Investigation of Optimized Control Methods for Permanent-Magnet Synchronous Motor Drives




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The prevalence of permanent-magnet synchronous motor (PMSM) drives in industry applications such as electric/hybrid vehicles has stimulated the need for optimized control methods. Theoretically, the dynamic performance, torque generation efficiency, and robustness are three primary metrics that control methods have sought to optimize. In industry applications, however, the drive’s overall system cost must also be taken into consideration. For PMSM drives, the controller unit accounts for a large portion of the end-product cost and more complicated control methods need more powerful controller units in order to be implemented. Therefore, the PMSM drive can be more affordable if the control methods have simpler structures.

Field-oriented control (FOC) schemes and V/f control schemes are most commonly used in PMSM drives. For sensorless PMSM FOC schemes, sliding-mode observer (SMO) is usually adopted to estimate rotor position in the mid- to high-speed range because of its robustness to parameter variations. However, the low-pass filters required in the SMO induce phase delay and cause estimation error which affects the torque generation efficiency. Recently, V/f control schemes are also becoming popular due to its simple structure and wide speed range. They take advantage of stabilizing loops to maintain control system stability without knowledge of rotor position. Therefore, costly rotor position sensors or complicated model based observers are not needed in V/f control schemes. However, the previously proposed stabilizing loops still require much computation effort to guarantee optimal torque generation efficiency. The insulated-gate bipolar transistor (IGBT) based voltage source inverter (VSI) is the standard industry solution for PMSM drives. In order to prevent DC bus short circuit fault, the dead time is inserted in switching signals, which results in current distortion on the other hand. There are previously proposed dead-time compensation methods for FOC schemes to address this issue. However, most of them require extra hardware or complicated signal processing algorithms. In addition, their compensation performance can still be affected by parameter variations. Furthermore, there is no dead-time compensation method which can be conveniently used by V/f control schemes.

The goal of this research is to develop optimized control methods with simpler structures to address aforementioned issues, which can be summarized as follows;

• develop an improved SMO with a new phase delay mitigation algorithm to reduce estimation error,

• develop a V/f sensorless control scheme for PMSM drives with simpler stabilizing loops while guaranteeing the premium performance and optimal torque generation efficiency,

• develop dead-time compensation methods which are robust to parameter variations and easy to be implemented and integrated with FOC and V/f control schemes.



Permanent magnet motors, Electric motors, Synchronous, Electric inverters


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