Abstract
In order to reduce the chattering caused by the discontinuity of the control function in the traditional sliding mode observer (SMO), this article proposes a sliding mode observer with phase-locked loop (PLL) to estimate the speed and position of the rotor. The back electromotive force (EMF) of a permanent magnet synchronous motor (PMSM) in a static coordinate system is accurately estimated by SMO, and then, PLL is constructed to combine the observed rotor position angle and back EMF to compensate the phase lag in angle estimation so as to obtain a more accurate speed. It solves the problems of poor robustness and complex algorithms in the traditional SMO prediction algorithm. The simulation results show that the SMO with PLL can effectively reduce the system chattering and effectively improve the accuracy of rotor speed and position estimation.
Highlights
Since electric drives for propulsion can eliminate the need for shafts and gearing while increasing vehicle stealth and power system flexibility, there has been a large number of advances on permanent magnet synchronous motors (PMSMs) for vehicle propulsion in power semiconductors, magnetic materials, and energy storage systems (Liu et al, 2018; Nguyen et al, 2018; Cui et al, 2020; Liu et al, 2021; Zhang et al, 2021; Fu et al, 2022)
It can be seen from Eq 5 that the phase of the back electromotive force (EMF) is related to the rotation angle of the motor, and the amplitude of the back EMF is related to the speed of the motor
The design steps of the synovial current observer are as follows: 1) a synovial current observer is designed based on the PMSM two-phase static coordinate system model; 2) the observed current is derived from the synovial current observer model; 3) the state equation of the current error is obtained by making a difference between the observed value of current and the actual value of current; 4) the observed value of back EMF is obtained from the error equation, and the rotor position θ can be estimated according to the observed value of back EMF; and 5) the angular speed ω can be obtained by differentiating θ
Summary
Since electric drives for propulsion can eliminate the need for shafts and gearing while increasing vehicle stealth and power system flexibility, there has been a large number of advances on permanent magnet synchronous motors (PMSMs) for vehicle propulsion in power semiconductors, magnetic materials, and energy storage systems (Liu et al, 2018; Nguyen et al, 2018; Cui et al, 2020; Liu et al, 2021; Zhang et al, 2021; Fu et al, 2022). Aiming at the chattering problem in the estimation of traditional SMO, a rotor position identification method of PLL is proposed based on the effective flux model (Zheng et al, 2015; Zhan et al, 2020; Zhao et al, 2020). Distinguished from traditional SMO, a sensorless control of the permanent magnet synchronous motor based on SMO with PLL has been designed to improve the accuracy of rotor speed and position estimation. The function of the PLL controller is to adjust θ^e 0 to determine the difference between the estimated position θ^ and the actual rotor position θ It weakens the influence of natural chattering and improves the robustness of position and speed estimation. The phase-locked loop is used to track the rotor speed and position, which effectively improves the estimation accuracy, and proves the correctness and feasibility of the proposed method.
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