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Power Electronics, IET

Issue 1 • Date January 2011

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Displaying Results 1 - 18 of 18
  • Average current controlled switching regulators with cascade boost converters

    Page(s): 1 - 10
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (892 KB)  

    A controller design methodology for an n-stage cascade boost converter is given using average current-mode control. This class of converters has n-LC filters; thus, it will exhibit 2n-order characteristic dynamics. The proposed scheme employs the inductor current of the input stage and the capacitor voltage of the output stage; thus, there are (n-1) capacitor voltages and (n-1) inductor currents that are not used for feedback purposes. The sensed current can also be used for one-cycle overload protection; therefore the full benefits of current-mode control are maintained. Owing to the fact that this scheme uses only a reduced set of variables for feedback, it is important to study the internal stability. The results given in this study allow the designer to easily pinpoint the control circuit parameters that optimise the converter-s performance. Experimental results are given for a 100 W switching regulator where the robustness of the proposed controller is tested under changes in the input voltage and output load. View full abstract»

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  • Bit-stream implementation of a phase-locked loop

    Page(s): 11 - 20
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (711 KB)  

    Bit-stream is a new technique for controlling power electronics applications by interconnecting appropriate control elements inside an field programmable gate array (FPGA). This paper presents a bit-stream-based phase locked loop (PLL), which is essential for the implementation of sophisticated power electronics control systems using bit-streams. The proposed PLL consists of a phase detector, loop filter and numerically controlled oscillator, each of which is designed using standard analogue methods and converted to equivalent bit-stream elements. The bit-stream-based PLL is modelled using Matlab/Simulink and ModelSim, and results show that the PLL successfully locks onto a 50 Hz three-phase voltage source. Experimental results of a prototype, constructed using an Altera Cyclone II FPGA and controlled using a bit-stream-based PLL, are presented and compared to a similar, microprocessor-based, PLL to demonstrate that the bit-stream-based PLL successfully locks onto the line voltage waveform. The practical viability of the proposed bit-stream PLL is investigated using a prototype three-phase, 3 kW, controlled rectifier. The experimental implementation of the PLL requires approximately 350 logic elements. View full abstract»

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  • Analysis, design and control of zero-voltage switching quasi-resonant-positive output super lift Luo converter

    Page(s): 21 - 28
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (889 KB)  

    This study presents the analysis, design and voltage regulation of a zero-voltage switching quasi-resonant-positive output super lift Luo converter with low switching losses for industrial applications requiring regulated output voltage. To increase the power packing density, a simple control method using an analogue resonant controller UC3861 is used to regulate the output voltage against load variation and supply disturbance. The performance of the controller is verified by developing a prototype model of the converter and experimental results are presented. The results reveal the superiority of using a single dedicated IC for voltage regulation. Also it is observed that the converter provides maximum efficiency of 95% at full load. View full abstract»

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  • Multilevel modulation method for mitigation of high du/dt-originated oscillating overvoltages at motor terminals

    Page(s): 29 - 38
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (617 KB)  

    Multilevel inverters have drawn wide interest in the field of high-power applications. Regardless of the attention paid to inverters, the overvoltage phenomenon, which is well known in two-level inverters, has not been investigated thoroughly in multilevel applications. The oscillating overvoltages occur after high du/dt voltage edges if the propagation delay of the motor cable is long compared to the voltage rise time. These oscillating voltages at the motor terminals cause, for example, partial discharges in the stator windings and deteriorate them. A multilevel modulation method that suppresses the oscillations is introduced in this study. The method is based on the timing of two consecutive voltage edges, so that the oscillations caused by the edges counteract each other. This counteraction mitigates the resulting oscillating voltage. The principles of the method are given in detail for a wide scale of multilevel inverter levels. The method is implementable to almost any multilevel inverter topology. Measurements with a 100 kVA, 3 kV series-connected H-Bridge inverter confirm the method. View full abstract»

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  • Control strategy for hardware simplification of voltage source converter-based power applications

    Page(s): 39 - 50
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (864 KB)  

    A hardware simplification control strategy for three-phase voltage-source-converter-based power applications is presented. The main goal of the proposal is to reduce the number of sensors needed to implement the controller while maintaining the high performance of the system. To this end, ac-voltage and dc-current sensors are replaced by software sensors based on state observers. Consequently, a more rugged, smaller and cheaper realisation can be accomplished. Regarding the voltage source converter controller, an energy function and the reactive power of the converter are considered as outputs for constructing a feedback law based on the feedback linearisation technique. In this way, internal dynamics is avoided. In order to improve controller performance, estimates of the load power and its time derivative are feedforwarded. The ac-voltages and load power estimates are obtained by designing a reduced-order non-linear observer. Several tests, with a realistic voltage source converter model that takes into account the switching power devices, validate the proposed technique. They evaluate the system performance in the presence of parameter uncertainties and disturbances in the AC input voltage. View full abstract»

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  • Small signal analysis and closed loop control design of active-clamped zero-voltage switched two inductor current-fed isolated DC-DC converter

    Page(s): 51 - 62
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1141 KB)  

    This study presents detailed small signal analysis and a closed loop control design of zero-voltage switched two inductor active-clamped current-fed isolated DC-DC converter. State-space averaging technique is used to derive the small signal model. A two-loop average current controller is designed for fixed frequency duty cycle modulation and works for wide input voltage and load variation. A complete design procedure is presented. A simple analogue controller is implemented. Experimental results for step-change in load are presented at different input voltage conditions. View full abstract»

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  • Injection-type hybrid active power filter in high-power grid with background harmonic voltage

    Page(s): 63 - 71
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (742 KB)  

    In this study, an injection type hybrid active power filter (IHAPF) and its correlative key techniques are researched. Furthermore, the influences on IHAPF made by background harmonic voltage in power grid are analysed in detail. The IHAPF using the proposed recursive integral controller and harmonic detection method can not only mitigate harmonic ip-iq currents but also compensate high-capacity reactive power. Nevertheless, background harmonic voltage in power grid may damage IHAPF because it may lead to resonance and sharp rise of DC-link voltage. Two methods, which are parameter designs for avoiding resonance and hysteresis control for eliminating sharp rise of DC-link voltage, have been proposed to restrain the influences. The system realisation of IHAPF is introduced. Industry application results have confirmed the validity of the IHAPF and the methods to restrain the influences caused by background harmonic voltage. View full abstract»

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  • Analysis and design of a higher-order T-type resonant convertor as a constant-current power supply

    Page(s): 72 - 80
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (618 KB)  

    A higher-order resonant convertor (RC), named LCLCL-T RC, is proposed in this study. It is shown that the convertor behaves as a constant-current (CC) source under certain operating conditions. The proposed convertor additionally offers inherent dc blocking for the isolation transformer and integration of all magnetic components reducing the number of discrete passive components in the circuit. A detailed analysis of the proposed convertor is presented. Closed-form expressions for convertor gain, component stresses, condition for convertor operation as a CC power supply and component design values optimised for minimum size of resonant network are derived. An experimental 250 W prototype convertor was designed, built and tested to demonstrate its CC source behaviour, good conversion efficiency and feasibility of the use of integrated magnetic component. View full abstract»

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  • Design and implementation of zero-voltageswitching quasi-resonant positive-output Luo converter using analog resonant controller UC3861

    Page(s): 81 - 88
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    This study presents the analysis, design and voltage regulation of a zero-voltage-switching quasi-resonant positive-output Luo converter with low switching losses for applications requiring constant power supply such as telemetry, computer and communication systems. To increase the power packing density, a simple control method using an analog resonant controller UC3861 is used to regulate the output voltage against load variation and supply disturbance. The performance of the controller is verified by developing a prototype model of the converter and experimental results are presented. The results reveal the superiority of using a single dedicated IC for voltage regulation. The efficiency of the converter is found to be 91%. View full abstract»

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  • Generalised pulse width modulation approach for DC capacitor voltage balancing in diode-clamped multilevel converters

    Page(s): 89 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1120 KB)  

    This study develops a generalised pulse width modulation (PWM) approach to eliminate both the low-frequency oscillations and imbalances in the dc-link capacitor voltages, which are the main drawbacks of diode clamped converters. The algorithm has been developed within the carrier-based PWM framework to facilitate its implementation in diode clamped converters with four or more levels. In addition, a generalised control strategy for dc voltage control is proposed and its stability is demonstrated. The good performance of the proposed modulation technique is demonstrated from simulation and experimental results for a four-level diode-clamped inverter. View full abstract»

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  • Multiphase dc-dc converter with high dynamic performance and high efficiency

    Page(s): 101 - 110
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (853 KB)  

    This study presents a novel voltage mode digital controller and a multiphase dc-dc converter with non-uniform current sharing to minimise the power consumption during stable load and very light load operation. To minimise the power consumption and provide fast dynamic response, a low-frequency phase is in parallel with a bi-directional high-frequency phase. The digital controller operates on a modification of the -phase dropping- principle. Depending on the speed of output load change, the bi-directional high-frequency phase will be activated, providing fast dynamic response, while a low-frequency phase is working all the time. The digital controller uses a look-up table control method, which is quite flexible and suitable for multiphase converters with phases switching at different frequencies. An experimental two-phase buck converter utilising the digital control method has been built. A comparison of the efficiency and dynamic performance between the high-frequency phase, low-frequency phase and multiphase has been made. In addition, the dynamic performance of the look-up table control methods has been compared with proportion integral and differential (PID) control method, and the efficiency of the multiphase converter has been compared with another phase drop method which is commonly used in previous works. View full abstract»

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  • Inherent clamp flyback-buck converter with winding cross-coupled inductors

    Page(s): 111 - 121
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (792 KB)  

    An isolated interleaved buck-type converter is deduced by inserting a third winding of the coupled inductor to each phase of the interleaved flyback converter. By making some topology modifications and adding one small clamp capacitor, the existed power switches of the derived flyback-buck converter can serve as the clamp switches for the interleaved phase to absorb the leakage energy of the coupled inductor and to reduce the switch turn-off voltage stress, which simplifies the circuit configuration and improves the circuit reliability. Furthermore, the current falling rate of the output diodes is limited by the leakage inductance to alleviate the output diode reverse-recovery problem. Finally, a 160-W 200-V-input 15-V-output prototype is built and tested to verify the improved performance of the proposed converter. View full abstract»

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  • Grid synchronisation with harmonics and reactive power compensation capability of a permanent magnet synchronous generator-based variable speed wind energy conversion system

    Page(s): 122 - 130
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (862 KB)  

    The power electronics plays an important role in the reliable operation of a modern wind energy conversion system (WECS). This study aims at the grid interconnection of a permanent magnet synchronous generator (PMSG)-based wind turbine with harmonics and reactive power compensation capability at the point of common coupling (PCC). The proposed system consists of two back-to-back connected converters with a common dc-link. The generator-side converter is used to achieve maximum power point tracking (MPPT). The grid-side converter is actively controlled to feed generated power as well as to supply the harmonics and reactive power demanded by the non-linear load at PCC, thus enabling the grid to supply only sinusoidal current at unity power factor. A model of directly driven PMSG-based variable speed WECS is developed and simulated in MATLAB/SPS environment. The effectiveness of proposed control approach is validated through extensive simulation and experimental results. View full abstract»

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  • Voltage-lift-type switched-inductor cells for enhancing DC-DC boost ability: Principles and integrations in Luo converter

    Page(s): 131 - 142
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (991 KB)  

    The concepts of voltage-lift-type switched-inductor cells have been proposed. The proposed circuit cells can be used to improve the boost abilities of those traditional transformerless DC-DC converters. More importantly, they can be fabricated as integrated cells and inserted into all the basic converters easily. All newly developed converters are applicable to those situations where high voltage transfer gains are required. The four-order Luo converter is taken as an example and integrated with the proposed switched-inductor cells. Both continuous conduction mode and discontinuous conduction mode operations are analysed. All theoretical results are supported by the corresponding simulation and experimental results. View full abstract»

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  • Time-optimal sliding-mode control for multi-quadrant buck converters

    Page(s): 143 - 150
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (658 KB)  

    A new development of time-optimal control systems in multi-quadrant buck converters for output regulation in minimum time is presented. Pontryagen's minimum principle is employed to obtain time-optimal control law for linear constrained input control systems. Applying this method, transient performance of system variables is improved for output regulation of any disturbance. Some numerical simulations and experimental results are shown to prove the effectiveness of the proposed technique in comparison to the classical sliding-mode control method. View full abstract»

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  • Soft-switched-controlled-ultra lift Luo converter

    Page(s): 151 - 158
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (817 KB)  

    This study presents the analysis, design and voltage regulation of a zero-voltage switching quasi-resonant-ultra lift Luo converter with low switching losses for communication circuits, telemetry and payload circuits, computer peripherals, battery charging of solar power panels etc. in micro satellites. To increase the power packing density, a simple control method using an analogue resonant controller UC3861 is used to regulate the output voltage against load variation and supply disturbance. The performance of the controller is verified by developing a prototype model of the converter and experimental results are presented. The results reveal the superiority of using a single dedicated IC for voltage regulation. Also it is observed that the converter provides maximum efficiency of 96-at full load. View full abstract»

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  • Digital-signal-processor-based DC/AC inverter with integral-compensation terminal sliding-mode control

    Page(s): 159 - 167
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (921 KB)  

    Classic terminal sliding-mode control (TSMC) has finite system-state convergence time and is robust against system disturbances and uncertainties, but TSMC may suffer from steady-state error problems under disturbed-system conditions. This study proposes to improve the performance of TSMC by the addition of integral compensation, which eliminates steady-state errors in the DC/AC inverter. Thus, the proposed controller provides robust performance in controlling the DC/AC inverter output to track the sinusoidal reference at steady state, and also provides fast response under varying load conditions. A real-time digital-signal-processor-based laboratory prototype is implemented to confirm the theoretical analysis and effectiveness of the proposed controller. View full abstract»

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  • Analysis, design and experimental results of a floating-output interleaved-input boost-derived DC-DC high-gain transformer-less converter

    Page(s): 168 - 180
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (951 KB)  

    In transformer-less energy systems sourced from low and unregulated voltage generated by a fuel cell or photovoltaic source, the voltage gain of the power electronic conditioning stage is required to be as high as possible. Although component parasitic elements limit the practically realisable voltage gain of any converter topology, this becomes a critical issue in the case of the basic step-up converter. In this study, a high-gain interleaved boost-derived converter topology is discussed. The proposed converter topology offers modularity, lower ripple for both input current and output voltage, and lower voltage and current ratings of the various circuit elements when compared to the basic boost converter. Analysis, design and key converter waveforms operating in the continuous conduction mode are provided along with design guidelines. Experimental results taken from a 1 kW laboratory prototype operating at 60 kHz are presented to confirm the validity of the analysis and design considerations. 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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