A Model Predictive Control Scheme with Minimum Common-Mode Voltage for PMSM Drive System Fed by VSI

Abstract

Common-mode voltage (CMV) brings shaft voltage and shaft current, and corrodes the bearings of the permanent-magnet synchronous machine (PMSM), which affects the reliability of the whole PMSM drive system. Since the CMV applied by the zero voltage vectors (ZVVs) is three times that applied by the active voltage vectors (AVVs), a modulation scheme achieving minimum CMV without ZVV is proposed and introduced into the model predictive control structure for the PMSM drive system. Firstly, the whole modulation range is divided into three regions, including the low voltage modulation region (LVMR), high voltage modulation region (HVMR), and over-voltage modulation region (OVMR). Meanwhile, the regional boundary expression is derived. Then, the active zero-state pulse width modulation (AZSPWM) is adopted in LVMR. To improve the steady-state performance, near-state pulse width modulation (NSPWM) without opposite ZVVs is applied to the HVMR. Furthermore, when the reference voltage vector (VV) is located in OVMR, an optimal scheme is proposed to improve the dynamic response. Under the premise of no ZVV existing in the whole modulation region, simulation and experimental results show that the proposed hybrid modulation method can improve the steady-state and dynamic performance of the PMSM drive system.

An Improved Near-State Pulse-Width Modulation with Low Switching Loss for a Permanent Magnet Synchronous Machine Drive System

“…According to [18], the NSPWM has a limited linearity region, which means it can only modulate the voltage in that the modulation index M is greater than 0.61. However, when PMSM operates at low speed, the NSPWM generates high CMV and does not modulate the reference voltage correctly.…”

“…However, the ripple of the current is too great [17]. In comparison, near-state PWM (NSPWM) adopts three adjacent active vectors to synthesize the reference vector; it can reduce the high-and low-frequency CMV simultaneously, and the steady state under NSPWM is better than that under AZSPWM [18]. It should be noted that no matter where the reference vector is located, there are two vector synthesis methods, and there exists one phase of switches in an inactive state.…”