High-power industrial drives

After the classification and a short review of the evolution, the different drive systems which became important in industrial applications are described. It is shown how motor, converter, and controls form a drive system. The specific characteristics of each system are emphasized in order to show which system is best suited for which kind of applications. Based on the development potential the paper also gives a projection for the future. The systems discussed include synchronous motors fed by externally commutated current source converters, induction motors fed by current source converters, cycloconverter fed synchronous motors, voltage source inverters, and slip power controlled drives     

Low-voltage, high-efficiency switch-mode high-power inverters forAC link converter applications

A 30 kVA high-frequency link converter, which consists of 6×5 kVA center-tap power block topologies operating in parallel, is considered for battery-fed DC-AC converter applications. Practical solutions for minimizing currents circulating between the different power blocks, avoiding transformer saturation in forced commutated center-tap topologies, and minimizing transistor-on losses are incorporated and illustrated by means of practical measurements and results. A simple single-capacitor snubber network, operating in parallel with a second-stage capacitor snubber, is used for these converter types. Typical applications include mobile and telecommunications uninterruptible power supply systems; high AC-voltage loads fed from photovoltaic or hybrid energy systems; and battery-fed, mobile, variable-speed AC and DC drives     

Optimization of a synchronous reluctance machine for a sensorless drive with a wide field-weakening range

For more than one century, electrical machines have been utilized for electrical drives. Nowadays, in most applications the electrical machine is fed by an inverter. Three types of machines are available for such purposes: the asynchronous induction machine, the permanent magnet excited synchronous machine and the synchronous reluctance machine. Reluctance machines represent an alternative to the other types when utilized in high-performance drives with a wide speed range. Due to the rotor saliency, these machines have an inherent suitability for a position-sensorless control. The parameters of a 5 kW machine with a maximum speed of 8000 rpm are evaluated by means of nonlinear finite element analyses. With regard to an application in a high-performance drive with a wide field-weakening range and a position-sensorless control scheme, the characteristics are calculated for the conventional reluctance machine as well as the reluctance machine with additional permanent magnets in the rotor. The comparison of the characteristics of the conventional reluctance machine and the permanent magnet assisted reluctance machine clearly shows the improved performance in terms of electromagnetic torque and power factor due to the interior permanent magnets. Thereby, the suitability for the application in position-sensorless drives due to the high effective saliency is preserved.     

A novel CSI-fed induction motor drive

Current source inverter (CSI) fed drives are employed in high power applications. The conventional CSI drives suffer from drawbacks such as harmonic resonance, unstable operation at low speed ranges, and torque pulsation. This paper presents a novel CSI drive which overcomes all these drawbacks and results in sinusoidal motor voltage and current even with CSI switching at fundamental frequency. The proposed CSI drive uses a three-level inverter as an active filter across motor terminals replacing the bulky ac capacitors used in the conventional drive. A sensorless vector controlled CSI drive based on proposed configuration is developed. The simulation and experimental results are presented. Experimental results show that the proposed drive has stable operation even at low speeds. Comparative results show that the proposed CSI drive has improved torque ripple compared to the conventional configuration.     

Analysis and validation of a real-time AC drive simulator

This paper presents the analysis and validation of a real-time AC drive simulator. Real-time simulation has been used for over a decade in power systems engineering to test controllers thoroughly, efficiently, and safely. The development and testing of large DC drives could benefit from this type of simulation, but real-time power system simulators have modeling restrictions preventing stable and accurate simulation of isolated drives switching at high frequencies. These restrictions can be overcome by combining in a single model both the power converter and motor models. After discussing the salient issues related to the real-time simulation of DC drives, a prototype real-time simulator for drives is described. Its ability to accurately emulate the behavior of large drives is demonstrated through two case studies. A first case study demonstrates the feasibility of simulating a drive of typical complexity in real-time. The second case study demonstrates how the controller for a PWM VSI fed induction motor, switching at 4 kHz, is designed, implemented in a microcontroller and tested in real-time using a simulated inverter, motor and load. Comparisons against results obtained with another simulation tool, which uses extremely accurate variable-step integration algorithms, demonstrates the validity of our approach.     

低通态电压和快速开关10kV IGCT的设计和特性

本文介绍了应用于6kV-7．2kV中低压装簧中，具有低的通态电压和快速开关的10kV IGCT的设计、实验研究和特性。对进行优化设计的10kV IGCT，我们通过对可以体现器件整体性能的阻断、通态和开关能力的测试，证实了应用在像铁路电网和中压驱动等高低频率开关中的两种不同器件的特性。     

A New Model-Based Technique for the Diagnosis of Rotor Faults in RFOC Induction Motor Drives

This paper proposes a new model-based diagnostic technique, which is the so-called virtual current technique (VCT), for the diagnosis of rotor faults in direct rotor field oriented controlled (DRFOC) induction motor drives. By measuring the oscillations at twice the slip frequency found in the rotor flux of the machine, and by conjugating this information with the knowledge of some motor parameters, as well as the parameters of the flux and current controllers, it is possible to generate a virtual magnetizing current which, after normalization, allows the detection and quantification of the extension of the fault. The proposed method allows one to overcome the major difficulties usually found in the diagnosis of rotor faults in closed-loop drives by providing information about the condition of the machine in a way that is independent of the working conditions of the drive such as the load level, reference speed, and bandwidth of the control loops. Although the VCT was primarily developed for traction drives used in railway applications, it can be incorporated in any DRFOC drive at almost no additional cost. Several simulation results, obtained with different types of DRFOC drives, as well as experimental results obtained in the laboratory, demonstrate the effectiveness of this new diagnostic approach.      

一种宽轴比带宽L频段圆极化贴片天线

圆极化全向天线由于其自身的性能特点,在现代无线应用中越来越受到广泛的关注。提出一种宽轴比带宽的L频段圆极化微波贴片天线,该天线有上下两个介质层,下层微带馈线耦合馈电,接地面蚀刻十字交叉缝隙以帮助实现圆极化和改善上层贴片的耦合度。设计结果显示,该天线3dB轴比带宽可以达到3．5％（1.0231．060GHz）,在有效带宽内天线增益高于5．68dBi,在中心频率点（1．04GHz）天线的前后瓣比高于20dB。     

Voltage stress on induction motors in medium-voltage (2300-6900-V)PWM GTO CSI drives

In order to reduce the cost and improve the efficiency of medium-voltage induction motor drives, it is desirable that no power transformers be used. The GTO current source inverter (CSI) drive can achieve this requirement. However, the transformerless design of the drive may introduce a high-voltage stress on motor windings, which may deteriorate the motor insulation life. In this paper, the line-to-ground and neutral-to-ground voltages of the motor fed by the GTO CSI are investigated. It is demonstrated that the maximum line-to-ground voltage applied to the motor could be twice as high as the motor-rated phase voltage. Computer simulation and experimental results from a 4000 V, 1250 HP drive are given to verify the theoretical analysis. The effects of DC link choke arrangement on the motor voltage stress are also discussed. This paper provides a valuable design guidance for the insulation of medium-voltage motors used in the GTO CSI drives     

Microprocessor-based control of steel rolling mill digital DCdrives

Algorithms are presented for the digital control of double-loop DC machine drives used for applications where severe constraints on motor speed and position render conventional constant-torque or power control inadequate, such as in steel rolling mill drives. It is shown that the heavy current demand associated with maximal acceleration control can be reduced by using a form of proportional control where, in addition to the conventional inner-loop current feedback, a distance feedback term sets the high limiting value of the speed feedback signal, thus reducing the motor armature current     

Bifurcation Analysis of Five-Phase Induction Motor Drives With Third Harmonic Injection

The interest in variable-speed multiphase induction- motor drives has substantially increased in recent years and novel proposals show good prospects for industrial implementation in high-power applications. The additional degrees of freedom existing in multiphase machines have allowed for new applications with high torque density by current harmonic injection in concentrated winding machines. This paper addresses, for the first time, the bifurcation analysis of a five-phase induction-motor drive when a third harmonic is injected for torque-enhancement purposes. The main focus of this paper is to present a mathematically based study of the nonlinear dynamics of the proposed drive with torque enhancement. The overall bifurcation analysis for both concentrated and distributed winding machines confirms that the harmonic injection provides not only torque enhancement but also more robust controllers. This further advantage offers improved performance of multiphase drives compared to their three-phase counterparts.     

Theoretical modelling and experimental identification of nonlinear torsional behaviour in harmonic drives

The demand for accurate and reliable positioning in industrial applications, especially in robotics and high-precusion machines, has led to the increased use of harmonic drives. The unique performance features of harmonic drives, such as high reduction ratio and high torque capacity in a compact geometry, justify their widespread application. However, nonlinear torsional compliance and friction are the most fundamental problems in these components, manifesting themselves as a combination of stiffening spring together with hysteresis at reversal points. Accurate modelling of the static and dynamic behaviour is expected to improve the performance of the system.This paper offers a model for torsional compliance of harmonic drives. A statistical measure of variation is defined, by which the reliability of the estimated parameters for different operating conditions, as well as the accuracy and integrity of the proposed model, are quantified. The model performance is assessed by simulation to verify the experimental results.Two test setups have been developed and built, which are employed to evaluate experimentally the behaviour of the system. Each setup comprises a different type of harmonic drive, namely the high load torque and the low load torque harmonic drive. The results show an accurate match between the simulation torque obtained from the identified model and the measured torque from the experiment, which indicates the reliability of the proposed model.     

Design and rating comparisons of PWM voltage source rectifiers and active power filters for AC drives with unity power factor

Given terminal constraints of unity power factor in ac drive applications, two ac drives are possible: one with a pulse-width modulation voltage source rectifier (PWM-VSR) and the other using a diode rectifier and an active power filter. Despite numerous publications for the two drives, the features and advantages between them have not been clearly explained. This paper presents a theoretical analysis and systematic comparison between the two drive topologies. Converter kVA ratings, dc-link voltage requirements, switch ratings, semiconductor losses, and reactive component designs are considered for the evaluations.     

Four-quadrant position sensorless control in SRM drives over the entire speed range

Proper synchronization of the excitation with respect to the rotor position is essential in optimal control of switched reluctance motor (SRM) drives. To avoid additional cost, size, and unreliability caused by the external position sensors, magnetic status of the SRM can be directly monitored to detect commutation instants. A one-to-one correspondence between magnetic status of the SRM and rotor position removes the need for an explicit access to the rotor position. In order to obtain a good precision over the entire speed range, educated modifications on the structure of the sensorless strategy is necessary. This is due to the impact of the operational regions on dynamic behavior of the SRM. In addition, introduction of SRM technology to industrial and domestic applications has raised the need for four-quadrant operation of the SRM drives. The present paper introduces a range of strategies that are necessary to accommodate this requirement in a sensorless format. Our experimental findings indicate that high-grade sensorless operation in a four-quadrant SRM drive is possible and can be integrated in a variety of applications.     

Adaptive Control of Harmonic Drives Based on Virtual Decomposition

Harmonic drives are interesting for robotic applications due to their attractive properties such as high reduction ratio, compact size, low mass, and coaxial assembly. However, the high friction and the dynamics of the flexspline are the main issues that significantly challenge the control systems. In this paper, an adaptive controller capable of adaptively compensating the friction, while incorporating the dynamics of the flexspline, is developed in both joint torque and joint-position control modes. The virtual decomposition control approach allows the dynamics of harmonic drives to be controlled separately from the conventional dynamics of the robots. Adaptive friction compensation and flexspline dynamics based control are the two main contributions of this paper. The$L_2/L_infty$stability and the$L_2$-gain-induced$H_infty$stability are guaranteed. Experimental results demonstrated in both time and frequency domains confirm the feasibility of the proposed approach.     

Leaky-Wave Slot Array Antenna Fed by a Dual Reflector System

A leaky-wave slot array antenna fed by a dual offset Gregorian reflector system is realized by pins in a parallel plate waveguide. The radiating part of the antenna is composed by parallel slots etched on one side of the same parallel plate waveguide. The dual offset Gregorian reflector system is fed by an arrangement constituted by two vias and a grid, also constituted by pins. Also this feed arrangement realizes a leaky type of radiation, this time inside the parallel plate waveguide. A prototype of the antenna has been designed, manufactured and successfully tested. The low profile, low cost and high efficiency of the antenna render it suited for a variety of radar or telecom applications.     

Large current rectifiers: State of the art and future trends

This paper presents the different technologies used in the generation of large controlled currents, in the kiloamperes range. After a brief review of processes requiring large currents, the paper discusses the working principles of thyristor phase-controlled rectifiers commonly used in these applications. Chopper-rectifiers using high-current insulated gate bipolar transistors are introduced as an alternative being considered in recent projects. The pulsewidth-modulated current-source rectifier, currently used in medium-voltage motor drives, is also analyzed as a future alternative for rectification in industrial processes. In addition, this paper presents the most important requirements and specifications to be considered in the applications of these high-power units. A system comparison is developed between thyristor and chopper-rectifiers in terms of quality of control, harmonics, power factor, losses, and efficiency.     

Improved torque fidelity in harmonic drive sensors through the union of two existing strategies

The torsional compliance of harmonic drives lends itself to torque sensing, but the elliptical wave generator in harmonic drives introduces a spatially dependent local torque ripple on the flexspline of harmonic drives. It is difficult to extract the applied torque signal from this local torque ripple if the applied torque is sensed at the flexspline of the harmonic drive. Previous methods have used spatially offset Wheatstone bridges or gain tuning to attenuate torque ripple. The authors have found that combining both of these techniques through a different wiring configuration can attenuate local torque ripple to /spl plusmn/0.5 N/spl middot/m, a better ripple reduction than either method alone. This local ripple reduction is adequate for large-range torque applications, but is not adequate for precision torque applications.     

Architectural strategies for high-throughput applications

In this article an architecture is presented which allows efficient ASIC implementations of high throughput applications. Examples of these applications can be found in real time video applications such as EDTV, IDTV and HDTV. A key issue in the architecture is to provide a balance between memory resources and processing resources. Special attention is paid to the communication between these two types of resources. Architectural techniques are proposed to solve bottlenecks in the memory bandwidth and conflicts between memory accesses. Architectures for address generation in combination with location assignment are presented. The flexibility of the architectural model allows an efficient hardware realization on an ASIC exploiting the inherent parallelism of a particular application. This is illustrated in the article using a complex video algorithm for Progressive Scan Conversion. The proposed architecture is used as a target architecture which drives the high-level synthesis approach of the PHIDEO compiler.