Search

In this paper, two three-phase ac drive systems with reduced number of components, named configurations S and H, are investigated. Configuration S uses multiple two-leg voltage source inverters in which all inverters share an extra-leg. Configuration H also employs multiple two-leg inverters but in this case the inverters share the midpoint of a capacitor bank in the dc-link, instead. These configurations are compared to configuration F that employs multiple three-leg inverters. The main characteristics of the machine drive systems are presented together with selected experimental results that demonstrate the feasibility of the proposed configurations. Index Terms--Induction machine, multiple ac machine drive, reduced components.

A general pulsewidth modulation (PWM) method for control of four-switch three-phase inverters is presented. The proposed vector PWM offers a simple method to select three or four vectors that effectively synthesize the desired output voltage, even in presence of voltage oscillations across the two dc-link capacitors. The method utilizes the so called space vector modulation, and includes its scalar version. Different vector combinations are compared. The effect of Wye and delta motor winding connections over the pulse width modulator is also considered. The common mode voltage generated by the four-switch three-phase converter is evaluated and compared to that provided by the standard six-switch three-phase inverter. Simulation and experimental results are presented to demonstrate the feasibility of the proposed approach. Index Terms--Common mode voltage, four-switch three-phase inverter, vector and scalar pulsewidth modulation (PWM).

This paper investigates a reduced switch count dc-link ac-ac five-leg converter for three-phase power conversion. The converter provides both an input rectifier and an output inverter by sharing a leg in order to reduce the number of power switches. Scalar and vector pulsewidth modulation techniques are presented and the concepts of local and global apportioning factors are introduced. A control technique that aims at maximizing the utilization of the dc-link voltage is proposed. A hysteresis current controller that allows operating with one leg being shared by the load and grid sides is developed. In addition, several relevant characteristics of the converter are addressed, such as voltage capability, harmonic distortion, shared-leg and capacitor currents, and power rating. The features of such a converter are compared to those of the six-leg and four-leg converters. Selected experimental results are presented. Index Terms--Converter modelling and control, five-leg converter, reduced switch count converter.

This paper proposes a technique to determine online the stator resistance and the stator leakage inductance of a four-phase induction machine in a four-phase drive system. These parameters are obtained by solving a least squares minimization problem. The technique is conceived to be used online with the drive strategy without disturbing the machine electromagnetic torque. Experimental results are used to demonstrate the feasibility of the proposed technique. Index Terms--Four-phase machine, induction machine drive, online estimation.

This paper classifies the pulse pulsed dc-link voltage (PDCLV) topologies in six types, depending on both the shape of the pulsed dc-link voltage waveform and the circuit ability to synchronize, or not, with external pulse width modulation (PWM) signals. Main features are compared for a large number of topologies in which the bridge devices commutate under zero-voltage-switching (ZVS) technique. The paper also presents a comparative study of the losses produced by these converters and discusses the principles they employ causing generation such losses. An overview of the control and PWM possibilities for these converters is given and an extensive bibliography is included. Index Terms--Pulsed dc-link voltage, voltage source inverter, zero-voltage-switching.

This paper investigates the use of different techniques for fault detection in voltage-fed asynchronous machine drive systems. With the proposed techniques it is possible to detect and identify the power switch in which the fault has occurred. Such detection requires the measurement of some voltages and is based on the analytical model of the voltage source inverter. Simulation and experimental results are presented to demonstrate the correctness of the proposed techniques. The results obtained so far indicate that it is possible to embed some fault-tolerant properties for the voltage-fed asynchronous machine drive system. Index Terms--Fault detection, motor drive system, voltage source inverter.

This paper investigates the use of a three-leg voltage source inverter topology for supplying two-phase induction motors. The paper also presents two pulse width modulation techniques for voltage control and a quasi time-invariant model to describe an unbalanced two-phase machine. The correctness of the proposed drive system was demonstrated through experimental results obtained with a laboratory prototype. Index Terms--Single-phase ac motor, three-leg inverter, two-phase ac motor.

This paper proposes two unidirectional single-phase ac–dc–ac converters with a reduced number of controlled switches composed of two three-leg converters connected in series. The proposed converters allow us to feed the load voltage with sinusoidal voltages with constant amplitude and frequency and to operate with sinusoidal grid current with a high power factor. The converters can then be used as uninterruptible power supplies and unified power quality conditioners for nonregenerative applications. The system model, space-vector pulse width modulation technique, and a complete control system are given. A method to regulate the dc-link voltages using the voltage vector redundancies is presented. The proposed topologies are compared with the conventional one in terms of operation range, capability to operate with a unity grid power factor, voltage harmonic distortions, semiconductor losses, and others characteristics. Simulation and experimental results in many operating conditions are provided to validate the feasibility of the system. [ABSTRACT FROM PUBLISHER]

The digital scalar pulse-width modulation (DSPWM) gathers the characteristics of simplicity of implementation found in the regular sampling with the flexibility of manipulation of the switching patterns in the space vector modulation (SVPWM). This paper establishes a correlation between the SVPWM and DSPWM techniques. It also shows how to make the DSPWM strategy equivalent to the SVPWM technique without loosing its simplicity of implementation. By using such equivalence concept a microprocessor-based scheme, which uses standard timer circuits and a simple software algorithm, is proposed to implement the DSPWM, technique. The introduction of the 'distribution ratio' in this technique, allows the development of a systematic approach for implementing of either conventional or any modified vector strategies without changing the modulator scheme. This corresponds to generate any attractive nonsinusoidal modulating signals (NSMS) in the carrier-based modulation techniques. Furthermore, the simple digital blocks can be easily implemented as an specialized integrated circuit. Simulated and experimental results demonstrate the validity of the proposed methods. Index Terms--Pulse-width modulation, three-phase inverter.

This paper proposes a technique to estimate the stator resistance of induction machines. The stator resistance is obtained by solving a least squares minimization problem, which solution also provides the value of the leakage inductance. The technique exploits the machine behavior with respect to zero-sequence quantities. It is conceived to be used on-line with the drive strategy without disturbing the angular shaft speed. Experimental results are used to demonstrate the feasibility of the proposed technique. Index Terms--Induction machine, stator resistance, parameter estimation.

This paper presents a universal active filter for harmonic and reactive power compensation for single-phase systems applications. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the system is derived and it is shown that the circulating current observed in the proposed active filter is an important quantity that must be controlled. A complete control system, including pulse-width modulation (PWM) techniques, is developed. Comparisons between the structures are made from weighted total harmonic distortion (WTHD). The steady-state analysis is also presented in order to demonstrate the possibility to obtain an optimum voltage angle reducing the current amplitude of both series and parallel converters and, consequently, the total losses of the system. Simulated and experimental results validate the theoretical considerations. [ABSTRACT FROM AUTHOR]

The use of linear parameter estimation techniques to determine the stator resistance, self-inductance of the stator winding, transient inductance, rotor time constant, as well as the angular shaft speed of a three-phase induction machine is investigated in this paper. In order to obtain results with maximum accuracy, some specific procedures to reduce the effect of the operating conditions on the quality of the estimates are investigated. Both computer and experimental results are used to anchor the main conclusions issued from this study. Index Terms - Induction machines, parameter estimation.

Features a study which established a correlation between the space vector pulse-width modulation (SVPWM) and digital scalar PWM (DSPWM) techniques. Strategy of DSPWM; Analysis of the space vector modulation; Procedure to obtain results equivalent to the SVPWM with the DSPWM implementation; Simulation results.

Presents information on a study which investigated the linear parameter estimation technique to determine the stator resistance, self-inductance of a stator winding machine employing a standard microcomputer-based alternating current-drive system. Illustration of the dynamic model of the study; How to estimate electrical parameters and speed; Characterization of the induction machine.