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Electric Power Applications, IEE Proceedings B

Issue 4 • Date Jul 1992

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Displaying Results 1 - 18 of 18
  • Pattern recognition applied to transient stability analysis of power systems with modelling including voltage and speed regulation

    Publication Year: 1992 , Page(s): 321 - 335
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    A pattern recognition approach to analyse transient stability using a higher order model is presented. A six order model based on two axis representation for generators including voltage and governor actions is described. Two pattern vectors based on physical considerations about the system behaviour are derived and several approximations on system trajectory are considered to deduce analytical formulas which can be computed quickly. To alleviate computational time, two discriminant analysis methods allowing reduction of pattern vectors are presented. These results are applied to an eight machine system with a three phase fault. The discriminatory power of the pattern vectors proposed is tested with the Bayes classifier and the k nearest neighbour rule. A comparison is given View full abstract»

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  • Synthesis of phase-modulated resonant DC/AC inverters and DC/DC convertors

    Publication Year: 1992 , Page(s): 387 - 394
    Cited by:  Papers (10)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    A simple analytical description of phase-modulated resonant DC/AC inverters and DC/DC convertors is presented. Principles of synthesis of these circuits are introduced. Various topologies of phase-modulated inverters and convertors are given. The basic cell of the phase-modulated inverter consists of two conventional resonant DC/AC inverters connected in parallel or in series with an AC load. The two inverters are synchronised to the same operating frequency and have a controllable phase shift between their output currents or voltages to control the overall output current, voltage, or power, depending upon the application. Phase-modulated resonant DC/DC convertor can be obtained by adding current-driven or voltage-driven rectifiers at the output of phase-modulated DC/AC inverters. Both phase-modulated inverters and convertors can operate at a fixed switching frequency, reducing EMI problems View full abstract»

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  • Analysis of frequency and amplitude modulation in the stabilisation of permanent-magnet synchronous/stepping motors

    Publication Year: 1992 , Page(s): 336 - 346
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    An analytical study of the hybrid permanent-magnet synchronous/stepping motor is presented in which possibilities for stabilising the machine are examined. It is shown that stability can be achieved by either frequency modulation or amplitude modulation of the supply at the `hunting' frequency of the motor/load combination. The characteristics of the electromagnetic damping-torque coefficient are investigated to determine the constraints involved in the development of satisfactory stabilisation schemes View full abstract»

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  • Dynamic characteristics of the class E DC/DC convertor using sampled-data modelling

    Publication Year: 1992 , Page(s): 409 - 417
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    Sampled-data modelling is used to examine the small-signal characteristics of the class E DC/DC convertor when operating with optimum switching conditions. The effects of circuit parasitics are quantified, the nature of the characteristics under reduced load is assessed and the effect on the characteristics of different values of transistor duty-ratio and resonant tank Q factor is considered. The computer package Matrixx is used in the calculation of the small-signal characteristics and practical results are included from a 1 MHz, 50 W convertor View full abstract»

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  • Waveform distortion and distortion power [power systems]

    Publication Year: 1992 , Page(s): 303 - 306
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    The distortionless conditions between nonsinusoidal voltages and currents are deduced, and the definitions of distortion current, distortion voltage and distortion power are introduced. The authors discuss some current formulas for nonsinusoidal power. In general the aim of compensation is not to reduce the distortion power but to raise the power factor to one. These two objectives are not directly related View full abstract»

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  • New technique for reducing cogging torque in a class of brushless DC motors

    Publication Year: 1992 , Page(s): 315 - 320
    Cited by:  Papers (10)  |  Patents (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    It is shown that the cogging torque in permanent magnet and brushless DC motors, where the number of magnet poles is close to the number of armature slots, can be reduced considerably by adjusting the width of the poles or the width of the slots. A design method to achieve this goal is presented. The influence of the slot opening on the cogging torque is thoroughly investigated theoretically and experimentally for a prototype View full abstract»

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  • Minimisation of unbalanced and reactive currents in three-phase asymmetrical circuits with nonsinusoidal voltage

    Publication Year: 1992 , Page(s): 347 - 354
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    Asymmetry of three-phase loads causes deterioration in the power factor and power quality of a circuit. Waveform distortion aggravates these unfavourable effects even more. A method of improving the power factor and the loading symmetry in a three-phase unbalanced circuit under nonsinusoidal conditions is presented. The method discussed is based on the source current orthogonal decomposition into the active, scattered, unbalanced, and reactive components, developed for three-phase asymmetrical systems. The author shows that this current decomposition provides the fundamentals for the design of passive compensators which can effectively reduce the unbalanced and reactive components of the source current under nonsinusoidal conditions View full abstract»

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  • Observers for field-oriented control of induction motor drives

    Publication Year: 1992 , Page(s): 381 - 386
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    One of the major problems associated with direct field-oriented control of induction motors is the sensitivity of the observer to variation of motor parameters. Various types of observer have been proposed but no complete study of sensitivities has been carried out. An analysis of the sensitivity of one class of observer, against the motor parameter variations, is presented. From the results of the analysis, a suitable observer is chosen and implemented as a part of a complete direct field-oriented control system. The results of the implementation are also presented View full abstract»

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  • Family of saturable reactor assisted soft-switching PWM DC-DC convertors

    Publication Year: 1992 , Page(s): 395 - 401
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A family of improved soft-switching pulse width modulation DC-DC convertors employing a saturable reactor assisted soft-switching technique are presented. These convertors use a small saturable reactor(s) to achieve efficient soft switching, and have advantages such as low switching and low conduction losses, wide load range and constant frequency operation. A steady-state analysis is illustrated for a forward/flyback hybrid convertor belonging to the family, and key experimental results are shown and discussed. The voltage conversion ratios and voltage/current stresses for components in the family of convertors are summarised View full abstract»

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  • Influence of number of poles per phase in switched reluctance motors

    Publication Year: 1992 , Page(s): 307 - 314
    Cited by:  Papers (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The authors seek to illuminate the influence of the choice of the number of pole pairs on the performance of switched reluctance motors. A simple model is analysed to obtain insight into this simple design choice, which has complex nonlinear effects. This understanding is tested against the results of computer modelling View full abstract»

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  • Calculation and measurement of rail impedances applicable to remote circuit fault currents

    Publication Year: 1992 , Page(s): 295 - 302
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The authors present a detailed analysis of appropriate electrical impedance models for steel railway rails suitable for power supply circuit transient calculations. They extend existing models to fully describe the skin effect, so that power circuit transient behaviour can be taken into account with little error in prediction of response. Practical measurements of rail impedance are compared with calculated values of circuit impedance and demonstrate an accuracy of within 9% for resistance and 18% for inductance. An associated paper (see ibid., vol.139, no.4, p.289-94, 1992) shows how this model can be used to predict remote short-circuit-fault substation current profiles View full abstract»

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  • Steady-state analysis and performance of a saturable reactor assisted soft-switching DC-DC convertor

    Publication Year: 1992 , Page(s): 281 - 288
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    A computer-aided steady-state analysis is presented for a saturable reactor assisted soft-switching DC-DC convertor. The convertor achieves efficient soft-switching without limitation for both load current and output voltage. The current and voltage waveforms, and performance characteristics are illustrated and discussed. The analytical results are presented in the form of normalised graphics. The experimental results indicate reasonable agreement with calculations View full abstract»

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  • Practical considerations in the optimisation of induction motor design

    Publication Year: 1992 , Page(s): 365 - 373
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    The method of sequential quadratic programming (SQP) for the solution of nonlinear constrained optimisation problems is applied to the optimisation of induction motor design. Factors which affect the optimisation process are investigated and the influence of these factors on the performance of the technique is studied in detail. Four induction motor designs, which are already in production, have been optimised taking these factors into account View full abstract»

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  • Calculation of the induced effects due to a lightning stroke

    Publication Year: 1992 , Page(s): 374 - 380
    Cited by:  Papers (12)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (388 KB)  

    A method for computing the effects of a direct lightning stroke on the protection system of an industrial building is presented. The proposed method is based on a `circuit-approach'. The lightning protection system and the `victim' circuits are simulated by means of an equivalent electrical network formed by resistances, inductances and capacitances, having all the branches coupled together. The lightning stroke is simulated by means of an ideal current source characterised by a pulse waveshape. Propagation phenomena are considered and the ionisation phenomena in the soil are taken into account by a nonlinear current-dependent electrical model, function of the electrode's shape and the ground resistivity. Two distinct points of impact of the lightning stroke to the protection system are considered. An analysis, in the frequency and in the time domain, of effects such as step voltages of EMF induced on power cables, coaxial cables, and loops is performed View full abstract»

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  • Calculation of remote short circuit fault currents for DC railways

    Publication Year: 1992 , Page(s): 289 - 294
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The authors present a technique for calculating the current time profile for a remote short circuit fault at a DC rapid transit railway substation. The profile is largely determined by steel rail impedance, which is shown to vary with time within the profile. An inverse Fourier transform, employing a novel antialiasing method, is applied to obtain the profile from frequency based impedance data. The technique is demonstrated to be accurate to within 10% with a comparison between a calculated profile and practically measured results obtained on a light rail system. The impedance data required in this technique can be obtained by either measurement or calculation and scaling of standard values using the method described in a companion paper (see ibid., vol. 139, no.4, p.295-302, 1992) View full abstract»

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  • Theoretical aspects of control of synchronous reluctance machines

    Publication Year: 1992 , Page(s): 355 - 364
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (632 KB)  

    The author presents a theoretical performance analysis of several control strategies for synchronous reluctance machines which are being fed from a current controlled inverter. The three main control strategies considered have as their objectives to allow maximum rated torque, maximum rate of change of torque and maximum power factor, respectively, from the machine. These control strategies are investigated to determine their limitations and inter-relationships. A technique for `field weakened' control of the machine is developed. It is shown that the rate of change of torque performance of the control strategies based on constant current angle is poor at lower angular velocities. A control strategy based on having constant current in the most inductive axis of the machine is shown to give better performance under these conditions, and a technique for moving between control strategies is developed View full abstract»

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  • Resolution corrected modulation: the practical realisation of ideal PWM waveforms

    Publication Year: 1992 , Page(s): 402 - 408
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    One extant problem with voltage-sourced PWM inverter drives is the physical, high power, realisation of `ideal', microprocessor-computed, PWM waveforms. Although there are many sources of waveform corruption in the `realisation' process, the authors concentrate on problems arising from the resolution/quantisation limitations imposed by the hardware timer used to translate the `ideal' PWM switching points into a time domain electrical signal. These problems are exacerbated at higher switching frequencies and lower output (fundamental) amplitudes for any given timer accuracy. Resolution corrected modulation (RCM) is a software technique proposed to compensate for the finite timer resolution limitations of practical timers. It involves applying integral vector feedback to any timing errors between the `ideal' PWM waveform and that physically realisable. The RCM effectively increases the resolution of a given timer by a minimum of 4 to 5 bits, allowing accurate PWM synthesis of waveforms using readily available (microcontroller) timing devices while maintaining a high PWM switching frequency View full abstract»

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  • Unbalance and harmonic studies for the Channel Tunnel railway system

    Publication Year: 1992 , Page(s): 418 - 420
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    The author comments on a paper by R. Barnes and K.T. Wong (see ibid., vol.138, no.2, p. 41-50, 1991) on the power supply for the Channel Tunnel rail link. Based on experience gained by Queensland Railways regarding negative phase sequences and harmonics, the author discusses some of the points raised by Barnes and Wong. The authors of the paper reply to the comments made by Hamoud View full abstract»

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