IEE Proceedings - Electric Power Applications
Volume 145, Issue 6, November 1998
Volumes & issues:
Volume 145, Issue 6
November 1998
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- Author(s): E. Spooner and A.C. Williamson
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 485 –496
- DOI: 10.1049/ip-epa:19982336
- Type: Article
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p.
485
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(12)
The modular permanent-magnet machine exhibits several new forms of load and no-load loss which could lead to poor efficiency and unacceptable temperature rise if not taken into account in the design. Four such losses are identified. An analytical electromagnetic model of the modular machine and its structure is developed and used to predict the losses. A test rig using modules which are representative of a full scale machine has provided data which validates the model. Use of the model for a typical full-scale design with enlarged modules reveals that the losses can be made acceptably low without special measures to screen the leakage fields which cause the loss. - Author(s): Z. Chen ; E. Spooner ; W.T. Norris ; A.C. Williamson
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 497 –508
- DOI: 10.1049/ip-epa:19981975
- Type: Article
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p.
497
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Voltage regulation can restrict the useful capacity of permanent-magnet generators. Wind power applications are acutely affected because of the cubic variation of power with speed. The solution adopted for a new form of modular permanent-magnet wind turbine generator was to employ a capacitor connected across the generator AC terminals providing additional excitation due to the capacitive current flowing in the stator coils. The resulting circuit displays unusual characteristics and its analysis must take account of nonlinearities introduced by rectifier loading, magnetic saturation and saliency of the permanent-magnet excitation system. The paper describes the circuit configuration adopted and its analysis by methods ranging from a linearised first approximation to a complete numerical simulation. The theoretical studies are supported by experimental results. Part of the analysis is arranged to assist the designer in the selection of capacitance. - Author(s): J. Wang ; W. Wang ; G.W. Jewell ; D. Howe
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 509 –518
- DOI: 10.1049/ip-epa:19982333
- Type: Article
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p.
509
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The paper describes the design and experimental characterisation of a small reciprocating linear permanent-magnet generator which has been developed for on-board generation of electrical power for telemetry vibration monitoring systems. A comprehensive design methodology, which embraces both the electromagnetic and mechanical design, is described. The electromagnetic design synthesis is based around analytical field solutions which allow the optimisation of the generator parameters, and is further verified by nonlinear electromagnetic finite-element analysis. Nonlinear structural finite-element analysis is employed to aid the design of flexural disc springs with the desired stiffness and stroke. The utility of the design methodology is illustrated by a design study and extensive experimental characterisation of a prototype device. - Author(s): P.G. Barrass and B.C. Mecrow
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 519 –527
- DOI: 10.1049/ip-epa:19981926
- Type: Article
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p.
519
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The theory and implementation of a flux-linkage controller applied to a switched reluctance machine drive are described. Analysis of the simplified discrete time load model shows that a simple flux-linkage controller can produce a ‘dead-beat’ system response. Comparison of the response from a discrete time PID current controller, hysteresis current controller and the new flux-linkage controller, show that the flux controller has a much improved response. The experimental controller is used to control an IGBT converter, driving a commercial 7.5 kW switched reluctance motor. A method of constant torque operation is introduced. This takes account of limitations imposed by the finite DC-link voltage and rotor speed when calculating the reference values. The method is based on ‘flux ramps’, where the ramps are chosen to give constant shaft torque, and remain within the capabilities of the power converter. Correct selection of the flux ramps allows constant torque operation to be achieved over a wide speed and torque range. Measured results for the experimental drive demonstrate the low torque ripple achieved for motoring and generating operation over a range of speed and torque values. - Author(s): F. Ishibashi ; S. Noda ; M. Mochizuki
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 528 –534
- DOI: 10.1049/ip-epa:19981927
- Type: Article
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p.
528
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Motors with low noise characteristics are increasingly in demand due to environmental considerations. The primary source of noise of these motors, in particular of the most widely produced 4- and 6-pole induction motors, is electromagnetic vibration. To gain a better understanding of this specific kind of vibration, the relationship between magnetic flux and mode of vibration is examined from a study of electromagnetic forces and the motor's mechanical response. The flux distribution of the motor is calculated by a finite element method (FEM), and from the results of this study, flux density over the motor's radial direction is analysed in the space and time domains. Similarly, the electromagnetic force waves are calculated by the Maxwell stress method and FEM analysis in the space and time domains. Using Fourier analysis, harmonics of these forces are obtained, and are subsequently used as applied forces in the study of mechanical vibration. The vibration behaviour of the motor caused by electromagnetic forces is simulated using FEM for structure analysis. The modes and amplitudes of vibration provided by these calculations are then compared with experimental results and the strong influence of the frequencies close to natural frequency on the modes of vibration is confirmed. - Author(s): Y. Konishi and M. Nakaoka
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 535 –543
- DOI: 10.1049/ip-epa:19982339
- Type: Article
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p.
535
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A method is described of selecting the optimum sine wave PWM patterns of a large-capacity current source-fed three-phase active PWM converter. Its performance evaluations are also described. A practical procedure is presented of designing a low-pass filter connected to suppress higher line current harmonics flowing into the utility-grid power source. A feasibility test is performed by using a 500 kVA three-phase active current-fed PWM converter, which has been modified. It is verified, from a practical point of view, that such conceptual considerations are more effective and acceptable in minimising higher harmonic current components flowing into the utility-grid AC power line. Furthermore, this experimental set-up provides highly efficient AC/DC PWM-PFC converter characteristics, under the operating condition of a unity power factor correction and sine wave line current shaping schemes. - Author(s): J.–J. Shieh and C.–T. Pan
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 544 –552
- DOI: 10.1049/ip-epa:19982332
- Type: Article
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p.
544
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A rather simple ROM-based current controller is proposed for a three-phase boost-type AC/DC converter to achieve a clean sinusoidal input current, controllable power factor, an adjustable DC voltage, a bidirectional power flow capability, a fixed switching frequency and one insensitive to input voltage distortion. Three control schemes are proposed and integrated in the same controller. As well as the basic scheme, there are a further two choices for either reducing almost half the switch loss or enhancing the availability of the converter, while one arm of the converter fails. A prototype is constructed, and experimental results validate the simulated results. - Author(s): R. Blundell ; L. Kupka ; S. Spiteri
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 553 –558
- DOI: 10.1049/ip-epa:19982337
- Type: Article
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p.
553
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The paper describes some important design considerations in developing a variable three-phase AC–DC converter with unity power factor and the minimum harmonic content of the line current using boost converter topology. The design details of expanding a single-phase converter into a three-phase system are presented. The article also describes the major problems encountered in carrying out such essential modifications, together with their practical solution. A detailed circuit design is included. The prototype circuit was tested for both resistive and inductive loads. The results of operating the converter with a typical DC motor load are also presented. - Author(s): S.J. Chiang ; T.L. Tai ; T.S. Lee
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 559 –567
- DOI: 10.1049/ip-epa:19982334
- Type: Article
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p.
559
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The authors present a novel variable-structure control (VSC) technique for UPS inverters. Unlike other VSC approaches in which all control objects are achieved by a single switching surface function, the proposed inverters employ multiloop control in which the regulation of output voltage as well as inductor current is in terms of its own VSC. In addition, the smooth function is adopted to prevent infinite switching of comparator and alleviate the chattering effect. It follows that the inverters are capable of being current-limited and switched with constant frequency. Owing to the robustness of VSC, the output voltages of the inverters have the features of low distortion, fast dynamic regulating speed and insensitivity to load and input voltage variations. A 2 kVA single-phase system is implemented, and both simulated and experimental results are provided to prove the effectiveness of the proposed approach. Applicability to three-phase systems, demonstrated by simulated results, is also included. - Author(s): P. Mutschler and M. Meinhardt
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 569 –576
- DOI: 10.1049/ip-epa:19982338
- Type: Article
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p.
569
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A new control concept for inverters with both DC-side and AC-side filter circuits is presented. As an example, the method is applied to a current source inverter (CSI). Oscillations of both filter circuits are actively damped by the proposed control method. The control method enables the use of much smaller filter elements, especially the DC-side inductor, compared with conventional control methods. The method is composed of two hysteresis controllers, one for controlling the direct current and the other one is a space-vector based hysteresis controller for the AC-side capacitor voltages. When the controlled quantity at the AC- or at the DC-side leaves its hysteresis area, each controller suggests a new switching state, which will force its controlled quantity back into its hysteresis area. But very often these two controllers compete with each other and make different suggestions. Then a compromise has to be found. To arrange such a compromise each controller assesses all possible switching states of the CSI. Each controller assigns a mark ranging from 6 (very good) to 1 (very bad) to each of the possible switching states. Then the marks from the DC-side controller and those from the AC side are multiplied for each of the seven possible switching states. The switching state that gains the highest multiplied mark is the optimum compromise and is realised by the CSI. - Author(s): P.G. Barbosa ; J.A. Santisteban ; E.H. Watanabe
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 577 –584
- DOI: 10.1049/ip-epa:19981932
- Type: Article
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p.
577
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The authors present a feasibility study of a shunt–series active power filter to be used with three-phase thyristor controlled rectifiers. The proposed active filter is based on two active power units: one shunt filter connected to the AC side and one series filter connected to the DC side of the rectifier. The filters may have a common DC link and the shunt filter is controlled using the concepts of the instantaneous real and imaginary powers (p–q power theory). The series filter is controlled in such a way as to cancel the output voltage ripple of the rectifier. Digital simulation results obtained from an electromagnetic transient program (EMTP) are presented to validate this study. Experimental results obtained with a small-scale laboratory prototype consisting of shunt and series filter operating separately are also presented to show their benefits. - Author(s): S.K. Chakravarthy
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 585 –592
- DOI: 10.1049/ip-epa:19982331
- Type: Article
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p.
585
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Spurious energisation occurs when at least one phase of an otherwise de-energised three-phase transformer remains energised. A transformer spuriously energised will certainly overheat although the probability of its occurrence is low. However, unpredictable nonlinear oscillations, which may be either periodic or quasiperiodic, will be setup as a consequence. The author uses the method of multiple-scales to analytically predict the type of oscillations when a transformer is spuriously energised. This will aid in identifying the conditions that cause qualitative change in the type of oscillation. The author shows that spurious energisation can result in either nonresonant or resonant modes depending on the parameters of the power network. The nature of oscillations in nonresonant mode are of vivid variety. However, the oscillations in the resonant mode are generally periodic. - Author(s): P.D. Evans and T. Okazaki
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 593 –599
- DOI: 10.1049/ip-epa:19982335
- Type: Article
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p.
593
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The characteristics and performance of a small prototype inductively-coupled fault current limiter (FCL) are described. The FCL in question has an unusual toroidal geometry in which primary and secondary coils are interleaved to minimise leakage fields and leakage inductance and maximise the effective utilisation of superconducting material. The paper investigates the effect of winding configurations and geometry on the electromagnetic properties of the FCL. The construction of the prototype uses superconducting secondary coils made from double-sided YBCO thick film layers on ring shaped zirconia substrates. The primary windings were made of planar coils of copper wire. An interleaved winding structure produces a leakage inductance that is less than one-tenth of that obtained with an equivalent ‘E’ core transformer. Computed and measured leakage impedance are shown to be in good agreement. Transient and current limiting measurements demonstrate that the proposed FCL displays typical characteristics. The advantages of interleaved winding configurations are demonstrated directly by varying the degree of interleaving of the windings on the prototype FCL. - Author(s): B. Hredzak ; S. Gair ; J.F. Eastham
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 600 –606
- DOI: 10.1049/ip-epa:19982012
- Type: Article
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p.
600
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Traditionally, the motors used in electric vehicles as direct wheel drives were built entirely into the vehicle wheel; this, however, increases the weight of the wheel. The drive arrangement described here utilises a permanent magnet, brushless, axial field double-sided disc motor. This type of machine, particularly the double-sided stator configuration, is attractive because rotor misaligninents perpendicular to the motion of the drive shaft can be accommodated. In such an arrangement, the stators of the machine can be mounted onto the chassis of the car and the rotor is allowed two degrees of freedom (rotational and transverse), and thereby directly drives the road wheel. Hence, a reduction in the unsprung mass of the wheel drive is achieved. However, there is a drawback: since the wheel is perturbed by the road surface roughness effects, the rotor moves between the outer stator assemblies (transversely), and consequently induces torque pulsations in the machine. Two separate control strategies to eliminate the torque pulsations caused by the rotor perturbation are investigated: modulation of the input motor current, and instantaneous torque control using a variable structure controller. The experimental results in each case show that both control strategies are effective in eliminating the torque pulsations. - Author(s): V. Krishna ; V.C. Ramesh ; N. Ong
- Source: IEE Proceedings - Electric Power Applications, Volume 145, Issue 6, p. 607 –612
- DOI: 10.1049/ip-epa:19982021
- Type: Article
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p.
607
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The efficiency of the power systems for steel mills has become more important due to global competition. At the same time, reliability continues to be a major concern because of the high costs of disrupting a continuous steel making process. An optimisation-based solution for the steel mill restoration problem is presented. This is a mixed integer programming problem and as such has many local minima. A new global optimisation algorithm called Navigator for solving this problem is presented. This is applied to a sample steel mill power system to provide many reasonable solutions from which the mill operator can select.
Parasitic losses in modular permanent-magnet generators
Capacitor-assisted excitation of permanent-magnet generators
Design and experimental characterisation of a linear reciprocating generator
Flux and torque control of switched reluctance machines
Numerical simulation of electromagnetic vibration of small induction motors
Current-fed three-phase converter with optimum PWM scheme and its practical input line filter design
ROM-based current controller for three-phase boost-type AC/DC converter
AC–DC converter with unity power factor and minimum harmonic content of line current: design considerations
Variable structure control of UPS inverters
Competitive hysteresis controllers - a control concept for inverters having oscillating DC- and AC-side state variables
Shunt-series active power filter for rectifiers AC and DC sides
Nonlinear oscillations due to spurious energisation of transformers
Toroidal inductively coupled superconducting fault current limiter with interleaved windings
Control of an EV drive with reduced unsprung mass
Optimisation approach to power restoration in steel mills
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