By Topic

Power Electronics, IET

Issue 1 • Date January 2012

Filter Results

Displaying Results 1 - 16 of 16
  • A three-phase unity power factor front-end rectifier for AC motor drive

    Page(s): 1 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1152 KB)  

    This study presents the bidirectional controlled switch-based high-frequency (HF) current injection circuit with simple gate control scheme. Improved power factor and total harmonic distortion (THD) of ac input line current of front-end rectifier for ac motor drive is achieved using this scheme. The gating pulses for feedback bidirectional controlled switches are generated at every zero-crossing instances of the respective phase voltages for the duration of π/6πrad. The analysis of the converter along with loss calculations is presented. In order to validate the concept, a prototype model of a converter for 5πkW power using voltage source converter feeding three-phase induction motor is designed in the laboratory. The sinusoidal pulse width modulation switching signals are generated by using DSP (TMS320F2812). The computer simulation results and experimental results are also presented. It is observed that HF current injection for the duration of one-third of phase voltage period results in a remarkable improvement in input current THD and power factor of the front-end rectifier. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis and implementation of a novel single-switch high step-up DC-DC converter

    Page(s): 11 - 21
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1012 KB)  

    A novel high step-up DC-DC converter, which is composed of one boost converter, two capacitors, two diodes and one coupled inductor, is presented in this study. The concept is that the two capacitors are charged in parallel and are discharged in series via the coupled inductor to achieve high step-up voltage gain under appropriate duty ratio. Also, the leakage-inductor energy of the coupled inductor is recycled and the voltage stress on the main switch can be reduced. Besides, the energy of leakage inductor can transfer to capacitor to increase voltage gain. Therefore low conduction resistance RDS(ON) of the main switch can be adopted to reduce the conduction loss. In addition, the reverse-recovery problem of the output diode is alleviated. Thus, the efficiency can be further improved. The operating principle and steady-state analysis are discussed in detail. Finally, a prototype circuit with input voltage 24 V, output voltage 400 V and output power 200 W is implemented in the laboratory to verify the performance of the proposed converter. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Solution trajectories for selective harmonic elimination pulse-width modulation for seven-level waveforms: analysis and implementation

    Page(s): 22 - 30
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1590 KB)  

    A detailed analysis of a seven-level selective harmonic elimination pulse-width modulation method suitable for multilevel DC-AC converters is presented in this study. Solution trajectories that cover the normal range of modulation indices typical for the operation of multilevel inverters are documented. The properties and characteristics of these solutions with regard to the distribution of switching instants (angles) to the levels of the waveform are also reported. Selected simulation and experimental results are included for both steady state operation and under dynamic changes of the modulation index and the output frequency. The results confirm the effectiveness of the method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Constrained model predictive control strategy for single-phase switch-mode rectifiers

    Page(s): 31 - 40
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1179 KB)  

    This study presents a new approach to the control problem of single-phase switch-mode rectifiers. The proposed approach is based on a particular model predictive control scheme, incorporated with soft constraints for the errors of the key control targets. This control system is free of portional integral (PI) controllers, which are responsible for poor dynamic performance. Control objectives of sinusoidal input current, approximately unity input power factor, and output voltage regulation are successfully met under both steady state and load or setpoint changes. Considering the significant advantages of multilevel operation, the reflected AC side voltage exhibits an appropriate three-level modulation. The developed control strategy involves improved performance compared with a model-based sliding mode one. The theoretical analysis is validated by measurements on a laboratory prototype, illustrating the feasibility and suitability of the proposed controller for this type of rectifiers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Virtual prototyping and pre-sizing methodology for buck DC-DC converters using genetic algorithms

    Page(s): 41 - 52
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1035 KB)  

    In this article, the authors study the pre-sizing approach of DC-DC buck converters useful for electronics and system designers. The pre-sizing step in an industrial process is suitable to obtain a preliminary precise sizing of a sub-system (here a buck DC-DC converter): it permits the system designer to perform a feasibility analysis of an overall system (e.g. that contains a buck DC-DC converter). First, static modelling of power devices is proposed: MOSFET, diode, inductor and heatsink. According to an industrial context, the MOSFETs, diodes and heatsinks fitting curves are issued from the manufacturer-s datasheets. Second, the objective functions are explained in the case of mixed integer programming problems. Then, the optimisation variables and constraints are highlighted. Third, a section describes the choice of a multi-objective optimisation technique that leads to genetic algorithms (GAs). Fourth, the optimisation results are given. The choice of a final solution of the pre-sizing approach is discussed, considering additional constraints such as diode and MOSFET junctions temperatures, switching frequency etc. The authors focus on the general aspect of the optimisation method proposed here. It can also be used by power electronics designers with the help of additional constraints in accordance to their specific applications. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Current injection-based DC-link capacitance estimation using support vector regression

    Page(s): 53 - 58
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (412 KB)  

    A novel online capacitance estimation method for a DC-link capacitor in a three-phase back-to-back pulse width modulation (PWM) converter is proposed. A controlled AC current with a frequency lower than the line frequency is injected into the input side, which then causes AC voltage ripples at the DC output side. With this AC voltage component extracted by band-pass filters, the capacitance is estimated by the support vector regression method without measuring the DC-link current. A function that defines the relation between a given capacitor power and its corresponding capacitance is determined using a set of training data. This function is then used to predict the output for the given input which is not included in the training set. The proposed method can simply be implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.146%. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dimmable driver for light-emitting diode with total harmonic distortion improved

    Page(s): 59 - 67
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (821 KB)  

    A novel dimmable light-emitting diode (LED) driver is presented. Via a simple concept, the total harmonic distortion and the power factor of the proposed LED driver are significantly improved as compared to the traditional LED drivers. Above all, there are no capacitor and no inductor in the main power stage of the proposed LED driver, thereby causing the life of the LED driver to be enhanced and the integral circuit design to be easy to achieve. Moreover, a new LED dimming strategy is presented. The basic operating principles of the LED driver are described in detail, along with some simulated and experimental results to demonstrate the effectiveness and feasibility of the proposed LED driver. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Development of non-linear controllers for a tri-state boost converter

    Page(s): 68 - 73
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (399 KB)  

    The development of non-linear controllers for a tri-state boost converter in the presence of an unknown load is addressed. In contrast to the conventional boost converter, the tri-state boost converter has two control inputs and does not have a right-half-plane zero. The controllers are designed using the average model of the tri-state boost converter to vary both the `boost` and `capacitor-charging` intervals using the average model of the tri-state boost converter to achieve fast response and a small inductor current. Experimental results to illustrate the features of the controllers are provided. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of an asymmetric modulation method for cascaded multilevel inverters

    Page(s): 74 - 85
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1128 KB)  

    Traditional means for implementing the switching of the power switches in multilevel converters is subharmonic pulse width modulation (SHPWM) or triangulation approach involving a comparison between a target reference waveform and several high-frequency carrier waveforms where all the power switches usually work at high switching frequency. The asymmetric modulation method (AMM) which is derived from hybrid modulation method is illustrated. The contribution of asymmetric modulation is to provide a general method of finding the locus of the output stepped-wave for the hybrid modulation method. This study also provides an illustration of the `Mathematic expression of modulation process` of SHPWM and AMM where it is easy to see how the two techniques are related, and the output expression of the AMM method can be easily obtained from the general N-level double-Fourier output expressions of SHPWM where cumbersome mathematical work has been avoided. Through the analysis of modulation process for SHPWM and AMM, results show that the AMM is an improved version of SHPWM method with optimised switching combination. Theoretical analysis, simulation and experimental results are provided to validate the feasibility of the proposed analysis method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Voltage allocation control for multi-module power conversion system with parallel-input and series-output connection

    Page(s): 86 - 94
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (871 KB)  

    Voltage allocation (VA) is analysed for a multi-module power conversion system using a parallel-input and series-output (PISO) connection with different power ratings. In PISO system, the multi-module converters with different power ratings cannot regulate total output voltage when one of the series module is operated in its voltage limited mode. Therefore an automatic master loop regulation (AMLR) control scheme is proposed to allocate output voltage of individual modules, as well as to regulate total output voltage and achieve power management. Presented also is a green-mode control (AMLR+backup module) that could shield backup module in light-load to improve light-load efficiency. Finally, by using green-mode control, the experimental prototypes of three PISO forward modules with different power ratings are implemented in order to achieve VA mechanism. The efficiency of the multi-module PISO system with the proposed control scheme in the light-load is improved by over 12+, as compared to the conventional control scheme. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Control technique for non-linear and unbalance compensation of an integrated magnetics-based three-phase series-shunt-compensated uninterruptible power supply

    Page(s): 95 - 105
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1011 KB)  

    Handling unbalanced and non-linear loads in a three-phase AC power supply has always been a difficult issue. This has been addressed in the literature by either using fast controllers in the fundamental rotating reference frame or using separate controllers in reference frames specific to the harmonics. In the former case, the controller needs to be fast and in the latter case, besides the need for many controllers, negative-sequence components need to be extracted from the measured signal. This study proposes a control scheme for harmonic and unbalance compensation of a three-phase uninterruptible power supply wherein the problems mentioned above are addressed. The control takes place in the fundamental positive-sequence reference frame using only a set of feedback and feed-forward compensators. The harmonic components are extracted by a process of frame transformations and used as feed-forward compensation terms in the positive-sequence fundamental reference frame. This study uses a method wherein the measured signal itself is used for fundamental negative-sequence compensation. As the feed-forward compensator handles the high-bandwidth components, the feedback compensator can be a simple low-bandwidth one. This control algorithm is explained and validated experimentally. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Minimisation of total harmonic distortion in a cascaded multilevel inverter by regulating voltages of dc sources

    Page(s): 106 - 114
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (878 KB)  

    Recently, a switching strategy based on minimisation of total harmonic distortion (MTHD) has been proposed. Normally, in multilevel flexible AC transmission systems, DC voltages of capacitors are changed. It is proposed to regulate this value on a predefined value. Thus, desired value is employed for optimising THD value. Results show effectiveness of the proposed method in minimising THD, when it is compared with the case of a multilevel inverter with constant DC sources. Genetic algorithm as a powerful tool is used to minimise THD as well as satisfy fundamental component. To verify theory and simulation results, a seven-level cascaded inverter-based hardware prototype is built. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-efficiency bidirectional DC-DC converter with coupled inductor

    Page(s): 115 - 123
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1025 KB)  

    This study presents a novel soft-switching bidirectional dc-dc converter with a coupled inductor. Transformer-based circuit topologies are commonly employed in conventional bidirectional converters and soft-switching techniques, including zero-voltage switching (ZVS) or zero-current switching (ZCS), are frequently applied to mitigate switching losses. Unfortunately, the use of more than four switches and several diodes in these transformer-based schemes increase production costs and reduce conversion efficiency. This work presents a coupled-inductor bidirectional converter scheme that utilises four power switches to achieve the goal of bidirectional current control. The high step-up and step-down ratios enable a battery module current with a low-voltage level to be injected into a high-voltage dc bus for subsequent utilisation. Experimental results based on a 24 V/200 V 800 W prototype are provided to verify the effectiveness of the proposed bidirectional converter. Since the voltage clamping, synchronous rectification and soft-switching techniques are utilised in the proposed circuit topology and the corresponding device specifications are adequately fulfilled, the proposed converter can provide highly efficient bidirectional power conversion in a wide range on the low-voltage side. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Low-inductance axial flux BLDC motor drive for more electric aircraft

    Page(s): 124 - 133
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1183 KB)  

    As aircraft technology is moving towards more electric architecture, use of electric motors in aircraft is increasing. Axial flux BLDC motors (brushless DC motors) are becoming popular in aero application because of their ability to meet the demand of light weight, high power density, high efficiency and high reliability. Axial flux BLDC motors, in general, and ironless axial flux BLDC motors, in particular, come with very low inductance Owing to this, they need special care to limit the magnitude of ripple current in motor winding. In most of the new more electric aircraft applications, BLDC motor needs to be driven from 300 or 600 Vdc bus. In such cases, particularly for operation from 600 Vdc bus, insulated-gate bipolar transistor (IGBT)-based inverters are used for BLDC motor drive. IGBT-based inverters have limitation on increasing the switching frequency, and hence they are not very suitable for driving BLDC motors with low winding inductance. In this study, a three-level neutral point clamped (NPC) inverter is proposed to drive axial flux BLDC motors. Operation of a BLDC motor driven from three-level NPC inverter is explained and experimental results are presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Variable turn pitch coils design for heating performance enhancement of commercial induction cooker

    Page(s): 134 - 141
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (730 KB)  

    This study aims to enhance heating performance of an induction cooker with convex bottom Chinese wok for commercial applications. Traditional single coil solution is first designed according to the wok shape. The theoretical closed-form expressions of the eddy currents in the wok are derived, and further verified by finite-element method (FEM) analysis. The results reveal the localised and uneven eddy currents distribution for the induction cooker with an evenly distributed single coil. Variable turn pitch (VTP) coils are then proposed to address the eddy currents distribution problem. Corresponding analytical equations are given to present the design process of the VTP coils. The resulting eddy currents distribution on the wok is validated to be improved by applying the VTP coils. The inductance characteristics of the proposed VTP coils are also studied by conducting FEM and physical measurements. Finally, a prototype of the proposed system is developed and has undergone comprehensive experiments. The experimental results validate the theoretical analysis, indicating that the heating performance of the induction cooker system would be remarkably enhanced by implementing the VTP coils. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Series hybrid active power filter based on controllable harmonic impedance

    Page(s): 142 - 148
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (779 KB)  

    In order to reduce inverter capacity and enhance system reliability, a novel series hybrid active power filter (APF) based on controllable harmonic impedance is proposed in this study. As the pulse-width-modulated inverter works as a controlled harmonic current source, the series transformer (ST) can exhibit the controllable impedance to harmonic current, which makes the impedance of primary winding of series transformer very high for all frequencies except for the fundamental, thus forcing all harmonic current components through the passive filters and therefore preventing harmonic currents from entering the main power system. Adopting the small self-inductance ST, the inverter and secondary winding of the ST need not endure the fundamental current but only endure the injected harmonic currents, and the LC fundamental tuned bypass can be omitted; so the cost of the proposed APF will be very low. The validity of the proposed APF is verified by the simulation and experimental results. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

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

Full Aims & Scope

Meet Our Editors

IET Research Journals
iet_pel@theiet.org