Peter B. Schmidt

Initial rotor angle detection of a nonsalient pole permanent magnet synchronous machine

This paper presents a technique that calculates the absolute angular position of a permanent magnet (PM) rotor within a pole pair at standstill. The algorithm works with nonsalient pole motors. By choosing an appropriate voltage pulse width and applying it to each phase winding, the stator currents partially saturate the stator iron, enabling the algorithm to discern between a north pole and a south pole, and subsequently, the absolute position. The scheme is computationally simple and does not rely on the knowledge of any of the motor parameters.

Rotor Position Estimation for Synchronous Machines Based on Equivalent EMF

This paper provides and analyzes a simple, robust, and universal model for rotor position estimation for synchronous machines. The rotor position is estimated using an equivalent electromotive force (EMF) model of a synchronous machine or, alternately, using a sliding-mode observer (SMO) based on the equivalent EMF model. The SMO provides fast convergence and low sensitivity to parameter variations. Experimental results with a 3.7-kW interior-permanent-magnet machine have validated the effectiveness of the proposed equivalent EMF scheme.

Notch filter tuning for resonant frequency reduction in dual inertia systems

This paper presents a technique to measure the resonant frequency of a dual inertia spring system using an FFT. The resonant frequency measurement and anti-resonant frequency calculation are utilized to tune an infinite impulse response notch filter to reduce the torsional oscillations in both the motor and load velocities. The simplicity and easy tuning of the filter makes it practical to implement in a DSP. The baseband performance of a resonant system would greatly improve.

A permanent magnet rotor containing an electrical winding to improve detection of motor angular position

Sensorless detection of rotor angular position is desirable for decreasing the cost and increasing the reliability of permanent magnet AC motor drive systems. This paper describes tests performed on a rotor that has surface mounted magnets and a conducting winding that links only the d-axis of the rotor. The conducting winding allows rotor angular position to be detected by stator-winding inductance variations.

An on-line position error compensation method for sensorless IPM motor drives using high frequency injection

This paper addresses the position error issue existing in sensorless IPM motor drives using the high frequency injection (HFI) method. A simple-to-design on-line compensation method is proposed based upon filter group delay theory, which substantially minimizes the error between the estimated position and the actual position caused by filters in a conventional HFI system. The method determines the position error compensation based upon a demodulation delay and a velocity or rotational frequency of the electrical machine. Experimental results with a 10-hp interior permanent magnet motor are presented showing improved sensorless performance using the proposed method.

Generalized stability control for open loop operation of motor drives

This paper proposes a general approach to designing a stability control for open-loop operation that can be used for either induction motor, permanent magnet synchronous motor, or any other motor drives. A speed or frequency set point is adjusted by a frequency compensation value to provide the stability control to mitigate hunting or motor stoppage. The proposed method can be utilized in either conventional motor drives or motor drives with an output filter and a transformer used for oil pump applications.

Equivalent EMF based position observers for sensorless synchronous machines

This paper provides a simple, robust, and universal position observer for position sensorless control of synchronous machines. The observer is designed using an equivalent EMF model of a synchronous machine or, alternately, using a sliding mode controller based on the equivalent EMF model. The sliding mode observer provides fast convergence and low sensitivity to parameter variations. Experimental results with a 5-hp Interior Permanent Magnet (IPM) machine have validated the effectiveness of the proposed equivalent EMF theory.

Sensorless control of a permanent magnet synchronous machine down to near zero speed applied to position motion control

This paper presents a sensorless estimation scheme that enables a permanent magnet nonsalient pole motor to be position controlled without the aid of position or velocity feedback transducers. A closed loop state space observer using two phase current feedback measurements and two phase voltage commands provide estimates for the unmeasured states: position and velocity. The estimates can be parameter sensitive. Therefore, this paper has modeled motor parameters and proposes to perform on-line identification to enhance the output of the observer.

Implementation and performance of position sensorless PMSM control in industrial drives

In recent years there has been increasing acceptance of position sensorless control in industrial products. This paper discusses the implementation and performance of a position sensorless permanent magnet synchronous motor (PMSM) control over the full speed range in a PMSM drive. Experimental results with a commercial drive which utilizes a sensorless scheme are presented in the paper.

Design and implementation of position sensorless starting control in industrial drives with output filter and transformer for oil/pump applications

This paper proposes a position sensorless control scheme for an induction and permanent magnetic motor drive with output filter and transformer. The proposed method provides sufficient starting torque with controlled drive/motor current. In addition, transformer saturation is addressed. The sensorless starting scheme presented in this paper has been implemented in a commercial drive for deep well applications.