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This article presents the sensorless low/zero speed estimation and control for permanent magnet synchronous machines (PMSMs) using the innovative search-based real-time commissioning method. An overview of continuous pulsating high frequency injection used in this article is given for different injection angles in the stationary frame of reference. The variations of the saliency at different injection angles and loading operating points of the machine are presented and analyzed. The commissioning, search, and offset of the proposed observer are also discussed. Experimental results showing the performance of the sensorless method are presented in both open-loop and sensorless closed-loop current control. In sensorless mode the PMSM drive is controlled through a rotor flux oriented algorithm which uses the estimated electrical rotor position instead of the encoder measurement. Results for both the estimated mechanical and electrical rotor positions are presented under varying load conditions and speed reversal through the zero-speed region. [ABSTRACT FROM AUTHOR]

This paper considers both flux and rotor position estimations for sensorless control of delta-connected cage induction machines (IMs) at low and zero frequency operation. The variation of leakage inductance due to either saturation or rotor slotting is tracked by measuring the derivative of the zero sequence current in response to the application of appropriate voltage test vectors. The method requires only a single extra sensor. It requires access to machine phase windings and is appropriate for integrated-type induction motor drives. Both a closed-slot and an open-slot machine is used to demonstrate rotor flux and rotor position tracking, respectively. Experimental results are presented showing sensorless torque control and sensorless speed and position control at low and zero frequencies. [ABSTRACT FROM AUTHOR]

This paper considers the position and speed estimation at low- and zero-frequency operations in standard delta- connected cage induction machines (IMs). A rotor-slot detection technique is used, where test vectors are injected during the pulsewidth-modulation (PWM) periods and the resulting zero- sequence-current derivatives (ZSCDs) are measured using a non-integrating Rogowski coil. The rotor slotting in a near-standard 30-kW symmetric IM is utilized for rotor-position tracking. The rotor-slot number was selected to yield a measurable "position-dependent" ZSC. Experimental results show the variation of the measured current signals with rotor position and how these are used for tracking of the rotor position. [ABSTRACT FROM AUTHOR]

It has been well established in the literature that inverter nonlinearity effects afflict saliency-based sensorless drives. The inverter nonlinearity leads to the generation of signals that corrupt the useful position information. The resulting effect differs depending on the injection approach utilized in the drive. Various compensation techniques to overcome this effect have been published in the literature. This paper is concerned with the zero-vector current-derivative technique. The effect of the varying on -state resistance of the inverter power devices on the position signal is investigated in detail. Knowledge of the source of the corrupting signals facilitates compensation and determines its applicability. Two approaches for inverter nonlinearity compensation are compared. The first approach utilizes a lookup table from offline-processed data, while the second one is a simpler approach based on the current-dependent resistance characteristic of the inverter switching devices. Experimental performance under sensorless condition is shown for both approaches. [ABSTRACT FROM PUBLISHER]