Zhiqiao Wu

Pulse-Width Modulation for Five-Phase Converters Based on Device Turn-on Times

High power, high reliability electric motor drives in such applications as electric ship propulsions, electric locomotives and hybrid electric vehicles require the use of high order phase electric machines run with multi-phase converters. Presently, five and asymmetrical six-phase machines with their associated converters are emerging industry standards. This paper presents a novel carrier-based pulse-width modulation technique for the five phase converters, which in applications is required to generate five phase fundamental frequency voltages with or without a third harmonic (of the fundamental frequency) component voltages. The modulation waveforms required to switch the devices in the converter legs are obtained by summing the turn-on times of the switching devices, which are calculated using the space vector representations of the converter switching states. The determination of the carrier-based modulation waveforms which with a high frequency sine-triangle generate the switching functions for the converter is set forth explicitly. The resulting carrier-based PWM modulation scheme is experimentally implemented with a TMS DSP for converter operation in the linear and over-modulation regions. Experimental results are presented to confirm theory

A control strategy for optimum efficiency operation of high performance interior permanent magnet motor drives

This paper, using the concept of input-output linearization with decoupling, sets forth the speed control of the interior permanent magnet motor drives which simultaneously ensures the minimization of the losses-the copper and core losses. This control scheme is unique in that saturation dependent parameters such as the d and q axis inductances and the armature reaction dependent magnet flux linkage are included in the controller structure formulation and implementation. The proposed control scheme differs from known schemes which are either based on perturbation and search methods or on steady curve fitted graphs that map the command q and d axis currents based on reference torque. Unlike these methods, an optimization formulation that dynamically determines the reference currents/voltages required to achieve high performance speed control and total loss minimization is used. The control structure methodology, the nature of the variations of the machine parameters and how they influence the machine efficiency are clearly laid out.

High performance speed sensor-less control of an induction motor drive using a minimalist single-phase PWM converter

Home appliances and comfort conditioners are yet to benefit from the recent developments in power electronics because of cost constraints. In this paper a speed sensor-less induction motor drive system with a reduced converter device counts (minimalist, sparse converter) and actuated from a single-phase system is proposed for such low cost applications. The analysis, control, dynamic and steady-state characteristics of the proposed drive are experimentally illustrated.

High-Performance Control of a Dual Stator Winding DC Power Induction Generator

This paper investigates the use of a dual stator winding squirrel-cage induction machine for generating dc power using series- or parallel-connected ac-dc pulse width modulation rectifiers. The operating principles and constraints when generating under minimum total copper-loss condition are explored using the machine steady-state model considering magnetizing flux saturation effects. Regulation of the dc voltage using concepts of the nonlinear input-output linearization method including the design of the controllers is set forth and confirmed to be effective by computer simulation results. Some experimental waveforms of the generator under load are also included in this paper

Modeling of a Dual Stator Winding Induction Machine Including the Effect of Main Flux Linkage Magnetic Saturation

The air-gap flux linkage of a dual-stator-winding squirrel-cage induction machine comprises of four fundamental flux components due to the currents flowing in the two stator windings with P1 and P2 pole numbers and the currents that they induce in the squirrel cage. In view of the dissimilar pole numbers of the stator windings and frequencies of the supply voltages, the air-gap flux linkage waveform is complex, particularly when the stator and rotor teeth are saturated. This paper explores this complexity using analytic computer simulation, finite-element analysis, and some experimental results. Furthermore, a fundamental component circuit model of the machine is set forth, which, with the use of a specially defined reference frame transformation, permits an accurate simulation of the transient and dynamic characteristics. Computer simulation results are validated by some experimental results obtained from a 2-hp machine.

High-Performance Control of a Boost AC–DC PWM Rectifier/Induction Generator System

This paper presents a control methodology for the dc voltage regulation of an induction generator/ac-dc boost rectifier system, in which the copper loss of the generator is minimized. With the aid of an input-output linearization technique, which linearizes and decouples the model equations in the synchronous reference frame, a rotor-flux-vector-control-type high performance is achieved. Steady-state analysis provides some insights into the operability regime of the generator. The effectiveness of the control scheme under different load conditions as well as varying rotor speeds has been demonstrated by computer simulations. Some experimental results have been included

Speed Control of a Dual Stator Winding Induction Machine

A dual stator winding induction machine having two stator winding sets and a squirrel-cage rotor structure has been identified as having a good low speed controllability. This paper therefore presents the speed control of a dual stator winding machine using the concepts of indirect rotor field orientation and input-output linearization formalism. With a torque partition coefficient, it is possible to vary the electromagnetic torques generated by the two stator windings, which at low speeds makes it possible for one winding set to be generating leading to an improvement of the flux linkage estimation. Simulation results are presented for various command speed profiles including zero speed operation showing the efficacy of the torque partition coefficient even at very low speed operation. This possibility of operating at low speeds including zero using model based flux estimation schemes set forth in this paper is one of the benefits of the dual stator winding induction machinery.

MRAS Speed Estimation and Full-Order Flux Observer for Dual Stator Winding Induction Motor Drives

A design methodology for the full-order flux observer and model reference adaptive mechanism (MRAS) to estimate flux linkages and rotor speed of the dual stator winding induction motor that ensures system stability under all operating conditions is set forth. The Butterworth polynomial and D- decomposition techniques are used to select observer and speed controller gains. Computer simulation results of the controlled sensor-less drive system confirm the adequacy of the proposed full-order flux observer and speed estimation scheme evidenced by the accurate rotor speed regulation.

Design and analysis of a five-phase interior permanent magnet generator with a non-integer number of stator slots per phase

Traditional electric machine design requiring the balancing of the phases both in phase voltage magnitudes and the angles between adjacent phases informs that the number of stator slots per phase must be an integer. There are situations however, where it is cheaper to use existing laminations for designs with non-integer number of slots per phase to build generators for specialized applications especially for DC power. In such cases a multi-phase design ensures a measure of fault tolerance and the unbalances in the phase angles between the winding phases have little effect on the quality of the output DC voltage. The methodology for the design of a five phase, 4-pole interior permanent magnet (IPM) generator using 36 slots as a source of DC power is outlined. Experimental results for the operation under healthy and faulty conditions (one and two phase windings open) are presented for verification of fault tolerance of multi-phase machines.

A Switching Loss Minimization Current Sensor-less Control for AC-DC Boost Rectifiers

This paper presents a switching loss minimization, current-sensor-less control algorithm for AC-DC boost rectifiers. The current sensors are eliminated by aligning the modulation signals with the line currents. The zero sequence signals added to the modulation signals are properly selected such that the switching devices are clamped at the regions where the phase currents are high. This method results in the reduction of the device switching losses. The steady state analysis and simulation results included in the paper validate the proposed control scheme. This simple and robust control scheme is especially good for high power low dc output voltage applications and it renders close to unity input power factor.