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Electric Power Applications, IEE Proceedings -

Issue 1 • Date Jan 1997

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Displaying Results 1 - 10 of 10
  • Simplified predictive instantaneous current control for single-phase and three-phase voltage-fed PFC converters

    Page(s): 46 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (756 KB)  

    An analogue controller-based predictive instantaneous current control scheme for single-phase and three-phase voltage-fed power factor correction (PFC) converters is proposed. Through a modification of the original control scheme for a digital controller-based single-phase converter, a simplified analogue controller-based single-phase version is obtained. Further, its three-phase version is obtained by employing a particular arrangement of the controller/modulator. The theory and implementation of the proposed simplified control for single-phase and three-phase power converters are described. Also, experimental results obtained from single-phase and three-phase prototype converters are shown to confirm the theory validity View full abstract»

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  • Estimation of speed and armature temperature in a brushed DC drive using the extended Kalman filter

    Page(s): 13 - 20
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (668 KB)  

    The closed-loop speed control of a DC motor drive requires a rotor-speed feedback signal which can be obtained using a speed measuring device. However this device adds to the cost of the drive and the number of electrical connections to the motor. The paper describes a method of speed estimation using armature voltage and current measurements that eliminates the speed measuring device. By including thermal effects in the estimation process, the effect of temperature variations on the speed estimate are minimised and an estimate of average armature temperature is produced. An extended Kalman filter observer for real-time estimation of speed and armature temperature is formulated using electrical, mechanical and thermal models of the motor. The observer is implemented using a TMS 320C30 digital signal processor system. A range of experimental results demonstrating the observer's steady-state and transient performance is presented for the particular case of a 3 kW machine with constant field current supplied from a phase-controlled rectifier, although the estimation method is applicable to DC motor drives of any power rating and configuration View full abstract»

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  • Optimising train movements through coast control using genetic algorithms

    Page(s): 65 - 73
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (860 KB)  

    A genetic algorithm (GA) is proposed to optimise train movements using appropriate coast control that can be integrated within automatic train operation (ATO) systems. The coast control output for a train changes with the interstation distances and gradient profiles, and the current operating conditions of the mass rapid transit (MRT) system, namely: (i) train schedules; (ii) expected passenger loads; and (iii) expected track voltages. The algorithm generates an optimum coast control based on evaluation of the punctuality, riding comfort and energy consumption. Before the train sets off to the designated station, a coast control table is generated that will be referenced by the train at runtime for deciding when to initiate coasting or resume motoring control. Each coast control table is encoded into variable length chromosomes with each gene representing the relative position between stations where coasting should be initiated or terminated. Each generation is evolved from mating of the paired equal-length chromosomes with possibilities of crossover, mutations, gene duplications and gene deletions. The key feature of this method is that it has a solid mathematical foundation. Effectively, the implementation provides good, credible and reasonably fast solutions for this variable dimensional and multiobjective optimisation problem. The algorithm has the potential for online implementation for producing a coast control lookup table for each interstation run before the train sets off. The results, although preliminary, suggest that the method is promising View full abstract»

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  • Eddy-current losses of surface-mounted permanent-magnet motors

    Page(s): 61 - 64
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (360 KB)  

    The paper presents an analytical method for estimating the eddy-current losses of surface-mounted permanent-magnet motors under load conditions. These losses are related to a fictitious voltage induced in a one-turn coil wound around a stator tooth. A simple method of calculating part of the load currents for this voltage is described. It is shown that only the windings found in adjacent slots to the stator tooth considered contribute to it. Waveforms of this fictitious voltage, including the load current effects, are shown. They illustrate the increase of eddy-current losses with motor load, particularly in conditions of advanced commutation View full abstract»

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  • Novel 18-step diode rectifier circuit with nonisolated phase shifting transformers

    Page(s): 1 - 5
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (392 KB)  

    A novel, economical three-phase AC/DC interface having no controllable switching devices is proposed. The key concept is the combined use of nonisolated phase-shifting transformers and DC-side interphase reactors having tapping diodes. The resultant AC input currents take the form of 18-step waveforms having a total harmonic distortion (THD) of 10.1%, which is roughly two thirds that of 12-step waveforms View full abstract»

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  • Indirect field-oriented induction motor drive with fuzzy detuning correction and efficiency optimisation controls

    Page(s): 37 - 45
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (728 KB)  

    The detuning correction and efficiency optimisation of an indirect field-oriented induction motor drive for achieving higher efficiency and better field-orientation characteristic are presented. First, the operating characteristics of an indirect field-oriented motor drive under detuned conditions are studied. A fuzzy controller is used to tune the slip gain online in the field-orientation mechanism to obtain a better decoupling control characteristic. At heavy loads, the rated flux of the motor is set to increase its torque generating capability. The determination of the stator flux current component for obtaining rated flux is suggested. At light loads, with the motor running at steady state, in addition to fuzzy slip gain adaptation, another fuzzy controller is used to reduce the stator flux current component from its rated value to minimise the stator input current and thus improve the efficiency of the motor drive. As the transient due to command or load torque change occurs the current adjustment action is temporary inhibited and the rated flux component current is set instead to obtain higher torque generating capability. Measured results show that both the efficiency and rotor speed dynamic responses are improved by the proposed fuzzy detuning correction control and efficiency optimisation control approaches View full abstract»

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  • Single-phase step-up/down rectifier with improved supply current waveform

    Page(s): 6 - 12
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The paper presents a novel single-phase rectifier with step-up/down characteristics. This is fundamentally based on the cascade combination of a diode bridge and a single-ended primary inductor power convertor. To sinusoidally waveshape the supply current with a near-unity power factor independent of the working conditions, a buffer capacitor is operated with voltage reversibility for the supply by arranging the auxiliary power switching device and diode. The circuit operation is macroscopically analysed by the state-space averaging method based on a DC equivalent circuit and such an operation is also simulated by a rigorous state-space method. Moreover, the tested setup, using two insulated-gate bipolar transistors and a 16-bit microcomputer, is implemented to experimentally investigate the steady-state and transient characteristics. The experimental and simulated results confirm the usefulness of the rectifier presented View full abstract»

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  • Stator resistance voltage-drop compensation for open-loop AC drives

    Page(s): 21 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (476 KB)  

    The paper presents two simple stator resistance voltage-drop compensation methods that maintain the stator flux linkage constant in the steady state and achieve approximately constant flux linkage during transient conditions. These methods are based on an induction motor model in a rotating reference frame. A mathematical analysis of the two possible alternatives is shown, indicating the stability limits for each. Practical results are then compared with the traditional volts/hertz (V/f) configuration and the stability limits verified View full abstract»

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  • Optimised input filter design and low-loss switching techniques for a practical matrix converter

    Page(s): 53 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (732 KB)  

    The matrix converter permits frequency conversion in a single-stage process. The perceived disadvantage of the matrix converter is that conduction losses are high. However, semi-soft current commutation and optimal sequence switching can be used to minimise commutation losses so that at high switching frequencies the total losses in the matrix converter can be less than those in a conventional rectifier-inverter combination. The viability of the matrix converter depends to a large extent on the size and cost of the input filter components required to meet international power quality standards. In this paper, filter designs are examined and guidelines established. Practical tests have been carried out on a 3.5 kW power converter to validate computer models. It is concluded that the matrix converter is viable if the right combination of semiconductor switching techniques and input filter design are employed View full abstract»

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  • State-space modelling and eigenvalue analysis of the slip energy recovery drive

    Page(s): 27 - 36
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (960 KB)  

    A fifth order linearised state-space model of the slip energy recovery drive (SERD) is elaborated, based on a simplified dq dynamic model which represents (with good accuracy) the dynamic behaviour of the drive. The eigenvalues of the SERD, calculated with the linearised model, are correlated with those of the conventional induction machine, and the effect of the external DC link filter and the inverter DC voltage is demonstrated. The variation of the drive eigenvalues for different operating conditions is presented both for motor and generator operation and a comparison is made with an equivalent voltage source inverter drive. Important transfer functions of the SERD, such as those concerning the response of the drive speed and torque for mechanical load and supply voltage disturbances and the design of the control system, are derived and their characteristics are discussed View full abstract»

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