6th International Conference on Power Electronics and Variable Speed Drives
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- Location: Nottingham, UK
- Conference date: 23-25 Sept. 1996
- ISBN: 0 85296 665 2
- Conference number: CP429
- The following topics were dealt with: power factor correction; supply harmonic control; induction motor drives; parameter identification; power semiconductor devices; DC motor drives; AC/DC power factor correction; soft switching power supplies; matrix conversion; special drives; resonant techniques; drive measurement; sensorless drives; speed estimators; speed observers; synchronous motor drives; convertor control; AC/DC convertors; small drives; fuzzy neural control; simulation; CAD; EMC modelling; power electronics; and variable speed drives
1 - 20 of 99 items found
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A DC to AC converter with thyristor inverter and active compensation
- Author(s): Z. Chen and E. Spooner
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A DC/AC converter based upon a grid-commutated thyristor inverter to process the power from a direct-drive variable-speed, modular PM generator in a wind energy conversion system is described. The inverter ignition angle can be adjusted continuously to control turbine speed so as to maximise energy capture. The reactive power and harmonic current output of the inverter are discussed. A compensation system including a voltage source inverter is introduced to minimise the harmonic distortion and to provide reactive power control. Several compensation schemes are considered. Experimental results from a laboratory model are presented along with computer simulation results which are in good agreement.
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Matrix converter application for direct-drive gas turbine generator sets
- Author(s): S.I. Vickers ; B.A.T. Al Zahawi ; R. Shuttleworth
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A new real-time control strategy for a matrix converter is presented. This has been optimised for use with high speed generators in directly driven gas turbine CHP units. The strategy is based on a microcontroller system with all calculations performed without the need for external, dedicated hardware. The results show that this approach can produce good quality outputs without introducing any limitations to the circuits inherent versatility.
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An efficient space vector modulation algorithm for AC-AC matrix converters: analysis and implementation
- Author(s): L. Zhang and C. Watthanasarn
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The paper presents a control strategy for matrix converters based on the space vector modulation technique (SVM). A novel and efficient modulation algorithm was developed and implemented using a digital signal processor (TMS320C30). The control scheme calculates the switch on/off intervals in real-time and can generate high switching-frequency control-pulses. A 2 kVA prototype IGBT-based matrix converter was constructed to verify the performance of the modulator. The output voltage and the input current waveforms generated by the converter are shown together with their frequency spectra.
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Investigation of a low-cost power factor correction circuit for use with voltage source induction motor drives
- Author(s): D. Butt ; M. Sumner ; J.C. Clare
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This paper evaluates the operation of a low cost circuit for improving the power factor of capacitively smoothed diode bridge rectifiers. The circuit employs an inductor and a star/delta transformer arrangement connected to the rectifier. Simulation and experimental results are compared and illustrate that the circuit can considerably improve the power factor of the system but at the expense of a reduction in efficiency. The influence of the voltage distortion on the operation of the circuit is also considered.
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Adaptive control of a current-fed active filter
- Author(s): S. Fukuda and S. Sugawa
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This paper proposes a simple and practical method for improving the performance of DSP-controlled active power filters (AF). The transfer function of a DSP-controlled AF has a phase-lag property because there is a calculation time delay in the control output, and the converter used for AF has first order lag characteristics. As AF has to generate high frequency compensation currents, the phase-lag property causes a serious deterioration in the filter performance. In the proposed system, an adaptive digital filter (ADF) operates as a series compensator and it compensates for the time-lag property of AF. ADF requires no additional hardware but only slight additional software. It was confirmed by experimental results that a simple two-tap ADF is very effective to improve the AF compensation performance.
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A control method for active power filters under unbalanced non-sinusoidal conditions
- Author(s): V. Soares ; P. Verdelho ; G. Marques
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This paper presents a new control method for shunt active filters. Its aim is to compensate current harmonics caused by nonlinear loads. The active power filter ideal performance with the control method proposed is analysed under unbalanced and nonsinusoidal mains voltages. The active power filter ideal performance with the control method proposed is compared with the p-q control method introduced by Akagi. Under balanced sinusoidal main voltages the two control methods lead to the same results. However under unbalanced or nonsinusoidal mains voltages the new control method proposed leads to better results.
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A novel circuit topology of three-phase active power filtering-based converter operating at discontinuous current mode control scheme
- Author(s): K. Hirachi ; T. Mii ; M. Nakaoka ; Y. Kato ; H. Terasaka
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The discontinuous current mode control scheme for AC-DC converter with active power filtering function and power factor correction has widespread use for single phase input power supplies, because this control scheme has practical advantages of simple configuration and cost-effectiveness. But it has not been practically adopted for three phase input power supplies because the characteristics of conventional control scheme have some disadvantages for three phase AC mains. Thus, to improve these disadvantages, a new circuit configuration with a discontinuous current mode control scheme suitable for three phase AC mains is proposed by the authors. This paper presents an operating principle and unique features of the proposed three phase active AC/DC converter topology on the basis of simulation results.
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Comparison of conducted RFI emission from different unity power factor AC/DC converters
- Author(s): J. Mahdavi and A.K. Shahriari
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Low frequency harmonic injection into AC power supply and small power factor are the main disadvantages of conventional AC/DC converters. Using current mode control, converter input current can have a sinusoidal form in phase with the power supply voltage. By solving the problem of power factor with high frequency switching current mode control, another problem arises-high frequency harmonics generated in the radio-frequency (RF) range from the converter. In this paper, an AC/DC converter with fixed topology (diode bridge+boost converter) is used and various current control methods are applied to it. After simulating the converter behavior, by using a standard network “line impedance stabilization network” between the AC power supply and the converter, conducted RF noise is calculated. Finally laboratory results are compared with simulation results.
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Novel single phase current source buck PFC with delta modulation control strategy
- Author(s): Hong-Ying Wu ; Xiao-Ming Yuan ; Jin-Fa Zhang ; Wei-Xun Lin
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A novel single-phase current-source PFC with buck-type input is proposed. Input current is indirectly controlled by delta modulation of the input capacitor voltage to deliver near sinusoidal AC current at unity power factor. A resonant filter is employed to reduce the output inductor. Some experimental and simulation results are given.
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A proposed predictive average current controller for four-wire boost rectifiers
- Author(s): M.E. Fraser and C.D. Manning
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A proposed predictive controller suitable for four-wire boost rectifiers is described. The predictive controller regulates the rectifier line currents and includes a method of providing true average current mode control. The performance of the rectifier is demonstrated using simulation results for a 80 kVA rated converter switching at 15 kHz. Practical requirements for the controller are discussed.
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An active filter for retrofit applications
- Author(s): Z. Daie Koozehkanani ; P. Mehta ; M. Darwish
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The increase in the occurrence of nonlinear loads in power systems has caused considerable concern to power utilities and manufacturers of power electronics equipment. To alleviate the problems caused by generation of current harmonics, there has been considerable interest in the use of active filters. This paper presents a new approach to the design of active filters which is developed from a unified approach described by Koozehkanani (1996). The proposed active filter configuration provides an alternative approach which has several advantages. Compared with the constant voltage and constant current types, this circuit is much simpler, and the switching frequency is lower, 4 kHz compared with frequencies of the order of 27 kHz. The flexibility afforded by this approach makes it suitable for retrofit applications because filters of this type can be connected to any part of a network. The experimental work reported here was carried out at 120 V supply voltage at power rating of 700 W.
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Reduction of EMI emission from power converters using soft-switching technique
- Author(s): H. Chung ; S.Y.R. Hui ; K.K. Tse
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Measurements of conducted and radiated electromagnetic interference (EMI) emission from hard-switched and fully soft-switched converters of similar power ratings are presented. Results indicate that EMI emission can be substantially reduced by using soft-switching technique in power converters. The fully soft-switching technique thus provides a useful solution to reduce EMI emission from switched mode power circuits.
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A power supply system with distortion eliminating properties
- Author(s): A. Kern and B.-H. Yu
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This paper introduces a novel design for controllable single phase switches powering various kinds of inductive and noninductive applications. The switch generates low distortions and the ensuing power factor is load independent and almost unity. It uses off the shelf components and is of a simple topology, promising a high reliability. The paper explains its theoretical concept and operating principle in conjunction with results of a first implementation.
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A study of the operation of a class E amplifier at 13.56 MHz
- Author(s): L.S. Tan and R.A. McMahon
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The performance of a single transistor class E amplifier operating at 13.56 MHz has been studied. Based on the operating data, parallel operation of devices has been achieved. Both circuits use the output capacitance of the transistor as one of the circuit elements. The method of selecting a suitable switch is described. An output power of 160 W at an efficiency of 78.3% has been obtained from the single device and two devices operating in parallel produced 286 W at an efficiency of 70.0%.
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Saturable reactor and lossless capacitor-assisted zero voltage transition asymmetrical PWM DC-DC converter with high-frequency transformer link
- Author(s): S. Hamada ; T. Mii ; T. Shimizu ; M. Nakaoka
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An improved half-bridge type ZVS-PWM DC-DC power converter with quasi resonant pole which makes use of a saturable reactor-assisted soft-switching technique is presented in this paper. The power converter with a high-frequency transformer link has many advantages such as lowered switching and reduced conduction losses, wide load operation range, constant frequency operation and minimized EMI. Its operating principle is illustrated and its steady-state circuit analysis is carried out. In order to demonstrate the remarkable effectiveness of the characteristic performances, experiments are carried out with a 150 W-200 kHz prototype DC-DC power converter using power MOSFETs.
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The role of converters and their control in the recovery of wave and wind energy
- Author(s): J.F. Childs
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Although mass generation of power from wave energy is still in its infancy, the OSPREY project has made a significant contribution to the development of the necessary technologies necessary to make the process viable. The power electronic interface plays a vital role in the system. It not only gives the opportunity to control the generator torque profile to ensure that optimum energy recovery is achieved, but also affords the luxury of being able to act and react to changes in environmental conditions. The author describes the synchronous and induction generator drive converters. The latter is based on the use of voltage source force commutated technology due to the need for four quadrant operation. IGBT (insulated gate bipolar transistor) based inverters offer the most advanced control and highest performance. At present this technology is available up to ratings of approximately 1.5 MW. GTO (gate turn off thyristor). The author also discusses constant speed, power and torque control. The addition of a wind turbine to OSPREY is also considered.
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Harmonic control in distorted voltage supply systems
- Author(s): C.W. Lu and A.C. Renfrew
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Robust active filter control schemes for harmonic compensation of unbalanced loads in nonideal systems with the presence of distorted and unbalanced supply are proposed. New approaches in terms of supply reference current acquisition and current switching control are proposed for single and three phase applications which ensure that the supply current will remain sinusoidal by introducing modifications to the application of instantaneous power theory. Simulation results have clearly verified the effectiveness of the proposed scheme.
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Very high bandwidth digital current controller for high-performance motor drives
- Author(s): P.C. Kjaer ; C. Cossar ; T.J.E. Miller
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A fully digital current controller for high-performance motor drives is presented. It is implemented in wired-logic (FPGA). This one-chip controller comprises features such as nonlinear delta-modulated (bang-bang) current control, PWM duty-cycle regulation by PI-loop with anti-windup, programmable and variable switching frequency, flux linkage observer, all for up to 4 phases with 12 bit resolution. The control loops can be executed and the phase currents sampled at rates selectable between 2.5 and 20 kHz. This new, fully digital hardware approach eliminates the noise problems and inflexibility of analog designs, avoids the computational overhead found in DSP software controllers, yet remains flexible and versatile. All the features have been implemented on one device. The design has potential for ASIC implementation as a single-chip current regulator. Tests demonstrate the versatility and performance of the controller and excellent dynamics and large-signal bandwidths in the kHz range are reported.
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Improved position control of a linear reluctance servo drive
- Author(s): C. Attaianese ; A. Damiano ; I. Marongiu ; C. Seatzu
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The control system improvements of a linear high anisotropy reluctance servo-drive are presented in the paper. The drive is position controlled and consists of a high thrust developing linear actuator supplied by a MOSFET converter. The early version of the system was provided by current and position loops. In the paper the control system is improved by implementing a speed loop also. The signal speed is obtained by properly filtering the position signal time derivative outputted by a potentiometric transducer. Simulation and experimental results executed on a prototype drive are presented to highlight the drive performance improvements.
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Variable structure control of a disc motor with lateral rotor movement
- Author(s): B. Hredzak ; S. Gair ; J.F. Eastham
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This paper investigates the effect of lateral movement of the rotor of an axial field permanent magnet disc motor when the drive shaft is perturbed by the load. This movement results in significant torque pulsations. It is shown that the torque pulsations can be eliminated using a variable structure control strategy. To implement a variable structure control, instantaneous torque feedback is necessary, this signal is obtained from a state space observer. The speed range of the machine is increased by flux weakening. This is implemented using a lookup table. One of the many possible applications of a disc motor with lateral movement is in an electric vehicle where the shaft directly drives the road wheel whilst the stators are connected to the chassis of the vehicle. This will result in vertical rotor movement while the vehicle is moving. Similarly this type of drive could be used to drive an electric motorbike, or could be used in any application where the rotor is moving out of alignment.
