Abstract
The six-phase motor control system has low torque ripple, low harmonic content, and high reliability; therefore, it is suitable for electric vehicles, aerospace, and other applications requiring high power output and reliability. This study presents a superior sensorless control system for a six-phase permanent magnet synchronous motor (PMSM). The mathematical model of a PMSM in a stationary coordinate system is presented. The information of motor speed and position is obtained by using a sliding mode observer (SMO). As torque ripple and harmonic components affect the back electromotive force (BEMF) estimated value through the traditional SMO, the function of the frequency-variable tracker of the stator current (FVTSC) is used instead of the traditional switching function. By improving the SMO method, the BEMF is estimated independently, and its precision is maintained under startup or variable-speed states. In order to improve the estimation accuracy and resistance ability of the observer, the rotor position error was taken as the disturbance term, and the third-order extended state observer (ESO) was constructed to estimate the rotational speed and rotor position through the motor mechanical motion equation. Finally, the effectiveness of the method is verified by simulation and experiment results. The proposed control strategy can effectively improve the dynamic and static performance of PMSM.
Highlights
Because of the high output power [1], low torque ripple [2], low harmonic content [3], and high reliability of the multiphase permanent magnet synchronous motor (PMSM) [4,5], this motor has broad application prospects in electric vehicles, ship propulsion, aerospace, and rail transit, all of which require high power and high reliability [6,7]
There are two types of sensorless position detection techniques: the first is a high-frequency injection (HFI) method which is suitable for low speeds and uses the rotor salient effect of the motor rotor to estimate the position and speed [10,11]
The advantage of this control method is that it is not sensitive to the change of motor parameters, and the estimation accuracy has nothing to do with the speed; the biggest disadvantage is that it is only suitable for the motor with a salient effect, and because of the injection of highfrequency signals, there is the problem of high-frequency noise
Summary
Because of the high output power [1], low torque ripple [2], low harmonic content [3], and high reliability of the multiphase PMSM [4,5], this motor has broad application prospects in electric vehicles, ship propulsion, aerospace, and rail transit, all of which require high power and high reliability [6,7]. Shao et al [21] proposed an integral SMO to compensate for the estimated BEMF error It solves the problems of chattering and phase delay, this method has a weak resistance to load disturbance and is not practical. Zhang et al [22] proposed a cascaded SMO using an adaptive sliding mode to observe the BEMF and compared three methods of angle estimation: phase-locked loop (PLL), second-order extended state observer (ESO), and non-smooth feedback observer (NSFO). The dual Y shift 30◦ six-phase PMSM with an isolated neutral point was investigated, and a new sliding mode sensorless control strategy was used to estimate the speed and rotor position. Taking the stator current components as the state variable, from Equation (7), we obtain: diα dt
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