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Electric Power Applications, IEE Proceedings B

Issue 6 • Date Nov 1990

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  • Stability of a PWM current-source rectifier/inverter fed induction motor drive

    Page(s): 348 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    The stability of pulse width modulated current-source rectifier/inverter fed induction motor drives is considered in the paper. Rectifier/inverter operations are considerably complicated because of the high frequency pulse width modulated switching of power devices. To investigate the system stability successfully, an analysis without a complete simulation is performed by introducing synchronously rotating reference frames at the input and output terminals. The linearised equations are easily obtained so the intrinsic open-loop instability and the effects of circuit parameters under closed-loop operation can be made clear by determination of their dominant roots. The relevance of the results is verified by the transient characteristics of the nonlinear model, with and without a PI controller for constant V/f control View full abstract»

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  • Microcontroller-based strategy for reactive power control and distortion compensation

    Page(s): 364 - 372
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    Compensation of the fundamental displacement and harmonic distortion currents drawn by nonlinear loads can be achieved by using a three-phase voltage-source inverter to generate an appropriate correction voltage. The real time feedback control scheme of the inverter presented in the paper is a full three-phase switching strategy based on a `periodic integral' version of the error sawtooth pulse-width modulation technique. The switching commands for the transistors within the inverter are generated by a 16-bit single-chip microcontroller. This device has sufficient computational power to implement all aspects of the controller tasks as well as handling the man/machine interface. The output waveform of the compensator is precisely determined by theoretically perfect tracking of the periodic reference signal to cancel the harmonic components up to the synthetised switching frequency (2.7 kHz). The value of the proposed algorithm is experimentally verified on a 5.5 kVA inverter circuit and is found to give very fast and precise compensation characteristics. Details are given for operation of the experimental system as well as the control algorithm implementation. Harmonic analysis of the voltage on the test system demonstrates the effectiveness of the developed control strategy for the compensator View full abstract»

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  • Power convertor circuits for switched reluctance motors with the minimum number of switches

    Page(s): 373 - 384
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    The phase windings of a doubly salient switched reluctance motor are fed with unipolar pulses of current from a suitable power convertor to control the speed and torque of the motor. A new range of power convertor circuits for the switched reluctance motor is proposed in this paper. The circuits allow the full supply voltage to be used to control the current in the phase windings and each switch is rated at close to the supply voltage. These power convertor circuits have fewer than two switches per phase winding. A new switching algorithm to control the switches connected to more than one phase winding is described. Equations predicting the ideal rotor angles for the commutation of the phase currents are derived for this new algorithm. Test results are given that clearly show the benefits of this new range of power convertor circuits over existing designs View full abstract»

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  • Strategy for the instantaneous torque control of permanent-magnet brushless DC drives

    Page(s): 355 - 363
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (504 KB)  

    The paper describes an instantaneous torque control for a permanent magnet motor driven in a brushless direct current drive configuration. The motor has high torque capabilities, which makes it suitable for direct drive applications, but unfortunately it suffers from torque pulsations when controlled by a conventional sinusoidal current controller. Instantaneous torque control is aimed at eliminating such torque pulsation, thereby improving speed and position control. The approach adopted is to design an instantaneous torque control algorithm based on a variable structure strategy in the dq rotating reference frame. The switching commands for the inverter are generated by the digital controller directly. The required instantaneous torque feedback information is estimated from knowledge of the motor parameters and measurements of instantaneous currents and rotor position. The performance of the proposed controller design and torque feedback technique are investigated in computer simulation studies and experimental implementations. Experimental results for drive applications using instantaneous torque control and conventional sinusoidal current control are evaluated and compared View full abstract»

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  • Nonlinear theory of the switched reluctance motor for rapid computer-aided design

    Page(s): 337 - 347
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (688 KB)  

    The nonlinear magnetisation characteristics are modelled analytically by piecewise first- or second-order functions of flux linkage against rotor position, with current as an undetermined parameter. The model is suitable for CAD and performance analysis, particularly at the stage of `sizing', or initial estimation, where accuracy can be traded for speed of computation. The model includes all the significant electromagnetic and dynamic characteristics of the SR motor. Its accuracy can be enhanced by means of correction factors derived from only two or three points on magnetisation curves that have been accurately measured or calculated by finite elements, permitting economy in the use of data that is expensive to generate. A piecewise analytical formula for instantaneous torque is also included, permitting the rapid calculation of mathematically smooth torque waveforms. Because the magnetisation curves do not need to be precalculated, stored or curve-fitted, the algorithms are extremely fast. The paper also presents a new method for calculating the unaligned magnetisation curve, based on dual-energy principles. Results are compared with test data for a range of motors View full abstract»

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