Scheduled System Maintenance on May 29th, 2015:
IEEE Xplore will be upgraded between 11:00 AM and 10:00 PM EDT. During this time there may be intermittent impact on performance. We apologize for any inconvenience.
By Topic

Electric Power Applications, IEE Proceedings -

Issue 5 • Date Sep 1997

Filter Results

Displaying Results 1 - 12 of 12
  • Improving the accuracy of the rotor resistance estimate for vector-controlled induction machines

    Publication Year: 1997 , Page(s): 285 - 294
    Cited by:  Papers (4)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    The estimation of rotor resistance in a vector-controlled induction machine is necessary to achieve high performance torque control. The extended Kalman filter (EKF) or the extended Luenberger observer (ELO) have been used to estimate this machine parameter. Three techniques are presented for use with the EKF and ELO which improve the accuracy of the rotor resistance estimate, either in both estimators, or in the EKF alone. These techniques are: the use of the synchronous two-axis (de-qe) frame model of the induction machine with the EKF, the inclusion of the core loss resistance to precalculate the phase currents used by the estimators, and the injection of a high frequency sine wave on the flux current reference command. These improvements are achieved without increasing the complexity of the estimation algorithms. The consequent improvements in the rotor resistance estimation are illustrated through simulation and practical implementation of a vector-controlled induction machine. A high performance digital signal processor (DSP) is used in the practical implementation View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of flux level on a CSI-fed field-oriented induction motor

    Publication Year: 1997 , Page(s): 295 - 300
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (464 KB)  

    A definite relation exists between the flux level, torque and slip speed of a vector controlled induction motor. An untuned vector controller generates an inappropriate slip frequency that changes the operating flux of the machine. This affects the electromagnetic torque linearity and dynamic performance of the drive system. For an induction motor with magnetic saturation, the ratio of flux and torque-producing components of stator current differs from unity for the maximum electromagnetic torque. With a linear model this ratio is unity. The dependence of this ratio for maximum torque output is explained for linear and nonlinear models of the machine. The torque characteristic is analysed with three aspects of magnetic state: true saturation curve, hard-limit saturation curve, and constant inductance model. Degradation in dynamic performance due to saturation for a CSI-fed system is presented View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Estimation of speed, stator temperature and rotor temperature in cage induction motor drive using the extended Kalman filter algorithm

    Publication Year: 1997 , Page(s): 301 - 309
    Cited by:  Papers (11)  |  Patents (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    Application of the extended Kalman filter (EKF) algorithm to the estimation of speed, stator temperature and rotor temperature in induction motor drives is described. The estimation technique is based on a closed-loop observer that incorporates mathematical models of the electrical, mechanical and thermal processes occurring within the induction motor. Speed and temperature estimation is independent of the drive's operating mode, though closed-loop estimation is possible only if stator currents are nonzero. The EKF algorithm used to perform the estimation process has been implemented using a TMS320C30 digital signal processor and experimental results demonstrate the effectiveness of the new estimation algorithm View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of skew, pole count and slot count on brushless motor radial force, cogging torque and back EMF

    Publication Year: 1997 , Page(s): 325 - 330
    Cited by:  Papers (48)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (656 KB)  

    Permanent magnet brushless motors are increasingly being used in high performance applications. In many of these applications, the acoustic noise and torque ripple characteristics of the motor are of primary concern. Because of this concern, it is important to understand the influence of the motor geometrical parameters of skew amount, pole count and slot count on the resulting motor characteristics of radial force, cogging torque and back EMF. While these relationships are understood intuitively and have been explored experimentally and predicted numerically, they have not been confirmed analytically for motors having any combination of skew amount, pole count and slot count. The paper fills this void by exploring these relationships analytically using a Fourier series. The influence of skew amount, pole count and slot count on motor radial force, cogging torque and back EMF are shown to confirm prior experimental and numerical results. More importantly, the derived analytical results provide valuable insight into the implications of common motor design choices View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Harmonic worst-case identification and filter optimal design of MRT systems using genetic algorithms

    Publication Year: 1997 , Page(s): 372 - 380
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (844 KB)  

    A mass rapid transit (MRT) operation results in harmonic distortions of AC supply systems. To estimate the effects of harmonics in the system, the worst case should be identified in order to determine whether the harmonic level is beyond the tolerable limit. Levels of voltage and current harmonic distortions in MRT supply systems are affected by train operating modes and system configurations. Harmonic worst-case identification can be treated as an optimisation problem in terms of train separations and traffic conditions. In the paper an approach based on a genetic algorithm (GA) is proposed for solving such problems. The worst-case information is then used in another GA search to place and size the corrective filters when required. Afterwards, the search for the worst case after correction is repeated. The approach uses approximate train movement and consumption models, and the AC/DC harmonic load flow for evaluating the overall harmonic distortion. Simulation results demonstrate the robustness of the approach, which is capable of solving highly nonlinear problems beyond the capability of conventional techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effect of minor harmonics on the performance of resonant harmonic filters in distribution systems

    Publication Year: 1997 , Page(s): 349 - 356
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    In spite of developing new methods for reducing waveform distortion in distribution systems, resonant harmonic filters (RHFs) remain the main devices for harmonic suppression. With an increase in the number of harmonic generating loads, RHFs often work at the voltage distorted by distant loads inside the supply system. Such filters are used, moreover, for harmonic suppression of not only single loads but also distributed nonlinear loads with a dense harmonic spectrum. Because of this, the load current may contain harmonics other than only those to which the filter is tuned. The voltage harmonics, as well as the current harmonics other than those to which the filter is tuned, are referred to as `minor harmonics' in this paper. These harmonics are often magnified by RHFs, causing a reduction of the filter effectiveness or even an increase in the waveform distortion. Factors that shape properties and performance of RHFs in distribution systems with minor harmonics are discussed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modelling of the coolant flow with heat flow controlled temperature sources in thermal networks [in induction motors]

    Publication Year: 1997 , Page(s): 338 - 342
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (424 KB)  

    The paper deals with modelling a coolant flow in thermal networks. It is shown that the coolant flow can be modelled by heat flow controlled temperature sources. Normal circuit analysis programs can be used to solve this kind of network. The model has been applied to a high-speed induction motor and to a standard induction motor. The test results are compared with the computed temperature values View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis and design of a three-level PWM converter system for railway-traction applications

    Publication Year: 1997 , Page(s): 357 - 371
    Cited by:  Papers (21)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1164 KB)  

    The paper analyses the merits and demerits of three-level PWM converters through the comparison with two-level PWM converters. A general method for analysing the switching modes of PWM converters is described and an analysis of the three-level PWM converter is presented as an example. A neutral-point voltage-balance-control algorithm together with its hardware and software implementation is presented. A three-step methodology of rapid prototyping by using CAD for the system design, using a real-time simulator for checking the implementation and using high-power testing for validating the system, is described View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Zero-voltage-switching three-phase single-stage power factor correction convertor

    Publication Year: 1997 , Page(s): 343 - 348
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    As an alternative to two-stage cascaded AC/DC power convertors, the paper presents a zero-voltage-switching (ZVS) single-state three phase rectifier with input/output isolation. The proposed rectifier contains five active devices driven by a simple PWM controller and operates in the discontinuous conduction mode (DCM) for the input power factor correction part and in the continuous conduction mode (CCM) for the DC/DC power conversion part. A simple circuit topology, ZVS, for all active devices and diodes and low device voltage and current stresses make the proposed power convertor attractive for low power (<10 kW) applications. Operational principles, analysis and design procedures are presented and verified by the experimental results obtained from a 5 kW prototype View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Minimising rotor losses in high-speed high-power permanent magnet synchronous generators with rectifier load

    Publication Year: 1997 , Page(s): 331 - 337
    Cited by:  Papers (33)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (624 KB)  

    In an early stage of the design of a high-speed 1400 kW synchronous generator with permanent magnet excitation and loaded by a rectifier, it became apparent that rotor losses are a major problem. The stator currents cause asynchronous components in the air-gap field. Analysis shows that a modified polyphase system reduces the number of these components. An approximate solution for the rotor losses caused by the asynchronous field components has been derived. The formulae show the effects of machine dimensions and harmonics and the effect of a conducting shield in the rotor. The main purpose of the study is to have a tool for making an early choice among several stator winding configurations. A modified nine-phase system, combined with a shield around the permanent magnet rotor, is a prospective option View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Robust PM synchronous motor servo drive with variable-structure model-output-following control

    Publication Year: 1997 , Page(s): 317 - 324
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (648 KB)  

    A variable-structure model-output-following controller is proposed in which only output from the plant is needed in the variable-structure control law to enhance the robustness of the control system. The position control of a permanent-magnet synchronous motor servo drive using the proposed control strategy is illustrated. First, an integral-proportional (IP) position controller is systematically designed according to the prescribed drive specifications of command tracking. To allow the specifications to be maintained under operating conditions, the state-space model of the systematically designed inner IP speed loop in the nominal case is chosen as the reference model. Then the proposed controller based on variable-structure control theory is designed and added in the inner speed loop to preserve the control performance. Simulation and experimental results show that the proposed control approach results in an accurate model-following characteristic and is robust with regard to plant parameter variations and external load disturbance View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Computer-optimised smooth-torque current waveforms for switched-reluctance motors

    Publication Year: 1997 , Page(s): 310 - 316
    Cited by:  Papers (19)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    The paper discusses the design of current waveforms for switched-reluctance motors, which give rise to a constant (ripple-free) torque. The waveforms are optimised by computer search techniques, to give the lowest RMS current per phase consistent with producing smooth torque. Furthermore, the waveforms are constrained to be within the converter's VA rating. Current waveforms and the associated voltage waveforms are given for an example motor over a wide speed range. At low speeds it is demonstrated that the waveforms increase the thermally limited output of the drive compared with `conventional' low-speed current waveforms, in addition to providing smooth torque. However, they give less output than waveforms optimised to give the most, thermally limited, mean torque irrespective of torque ripple View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.