Dead-time effect and current regulation quality analysis for a sliding-mode position observer-based sensorless IPMSM drives

This paper presents an extended back electromotive force (EMF)-based discrete sliding-mode observer (SMO) for rotor position/speed sensorless control of interior permanent magnet synchronous machines (IPMSMs). Normally, the dead-time effects in voltage source inverters are often ignored or assumed to be fully compensated when designing a position observer. However, for high-voltage and high-power applications, the difference between the command voltages and terminal voltages cannot be ignored. In this paper, the periodically oscillating position estimation error caused by the dead-time effect is analyzed. Then a dead-time compensation algorithm is proposed to solve this problem. Moreover, since the measured current is an input of the position observer, current regulation and position estimation will affect with each other in the closed-loop sensorless control. The performance of the proposed discrete SMO with the dead-time compensation scheme is validated by a practical high-power IPMSM drive system used in off-road hybrid electric vehicles. The relationship among dead-time effect, current regulation, and position estimation are also evaluated by using the test stand.