Signal injection method without torque ripple based on maximum torque control frame

Abstract

This paper presents a new signal injection method without torque ripple for sensorless controls of salient‐pole synchronous motors at low speeds. At low speeds, since the back electromotive force (EMF) including position information decreases, additional signals are injected to estimate position information of saliency. The torque ripple caused by the injections of signal currents can be represented by a cross product of a virtual flux and a differential current vector. An f‐axis of maximum torque control frame is defined to the direction of the virtual flux. Therefore, signal injection without torque ripple is realized by using the f‐axis current. In this paper, a signal injection method with f‐axis current is proposed, and the effects of the estimation error are discussed to apply the method for position‐sensor‐less controls. The proposed injection method allows us to flexibly design frequencies of the signal current. The validity of the proposed method and applicability to position estimation are confirmed by experimental tests. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Maximum Torque Response Control based on Maximum Torque Control Frame

“…(II) The current change in the f -axis does not affect the torque (9) . (III) The current change in the t-axis achieves the maximum torque response.…”

“…MTPA Control based on the f -t Axes (9) (10) In this section, we describe the relation between the MTPA condition and the f -t axes. The current vector i dq can be represented with the current amplitude I and the current phase angle θ i as follows:…”

“…Hence, torque control with voltage limit methods and overmodulation methods have been studied (2)- (8) . We defined the maximum torque control frame, which is denoted by the f -t axes to separate a current vector into two components related to the magnetic flux component and the motor torque component (9) . We have applied the f -axis current to the signal injection method without causing torque ripple for sensorless control (9) and the maximum-torque-perampere(MTPA) control method (10) .…”

Sensorless IPMSM position estimation based on multi SVPWM with elimination of inverter nonlinear effects

“…In the signal injection techniques based on the saliency, a signal is usually injected in the αβ or dq components [7][8][9]. These methods work well at low speed and zero speed, but signal extraction with low-pass filter (LPF) will tend to degrade the time response of the vector control.…”

Novel PWM scheme with multiphase SVPWM for reducing current ripple

“…a) Position estimation based on high-frequency (HF) signal injection An HF signal, which can be a rotating voltage vector, an alternating voltage vector or a pulse pattern, is usually injected at the af3 or dq components [3]- [5]. The response signal is usually evaluated from the HF current, current derivative or HF voltage.…”