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Electric Power Applications, IEE Proceedings -

Issue 3 • Date May 1998

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Displaying Results 1 - 17 of 17
  • Multiple-page-mapping backpropagation neural network for constant tension control

    Page(s): 239 - 245
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    Constant tension control is widely required in industrial applications. Because of random tension interference, motor running speed vibration usually occurs. Tension control is a way to minimise the effect of random tension interference, however, the tension modification reference is another interference to the speed control system. The rewinding roll drive of a metal-film coating machine is a system with multiple closed loops and multiple input and output variables. Desired speed and tension responses are difficult to achieve by implementing conventional analogue proportional-plus-integral (PI) control. The paper introduces an artificial neural network algorithm that can successfully isolate cross coupling between the speed and tension control loops, and both loops can operate quasi-independently. It overcomes the disadvantages of traditional PI control systems. To handle the variation of the rewinding roll diameter, multiple pages of the network are applied. This technique can treat a dynamic nonlinear system as a quasistatic linear control system. Therefore this method decouples the speed and tension-control paths, and both control paths can independently operate in a quasistatic state. Simulation results show the effectiveness of this control algorithm View full abstract»

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  • Harmonic analysis of parallel-connected 12-pulse uncontrolled rectifier without an interphase transformer

    Page(s): 253 - 260
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    The author presents a harmonic analysis of a parallel-connected 12-pulse uncontrolled bridge rectifier without an interphase transformer (IPT). Five normal operating modes of the specific rectifier circuit are classified, using an analytical method by deriving instantaneous AC current and DC voltage waveform equations. The discrete Fourier transformation algorithm is then carried out to obtain both current and voltage harmonic contents. Both the AC current and DC voltage harmonics for rectifiers with and without an IPT have been investigated to discuss the influence of the IPT on rectifier harmonics. Simulation results reveal that discrepancies in harmonic contents of both AC current and DC voltage of the two rectifier circuits are marked. It is noted that, for extremely light load up to rated load conditions, the total harmonic distortion (THD) of line-supply current is reduced, while the THD of DC output voltage is increased when the IPT is deleted from the rectifier circuit View full abstract»

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  • Energy conversion by nonlinear permanent magnet machines

    Page(s): 193 - 198
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    Stored energy and coenergy are defined for a permanent magnet system. It is shown that either stored energy or coenergy may be used to determine permanent magnet reluctance torque where the magnetisation characteristics of regions within the system are arbitrary. It is shown how residual magnetism may be incorporated into classical electromechanical coupling theory. It is, therefore, shown how general equations for torque can be derived for nonlinear permanent magnet systems from classical electromechanical coupling theory. The approximation made in deriving a simplified equation for torque in a linear system is described. Finally, the validity of the first quadrant representation of the rate of change of coenergy within a permanent magnet material, relevant to CAD systems on electromagnetics, is demonstrated View full abstract»

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  • Modelling of resonant switched-mode converters using SIMULINK

    Page(s): 159 - 163
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    A method of modelling DC-DC converters has been developed using SIMULINK. For the flyback quasiresonant converter, the equations for the state variables and the active and passive switches have been derived and a corresponding SIMULINK model has been constructed. Submodels for the different parts of the controller have also been constructed, and the complete system has been simulated. This modelling technique requires less memory and CPU time than SPICE View full abstract»

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  • Improved optimisation method using genetic algorithms for mass transit signalling block-layout design

    Page(s): 266 - 272
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    The application of an improved optimisation technique to an existing block-layout design process is proposed for equi-block n-aspect (n⩾2) mass transit signalling systems. The approach is built upon previous published work by applying genetic algorithms (GA) in place of conventional gradient search methods. The genetic algorithms have been proven theoretically and empirically for providing multiple-point search, as well as robust and global convergence in complex search spaces. Such characteristics have enabled GAs to simplify the original approach and to broaden its scope for dealing with either changes of the objective function or changes of the signalling scheme. In the proposed formulation, a railway line between two stations is divided into three sections, namely: a constraint section, a stretchable section and a critical section. Since each of these sections is prescribed with a different headway design criterion, GA is applied separately to each section to optimise the layout of block joints and their positions within each section. Train performance simulation is then used to verify each optimised signalling design against the overall requirements of mass transit signalling systems operation. It is also used to calculate the objective function for each candidate solution as generated by GA. Comparative studies are presented to show improvements made by GAs over conventional optimisation techniques View full abstract»

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  • Choice of drives for electric vehicles: a comparison between two permanent magnet AC machines

    Page(s): 247 - 252
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Most motors for electric vehicles are based on the DC machine, nevertheless, the brushless surface mounted permanent magnet AC machine seems to be a good alternative. The authors propose a method of design and a comparison of two types of brushless machine that takes into account the requirements for the propulsion of electric vehicles. Two types of AC machine are designed taking into account the limitations due to the limited voltage power supply in terms of the airgap magnetic field shape and the corresponding stator current waveforms. Finally, a very simple analytical optimal design is proposed and verified both by numerical simulations and prototypes realisation View full abstract»

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  • Impact of high-speed railway loads on a longitudinal power system

    Page(s): 261 - 265
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The impact of the upcoming high-speed railway loads on the characteristics of the Taiwan Power System (Taipower) is investigated. A newly developed three-phase Newton optimal power flow method is adopted as an analytical tool. The voltage unbalance ratio, under-load-tap-changer adjustment, generator voltages, voltages of high speed railway stations, and the static voltage stability problem are examined. It is found that the Taipower system still has good characteristics when single-phase high-speed loads are imposed on the system View full abstract»

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  • State-space d-q axis models of saturated salient pole synchronous machines

    Page(s): 206 - 216
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    Transient d-q axis models of saturated salient pole synchronous machines, available today, are those in which either all the winding currents or all the winding flux linkages are selected as state-space variables. A general, six-winding salient pole saturated synchronous machine is discussed and it is shown that numerous alternative models, with different sets of state-space variables, may be derived. A single saturation factor approach is utilised for main flux saturation representation. Two distinct types of saturated machine models are identified and a procedure is described that enables the formation of 37 different state-space models. A number of models are given in the final developed form. The procedure and the novel models are verified by an extensive simulation study, whose main results are included. Advantages of some of the models over the existing ones and their applicability are discussed View full abstract»

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  • Hybrid controller using a neural network for a PM synchronous servo-motor drive

    Page(s): 223 - 230
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (696 KB)  

    A permanent magnet (PM) synchronous servo-motor drive with a hybrid controller, which combines the advantages of the integral-proportional (IP) controller and the neural network, is introduced for both speed and position control. First, the IP speed and position controllers are designed according to the estimated plant model to match the time-domain command tracking specifications. Then the resulting closed-loop tracking transfer function of the speed-control system is used as the reference model, and an adaptive signal generated from the neural-network controller, whose connective weights are trained on-line using the proposed delta adaptation law according to the model-following error of the outputs, is added to the speed-control system to preserve a favourable model-following characteristic under various operating conditions. To demonstrate the effectiveness of the proposed hybrid controller, the control scheme is also implemented for the position-control system View full abstract»

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  • Experimental validation of 5 kN model electromagnetic vibration damper and design of a real-size 120 kN machine

    Page(s): 185 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (752 KB)  

    The electromagnetic vibration damper consists of a stator including many phases (24 for the model, 16 for the real-size machine) and a solid smooth rotor. The drive device provides four-quadrant operation for each phase. The authors present the experimental validation of the 5 kN model machine, with its electronic power drive. A complete computational model is described and validated. The study is then applied to the design of a real-size 120 kN machine View full abstract»

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  • Position control of a vector controlled induction machine using Slotine's sliding mode control approach

    Page(s): 231 - 238
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    The paper demonstrates that invariant regulator and superior servo performance can be obtained, compared to a fixed-gain controller, using Slotine's method of sliding mode control for position control of a vector-controlled induction machine. The position control scheme consists of a standard indirect vector-control implementation for torque control, without rotor resistance identification, with an outer sliding mode position control loop. An important feature of this technique is that robustness to parameter variation can be achieved, and stability assured, through the control law design, assuming the bounds on the parameter variations are known. The resulting nonlinear control law is computationally simple. These improvements are practically demonstrated for variations in the load inertia and mismatch between the actual rotor resistance and the vector controller's assumed value View full abstract»

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  • Modelling of electromagnetic excitation forces of small induction motor for vibration and noise analysis

    Page(s): 199 - 205
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    The authors present a simple method for calculating electromagnetic excitation forces in the airgap between stator and rotor of a five horse power three-phase squirrel cage induction motor, which are significantly responsible for the noise and vibration in the high frequency range under operating conditions. The method proposed adopts the classical transformer model to represent the electromagnetic circuit in the motor and takes into account skew of the rotor slot and fluctuations of the permeance due to rotor rotations in estimating the electromagnetic excitation forces at each tooth of the stator. The effects of rotor eccentricity and slot opening on the excitation forces are then analysed. Estimated electromagnetic forces are compared with measurements obtained by placing a flux-detecting coil on a stator tooth. The capabilities of the method are illustrated View full abstract»

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  • Speed control of ultrasonic motors by adaptive control with a simplified mathematical model

    Page(s): 180 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (440 KB)  

    The ultrasonic motor is a new type of motor. Some mathematical models for the ultrasonic motor have been reported. However, these models are very complex to apply to control of the motor, and therefore speed or position controllers for this type of motor have been designed based on proportional and integral controllers or fuzzy controllers. Since these controllers cannot take account of the motor's dynamics, a simple and convenient mathematical model of the ultrasonic motor is necessary in order to achieve high control performance. The authors propose a simplified mathematical model for the ultrasonic motor, which is expressed by a difference equation, and they then design a speed controller based on adaptive control theory. Adaptive control is attractive for controlling the ultrasonic motor because its speed characteristics vary with drive conditions. The effectiveness of the proposed control scheme is demonstrated by experiments. Furthermore, the paper indicates the influence of control delay and model orders on the mathematical model experimentally View full abstract»

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  • Full-order estimator for induction motor states and parameters

    Page(s): 169 - 179
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1056 KB)  

    In direct vector control of induction machines, the instantaneous rotor flux vector is measured using sensors, estimators or a combination of both. Since the basic Kalman filter is a state estimator, its use in vector-controlled schemes has received much attention, including reduced-order variants. The paper describes the application of the Kalman filter to rotor current estimators for the direct scheme. The method used is termed full order, and is advocated as an alternative to reduced-order schemes which have been developed to aid real-time implementation. A novel approximate full-order form using steady-state gain values is shown to give encouraging results while yielding a useful computational saving. Also described is the application of the full extended Kalman filter algorithm to the online estimation of rotor resistance in an induction motor drive. Required for the slip-calculation algorithm of indirect vector control. Temperature variations in rotor resistance can be tracked as they occur. These performance advantages are illustrated by experimental results from a typical open-loop-controlled drive View full abstract»

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  • Optimal nonlinear firing angle control of converter-fed DC drive systems

    Page(s): 217 - 222
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    A firing angle control of DC drive systems consisting of a DC motor fed by a three-phase thyristor rectifier is proposed. The two main types of DC machine, namely the series-connected and the shunt-connected, are considered and their complete nonlinear continuous-time models together with the nonlinear model of the rectifier are used. For control purposes, suitable nonlinear transformations are introduced to modify the nonlinear models of the DC drive systems into partly linear ones. Consequently, feedback linearisation methods combined with optimal control designs are applied to provide proportional-integral control strategies. However, since the firing angle control is in practice applied at distinct instants, the resulting continuous-time control schemes are transformed into discrete-time ones with the sampling time varying in accordance to the firing angle changes. Extensive simulation studies have been conducted to evaluate the effectiveness of the proposed method View full abstract»

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  • New class of dual voltage converters for switched reluctance drives

    Page(s): 164 - 168
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    An entirely new class of dual voltage switched reluctance drives is presented. New power converter circuits are introduced, which allow a switched reluctance motor to operate from either an AC mains or a battery supply, with minimal extra power semiconductor components and no extra transformer. Battery charging is achieved without additional components. These converters offer considerable cost savings and flexibility when compared with conventional solutions to the problem of creating a system that can operate from both AC mains supply and battery View full abstract»

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  • Real-time emulation for power equipment development. II. The virtual machine

    Page(s): 153 - 158
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    For pt.I see ibid., vol.145, no.2, p.92-7 (1998). Power electronic control of electromechanical systems has become common. These systems employ electronic components which switch at high frequency and have very complex interactions. The load which they supply is often intricate in itself and difficult (or often impossible) to create in an experimental environment. It would be advantageous to replace the electromechanics with a solid-state equivalent which can be flexibly programmed to emulate the real system. The paper is concerned with describing this idea, illustrating the concept by emulating an electric motor and its associated mechanical load. The phrase `virtual machine' has been coined to describe the system. It gives/takes power from the electronic converter to match as closely as possible the real electrical machine and load. The virtual machine is effectively a dynamically controllable source/sink which is capable of providing a bidirectional power level interface to a power electronic converter. Using the virtual machine, a power electronic converter can be tested in diverse applications and under a wide variety of loading conditions without the need for any electromechanics. Test results show that close agreement between the virtual and real systems is possible. The limits imposed by practical implementation of the concept are also examined View full abstract»

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