laboratory-developed prototype SPMSM that was designed and fabricated by the authors. The experimental results are found to be in excellent agreement with the FEM-based simulation results. The complete initial position estimation method takes less than 1 s of real time, which is typically less than the precharging time of standard commercial inverters. Keywords. Surface-mounted PMSM; initial position estimation; finite-element method (FEM); selfinductance; coupled co-simulation; V/f control.
1. Introduction Permanent magnet synchronous motors (PMSMs) dynamically require the knowledge of rotor position at every instant for proper operation and control. Usually, encoders, resolvers or Hall-sensors are used to obtain the rotor position. However, these additional elements increase the overall size and cost of the system and also reduce its reliability. Hence, emphasis is laid on position sensorless control of these motors. In most of the cases, the rotor position information is
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