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Power Electronics, IET

Issue 3 • Date May 2010

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Displaying Results 1 - 14 of 14
  • Single-stage high power factor half-bridge resonant technique for linear ultrasonic motor driving circuit

    Page(s): 315 - 322
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (651 KB)  

    This study addresses the design and analysis of a single-stage high power factor half-bridge driver, which is composed of a half-bridge resonant inverter and a buck-boost converter, for a linear ultrasonic motor (LUSM). LUSMs have found their applications in miniaturised actuators and precision position manufacturing industries due to their merits of miniaturisation and high resolution. The triggering signals of both the active switches are generated using asymmetrical pulse-width modulation technique to achieve zero-voltage switching and zero-current switching using proper designed circuit parameters. Then, liquid chromatography resonant technique is adopted to produce 39.6-kHz sinusoidal voltage output. A laboratory-made circuit is built to test the circuit topology. Satisfying results are obtained to verify the validity of the proposed topology. View full abstract»

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  • Control strategy and space vector modulation for three-leg four-wire voltage source inverters under unbalanced load conditions

    Page(s): 323 - 333
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (933 KB)  

    One of the desirable characteristics of inverters in three-phase systems is the ability to feed unbalanced/non-linear loads with voltage and frequency nominal values. Therefore three-leg four-wire inverters are expected to play an essential role in future power systems because of their ability to handle the neutral current caused by unbalanced or non-linear loads. This study introduces an original control method in combination with three-dimensional space-vector modulation (3D-SVM) strategy. The steps for the 3D-SVM implementation are identified. The switching vectors, 3D-SVM diagrams and the boundary planes equations, as well as the matrices for the duty cycles and symmetric switching sequences are discussed in detail. Experimental results including different loads are presented to validate the proposed SVM control strategy for three-leg four-wire voltage source inverters. The experimental results of this study show that the developed control scheme in combination with three-leg four-wire inverters can carry out the grid feeding requirements and supply good power quality to loads under extreme unbalanced conditions efficiently. View full abstract»

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  • Reduction of voltage harmonics using optimisation-based combined approach

    Page(s): 334 - 344
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (838 KB)  

    Voltage harmonics elimination problem in a micro-grid consisting of different types of distributed generation systems is addressed. In the proposed scheme, harmonic elimination is achieved by providing optimisation-based technique to some distributed generation-connected inverters and the sine pulse-width modulation (PWM) technique to other inverters connected to same micro-grid system. The lower order harmonics are eliminated with the help of particle swarm optimisation-based selected harmonic elimination technique applied to the PWM inverters. The higher order harmonics present in the micro-grid voltage waveform will be reduced by the dominant harmonics of same order generated in opposite phase by sine PWM inverter. This is achieved by varying the phase angle of the carrier wave of the sine PWM inverter, which generates the dominant harmonics with sidebands very close to the amplitude of prominent voltage harmonics present in the system but in opposite polarity. The same is validated by simulation as well as by suitable experiments. View full abstract»

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  • Three-level zero-voltage switching pulse-width modulation DC-DC boost converter with active clamping

    Page(s): 345 - 354
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (913 KB)  

    DC-DC step-up converters for high-output voltage applications typically demand high voltage devices, leading to high conduction and switching losses. This identified demand has motivated research on active clamping and multi-level topologies. On this context, this study presents the study of a novel DC-DC boost converter with three-level boost-type active clamping, zero-voltage switching (ZVS) soft-switching and constant frequency pulse-width modulation. As shown analytically and through experimental results, high efficiency and reduced voltage ratings for the power semiconductors are achieved, thus, making the topology suitable for converters requiring high-output DC voltage. Furthermore, a topological modification for achieving ZVS operation in all semiconductors and other types of switching cells for boost-type converters is introduced. View full abstract»

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  • Improved 48-pulse static synchronous compensator for high-voltage applications

    Page(s): 355 - 368
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1860 KB)  

    A modified three-level 48-pulse ??100??MVAr static synchronous compensator (STATCOM) employing four pairs of elementary six-pulse neutral-point diode-clamped gate turn-off thyristor-based voltage source converters with fundamental frequency switching modulation is realised using angle control methodology and pre-calculated dead angle (the duration in which converter-terminal voltage is clamped to zero) in d-q synchronous rotating frame. With a magnetics configuration designed for summing up of output voltages of four converter pairs and simultaneously stepping up of its voltage to the transmission level, and employing proportional and integral controllers in the control, the operating performance equivalent to 96-pulse STATCOM is achieved through optimising harmonics distortion. This compensator is modelled and its performance is simulated in MATLAB using SimPowerSystem toolbox for voltage regulation in transmission system. The obtained results show reasonably good characteristics of the compensator to control system dynamics under steady-state and dynamic system conditions. View full abstract»

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  • Step-up DC-DC converter by coupled inductor and voltage-lift technique

    Page(s): 369 - 378
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    A DC-DC converter with high step-up voltage gain is presented. The proposed converter uses the coupled inductor and the voltage-lift technique to achieve high step-up voltage gain. Additionally, the voltage on the active switch is clamped, and the energy stored in the leakage inductor is recycled in the proposed converter. Therefore the voltage stress on the active switch is reduced, and the conversion efficiency is improved. Finally, a laboratory prototype circuit with input voltage 12-V, output voltage 100-V and output power 35-W is implemented to demonstrate the performance of the proposed converter. View full abstract»

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  • Calculations of capacitive couplings in induction generators to analyse shaft voltage

    Page(s): 379 - 390
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1308 KB)  

    This study deals with the analysis of the parameters that are effective in shaft voltage generation of induction generators. It focuses on different parasitic capacitive couplings by mathematical equations, finite-element simulations and experiments. The effects of different design parameters have been studied on proposed capacitances and resultant shaft voltage. Some parameters can change proposed capacitive coupling such as stator slot tooth, the gap between slot tooth and winding and the height of the slot tooth, as well as the air gap between the rotor and the stator. This analysis can be used in a primary stage of a generator design to reduce motor shaft voltage and to avoid additional costs of resultant bearing current mitigation. View full abstract»

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  • Multi-pulse train control technique for buck converter in discontinuous conduction mode

    Page(s): 391 - 399
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (602 KB)  

    Multi-pulse train (MPT) control technique, a novel control technique for the control of switching DC-DC converters is proposed here. Unlike traditional pulse train (PT) control technique, which realises the output voltage regulation of switching DC-DC converters by a combination of two different control pulses, MPT control technique extends these two different pulses to multi-level pulses, and thus overcomes the drawback of relatively large output voltage ripple of PT control switching DC-DC converters. Buck converter operating in discontinuous conduction mode is taken as an example to illustrate the operation principle of MPT control technique. Comprehensive analysis on the control pulse combination within a MPT repetition cycle is performed and verified by simulation and experimental results. It also shows that MPT control buck converter has much lower output voltage ripple than PT control technique, and much better transient performance than traditional pulse-width modulation buck converter. View full abstract»

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  • Full-order averaging modelling of zero-voltage-switching phase-shift bidirectional DC-DC converters

    Page(s): 400 - 410
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (592 KB)  

    Full-order small-signal modelling and dynamic analysis of zero-voltage-switching (ZVS) phase-shift bidirectional DC-DC converters is studied. A general modelling method is proposed to develop the discrete-time average model. This full-order model takes into account the leakage inductance current and the resonant transition intervals in order to realise ZVS. Both the leakage inductance current and the resonant transition intervals are the key to accurately predict the dynamic behaviour of the converter. A control-to-output-voltage transfer function is derived for the dual active bridge DC-DC converter, which is taken as an example to illustrate the modelling procedure. Experimental results confirm that the new model correctly predicts the small-signal frequency response up to one-third of the switching frequency and is more accurate than the previously presented models. View full abstract»

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  • Power quality improvement in load commutated inverter-fed synchronous motor drives

    Page(s): 411 - 428
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1282 KB)  

    The load commutated inverter (LCI)-fed synchronous motor (SM) drive, also known as commutatorless motor (CLM) drive, is popular in high power applications. Most promising features of these drives include high efficiency, economic operation, flexibility of operation and variable speed in high power range, which led to their applications in blowers, fans, pumps, mill drives for a range of industries as mining, water treatment plants, chemical, paper, textile, cement, rolling mills and petrochemical plants. However, the power quality (PQ) concerns have resulted in a set-back for such applications of these drives. This study investigates various topologies for the mitigation of PQ problems in LCI-fed SM drives using multi-pulse AC-DC converters. A set of hybrid topologies is proposed to feed CLM, which use a multi-winding transformer and diode rectifiers with a chopper cascaded named as -rectifier-chopper-. These topologies improve PQ at AC mains, that is, reduce total harmonic distortion in the input current and correct the power factor. It also presents a basis for selection of a suitable AC-DC converter for PQ improvement at the input AC mains of the LCI-fed SM drives. View full abstract»

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  • Analysis and implementation of an active clamping zero-voltage turn-on switching/zero-current turn-off switching converter

    Page(s): 429 - 437
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (926 KB)  

    A new isolated dc/dc converter with zero-voltage turn-on switching (ZVS) of power switches and zero-current turn-off switching (ZCS) of diodes is presented. In conventional flyback converters, the main drawbacks are high voltage stresses on power devices, large transformer size and serious reverse recovery current, which resulted in high voltage spikes across output diode. To solve these problems, a buck-boost type of active-clamp circuit is connected in parallel with the primary winding to clamp the voltage spike across the power switch, to recycle the energy stored in the leakage and magnetising inductances of the transformer and to realise the turn-on ZVS by utilising the leakage inductance and output capacitance of the switch. The leakage inductance and the resonant capacitance on the secondary side are resonant to allow the output diodes to turn off at ZCS. Thus, the switching losses and thermal stresses of switches and diodes are reduced, the output diode has no reverse recovery problem and voltage stresses of the output diodes are clamped to the output voltage. Experiments conducted on a laboratory prototype rated at 270 W are provided to verify the effectiveness of the proposed converter. View full abstract»

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  • Intermediate-scale instability in two-stage power-factor correction converters

    Page(s): 438 - 445
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (525 KB)  

    Intermediate-scale instability is investigated for two-stage power-factor correction (PFC) converters, which are practical and popular design solutions for medium-to-high power applications. The circuits employ a cascade configuration of a pre-regulator Boost PFC converter with an average current mode control to achieve a near unity power factor and a post-regulator DC-DC Buck converter with a voltage feedback control to regulate the output voltage. The intermediate-scale instability manifests itself as local oscillations within a line cycle, whose oscillation frequency is between the line frequency and the switching frequency. Based on the assumptions that the rectified line voltage can be represented by its root mean square value and the post-regulator DC-DC Buck converter can be considered as a constant power sink, the small-signal model is established, and the underlying mechanism of such intermediate-scale instability is studied further. Finally, experimental results are given for the verification of analytical results. View full abstract»

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  • Controller area network fusing management system in a 14 V/42 V automotive electrical architecture

    Page(s): 446 - 453
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (709 KB)  

    The use of a dual voltage system 14 V/42 V in the electric system of cars has many advantages such as improved fuel consumption, reduced emissions and increased passenger comfort and safety. However, the inclusion of a new power supply introduces new possible short-circuit (SC) situations. The fusing management system (FMS) is responsible for managing the 14 V-ground (gnd), 42 V-gnd and 14 42 V SCs, with the objective of eliminating them as soon as possible in order to reduce the harmful effects on wires, batteries and electrical loads. An FMS implementation in an electric vehicle platform s prototype is shown, using SMARTFETs and the presented Fuse Management strategy in order to substitute actual passive fuses and the controller area network as a communications protocol. The philosophy used in the FMS, its main benefits and the experimental results obtained with 14 V-gnd, 14 42 V and 42 V-gnd SCs are presented. This strategy is also extensible to future electric vehicle architectures. View full abstract»

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  • Modified sinusoidal pulse-width modulation operation technique of an AC-AC single-phase converter to optimise the power factor

    Page(s): 454 - 464
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1202 KB)  

    A modified sinusoidal pulse-width modulation (sPWM) switching technique is suggested for the operation of a power electronic converter to control the power and to optimise the power factor (PF). The idea is to shift the delayed grid current to the grid voltage, through a modification of the classical sPWM converter switching technique in order to improve the PF. In this way, the decrease in the phase angle between the fundamental current harmonic and the voltage at the grid side is feasible, and consequently, the use of compensation capacitors can be avoided. Consequently, the PF optimisation as well as an improvement in the power efficiency can be achieved. The effect of the proposed switching technique on the PF and the power efficiency is investigated via simulation using the software Matlab/Simulink as well as through appropriate experiments. For the experimental investigation, a prototype has been designed and constructed in the laboratory. The proposed modification of the sPWM converter operation has been applied in a single-phase AC-AC PWM converter supplying a resistive-inductive load. View full abstract»

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Aims & Scope

IET Power Electronics brings together five principal power electronics themes including: applications of power semiconductor technology; circuits; devices; techniques; and performance management.

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