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Electric Power Applications, IEE Proceedings -

Issue 1 • Date 9 Jan. 2004

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Displaying Results 1 - 18 of 18
  • Cost effective phase shifted pulse modulation soft switching high frequency inverter for induction heating applications

    Page(s): 19 - 25
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    A cost-effective high-efficiency high-frequency inverter with a PSM (phase-shifted pulse modulation) scheme is proposed for medium power (5-30 kW) induction heating applications. This inverter topology can achieve soft switching commutation in a wide range of power regulation, without an auxiliary active resonant snubber circuit. The high-frequency PSM control scheme presented can provide not only effective power regulation of the proposed inverter using IGBTs, but also soft switching commutation. Theoretical equations for the soft switching operation region are derived from the practical consideration of the gate pulse control strategy, in which the soft switching operation is limited only by the duration of dead time. Through experimental comparison of switching losses in the two-in-one IGBT power module, consideration is given to how much the effect of soft switching can improve actual efficiency. In this discussion, the cost effective high-efficiency inverter circuit topology is realised. The proposed inverter accomplishes soft switching operation over a wide power regulation range. The actual power conversion efficiency reached was 96.7%. View full abstract»

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  • Voltage harmonic elimination in PWM AC chopper using genetic algorithm

    Page(s): 26 - 31
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (306 KB)  

    A method of voltage harmonic elimination in a pulse-width modulated AC/AC voltage converter using genetic algorithms (GA) is proposed. The output voltage of the AC chopper with k pulses per half cycle is written in terms of switching angles using Fourier series, and the best switching angles are identified with the dual objectives of harmonic elimination and output voltage regulation. The problem is redrafted as an optimisation task, and a solution is sought through GAs. For performance comparison of GAs, other optimisation methods such as Rosenbrock's rotating coordinates method, the random search method and the Newton-Rasphson method are also applied to the present problem. Comparison shows that the genetic algorithm method is on a par with conventional optimisation methods. In addition, the GA approach has several advantages, such as a reduced computational burden, faster convergence and guaranteed global optima in most cases. The theoretical findings are verified through experimental results. View full abstract»

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  • Sliding and fuzzy control of a boost converter using an 8-bit microcontroller

    Page(s): 5 - 11
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (377 KB)  

    A two-loop control method for a boost converter, which combines fuzzy and sliding-mode methodologies, is presented. An inner loop controls the inductor current through a sliding surface whose reference signal is given by a slower outer loop. This outer loop employs a fuzzy logic mechanism to implement a PI controller that guarantees output voltage regulation and results in an excellent transient response during start-up. The controller implementation requires standard analogue devices for the inner loop and an inexpensive 8-bit microcontroller for the outer loop. Experimental results are in good agreement with the theoretical predictions and show a better dynamic performance than those obtained by means of classical analogue two-loop techniques. View full abstract»

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  • Analysis and design of a cost-effective series connected AC voltage regulator

    Page(s): 107 - 115
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (507 KB)  

    An improved series connected AC voltage regulator for low cost applications is considered. The proposed system comprises a diode rectifier and a switching inverter stage that has the capability of continuously regulating sustained voltage swells and sags. It maintains the desired load voltage level with only unidirectional energy transmission, which is different from conventional units that can regulate only one direction of voltage fluctuation with the same circuit structure. Theoretical analysis has been achieved based on the power flow theory. Prototype case studies have demonstrated the effectiveness and performance of this voltage regulator. View full abstract»

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  • High frequency voltage-fed inverter with phase-shift control for induction heating

    Page(s): 12 - 18
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    A voltage-fed resonant LCL inverter with phase-shift control is presented. The control strategy is seen to offer advantages in the megahertz operating region where a constant switching frequency is required. The inverter topology is inherently modular and higher output powers may therefore be readily achieved by adding additional MOSFET switching cells, the devices in each cell having only a modest rating. The inverter steady-state operation is analysed using fundamental frequency analysis. The predictions are verified through time-domain simulations and measurements of a 1.6 MHz 1 kW prototype. View full abstract»

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  • High-frequency flyback-type soft-switching PWM DC-DC power converter with energy recovery transformer and auxiliary passive lossless snubbers

    Page(s): 32 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (346 KB)  

    A two-switch high-frequency flyback-type zero voltage soft-switching PWM DC-DC power converter for use in auxilary power supplies is proposed. Its basic building block is composed of two active power switches and a flyback high frequency transformer. In addition, two passive lossless snubbers with power regeneration loops for energy recovery that consist of a three-turn auxiliary high frequency transformer, auxiliary capacitors and diodes, are introduced to achieve zero voltage soft switching in the full range of light to full load conditions. The power converter has the advantages of a low cost circuit configuration, a simple control scheme and a high efficiency. The converter's operating principle is described and to in order determine circuit parameters, some practical design considerations are discussed. The effectiveness of the proposed power converter is evaluated and is compared to a hard-switching PWM DC-DC converter. The comparative electromagnetic conductive noise characteristics of both DC-DC power converter circuits are also investigated. View full abstract»

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  • High-performance line conditioner with output voltage regulation and power factor correction

    Page(s): 91 - 97
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (394 KB)  

    A high-performance line conditioner with excellent efficiency and power factor is proposed. The line conditioner consists of a three-leg rectifier-inverter, which operates as a boost converter and a buck converter. This boost-buck topology enables constant output voltage regulation, irrespective of input voltage disturbances. In addition the three-leg bridge can reduce the number of switching devices and system loss, while maintaining the capabilities of power factor correction and good output voltage regulation. The power factor controller for the single-phase pulse-width modulated (PWM) rectifier is derived using the feedback linearisation concept. The inverter side acts as a voltage regulator with current-limiting capability for impulsive loads. The disturbance of input voltage is detected using a fast-sensing technique. Experimental results obtained on a 3 kVA prototype show a normal efficiency of over 95% and input power factor of over 99%. View full abstract»

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  • Performance of line start permanent magnet synchronous motor with single-phase supply system

    Page(s): 83 - 90
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (339 KB)  

    The operation of a three-phase induction motor from a single-phase supply with a capacitor in circuit is well known. While detailed investigations on the performance of the induction motor under such operating conditions are well reported in the literature, no such work is reported for the synchronous motor. The line-start permanent-magnet synchronous motor (LSPMSM) is actively being considered as an energy efficient alternative to the induction motor in general purpose, heavy duty applications. The paper presents an analytical and experimental evaluation on the performance of a three-phase LSPMSM fed from a single-phase supply. This analysis is carried out using symmetrical component theory. A capacitor is connected across two stator phases during starting and running. Estimation of the capacitor value to achieve the desired objectives, such as minimum unbalance, maximum power factor, maximum torque or maximum efficiency, is carried out. Load tests are conducted to validate the simulation results. View full abstract»

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  • Improved DSP-controlled online UPS system with high real output power

    Page(s): 121 - 127
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (399 KB)  

    A circuit topology is proposed for single-phase online UPS systems. The proposed circuit incorporates a built-in bidirectional AC/DC converter, which provides power factor correction and active power filtering. The input stage, based on a bidirectional AC/DC converter, functions as a rectifier with unity power factor correction for normal AC line mode operation, and as an active power filter for outage mode operation. During input power failure, the bidirectional AC/DC converter functions as an active power filter, providing reactive power to the load. Simultaneously, the DC/AC voltage inverter output stage supplies real power from the battery bank to the critical load. The real power capability is improved compared with that of a conventional online UPS system, and extra loads can be connected to the UPS system during outage. The power circuit of the proposed UPS system is presented and analysed. Circuit models are derived and a UPS digital control system using a digital signal processor (DSP) is developed. Finally, simulated and experimental results obtained from a laboratory prototype are presented to confirm the feasibility and features of the proposed UPS scheme. View full abstract»

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  • Comparative analysis of limited field weakening capability of surface mounted permanent magnet machines

    Page(s): 76 - 82
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (405 KB)  

    This investigation focuses on the comparison of five different surface mounted magnet rotor designs for electric vehicles with limited field weakening range. Using finite element calculations both base speed and maximum speed under field weakening conditions are taken into consideration. An algorithm determines the minimum current needed to suit specific torque and maximum voltage requirements. Furthermore, the algorithm reacts to the presence of saliency by slightly shifting the q-axis current into the d-axis, thus reducing the overall current. The results show that filling the pole gap with rotor iron and thereby introducing reluctance gives the best results in terms of high torque/current ratio both at base speed and maximum speed under field weakening conditions. View full abstract»

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  • Improvement of low speed operation of electric machine with an inertia identification using ROELO

    Page(s): 116 - 120
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (339 KB)  

    A new scheme to estimate the moment of inertia in the motor drive system in very low speed is proposed. The simple speed estimation scheme, which is used in most servo systems for low-speed operation, is sensitivity to variations in machine parameters especially the moment of inertia. To estimate the motor inertia value, a reduced-order extended Luenberger observer (ROELO) is applied. The effectiveness of the proposed ROELO is verified by simulation and experiment. View full abstract»

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  • Analysis and implementation of a three-phase two-leg neutral point clamped converter based on space vector PWM for power factor correction

    Page(s): 38 - 46
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (431 KB)  

    A three-phase two-leg neutral point clamped converter with space vector pulsewidth modulation scheme is presented for power factor correction. The adopted three-level converter has fewer power switches than the conventional three-level three-leg converter. Only eight power switches and four clamping diodes with a voltage stress of half the DC bus voltage are adopted in the circuit configuration. A space vector pulsewidth modulation scheme is adopted to reduce the switching state of power switches. Based on the adopted control scheme, a proper voltage vector is generated on the AC terminal for drawing the sinusoidal line currents with unity power factor. The simulation and experimental results are provided to verify the effectiveness of the proposed control strategy. View full abstract»

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  • Sensorless control of a PM synchronous motor for direct drive washer without rotor position sensors

    Page(s): 61 - 69
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    Sensorless control of a PM synchronous motor for direct drive washers with parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and the model of the position estimator. The stator resistance is measured near zero speed when the motor changes its rotating direction. The variation of the stator resistance and back EMF constant due to the temperature variation is compensated for in the model of the position estimator. The gains in the position estimator are also adapted according to motor speed. The increase in the DC link voltage caused by the regenerated power at braking is reduced by adding the extra γ-axis current in the DC link capacitor voltage controller. View full abstract»

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  • Improved modification of the single-switch AC-AC converter for induction heating applications

    Page(s): 1 - 4
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (293 KB)  

    A new single-switch parallel resonant converter for induction heating is introduced. The circuit consists of the input LC-filter, bridge rectifier and only one controlled power switch. The switch operates in a soft commutation mode and serves as a high frequency generator. The improved scheme of the above converter is based on the prototype, which was previously introduced by the present authors, and avoids its shortcomings, i.e. the presence of the DC-component in the load current. The steady-state analysis of the converter operation is given. The theoretical analysis and computer simulation are in good agreement with the experimental results. View full abstract»

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  • Intelligent solid-state voltage restorer for voltage swell/sag and harmonics

    Page(s): 98 - 106
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    Voltage swell/sag along with extended undervoltage conditions and voltage harmonics are of vital concern to the majority of industries today. A neural network control method for the problems of voltage sag/swell and harmonics is proposed. A novel topology of the AC-AC boost converter solves the problems of voltage swell/sag, while a voltage controlled-voltage source inverter working as a series isolator compensates the harmonics contained in the voltage at the point of common coupling (PCC). The composite converter, named a solid-state voltage restorer, uses an injection transformer with three windings. The primary winding injects a voltage in series with the line to regulate the load voltage to a desired value with a sinusoidal shape. The centre tap secondary winding is connected to an AC-AC boost converter. The tertiary winding is connected to a DC-AC inverter to compensate harmonics in the voltage at the PCC. The neural network based control technique of the AC-AC converter helps to correct the wave shape and amplitude of the voltage to feed sensitive load at rated voltage conditions. A detailed design of the neural network methodology is given and a mathematical model of the voltage restorer is used to simulate its performance. Simulation results are discussed in detail. View full abstract»

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  • Nonlinear modelling of switched reluctance motors using artificial intelligence techniques

    Page(s): 53 - 60
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (401 KB)  

    This paper develops and compares different techniques for the modelling of a switched reluctance motor (SRM) in view of its nonlinear magnetisation characteristics due to the doubly salient structure. A complete range of models based on fuzzy logic, neuro-fuzzy and neural network approach is developed. All models are separately simulated and applied for nonlinear modelling, especially for finding the rotor angle positions at different currents, from a suitable measured data set for an associated SRM. The data comprised flux linkage, current and rotor position. All models are constructed to allow them to be modelled as a function of flux linkage against current with rotor position as an undetermined parameter. The models' evaluation results are compared with the measured values, and the error analyses are given to determine the performance of the developed models. The error analyses have shown great accuracy and successful modelling of SRMs using artificial intelligence techniques. View full abstract»

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  • Analysis and visualisation of flow around blades of axial fans for large capacity open-type motors

    Page(s): 70 - 75
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (386 KB)  

    A study of the airflow around blades of axial fans for large capacity open type motors is presented. In these motors, air for cooling is blown onto stator windings and rotor bars by means of axial fans placed beside the laminated iron core. The paths from the intake opening to the axial fans and from the laminate iron core to the exhaust opening twist tightly in order to reduce noise. The ventilation resistance of axial fans for motors is much greater than that of common fans for creating draughts. The operating flow rate is much less than for fans without ventilation resistance. Numerical flow analysis was performed on the flow around the blade at this operating point. It was confirmed that there was a large flow segregation where air did not flow along surfaces on the negative pressure side of blades. This was also observed in a flow visualisation experiment. View full abstract»

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  • High frequency PWM controlled step-up chopper type DC-DC power converters with reduced peak switch voltage stress

    Page(s): 47 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (413 KB)  

    An advanced two-quadrant PWM controlled chopper type DC-DC power converter with lowered peak switch voltage stress, which is effectively used for parallel processing type small-scale UPS applications and utility interactive new energy interface distributed power supplies, is presented. In addition, a coupled inductor-assisted zero-voltage soft-switching PWM step-up chopper controlled type DC-DC power converter is also proposed and discussed. These two DC-DC converter circuit topologies are evaluated and compared on the basis of simulation and experimental results by a 1 kW 50 kHz breadboard setup using MOSFETs. The electromagnetic conductive noise characteristics of both converter circuits are also compared through experimentation. View full abstract»

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