Sensorless Control for IPMSM Based on Adaptive Super-Twisting Sliding-Mode Observer and Improved Phase-Locked Loop

Abstract

In traditional sensorless control of the interior permanent magnet synchronous motors(IPMSMs) for medium and high speed domains, a control strategy based on a sliding-mode observer(SMO) and phase-locked loop (PLL) is widely applied. A new strategy for IPMSM sensorless controlbased on an adaptive super-twisting sliding-mode observer and improved phase-locked loop isproposed in this paper. A super-twisting sliding-mode observer (STO) can eliminate the chatteringproblem without low-pass filters (LPFs), which is an effective method to obtain the estimated backelectromotive forces (EMFs). However, the constant sliding-mode gains in STO may causeinstability in the high speed domain and chattering in the low speed domain. The speed-relatedadaptive gains are proposed to achieve the accurate estimation of the observer in wide speed rangeand the corresponding stability is proved. When the speed of IPMSM is reversed, the traditionalPLL will lose its accuracy, resulting in a position estimation error of 180°. The improved PLL basedon a simple strategy for signal reconstruction of back EMF is proposed to ensure that the motor canrealize the direction switching of speed stably. The proposed strategy is verified by experimentaltesting with a 60-kW IPMSM sensorless drive.