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Electric Power Applications, IEE Proceedings -

Issue 3 • Date May 2001

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Displaying Results 1 - 9 of 9
  • Field-weakening regime for brushless DC motors based on instantaneous power theory

    Page(s): 265 - 271
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (432 KB)  

    Permanent magnet excitation is beneficial in AC machines in which the flux is required to remain substantially constant. However in inverter-fed drives, where it is necessary to reduce the flux in order to operate above base speed with limited supply voltage, constant rotor excitation becomes a serious drawback. The conventional method used to achieve flux-weakening in permanent magnet motors involves phase advancing the stator currents with respect to the back EMF. The paper reviews the instantaneous power theory and investigates the use of the imaginary power component as an alternative means of providing field weakening in brushless DC motors. Apart from better performance at base speed, this regime is also shown to provide a wider speed range than the conventional method, without any significant current distortion View full abstract»

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  • Integrated power factor compensator based on sliding mode controller

    Page(s): 237 - 244
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    Active power filters are an important means to increase power quality, due to wide use of nonlinear loads and switching mode power converters. The paper presents a simple control strategy which has employed the switching mode rectifier to work simultaneously as a power factor corrector and an active power filter, to decrease current harmonics drawn from a nonlinear load. As no additional active power filter is needed, the cost of this configuration is lower than that of the conventional active power filter configuration. A sliding mode controller is used in the current control loop to achieve fast dynamics. Only the source currents have been measured in the proposed control scheme to reduce the elements of current sensors needed in the conventional control approach. A simple proportional-integral controller is adopted in the voltage control loop to achieve slow dynamics. The proposed scheme can achieve high power factor, current harmonic elimination and no dedicated active power filter. A diode rectifier feeds the capacitive load as the nonlinear load is taken on AC mains to demonstrate the effectiveness of the proposed active rectifier for reactive power and current harmonic compensation View full abstract»

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  • H∞ control of induction motor drives

    Page(s): 272 - 278
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    H∞ control theory is applied in order to design a state feedback static controller for field oriented control of an induction motor fed by a VSI. From a theoretical point of view, H∞ control theory cannot be applied to induction motor drives because of intrinsic system nonlinearity, but a linear plant can be set up using the same assumptions that are at the basis of field oriented control. Thus, H∞ control theory can be successfully used to set up a state feedback controller for field oriented control of an induction motor. The performances of the control system are numerically analysed and experimentally verified to prove the validity of the design procedure. The results confirm that good dynamic performances and high robustness to variations of system parameters can be achieved by means of the proposed controller View full abstract»

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  • Robust control for induction servo motor drive

    Page(s): 279 - 286
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (532 KB)  

    The design and properties of a robust control system for an induction servo motor drive to track periodic commands are addressed. The presentation of robust control for the indirect field-oriented induction servo motor drive system is divided into three parts: state feedback controller, feedforward controller and disturbance controller. The adaptation laws of control gains in the robust control system are derived in terms of the Lyapunov stability theorem. In the whole design process, prior knowledge of the controlled plant is not necessary and the asymptotic stability of the control system can be guaranteed. It has learning ability similar to intelligent control, but with a simpler control framework. With the proposed robust control system, the drive possesses the advantages of good tracking control performance and robustness to uncertainties. The effectiveness of the proposed control scheme is verified by both the simulated and experimental results View full abstract»

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  • Design optimisation of a resonant turn-off snubber for high-power converters

    Page(s): 229 - 236
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (540 KB)  

    An active resonant turn-off snubber suited for high-power IGBT converters is presented. The main feature of the snubber is that the maximum current rating of the auxiliary switching devices is small compared with that of the main switches. The basic operation of the snubber is described. This is followed by a detailed analysis of the losses in the circuit, which gives rise to an optimum snubber design procedure. An experimental version of the snubber is evaluated on an IGBT phase-arm, and detailed measurements of the efficiency of the converter are taken. The experimental results are in close agreement with the theoretical predictions View full abstract»

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  • Performance evaluation of doubly-fed twin stator induction machine drive with voltage and current space vector control schemes

    Page(s): 287 - 292
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    The doubly-fed twin stator induction machine (DFTSIM) is of interest as an adjustable speed drive (ASD) and a variable speed generator (VSG), as it combines the advantages of a brushless drive with the potential for high-voltage, high-power and limited speed range applications. Previous work on the DFTSIM (or its equivalent brushless doubly-fed machine) has considered steady state performance with open loop control or dynamic performance with closed loop control, but has not considered an overall performance evaluation with an appropriate closed loop speed control. The comparative dynamic and steady state performance of a laboratory DFTSIM drive using `voltage space vector control' and `current space vector control' schemes is discussed. While the magnitude of the control winding voltage (or current) space vector is dynamically controlled to obtain the desired torque in a speed control loop, its position is regulated to operate the machine in synchronous mode. Results show that the maximum efficiency for the voltage space vector control is slightly higher than that for the current space vector control scheme, but the current space vector control offers better dynamic response and minimum converter voltampere requirement. Although the reduction in the converter VA rating with the DFTSIM drive is similar to that achievable with a slip power recovery drive, the brushless DFTSIM drive has a greater potential for applications requiring high reliability and low maintenance. Further, the DFTSIM is a viable alternative in the context of nonconventional power generation such as wind and small hydro View full abstract»

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  • Vibration behaviour of stators of switched reluctance motors

    Page(s): 257 - 264
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    2D and 3D finite-element techniques are used to investigate the influence of geometric asymmetries and the leading dimensions of the stator core, namely the diameter and thickness of the yoke, the width and number of poles, the lamination notches, and the stator windings on the natural frequencies and vibration modes of switched reluctance motors. Predictions are validated against measurements on various experimental models. Both finite-element analysis and experimental measurements are used to quantify the influence of the mass and stiffness of the laminated core and the windings on the natural frequencies and vibration modes, and thereby to obtain the effective material properties View full abstract»

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  • Real-time detection using wavelet transform and neural network of short-circuit faults within a train in DC transit systems

    Page(s): 251 - 256
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (448 KB)  

    A method is proposed for the real-time detection of DC-link short-circuit faults in DC transit systems. The discrete wavelet transform is implemented to detect any surges in the DC third-rail current waveform. In the event of a surge the wavelet transform extracts a feature vector from the current waveform and feeds it to a self-organising neural network. The neural network determines whether the feature vector belongs to a normal or a fault current surge View full abstract»

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  • Steady-state algorithm for switching power electronic devices

    Page(s): 245 - 250
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    Obtaining the steady-state operation of a power electronic device by means of brute force computer simulation is not feasible in many practical cases. Fast steady-state algorithms that formulate the steady-state problem as a boundary problem and solve it using Newton's method have been proposed to overcome this difficulty. These algorithms are known as shooting algorithms. An extension of the shooting algorithm for piecewise linear circuits is provided. The complete Jacobian matrix that takes into account the switching instants variation is analytically derived for a state variable formulation of the steady-state problem of a piecewise linear circuit. A computer program PWiseSS based on this algorithm is used to solve a previously proposed test circuit of difficult convergence as well as to solve a realistic six-pulse converter of interest to the power electronics engineer View full abstract»

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