IET Power Electronics
Print ISSN
1755-4535
Online ISSN 1755-4543
Online ISSN 1755-4543
IET Power Electronics brings together five principal power electronics themes. The submission of high quality research that focuses on one or more of these themes is strongly encouraged;
- Applications of power semiconductor technology for the control and conversion of electric power in: electric machine drives; all forms of transport; manufacturing; heating; lighting; building services and industrial scale power conditioning.
- Circuits commonly used including: all types of converters; inverters; active filters; switched mode power and uninterruptible power supplies.
- Devices used in power electronic applications including: power semiconductor devices; photovoltaic devices; passive components; wound components; batteries and fuses.
- Techniques for controlling, analysing, modelling and/or simulation of power electronics circuits and complete power electronic systems.
- Performance management of power electronic systems including: power factor correction and harmonic spectrum management; thermal management; EMC and noise mitigation; fusing and protection.
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Latest content
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Auto-tuning scheme for improved current sharing of multiphase DC–DC converters
- Author(s): J.-T. Su; C.-W. Lin
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p.
1605
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(9)
In this study, an auto-tuning scheme is presented to realise simple and accurate calibration, for improved current sharing in multiphase DC–DC converters. The proposed control scheme is based on a look-up table method to automatically tune the pre-stored parameters to obtain the same effect as equal output inductance and direct current resistor (DCR). It ensures that time constant is perfectly matched in a conventional DCR current-sensing technique. The proposed scheme provides a low-cost solution with ease of implementation because it is fully designed using a digital control technique without any external phase compensation elements. The proposed scheme is verified on a two-phase interleaved DC–DC buck converter with a 12-V input and a 1-V, 40-A output. Simulation and experimental results are presented to demonstrate the theoretical analysis.
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Single-stage driver for supplying high-power light-emitting-diodes with universal utility-line input voltages
- Author(s): C.-A. Cheng; H.-L. Cheng; F.-L. Yang; C.-W. Ku
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p.
1614
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(10)
The conventional two-stage non-isolated driver for high-power light-emitting diodes (LEDs) is composed of a power-factor-correction (PFC) converter with a non-isolated flyback converter for regulating the output voltage/current for supplying LEDs. However, large numbers of circuit components are required and the total efficiency is limited because of two-stage power conversion. This study proposes a high-power LEDs driver based on a single-stage topology. The presented driver combines a buck-boost PFC converter with a non-isolated flyback converter with two output windings connected in series into a single-stage power-conversion circuit. The proposed driver offers high power factor, high efficiency, low total-harmonics-distortion (THD) of input utility-line current, cost-effectiveness and a constant-output voltage along with limited-output-current control scheme. Finally, a prototype driver is developed and tested in order to supply a 100 W LED light bar module with universal utility-line input voltages for indoor or outdoor general lighting applications. Operational analysis, design equations, a design example and experimental results provided by examining three LED light bar modules demonstrate the feasibility of the proposed circuit.
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Dynamics analysis of a low-voltage stress single-stage high-power factor correction ac/dc flyback converter
- Author(s): S.P. Yang; S.J. Chen; J.L. Lin
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p.
1624
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In this study, by integrating a power factor correction buck-boost cell with a dc/dc flyback cell and adding an auxiliary transformer for energy-divider approach, a single-stage high-power factor correction (HPFC) ac/dc flyback converter with low-voltage stress is proposed. The proposed converter exhibits the capabilities of high-power factor and low-voltage stress across the bulk capacitor when its dc/dc cell operates in continuous conduction mode. In this study, the operating principle is presented. The small-signal model of the proposed converter is also derived herein. It shows that the proposed converter with an auxiliary transformer exhibits better dynamical behaviour than the single-stage HPFC ac/dc flyback converter without an auxiliary transformer. Moreover, a proportional-integral controller is well designed for output voltage regulation. Finally, the accuracy of theoretical analysis and performances of overall system are thereby validated by experimental results.
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Three-phase dual-output six-switch inverter
- Author(s): M. Heydari; A.Yazdian Varjani; M. Mohamadian; A. Fatemi
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p.
1634
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A novel dual-output six-switch inverter topology is proposed in this study for independently supplying two three-phase loads. This inverter employs less number of semiconductor devices compared with former dual-output inverters proposed so far in the literature. Reducing the number of switches and hence drive and control circuits may result in a reduction in overall cost of the system, may reduce its semiconductor power loss and as a result increases efficiency and reliability especially in applications with low and medium voltage and power ratings. The new configuration is introduced and carrier-based pulse-width modulation (PWM) schemes for its two defined modes of operation (constant frequency and variable frequency modes) are developed. Analysis of sizing of the DC-link capacitors is also performed so as to minimise the DC-link voltage ripple and to reduce the value of DC-link capacitors. Furthermore, loss profile of the system is studied and the results are compared with counterpart topologies. Simulation and experimental results are presented to verify the authenticity of the theoretical model.
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Implementation of a parallel zero-voltage switching DC–DC converter with fewer active switches
- Author(s): B.R. Lin; C.H. Liu
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p.
1651
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A parallel soft-switching DC–DC converter with fewer switch count is presented to achieve zero-voltage switching (ZVS), load current sharing and partially output ripple current cancellation. Two buck-type converters are connected in parallel to achieve load current sharing. Only two MOSFETs are used in the proposed converter instead of four switches in a conventional parallel ZVS forward converter. Therefore the proposed converter has fewer active switches. Current-doubler rectifiers are used in the output side in order to achieve partially ripple current cancellation. Therefore the current ripple on output capacitor is decreased and the size of the output choke and output capacitor are reduced. An active snubber is connected between two power transformers to absorb the energy stored in the leakage and magnetising inductances of transformers, to limit voltage stresses across switches, and to achieve ZVS turn-on for all switches. The ZVS turn-on is implemented in the transition interval of two complementary switches such that the switching losses and thermal stresses on semiconductors are reduced. Operation principle, circuit analysis and design example are discussed in detail. Finally, experimental results for a 360 W (12 V/30 A) prototype were presented to verify the effectiveness of the proposed converter.
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Application of cascaded H-bridge distribution-static synchronous series compensator in electrical distribution system power flow control
- Author(s): M. Saradarzadeh; S. Farhangi; J.L. Schanen; P-O. Jeannin; D. Frey
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p.
1660
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In this study, the power flow control of the electrical distribution network using multilevel converter-based distribution-static synchronous series compensator is presented. The conventional radial distribution network can be changed into a meshed grid because of this device. Using multilevel converter topology, the device can be installed directly in series with the line, connecting two separate feeders from different substations together. Two control methods are proposed to control the power flow in the line. The first control strategy uses a fixed DC bus voltage. Enhancing the performance of the multilevel converter, a novel control strategy using variable DC bus voltage is introduced while maintaining the appropriate dynamic response. The new strategy can reduce the total harmonic distortion (THD) of the injected voltage and losses of the power converter compared with the fixed DC bus method. A new soft start method is also proposed to connect the separate feeders together safely. The feasibility of the control strategies is investigated through simulation and experimental results.
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Low-frequency current ripple reduction in front-end boost converter with single-phase inverter load
- Author(s): A. Ale Ahmad; A. Abrishamifar; S. Samadi
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p.
1676
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The low-frequency current ripple that always appears at the input of the single-phase DC/AC inverters decreases the lifetime of DC voltage sources, such as fuel cells and chemical batteries. In this study, based on series and parallel feedback theory, a proportional-integral (PI) controller is designed for the front-end boost converter in two-stage power converters. This controller increases the output impedance of the boost converter, which reduces the low-frequency current ripple at the input of this two-stage converter. Since the designed controller corrupts the dynamic response of the boost converter, the DC-link voltage severely over/undershoots in step load conditions. Overcoming this issue by employing a non-linear gain in the forward path is shown. By applying this proposed technique, the output voltage over/undershoot stays in an acceptable range. Therefore both the low-frequency input current ripple and the DC-link over/undershoot problems disappear simultaneously without employing any additional equipment, especially a bulky DC capacitor. The simulation and experimental results for a 2.5 kW prototype confirm the performance of the proposed idea.
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Design of energy-saving adaptive fast-charging control strategy for Li-FePO4 battery module
- Author(s): R.J. Wai; S.J. Jhung
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p.
1684
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(10)
In this study, an energy-saving adaptive fast-charging strategy is developed and applied to a Li-FePO4 battery module. In this strategy, there are three options including an adaptive constant current (CC)/constant voltage (CV) control scheme, an adaptive variable current (VC) control scheme, and an adaptive current–voltage control scheme to be selected by the user. The objectives of fast charging and energy saving can be simultaneously achieved by the well-designed circuit components in a charge circuit (i.e. a boost converter) plus the proposed adaptive fast-charging strategy. In this study, the maximum conversion efficiency of the boost converter is 97.7% and its average conversion efficiency is over 95%. Moreover, the charge speed and energy saving of a CC/CV framework with a conventional proportional–integral control scheme can be enhanced to reach uppermost 19.2 and 1.33% improvement rates by the adaptive current–voltage control scheme and the adaptive VC control scheme, respectively.
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Performance of cascaded multilevel inverter by employing single and three-phase transformers
- Author(s): A.K. Panda; Y. Suresh
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p.
1694
–1705
(12)
Among the mature multilevel converter topologies, cascaded multilevel H-bridge inverter is promising one which is an alternative for grid-connected photovoltaic/wind-power generator, flexible alternating current systems and motor drive applications. In this study, a cascaded multilevel inverter with low-frequency three-phase transformers and a single dc power source is proposed. This new topology aims to reduce the number of components and so reduce the complexity of the circuit. As three-phase transformer is employed harmonic components of the output voltage and switching losses can be diminished considerably. To evaluate its relative performance it is compared with the conventional converters. Computer aided simulations are performed through Matlab/Simulink and simulation results are presented to verify the performance of proposed cascaded multilevel inverter. Further it is validated with prototype experiments.
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Unified model to derive control-to-output transfer function of peak current-mode-controlled pulse-width modulated dc–dc converters in continuous conduction mode
- Author(s): N. Kondrath; M.K. Kazimierczuk
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p.
1706
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A unified model to derive the control-to-output transfer function of peak current-mode (PCM)-controlled pulse-width modulated dc–dc converters for continuous conduction mode (CCM) is presented. The control-to-output transfer function represents the plant transfer function for the outer-voltage loop and is required to design the outer loop. Control-to-output transfer functions for PCM-controlled pulse-width-modulated dc–dc buck-boost, boost and buck converters are derived and illustrated for selected values of perturbation ratio using MATLAB. Experimental results are given to verify the presented theory for PCM-controlled buck converter.
