Mark M. Harbaugh

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.

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.

Implementation Issues in Voltage Zero Sequence-Based Encoderless Techniques

Recent articles demonstrate that sensorless drives for induction motors can operate at zero-electrical and mechanical frequencies with the aid of high-frequency signal injection techniques and processing the zero-sequence voltage signals. The paper presents some practical implementation issues affecting the performance of such a technique and shows how to improve the quality of the estimated angle. All the assessments are experimentally proved and have a general value that can be extended to other sensorless techniques injecting high-frequency signal.

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.

Integrated multi-drive configuration for starter-alternator applications

The paper presents a study of an Integrated Multi-Drive (IMD) system, obtained by redesigning the stator winding of a standard electrical machine to derive a combination of several Sub-Machines (SMs). A single SM consists of an independent three-phase stator winding set sharing a common magnetic circuit including the rotor with the other SMs. Exploiting independent vector control for each SMs, the proposed structure can be considered as a complex electromechanical system with newer perspectives compared to standard single-shaft multi-drives systems where the machines are not magnetically coupled. In the paper, a new IMD configuration has been experimentally tested addressing starter-alternator application. Study results highlight the potential and flexibility of proposed integrated IMD to realize an energy conversion process with controllable multidirectional power flows, also providing a satisfying dynamic behavior to the system.

Vector Control Strategy for Multidirectional Power Flow in Integrated Multidrives Starter-Alternator Applications

The paper deals with the analysis and implementation of a vector control strategy devoted to integrated multidrive systems used in starter alternator applications with several dc buses at different voltage levels. The electromechanical system of the considered multidrive topology is obtained by splitting the conventional stator winding of an induction machine into different n three-phase subunits, maintaining the same magnetomotive force distribution and sharing the same rotor. Each stator unit together with rotor can be considered a submotor, thus the entire electromagnetic system behavior can be considered as the combination of all submotors contributions. The submotors are suitably supplied through standard three-phase inverters whose technical specifications are also established according to the storage unit voltage levels. First, a detailed mathematical representation of the electromagnetic system has been developed, then the conditions to carry out the field orientation in each generic subdrive are determined. Addressing a starter-alternator system, the integrated multidrive configuration has been experimentally tested, highlighting the capability of the proposed approach to efficiently handle multidirectional power flows among the storage units and mechanical system while ensuring high dynamic performance.

On-line stator resistance and permanent magnet flux linkage identification on open-end winding PMSM drives

This paper deals with the development and implementation of an on-line stator resistance and permanent magnet flux linkage identification approach devoted to three-phase and open-end winding permanent magnet synchronous motor drives. In particular, the stator resistance and the permanent magnet flux linkage variations are independently determined by exploiting a current vector control strategy, in which one of the phase currents is continuously maintained to zero while the others are suitably modified in order to establish the same rotating magnetomotive force. Moreover, other motor parameters can be evaluated after re-establishing the normal operation of the drive, under the same operating conditions. As will be demonstrated, neither additional sensors nor special tests are required in the proposed method; Motor electrical parameters can be “on-line” estimated in a wide operating range, avoiding any detrimental impact on the torque capability of the PMSM drive.