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Power Electronics, IET

Issue 2 • Date June 2008

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Displaying Results 1 - 11 of 11
  • Systematic analytical-based generalised algorithm for multilevel space vector modulation with a fixed execution time

    Publication Year: 2008 , Page(s): 175 - 193
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1282 KB)  

    A generalised algorithm is proposed for multilevel space vector modulation (SVM), which is applicable to any number of levels. The algorithm is based on numerical analysis and gives a fixed execution time when implemented in a digital signal processor, irrespective of the number of levels. In addition, the algorithm procedures eliminate the difficulty in determining the reference vector location, the on-time calculations and switching state selection. A visualisation of the multilevel SVM analysis is detailed, without using any representative technique. The redundant paths can be readily utilised for capacitor balancing. The proposed algorithm caters for over modulation and minimum pulse, and is validated by Matlab/Simulink simulations and practical implementation. A 6 kW three-level active power filter is implemented practically using the proposed algorithm. It is shown that the algorithm is readily codable and time efficient. View full abstract»

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  • Bridgeless dual-boost rectifier with reduced diode reverse-recovery problems for power-factor correction

    Publication Year: 2008 , Page(s): 194 - 202
    Cited by:  Papers (24)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (661 KB)  

    A bridgeless dual-boost rectifier with reduced diode reverse-recovery problems is proposed for power-factor correction (PFC). In the proposed rectifier, conduction losses are lowered by essentially eliminating the full-bridge diode rectifier. The body diodes of the power switches are utilised as output diodes. A coupled inductor is designed to reduce the reverse-recovery problems of the body diodes. Zero-current switching is realised when the body diodes are turned off. In addition, for the use of this topology in a practical design, a control strategy is suggested by employing the linear peak current mode (LPCM) control. The LPCM control is implemented on leading-edge modulation, providing an efficient control scheme to obtain a high power-factor. The proposed rectifier is investigated theoretically and its design considerations are provided in detail. Finally, the experimental results based on a 500 W prototype are discussed to evaluate the performance of the proposed rectifier for a PFC circuit. View full abstract»

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  • Design of a sinusoidal current source using a sliding-mode-controlled asymmetrical full-bridge multilevel converter

    Publication Year: 2008 , Page(s): 203 - 213
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    An analysis and design of an asymmetrical full-bridge multilevel converter in sliding-mode operation for inverter applications in small power systems are presented. A five-level sinusoidal current source inverter is proposed with the lowest number of controllable devices and the simplest control electronics. The current source nature of the inverter is achieved by means of a sliding-mode control loop forcing the inverter output current to track a sinusoidal reference. The theoretical predictions have been verified by experiments in a 1 kW prototype in both stand-alone and grid connection operations. View full abstract»

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  • Family of zero current zero voltage transition PWM converters

    Publication Year: 2008 , Page(s): 214 - 223
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (664 KB)  

    A new auxiliary circuit is introduced for buck, buck-boost, forward and flyback converters. This auxiliary circuit provides zero current, zero voltage switching condition for the main switch while providing zero current switching condition for the auxiliary switch and diodes. In this converter family, there is no additional voltage and current stress on the main switch. The proposed auxiliary circuit is applied to a buck converter and the resulting ZCZVT PWM buck converter is analysed and its operating modes are presented. A simple design method for auxiliary circuit is discussed. The experimental results of a 175 W ZCZVT buck converter operating at 100 KHz are presented. Other converter topologies with the proposed auxiliary circuit are also introduced. View full abstract»

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  • Analysis of the two-quadrant converter with rectifier with near sinusoidal input currents

    Publication Year: 2008 , Page(s): 224 - 234
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (917 KB)  

    A new topology for a two-quadrant converter is presented. In the AC/DC transfer mode, the converter works as a rectifier with near sinusoidal input currents, whereas in the DC/AC transfer mode, it works as a square-wave pulse switching inverter. The converter is characterised by smaller power losses and reduced electromagnetic interference problems. Possible applications in adjustable speed drive with regenerative braking, wind energy conversion systems and small hydro interconnections with induction generators are also discussed. View full abstract»

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  • Real-time implementation of grey fuzzy terminal sliding mode control for PWM DC-AC converters

    Publication Year: 2008 , Page(s): 235 - 244
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (678 KB)  

    Classical terminal sliding mode control (TSMC) has finite system state convergence time and is insensitive to disturbances and uncertainties within expected limits. However, TSMC may chatter when uncertainty values are overestimated or may exhibit a steady-state error when uncertainty values are underestimated. An improved TSMC is proposed by the use of a mathematically simple and computationally fast grey prediction (GP) methodology, which is then fine-tuned by the use of fuzzy control methodology for PWM DC-AC converters. First, GP methodology is employed to deal with classical TSMC chattering and steady-state error problems. Fuzzy control is then used to tune the GP forecasting value for improved rise time and overshoot characteristics. The system is evaluated by simulation and also by real experiment. Both evaluation methods confirm that the proposed controller achieves low total harmonic distortion under non-linear loading conditions and fast dynamic response under transient loading conditions. Because the proposed grey-fuzzy TSMC methodology is simpler to implement than prior methods and offers more efficient computation, it will be of interest to designers of related control systems. View full abstract»

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  • Structures of transformerless step-up and step-down controlled rectifiers

    Publication Year: 2008 , Page(s): 245 - 254
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (300 KB)  

    New single-switch structures of single- and three-phase transformerless controlled rectifiers are proposed and analysed. These structures consist of a common rectifier, an input inductor filter, a high-frequency operated switch and a diode-capacitor ladder network. The latter, in its known application as a multiplier, is used for increasing the input voltage. A new scheme of a diode-capacitor network, which can be used as a divider to reduce the input voltage, is also proposed. The detailed analysis of the steady-state mode is performed and simple formulas for the calculation of step-up and step-down rates of the voltage are derived. Transient analysis of the proposed circuits, by solving the recurrent equations and by using the z-transform, is also performed. Since the proposed schemes do not consist of any transformers and/or any inverters, their operation is very efficient; no high harmonics and/or a DC component are produced, and so the input current and voltage waveform are close to the sinusoid. The power factor of such structures reaches unity and their weight is low, compared with those having a transformer. A laboratory model of one of the proposed structures has been built and tested. The experimental results confirm the convertergraves efficiency and the correctness of the theoretical analysis. View full abstract»

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  • Comparative evaluation of modulation methods of a three-phase buck + boost PWM rectifier. Part I: Theoretical analysis

    Publication Year: 2008 , Page(s): 255 - 267
    Cited by:  Papers (15)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (278 KB)  

    Different switching state sequences of a three-phase three-switch buck-type unity power factor PWM rectifier with integrated DC/DC boost output stage are presented. They are analysed concerning switching losses and ripple components at the input (filter capacitor voltage ripple) and at the output (DC link current inductor ripple). For a fair comparison, pulse frequencies of different modulation methods are adopted in order to achieve the same switching losses. The rms value and envelopes and time behaviour of the ripple components are analysed analytically and by simulation, and one advantageous modulation method is determined. The paper provides the basis for a subsequent experimental verification, which is performed in part II. View full abstract»

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  • Comparative evaluation of modulation methods of a three-phase buck + boost PWM rectifier. Part II: Experimental verification

    Publication Year: 2008 , Page(s): 268 - 274
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (837 KB)  

    This paper presents experimental results of a comparative evaluation of two different modulation methods for a three-phase buck+boost PWM rectifier. The measurements, which are performed on a 5 kW digital signal processor controlled prototype, verify the analytical calculations and simulations in part I and identify one modulation method to be clearly superior regarding the input filter capacitor voltage ripple and the DC link inductor ripple values. Finally, also the EMC noise emission levels are comparatively analysed for the modulation methods. View full abstract»

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  • Multi-function zero-voltage and zero-current switching phase shift modulation converter using a cycloconverter with bi-directional switches

    Publication Year: 2008 , Page(s): 275 - 286
    Cited by:  Papers (8)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    A novel voltage source full-bridge DC-DC converter with phase shift modulation using a high-frequency cycloconverter is proposed. Both zero-voltage and zero-current switching (ZVZCS) commutation for full-bridge active power switches and zero-voltage switching operation for cycloconverter bi-directional switches are obtained. Soft switching operation is provided in a wide range of voltage regulation without utilising an auxiliary inductor in the primary side of an isolating transformer. To implement this DC-DC converter as a multi-function DC-AC inverter, a reference signal is traced by the control system to adjust the output voltage according to the variations of the reference signal. Therefore desired output waveforms are provided by selected reference signals. Hence the proposed circuit operates as a multi-function converter. Based on the simulation and experimental results, the steady-state operation principles of the converter are analysed and discussed. Experimental results from a 24 V-DC input and 20 kHz fixed switching frequency laboratory prototype is presented to introduce both the switching operation and the multi-function performance of the converter. View full abstract»

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  • A 28-pulse AC-DC converter for line current harmonic reduction

    Publication Year: 2008 , Page(s): 287 - 295
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (908 KB)  

    A novel transformer for 28-pulse AC-DC converter configuration is designed, modelled and simulated to feed isolated DC varying loads. The proposed transformer is suitable for large current rating rectifiers such as electric-aircraft power supply, electro-winning, electro-chemical processes, induction heating, plasma torches and so on, where isolation is required mainly for stepping down the supply voltage. It consists of two paralleled 14-pulse AC-DC converters involving seven-phase shifted AC fed diode bridges. It improves power quality at AC mains and it meets power quality IEEE-519 standards requirements at varying loads. 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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