Adaptive Second-Order Active-Flux Observer for Sensorless Control of PMSMs With MRAS-Based VSI Nonlinearity Compensation

Abstract

This paper proposes an adaptive second-order active-flux observer (ASO-AFO) for sensorless control of permanent magnet synchronous machines (PMSMs) with on-line voltage source inverter (VSI) non-linearity compensation, which is based on the model reference adaptive system (MRAS). First, an ASO-AFO is introduced to observe the active flux. The parameters of the observer are speed-adaptive, thus reducing the observation error in different speed ranges. Then, a method based on MRAS is proposed to compensate the VSI non-linearity. The VSI non-linearity makes the actual voltage different from the ideal output voltage, resulting in a specific harmonic current vector in addition to the fundamental current vector. The fundamental current vector and the current vector composed of the fundamental and harmonic current vectors are selected as the output of the reference model and adaptive model. The cross-product of their output reflects the severity of the VSI non-linearity. The root mean square (RMS) value of the cross-product is selected as the objective function. The non-linearity is compensated by minimizing the objective function, which is realized by the gradient descent method. Finally, the effectiveness of the proposed ASO-AFO with MRAS-based VSI non-linearity compensation is verified by comprehensive experiments.