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Power Electronics, IET

Issue 1 • Date January 2010

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Displaying Results 1 - 14 of 14
  • Evaluation of insulated gate bipolar transistor protection with ZnO thick films varistors

    Page(s): 1 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    To have efficient protection of insulated gate bipolar transistor (IGBT) against various electrical voltage overshoots, screen-printed zinc oxide (ZnO) varistors have been developed using a planar structure. These varistors exhibit a breakdown voltage higher than 600 V and a non-linear coefficient up to 40. Some samples have been tested in real operations conditions to protect 1200 V IGBT in the case of unclamped inductive switching operations (default on the freewheeling diode). The results have shown the high efficiency of the designed varistors by clamping the voltage overshoot appearing on the IGBT. Optimising of the fabrication process (mechanical pressure or not on ZnO layers, ZnO thickness, electrode and substrate nature), lead to dissipated energy density of 105 J/cm3. View full abstract»

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  • Effect of supply voltage asymmetry on IRP p-q-based switching compensator control

    Page(s): 11 - 17
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (217 KB)  

    Results of a study on how the supply voltage asymmetry affects the reference signal for switching compensator control, in a situation when this signal is generated using the instantaneous reactive power (IRP) p-q theory are presented. According to the IRP p-q approach, the compensator should compensate IRP and the alternating component of the instantaneous active power of the load. However, that in the presence of the supply voltage asymmetry, even an ideal, unity power factor load has an instantaneous active power with a non-zero alternating component is demonstrated. According to IRP p-q theory-based approach, it should be compensated and this requires that a distorted current be injected into the distribution system. It means that in the presence of the supply voltage asymmetry, the algorithms based on the IRP p-q theory generate a non-sinusoidal reference signal for the compensator control, even when voltages and currents in the system are sinusoidal. View full abstract»

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  • High efficiency asymmetrical half-bridge flyback converter using a new voltage-driven synchronous rectifier

    Page(s): 18 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1690 KB)  

    This study presents a high efficiency asymmetrical half-bridge flyback converter using a new voltage-driven synchronous rectifier that operates over a universal input voltage range (75-265-V) with a fixed 5-V DC output voltage. Both power semiconductor switches of the proposed converter primary operate asymmetrically under zero voltage switching to achieve high efficiency and low switch voltage stress. Because the proposed converter uses the transformer leakage inductance as its resonant inductance, its structure is simplified. The proposed synchronous rectifier can cover a universal input voltage range and can maintain control in a narrow switching period, features that are essential in converters with universal input voltage. The synchronous rectifier switch of the proposed converter conducts under zero voltage/zero current switching conditions with a discontinuous conduction mode. The operational principle and steady state analysis of the proposed converter are explained, and a design example for a 100-W prototype is discussed in detail. Experimental results for the designed prototype converter with universal input voltage are shown. The author also shows that the efficiency of the proposed converter can be improved significantly. View full abstract»

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  • Novel true zero current turn-on and turn-off converter family: analysis and experimental results

    Page(s): 33 - 42
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (957 KB)  

    A novel soft-commutation cell capable of providing zero current switching (ZCS) operation keeping the main switch current equal to the load current is presented. Substituting the typical pulse width modulation cell found in classic power converter structures by the presented ZCS cell and taking to account the invariance principle, a new ZCS converter family could be achieved and it is also presented here. The operation and main properties of this cell are also included. A theoretical approach for the design of the proposed cell applied to a DC-DC buck converter is presented and corroborated by the experimental results with an 800 W laboratory prototype. View full abstract»

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  • Limits of predictive current-ripple suppression in switching power-supply ICs

    Page(s): 43 - 53
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (647 KB)  

    Large inductance requirements (for accuracy) in switching power supplies for portable applications impede system-on-chip (SoC) integration and therefore form-factor reduction because on-chip inductances are invariably low and off-chip inductors intolerably obtrusive. Cancelling the current ripple of innately small on-chip inductors, however, keeps the effective output current ripple and its resulting output voltage variation (i.e. accuracy) within acceptable window limits (e.g. 50-200 mA and 20-50 mV), effectively multiplying the on-chip inductance and circumventing the need for bulky off-chip inductors. To this end, while gyrators and other voltage-mode inductor multiplier circuitry simulate relatively high inductances, they cannot supply the 250-750 mW loads typically attached to battery-powered switching regulators, which the predictive current-mode multipliers discussed in this paper can. The basic objective is to cancel the ac inductor current ripple with an inverting ac replica and allow the on-chip inductor to source the full dc load. Ac mismatches in the form of amplitude, delay and non-linearity, however, limit the extent to which the original ac ripple is cancelled, constraining the inductor multiplication factor to finite values. The foregoing paper describes, illustrates and derives the effects of these mismatches on the multiplication factor and shows how realistic non-idealities (e.g. up to 10% gain error and less than 10 ns of delay) can yield inductance multiplication factors of 125 H/H at 100 kHz and 11.5 H/H at 10 MHz in a practical switching dc-dc power-supply integrated circuit (IC). View full abstract»

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  • Design and application of a hybrid active power filter with injection circuit

    Page(s): 54 - 64
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (691 KB)  

    In this study, a novel hybrid active power filter (HAPF) with injection circuit is proposed. It shows great promise in reducing harmonics and improving the power factor with a relatively low-capacity active power filter (APF). As a project in a copper-foil factory in eastern China, the parameters design method of HAPF with injection circuit is put forward here. A multi-objective genetic algorithm is proposed to optimise the design of the output filter parameters, which can meet the requirement of the whole harmonic cancelling system better than the ones designed just by experience. This study focuses on the stability of the power system, so the resonance characteristic of the system when the passive power filter works is discussed particularly. This method can help design the other kind of filtering system for high-capacity applications. A 3600-kvar HAPF prototype with 200-kvar APF has been developed for the copper mill. Both simulation and application results have shown that the proposed HAPF is good in harmonics elimination and reactive power compensation. View full abstract»

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  • Frequency reduction schemes for back-to-back connected, diode-clamped multilevel converters

    Page(s): 65 - 74
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (753 KB)  

    Two new switching schemes for back-to-back connected diode-clamped multilevel converters that reduce the devices switching frequency while maintaining capacitor balancing are presented. Comparisons are made between a previously reported `optimal` balancing strategy and the two proposed switching techniques using data gathered from a prototype five-level, back-to-back connected, diode-clamped multilevel converter. The proposed schemes are shown to allow as much as 35` reduction in switching frequency when compared to the optimal balancing case while also balancing the voltages across the series connected DC-link capacitors. The back-to-back connected, multilevel converter excites a permanent magnet synchronous motor to obtain the experimental data and verify the proposed switching schemes. View full abstract»

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  • LMI robust control design for boost PWM converters

    Page(s): 75 - 85
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (539 KB)  

    This work presents an analytical study and an experimental verification of a robust control design based on a linear matrix inequalities (LMI) framework for boost regulators. With the proposed LMI method, non-linearities and uncertainties are modelled as a convex polytope. Thus, the LMI constraints permit to robustly guarantee a certain perturbation rejection level and a region of pole location. With this approach, the multiobjective robust controller is computed automatically by a standard optimisation algorithm. The proposed method results in a state-feedback law efficiently implementable by operational amplifiers. PSIM simulations and experimental results obtained from a prototype are used to validate this approach. The results obtained are compared with a conventional PID controller. View full abstract»

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  • Hamel locus design of self-oscillating DC-DC resonant converters

    Page(s): 86 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (750 KB)  

    The study presents a technique for analysing and controlling resonant DC-DC converters in a self-oscillating manner. Self-oscillating converters benefit from higher efficiency and higher power density than their non-self-oscillating counterparts since they can be operated closer to the tank resonant frequency. The analysis necessary to predict the behaviour of such converters, based on the construction of Hamel loci, is developed. The impact of parasitic circuit elements is also inherently accommodated. Operation is based on the behaviour of a relay with a negative hysteresis transition. The proposed self-oscillating mechanism is therefore simple and cost effective to implement. Results from a prototype converter are included in order to verify the underlying theoretical principles. View full abstract»

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  • New mathematical model for analysing three-phase controlled rectifier using switching functions

    Page(s): 95 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (841 KB)  

    The aim of this study is to present a set of closed-form analytical equations in order to enable the computation of the three-phase bridge rectifier steady-state performance estimation. The proposed method presented in this study is a fast, accurate and effective mathematical model for analysing three-phase full-wave controlled rectifiers. The steady-state mathematical model is based on the derivation of an appropriate set of switching functions using the general switching matrix circuit (GSMC) techniques. Once the switching functions are derived, the output current, input current and output dc voltage can all be easily derived and generated from the application of this technique. The effect of overlap is accurately modelled and the distortion (notches), frequency content on the input (voltage and current) and output voltage distortion are derived. The proposed mathematical model, unlike conventional analytical methods, can be integrated in the design of active filters. Furthermore, the output voltage reduction, the rms, average and peak values of voltages and currents for the thyristors and any other semiconductor devices used are readily available for the designer by direct substitution into closed-form equations without any need for the waste of time for worst-case scenario simulations. This method can also be applied to other types of converters, specifically to all voltage fed power converters. View full abstract»

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  • Approach to low-cost prevention of DC injection in transformerless grid connected inverters

    Page(s): 111 - 119
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (551 KB)  

    With the growing popularity of distributed generation, there are concerns over the effects that distributed generators may have on power quality. One highly important aspect often overlooked when considering power quality is DC current and the effects that it may have on distribution components. This study considers the problems associated with DC current injection into the electricity distribution network from transformerless grid connected inverters. A new method of preventing differential mode DC injection from transformerless inverters is proposed which eliminates the need for a bulky and costly isolation transformer. This technique is experimentally validated and its benefits regarding DC injection reduction are shown. View full abstract»

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  • Five-level cascade asymmetric multilevel converter

    Page(s): 120 - 128
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    A five-level cascaded asymmetric multilevel converter is analysed and designed. This topology synthesises five voltage levels with a reduced number of components when compared to the most common symmetric topologies. It allows getting more voltage levels with less switching states. Its behaviour is similar to a hybrid converter with the advantage of working with only one DC bus. It does not present the usual drawbacks of symmetrical topologies. The cascaded asymmetric converter, presented here, appears as a very attractive alternative among the five-level converters with no voltage balancing problem. The performance of the proposed topology is evaluated with Pspice simulations in different applications. View full abstract»

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  • A DC-DC multilevel boost converter

    Page(s): 129 - 137
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (613 KB)  

    A DC-DC converter topology is proposed. The DC-DC multilevel boost converter (MBC) is a pulse-width modulation (PWM)-based DC-DC converter, which combines the boost converter and the switched capacitor function to provide different output voltages and a self-balanced voltage using only one driven switch, one inductor, 2N-1 diodes and 2N-1 capacitors for an Nx MBC. It is proposed to be used as DC link in applications where several controlled voltage levels are required with self-balancing and unidirectional current flow, such as photovoltaic (PV) or fuel cell generation systems with multilevel inverters; each device blocks only one voltage level, achieving high-voltage converters with low-voltage devices. The major advantages of this topology are: a continuous input current, a large conversion ratio without extreme duty cycle and without transformer, which allow high switching frequency. It can be built in a modular way and more levels can be added without modifying the main circuit. The proposed converter is simulated and prototyped; experimental results prove the proposition's principle. View full abstract»

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  • An efficient algorithm for generalised single-phase converter

    Page(s): 138 - 145
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (913 KB)  

    This paper describes the various common converters and illustrates the working principle of single phase matrix converter that shows a single topology capable of performing all function required in basic converter. An algorithm is developed that enables a single-phase matrix converter (SPMC) to perform functions of a generalised single phase power electronics converter such as acting as a frequency changer, rectifier, inverter and chopper. This reduces the need for new converter hardware. The algorithm is implemented on computer simulation software Orcad Capture CIS version 9.1. Simulation results are presented for all five types of converters with a control input variable that decides the 1) type of converter and 2) type of output waveform. The simulated results verify the working and operation of a generalised converter based on SPMC. 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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