Gan Dong

Current Regulation in Four-Leg Voltage-Source Converters

Three-phase four-leg voltage-source converters by virtue of the fourth leg connected to the neutral points of the wye-connected loads effectively handle the zero-sequence currents and voltages occasioned by connected load impedance imbalances and/or nonlinearity of loads. This paper develops a generalized carrier-based pulsewidth-modulation scheme for this converter which with a natural reference-frame control scheme that directly controls the actual load currents ensures current regulation irrespectively of the nature of the load. The proposed modulation and control schemes are effectively validated by computer simulation and experimental results for the converter operation in the linear and overmodulation regions.

Generalized discontinuous carrier-based PWM modulation scheme for multi-phase converter-machine systems

Using an expanded reference frame transformation expressed in the complex-variable form, the possibilities offered by multi-phase converters, using carrier-based, sine-triangle pulse-width modulation to generate voltages of different frequencies to actuate multi-phase electric machines are set forth. The generalized expressions for the modulation signals, including the neutral voltage component to be compared with the high frequency triangle waveform to synthesize reference voltages for both five and six-phase converter-electric machines are determined. How the inclusion of the neutral voltage affects the modulation signals and the voltage gain and waveform quality is discussed. Some experimental results of synthesized five phase converter voltage waveforms are provided to validate the voltage waveform synthesis using carrier-based generalized (dis)continuous pulse-width modulation for operation in both the under and over- modulation regimes.

Efficiency Optimizing Control of Induction Motor Using Natural Variables

This paper presents a new approach of optimizing the efficiency of induction-motor drives through minimizing the copper and core losses. The induction-machine model, which accounts for the varying core-loss resistance and saturation dependent magnetizing inductance, uses natural and reference frame independent quantities as state variables. Utilization of the nonlinear geometric control methodology of input-output linearization with decoupling permits the implementation of the control in the stationary reference frame. This approach eliminates the need of synchronous reference transformation and flux alignment required in classical vector control schemes. The new efficiency optimizing formulation yields a reference rotor flux, which ensures a minimum loss and yields an improved efficiency of the drive system especially when driving part load. The proposed scheme and its advantages are demonstrated both by computer simulations and some experimental results for motor speed control

Efficiency optimizing control of induction motor using natural variables

This paper presents a new approach of optimizing the efficiency of induction motor drives through minimizing the copper and core losses. The induction machine model which accounts for the varying core loss resistance and saturation dependent magnetizing inductance uses natural and reference frame independent quantities as state variables. Utilization of the nonlinear geometric control methodology of input-output linearization with decoupling, permits the implementation of the control in the stationary reference frame. This approach eliminates the need of synchronous reference transformation and flux alignment required in classical vector control schemes. The new efficiency optimizing formulation yields a reference rotor flux which ensures minimum loss and yields an improved efficiency of the drive system especially when driving part-load. The proposed scheme and their advantages are demonstrated both by computer simulations and some experimental results for motor speed control.

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

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.

Design Issues of Natural Reference Frame Current Regulators with Application to Four-leg Converters

Three-phase, four leg voltage source converters by virtue of the fourth leg connected to the neutral points of the wye-connected loads effectively handle the zero sequence currents and voltages occasioned by load impedance imbalances and/or nonlinearity of loads. This paper outlines a generalized carrier-based pulse-width modulation scheme for this converter which with a natural reference frame control scheme directly controlling the actual load currents ensure current regulation irrespectively of the nature of the load. The controller structure and design are discussed explicitly with attention paid to considerations leading to the selection of the controller parameters yielding satisfactory location of system poles and zeros. The proposed modulation and control schemes are effectively validated by computer simulation and experimental results for the converter operation in the linear and overmodulation regions

Sensorless control of induction motor using natural variables with loss minimization

This paper presents an approach to sensorless speed control an efficiency-optimized induction motor using natural and reference frame independent quantities as state variables - the square of the magnitude of rotor flux linkage, active and reactive torques and rotor speed. Utilization of the nonlinear geometric control methodology of input-output linearization with decoupling permits the implementation of the control in the stationary reference frame. This approach eliminates the use of synchronous reference transformation and flux alignment required in classical vector control schemes. The proposed sensorless speed method uses both the rotor voltage equations, which are shown to provide good rotor speed estimation. The efficiency of the induction motor is realized by choosing the optimal: reference rotor flux linkage using an efficiency optimizing formulation. The proposed scheme and their advantages are demonstrated both by computer simulations and some experimental results for motor speed control

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.

Analysis of a synchronous reluctance machine with an auxiliary single-phase winding

A three-phase synchronous reluctance machine having an axially laminated rotor structure and an auxiliary DC source fed single-phase control winding has utility as either as a high-speed generator or a high-torque, low-speed motor. This paper provides an understanding of its operation using electric circuit and electromagnetic field concepts in the process of which some insights are provided into the design of the windings, conditions for torque production and generation of electric power when operating in the motoring or generating modes. Some confirmatory experimental results of analytical developments are provided showing performance characteristics of an experimental machine.