Combined Active Flux and High-Frequency Injection Methods for Sensorless Direct-Flux Vector Control of Synchronous Reluctance Machines

Abstract

This paper proposes a sensorless control scheme for synchronous reluctance (SyR) motor drives based on the direct-flux vector control (DFVC) method. The control operates in stator-fluxoriented coordinates, using constant switching frequency. A hybrid position and speed observer is proposed, based on the combination of the active flux concept and high-frequency signal injection and demodulation. The two methods are fused together to form a unique position and speed estimate signals, with seamless transition between the two models based on reference speed. The proposed observer covers a wide speed range, from standstill operation at full load to flux weakening (FW). Furthermore, it is inherently immune from position estimation error caused by cross saturation, as proven mathematically and experimentally. The motor is operated according to the maximum torque per ampere (MTPA) law. Specific issues related to MTPA around zero torque are addressed in this paper. The proposed control technique extends the range of application of the DFVC to encoderless drives, and can be usefully adopted in those applications where both zero-speed and FW speed range operations are necessary, such as home appliances, or automotive and aerospace actuators and generators. A 2.2-kW SyR motor prototype was tested to verify the feasibility of the proposed method. Key tuning aspects are addressed in this paper.

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

“…This method is based on the salient pole effect of the motor, which is mainly used in zero and low speed domains. The second one is called back EMF based methods [10][11][12][13][14][15][16][17][18][19], which utilizes the estimated back EMF signals to obtain the position information of the motor. Because the magnitude of back EMF is in proportion to the speed of the motor, the performance of back EMF based methods at ultra-low and zero speed is extremely poor [11].…”

“…Because the magnitude of back EMF is in proportion to the speed of the motor, the performance of back EMF based methods at ultra-low and zero speed is extremely poor [11]. Hence, back EMF based methods and signal injection methods are usually combined to achieve sensorless control for a whole speed range [12][13][14]. Back EMF based methods primarily includes the model adaptive method (MRAS) [16], the Kalman filtering method (EKF) [17], and the sliding mode observer (SMO) [2,18,19], etc.…”

Observers for Sensorless Synchronous Motor Drives: Framework for Design and Analysis

“…If the application requires sustained operation at very low speeds in a loaded condition, the observer should be combined with a signal-injection scheme, cf. [2]- [4], [15]- [17], [19]- [23].…”

A Novel High Frequency Signal Injection Strategy for Self-Sensing Control of Electric AC Machine Drives

“…These methods are classified into two main categories: category 1, model based techniques: Artificial intelligence techniques [1], nonlinear observers [2], MRAS [3] methods. category 2, saliency based techniques by injected a HF signal [4], [5]. In this paper, category 2 is considered.…”