Discrete-Time Observer Design for Sensorless Synchronous Motor Drives

Abstract

Abstract-This paper deals with the speed and position estimation of interior permanent-magnet synchronous motor (IPMSM) and synchronous reluctance motor (SyRM) drives. A speedadaptive full-order observer is designed and analyzed in the discrete-time domain. The observer design is based on the exact discrete-time motor model, which inherently takes the delays in the control system into account. The proposed observer is experimentally evaluated using a 6.7-kW SyRM drive. The analysis and experimental results indicate that drastic performance improvements can be obtained with the direct discrete-time design, especially if the sampling frequency is relatively low compared to the fundamental frequency.

Position estimation for synchronous motor drives: Unified framework for design and analysis

“…The nonlinear estimation-error dynamics consisting of (2)- (4) and (6)- (8) can be linearized for analysis purposes [3], [4], [12]. The operating-point quantities are marked with the subscript 0.…”

“…where β = −ψ aq0 /ψ ad0 is an auxiliary variable [4], [12]. As special cases, β = 0 holds for nonsalient machines and β = i q0 /i d0 for SyRMs.…”

“…These kind of industrial drives should obviously be sensorless for cost savings. A fundamental-wave rotor-position observer, based on a mathematical motor model, is a core algorithm in sensorless control [1]- [12]. The observer should provide (locally) stable and sufficiently fast estimation-error dynamics at all speeds and loads (except in the zero-speed condition, which is unobservable).…”

“…For salient machines, the estimation-error dynamics have been rigorously analyzed only in a few papers [3]- [5], [8], [12]. A concept of the fictitious flux has been used in order to turn the salient machine model into a more favourable nonsalient form [5].…”

“…In the MTPA mode, the minimum value of 0.77 p.u. for the d-axis flux is used, corresponding to [12].…”