By Topic

Popular Articles (November 2014)

Includes the top 50 most frequently downloaded documents for this publication according to the most recent monthly usage statistics.
  • 1. 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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  • 2. Overview of wireless power transfer technologies for electric vehicle battery charging

    Page(s): 60 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (486 KB)  

    In this study, a comprehensive review of existing technological solutions for wireless power transfer used in electric vehicle battery chargers is given. The concept of each solution is thoroughly reviewed and the feasibility is evaluated considering the present limitations in power electronics technology, cost and consumer acceptance. In addition, the challenges and advantages of each technology are discussed. Finally, a thorough comparison is made and a proposed mixed conductive/wireless charging system solution is suggested to solve the inherent existing problems. View full abstract»

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  • 3. Study of a non-isolated bidirectional DC-DC converter

    Page(s): 30 - 37
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (948 KB)  

    The study presents a non-isolated bidirectional DC-DC converter, which has simple circuit structure. The control strategy is easily implemented. Also, the synchronous rectifier technique is used to reduce the losses. The voltage gain of the proposed converter is the half and the double of the conventional bidirectional DC-DC buck/boost converter in the step-down and step-up modes, respectively. Therefore the proposed converter can be operated in wide-voltage-conversion range than the conventional bidirectional converter. The voltage stresses on the switches of the proposed converter are a half of the high-voltage side. In addition, the operating principle and steady-state analyses are discussed. Finally, a prototype circuit is implemented to verify the performance of the proposed converter. View full abstract»

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  • 4. High-efficiency two-switch tri-state buck-boost power factor correction converter with fast dynamic response and low-inductor current ripple

    Page(s): 1544 - 1554
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1596 KB)  

    Two-switch tri-state buck-boost power factor correction (PFC) converter operating in pseudo-continuous conduction mode is proposed and analysed in this study. Different from tri-state boost PFC converter, the proposed two-switch tri-state buck-boost PFC converter does not need additional power switch to provide the additional degree of control freedom. Therefore it does not increase the complexity and affect the power conversion efficiency of the PFC converter as in the case of tri-state boost PFC converter. For the proposed two-switch tri-state buck-boost PFC converter, the current control loop and voltage control loop are decoupled, a simple voltage control loop with faster dynamic response can be designed to realise output voltage regulation and the additional degree of control freedom introduced by inductor current freewheeling stage helps to achieve unity power factor control. The operation principle, the input current, the inductor current ripple, the switch component stress and the small-signal characteristics of the proposed two-switch tri-state buck-boost PFC converter are analysed. The simulation and experimental results show that the proposed two-switch tri-state buck-boost PFC converter benefits with fast dynamic response, high-efficiency and low-inductor current ripple over single-switch buck-boost PFC converter or two-switch buck-boost PFC converter operating in continuous conduction mode and discontinuous conduction mode. View full abstract»

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  • 5. A transformerless modular step-up dc-dc converter for high power applications

    Page(s): 2190 - 2199
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (809 KB)  

    This study presents a new step-up dc-dc converter topology suitable for medium voltage, megawatt scale applications. The proposed converter interconnects unipolar or bipolar dc networks using a single inductor and a modular active switching network. The active switching network contains multiple series-connected identical converter modules. Each module consists of four switches and one capacitor. The modular nature of the switching network allows scalable implementation of the converter, and utilisation of low-voltage switches and capacitors. The proposed converter avoids the use of medium-frequency isolation transformers. Soft switching is utilised to reduce the converter's switching losses. An analytical model of the converter is developed to facilitate converter design. Theoretical predictions are supported by a 7.6 kW scaled laboratory prototype achieving an efficiency of as high as 93.2%. View full abstract»

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  • 6. Methodology for the optimal design of transformerless grid-connected PV inverters

    Page(s): 1491 - 1499
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (455 KB)  

    The transformerless photovoltaic (PV) inverters are the major functional units of modern grid-connected PV energy production systems. In this study, a new optimisation technique is presented for the calculation of the optimal types and values of the components comprising a transformerless PV inverter, such that the PV inverter levelised cost of the generated electricity is minimised. The proposed method constitutes a systematic design process, which is capable to explore the impact of the PV inverter configuration on the trade-off between the PV inverter manufacturing cost and the power losses affecting the corresponding energy production. The design optimisation results demonstrate that the optimal values of the PV inverter design variables depend on the inverter specifications, the technical and economical characteristics of the components used to build the PV inverter and the meteorological conditions prevailing at the installation area. Compared with non-optimised transformerless inverters, the PV inverter structures derived using the proposed design optimisation methodology exhibit lower manufacturing cost and simultaneously are capable of producing more energy into the electric grid system. View full abstract»

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  • 7. Hybrid phase shifted full bridge and LLC half bridge DC-DC converter for low-voltage and high-current output applications

    Page(s): 1832 - 1840
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (952 KB)  

    A hybrid phase shifted full bridge (PSFB) and LLC half bridge (HB) DC-DC converter for low-voltage and high-current output applications is proposed in this study. The PSFB shares its lagging leg with the LLC-HB and their outputs are parallel connected. When the output current is small, the energy of LLC circuit in combination with the energy stored in the leakage inductance of PSFB's transformer can help the lagging leg switches to achieve zero voltage switching (ZVS) turn on, which can reduce voltage stress and avoid annoying voltage spikes over switches. For the power distribution at rated power, the PSFB converter undergoes most of the power whereas the LLC-HB converter working as an auxiliary part converts only a small portion of the total power. To improve the conversion efficiency, synchronous rectification technique for the PSFB DC-DC converter is implemented. The design principle is given in view of ZVS for lagging leg switches and low transconductance of LLC converter. The validity of the proposed converter has been verified by experimental results of a 2.5 kW prototype. View full abstract»

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  • 8. Small-capacity grid-connected solar power generation system

    Page(s): 2717 - 2725
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (717 KB)

    A small-capacity grid-connected solar power generation system, configured by a dual-output DC-DC power converter and a seven-level inverter, is proposed in this study. Voltage doubler based topology is used to configure the dual-output DC-DC power converter to convert the output voltage of a solar cell array into two dependent voltage sources with multiple relationships. The grid-connected seven-level inverter is configured by a dual-buck power converter and a full-bridge power converter. The dual-buck power converter is switched at high-frequency pulse-width modulation to generate a four-level DC voltage. The full-bridge power converter is switched synchronous with the utility voltage, to convert the four-level DC voltage into a seven-level AC voltage. The proposed solar power generation system generates a sinusoidal output current in phase with the utility voltage. The novelty of this proposed seven-level inverter is that two asymmetric DC voltage sources are used to increase the voltage levels and only two of the six power electronic switches in the seven-level inverter are switched at high frequency. A prototype is developed and tested to verify the performance of the proposed solar power generation system. The experimental results show that the proposed solar power generation system has the expected performance. View full abstract»

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  • 9. Generalised transformerless ultra step-up DC–DC converter with reduced voltage stress on semiconductors

    Page(s): 2791 - 2805
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1046 KB)

    A non-isolated DC-DC converter with high-voltage gain and low-voltage stress across the semiconductors is proposed in this study. The proposed converter consists of n stages of diode-capacitor-inductor (D-C-L) units at the input side and m units of voltage multiplier cells (VMCs) at the output side. Increasing of D-C-L units and VMCs, lead to high-voltage gain at low duty cycle. Lower values of duty cycle will result in increasing of converter controllability and increasing of operation region. Also by increasing of VMCs, the voltage stress across the main switch and other semiconductors is reduced severely. Decreasing of voltage stress across the main switch leads to use a switch with lower RDS-ON that reduces on state losses of the proposed converter. Besides, by decreasing of voltage stress across the diode rectifiers, diodes with less forward voltage drop can be adopted. The circuit performance will be compared with other solutions that were previously proposed for voltage step-up in the terms of voltage gain, main switch voltage stress and number of components. Finally, a 357 V-65.5 W laboratory prototype with 92% conversion efficiency is built in order to prove the satisfying operation of the proposed converter and carried mathematical analysis. View full abstract»

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  • 10. Application of shunt active power filter for harmonic reduction and reactive power compensation in three-phase four-wire systems

    Page(s): 2825 - 2836
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1541 KB)

    This study deals with the analysis and implementation of compensation algorithms applied to a shunt active power filter, which uses three single-phase full-bridge converters sharing the same dc-bus voltage. The shunt filter is applied to three-phase four-wire systems, performing harmonic current suppression, reactive power compensation and power factor improvement. In addition, load unbalances compensation is also carried out. Two different control strategies are presented. In the first strategy, which is called independent current control, the currents of the three-phase power source are independently compensated performing harmonic suppression and load reactive power compensation, that is, the three-phase four-wire system is treated as three independent single-phase systems. In the second strategy, in addition to harmonic suppression and load reactive power compensation, the shunt filter also performs load unbalance compensation, resulting in sinusoidal and balanced source currents. The compensating algorithms are evaluated by means of several experimental test conditions, in order to validate the theoretical development and analyse the performance of the shunt filter. View full abstract»

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  • 11. Bidirectional DC-DC soft-switching converter for stand-alone photovoltaic power generation systems

    Page(s): 1557 - 1565
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (980 KB)  

    In this study, the authors focused on developing a bidirectional power converter for a stand-alone photovoltaic power generation system when a lithium-ion battery is used to regulate the power supply. Also, a small-scale air-conditioner was provided as the load for the bidirectional power converter developed to examine the efficiency of the converter. The overall framework of the proposed system comprised a maximum power point tracking controller, bidirectional buck-boost soft-switching converter, lithium-ion battery and small-scale air-conditioner. By attaching a resonant branch to a general bidirectional buck-boost converter and applying a simple switching signal control, soft switching was achieved, thereby increasing the power conversion efficiency of the photovoltaic power generation system. Some measurement results are made to verify the feasibility of the developed bidirectional dc-dc soft-switching converter for stand-alone photovoltaic power generation systems. View full abstract»

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  • 12. 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»

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  • 13. Harmonic power compensation capacity of shunt active power filter and its relationship with design parameters

    Page(s): 418 - 430
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1004 KB)  

    In this study, the equation for the reactive and harmonic power compensation of a shunt active power filter (APF) system has been derived by studying the power exchange mechanism and power tetrahedron phasor diagram. The switching dynamics of a voltage source inverter (VSI)-based three-phase, three-wire (three-leg /half-bridge) shunt APF system with hysteresis band current control has been studied and verified by simulation. The relation between the design parameters and their effects on the active losses has also been identified. Detailed calculation and extensive simulation have been performed for a three-phase, three-wire shunt APF implemented in a 400VL-L distribution system, as an example, to study the effects of design parameter selection and their role in active power loss calculation. Simulated and calculated results are presented for the important design parameters for different switching frequencies together with their associated losses and kVA ratings. The procedure can be followed to design the parameters for other topologies, such as three-phase, four-wire or single-phase systems. View full abstract»

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  • 14. Finite control set predictive control based on Lyapunov function for three-phase voltage source inverters

    Page(s): 2726 - 2732
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (778 KB)

    A Lyapunov-function-based technique for finite control set predictive control is proposed to control the load currents of three-phase voltage source inverters (VSIs). The developed technique, based on a discrete-time model of a VSI, determines a control law using the Lyapunov function. Based on the Lyapunov stability analysis considering inevitable quantisation errors between the proposed control law and control actions selected from the inherent finite control set of the VSI, all signals of the closed-loop dynamics are uniformly ultimately bounded and the current control errors converge to a neighbourhood of the origin. In addition to rendering the finite control set predictive control system globally stable, the proposed Lyapunov-function-based finite control set predictive control reduces the amount of calculations required to predict a future variable by half compared with the conventional finite control set predictive control, resulting in lower actuation time delay. Experimental results with three-phase VSIs are presented to validate the proposed Lyapunov-function-based control method. View full abstract»

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  • 15. DC–DC converter with high voltage gain and reduced switch stress

    Page(s): 2564 - 2571
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (825 KB)

    In this study, a novel high step-up dc-dc converter with high voltage gain and reduced switch stress is proposed. Utilising the coupled inductor to replace the boost inductor for high step-up converter is widely used in the application of high voltage gain converter. It can not only achieve a high voltage gain but also use the core effectively by using the coupled inductor. The techniques of voltage lift, voltage multiplier and clamp mode are also used in the proposed topology. Furthermore, the proposed converter can avoid the extreme duty cycle that will cause a lot of conduction losses. The leakage inductance energy of the coupled inductor will cause a huge voltage on the components of circuit, so that it needs to choose the components with high voltage and current ratings; then the efficiency is reduced and the cost is increased. The converter proposed in this paper can not only recycle the leakage inductance energy to the output but also increase the efficiency. A 300 W prototype converter which is implemented with an input voltage of 26 V and an output voltage of 400 V will demonstrate the effectiveness of this proposed converter. View full abstract»

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  • 16. Power electronic configuration for the operation of PV system in combined grid-connected and stand-alone modes

    Page(s): 640 - 647
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (930 KB)  

    A simple photovoltaic (PV) system capable of operating in both grid-connected mode and stand-alone mode using multilevel boost converter (MBC) and line commutated inverter (LCI) has been developed for extracting the maximum power and feeding it to a single phase utility grid and stand-alone system simultaneously. Theoretical analysis of the proposed system is done and the duty ratio of the MBC is estimated for extracting maximum power from PV array. For a fixed firing angle of LCI, the proposed system is able to track the maximum power with the determined duty ratio which remains the same for all irradiations. This is the major advantage of the proposed system which eliminates the use of a separate maximum power point tracking (MPPT) controller. Experiments have been conducted on a 80 V, 9.4 A PV array feeding a 110 V single phase grid and a 230 V, 100 W DC motor. The MBC extracts maximum power from the PV array and feeds the major portion of power to the single phase utility grid via LCI and the remaining power to separately excited DC motor. It was found that the theoretical analysis, simulation and experimental results closely correlate with each other and proves the effectiveness of the proposed configuration. View full abstract»

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  • 17. Static synchronous compensators (STATCOM): a review

    Page(s): 297 - 324
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (961 KB)  

    Fast acting static synchronous compensator (STATCOM), a representative of FACTS family, is a promising technology being extensively used as the state-of-the-art dynamic shunt compensator for reactive power control in transmission and distribution system. Over the last couple of decades, researchers and engineers have made path-breaking research on this technology and by virtue of which, many STATCOM controllers based on the self-commutating solid-state voltage-source converter (VSC) have been developed and commercially put in operation to control system dynamics under stressed conditions. Because of its many attributes, STATCOM has emerged as a qualitatively superior controller relative to the line commutating static VAR compensator (SVC). This controller is called with different terminologies as STATic COMpensator advanced static VAR compensator, advanced static VAR generator or static VAR generator, STATic CONdenser, synchronous solid-state VAR compensator, VSC-based SVC or self-commutated SVC or static synchronous compensator (SSC or S2C). The development of STATCOM controller employing various solid-state converter topologies, magnetics configurations, control algorithms, switching techniques and so on, has been well reported in literature with its versatile applications in power system. A review on the state-of-the-art STATCOM technology and further research potential are presented classifying more than 300 research publications. View full abstract»

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  • 18. Analysis and implementation of a new single-switch buck??boost DC/DC converter

    Page(s): 1906 - 1914
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (853 KB)  

    In this study, a novel buck-boost DC/DC converter is presented. The circuit structure of the proposed converter consists of a single power switch, two diodes and some energy storage elements. Employing only a single power switch reduces the implementation cost and switching power losses. The proposed converter has higher voltage gain in step-up mode in comparison with conventional buck-boost and Cuk converter. In addition, this converter expands the continuous conduction mode (CCM) operational region. The presented converter has three operation modes in CCM. The second mode reduces the voltage stresses across the capacitors. Therefore the current stresses on diodes are also reduced. To verify the operation of the proposed converter, the experimental results are provided using a hardware prototype. View full abstract»

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  • 19. 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»

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  • 20. Analysis of THD and output voltage performance for cascaded multilevel inverter using carrier pulse width modulation techniques

    Page(s): 951 - 958
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1085 KB)  

    Multilevel inverter is used in applications that need high voltage and high current. The topologies of multilevel inverter have several advantages such as lower total harmonic distortion (THD), lower electro magnetic interference (EMI) generation, high output voltage. The main feature of multilevel inverter is the ability to reduce the voltage stress on each power device due to the utilisation of multilevel on the DC bus. The advent of multilevel inverter topologies has caused variety of pulse width modulation strategies. In this paper, various carrier pulse width modulation techniques are proposed, which can minimise the total harmonic distortion and enhances the output voltages from five level inverter. Three methodologies adopting the constant switching frequency (CSF), variable switching frequency (VSF), and phase shifted pulse width modulation (PSPWM) concepts are proposed in this paper. The above methodologies divided into two techniques like subharmonic pulse width modulation which minimises total harmonic distortion and switching frequency optimal pulse width modulation which enhances the output voltages. Field programmable gate array (FPGA) has been chosen to implement the pulse width modulation due its fast proto typing, simple hardware and software design. The simulation and experimental results are presented.Multilevel inverter is used in applications that need high voltage and high current. The topologies of multilevel inverter have several advantages such as lower total harmonic distortion (THD), lower electro magnetic interference (EMI) generation, high output voltage. The main feature of multilevel inverter is the ability to reduce the voltage stress on each power device due to the utilisation of multilevel on the DC bus. The advent of multilevel inverter topologies has caused variety of pulse width modulation strategies. In this paper, various carrier pulse width modulation techniques are proposed, which can minimise the total harmonic distortion a- d enhances the output voltages from five level inverter. Three methodologies adopting the constant switching frequency (CSF), variable switching frequency (VSF), and phase shifted pulse width modulation (PSPWM) concepts are proposed in this paper. The above methodologies divided into two techniques like subharmonic pulse width modulation which minimises total harmonic distortion and switching frequency optimal pulse width modulation which enhances the output voltages. Field programmable gate array (FPGA) has been chosen to implement the pulse width modulation due its fast proto typing, simple hardware and software design. The simulation and experimental results are presented. View full abstract»

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  • 21. Voltage unbalance and harmonics compensation for islanded microgrid inverters

    Page(s): 1055 - 1063
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1092 KB)  

    Voltage source inverters (VSIs) are usually used for all kinds of distributed generation interfaces in a microgrid. It is the microgrid's superiority to power the local loads continuously when the utility fails. When in islanded mode, the voltage and frequency of the microgrid are determined by the VSIs; therefore the power quality can be deteriorated under unbalanced and non-linear loads. A voltage unbalance and harmonics compensation strategy for the VSIs in islanded microgrid is proposed in this study. This method is implemented in a single synchronous reference frame (SRF) and is responsible for both the voltage unbalance and harmonic compensation. Furthermore, the virtual impedance loop is modified to improve the compensation effect. The impedance model of the VSI is built to explain the compensation ability of the proposed strategy. The whole control system mainly includes power droop controllers, a modified virtual impedance loop and inner SRF-based voltage unbalance and harmonics compensators. The proposed strategy is demonstrated in detail and validated with simulations and experiments. View full abstract»

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  • 22. Closed-loop hybrid direct torque control for medium voltage induction motor drive for performance improvement

    Page(s): 31 - 40
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1934 KB)  

    This study presents the hybrid direct torque control (HDTC) method for medium voltage-range induction motor (IM) drive. The control method comprising the torque control by rotor-reference frame quadrature-axis current instead-of conventional DTC and speed control similar as in space-vector-modulation (SVM)-DTC is proposed. Hence the scheme is referred as HDTC. A carrier-based space-vector-modulation controlled five-level diode-clamped multilevel inverter with proposed control scheme is providing promising-step towards performance enhancement of IM drive in respect of torque ripple contents and steady-state performance over wide speed-range. The effectiveness of the proposed control scheme is confirmed by comparison with DTC in matlab-simulink. A prototype is fabricated for three-phase, 3-HP IM. A 32-bit fixed-point DSP-based control algorithm is developed for DTC and the proposed control scheme. Experimental results show qualitative improvement in performance in terms of reduction in torque ripple by 30%, fast dynamic response even at low speed and improvement in steady state characteristics. View full abstract»

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  • 23. Comparison of power losses, current and voltage stresses of semiconductors in voltage source transformerless multilevel inverters

    Page(s): 2743 - 2757
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1526 KB)

    The power losses, current and voltage stresses in semiconductor devices in voltage source transformerless multilevel inverters (VSTMLIs) topologies are unequal, depending on the switching states, the duty ratio, the levels of output voltage, the load power factor and the depth of modulation index. Non-uniform power loss profiles mean both unequal junction temperature and power rating in semiconductors. In this study, a comparison of power losses, current and voltage stresses in semiconductors of VSTMLIs is performed. Initially, the structural characteristics and operating principles of dominant VSTMLIs with sinusoidal pulse width modulation are analysed. Then, modifications of existing VSTMLIs and simplified multilevel topologies are proposed, which achieve a further reduction in switch count and power losses in semiconductors. The proposed modified circuitries are suitable for converting existing four-level VSTMLI topologies into five-level ones. This conversion is desirable, when a zero output voltage level under no-load conditions or low modulation indices should be obtained. Power losses in semiconductors are calculated analytically and then confirmed by simulation. A comparative presentation of profiles of power losses, current and voltage stresses in semiconductors of the examined VSTMLIs is analytically carried out. The obtained results are valuable for sizing and selecting the semiconductors in VSTMLIs. View full abstract»

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  • 24. Analysis, design and control of single-phase three-level power factor correction rectifier fed switched reluctance motor drive

    Page(s): 1499 - 1508
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1743 KB)  

    In this study, a single-phase three-level power factor correction (PFC) rectifier fed switched reluctance motor (SRM) drive is proposed for improving the power quality at ac mains. The asymmetry in the dc-link capacitors voltages of the midpoint converter fed SRM drive is improved by using a single-phase three-level PFC rectifier. This PFC rectifier configuration uses two active semiconductor switches, an inductor and operates as a boost PFC rectifier. The proposed single-phase three-level PFC rectifier fed SRM drive is designed, modelled and its performance is simulated in MATLAB/Simulink. The simulated performance of the proposed single-phase three-level PFC rectifier fed SRM drive is experimentally validated for dc-link capacitors voltage balancing and power quality improvement. View full abstract»

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  • 25. Pulse-width modulation control strategy for high efficiency LLC resonant converter with light load applications

    Page(s): 2887 - 2894
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (937 KB)

    LLC resonant converters, generally adopting frequency modulation control, can hardly achieve high efficiency under both heavy and light load conditions. Especially under light load conditions, the high-switching frequency seriously degrades converter's efficiency. This study propose a new pulse-width modulation (PWM) control strategy for LLC resonant converters under light load applications on the premise of no change in the main circuit structure. The voltage gain of the converter is regulated by varying duty ratio instead of increasing switching frequency and therefore zero-current switching for rectifier diodes can be realised under light load conditions. With the proposed PWM control strategy, the gain is not affected by the load variations and an optimal design of the magnetic components is possible, therefore the efficiency is further improved by reducing both the switching losses and the losses in magnetic components. Experimental results demonstrate the effectiveness of the proposed PWM strategy by increasing the efficiency of LCC resonant converter, especially under light load conditions. View full abstract»

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  • 26. Improved control strategy with grid-voltage feedforward for LCL-filter-based inverter connected to weak grid

    Page(s): 2660 - 2671
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1562 KB)

    In grid-connected LCL-filtered inverters, the dual-loop current control is widely used. The LCL resonance is highly damped by proper feedback of the capacitor current. To suppress low-frequency current harmonics, a grid-voltage feedforward is commonly used. However, the system performance with such control is declined when connecting to a weak grid. Phase and gain margins are largely reduced while the proportional feedforward is used. The margins get worse and instability is aroused if the derivative feedforward is further implemented. Besides, a negative impact on the rejection of grid-voltage-induced harmonics is produced. To improve the control performance in the weak grid case, an adaptive control has been proposed. Adopting the estimated grid impedance, the signal for the grid-voltage feedforward is modified and the controller is adjusted with an adaptive rule to maintain a good phase margin or a high bandwidth. Performances of the inverter with the typical and the proposed methods are compared. Simulation and experimental results have demonstrated that the grid-connected LCL-filtered inverter with the proposed method produced a high-quality current while large grid impedance existed. View full abstract»

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  • 27. Three-phase interleaved high-step-up converter with coupled-inductor-based voltage quadrupler

    Page(s): 1841 - 1849
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1078 KB)  

    This paper proposes a high-efficient DC-DC solution with the features of galvanic isolation, high-voltage gain, zero voltage switching operation, low input current ripple and high-power density. The converter is implemented by a three-phase coupled inductor bridge to remove the bulky input electrolytic capacitors. The introduced active clamp circuit recycles the energy stored in the leakage inductance and absorbs the voltage spikes on the main switch voltage. The series configuration with a voltage doubler at the second side contributes to a high-voltage gain and reduces the voltage stress across the rectifier devices. The output diode reverse-recovery problem is naturally mitigated by the leakage inductance of the coupled inductors. Moreover, the active control with a neutral-point potential balance and a phase-deficient operation of the proposed converter are also studied. A converter prototype is designed and evaluated to verify the theoretical analysis and demonstrate a superior performance over the prior studies. View full abstract»

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  • 28. Analysis, design and digital implementation of a shunt active power filter with different schemes of reference current generation

    Page(s): 627 - 639
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1473 KB)  

    To reduce the harmonics injected by non-linear loads, power quality improvement devices like shunt active power filters (SAPFs) are commonly employed. This study presents a digital signal processor (DSP) TMS320LF2407A based hardware implementation of current error space phasor-based hysteresis controller for SAPF. The proposed controller-based SAPF allows precise compensation of harmonic currents. Design considerations for practical implementation of the proposed space phasor-based current error hysteresis controller for SAPF are explained here. Performance analysis of space phasor-based current error hysteresis controller for SAPF is explained in the study. The controller's self-adaptive nature is studied for different logics of necessary sector changes. Here, the versatile nature of the controller is proved by analysing its performance for different reference compensating current generation methods. The proposed controller works on the principle of switching voltage vectors adjacent to the desired output voltage vector of SAPF (voltage vector at the point of common coupling). This strategy helps in restricting the current error within the desired hexagonal boundary. A comparative study of DSP-based implementation for two different schemes of reference compensating currents generation is presented in this study. Instantaneous reactive power theory and Fryze current computation methods are chosen for this comparative study. Experimental results of reference compensating currents generated by different strategies using DSP are presented in this study. View full abstract»

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  • 29. Analysis, design and implementation of isolated bidirectional converter with winding-cross-coupled inductors for high step-up and high step-down conversion system

    Page(s): 67 - 77
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1399 KB)  

    In this study, a zero voltage switching (ZVS) isolated bidirectional DC/DC converter is proposed for high step-up and high step-down conversion systems. In the low voltage side, an interleaved Buck and Boost converter is employed to reduce the current ripple and improve the power level. In the high voltage side, a modified three-level structure is adopted to bring each power switch sustain half of the high bus voltage, which makes the low voltage rated MOSFETs available for the performance improvement. Two coupled inductors are interleaved in the low voltage side and in series in the high voltage side, which can not only serve as the filter inductors for the current ripple cancellation, but also as the transformer for isolation, which is named as winding-cross-coupled inductors. As a result, the magnetic size can be reduced to enhance the power density. ZVS operation is ensured from light load to full load conditions by the advanced pulse width modulation plus phase shift control strategy. The voltage regulation and transferred power are decoupled for easy design and implementation. Finally, a 1.5 kW 48 V/800 V prototype is built to verify the effectiveness of the proposed converter. View full abstract»

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  • 30. Analysis and implementation of a modular isolated zero-voltage switching bidirectional dc-dc converter

    Page(s): 2035 - 2049
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1585 KB)  

    A new topology of modular isolated bidirectional dc-dc converter is proposed. The proposed modular converter has interesting features in terms of low switching losses, bidirectional power flow and less number of switching device. In comparison with similar topologies, the reduction in the switching device number does not decrease the proposed converter power rating. Also, the simple modular structure, high-frequency operation, zero-voltage switching (ZVS) capability and less number of switching device make the extended configuration of the proposed converter suitable for high-power applications. The ZVS capability without using any auxiliary circuit is one of the most important specifications of the proposed converter. The design of the proposed converter, based on the connection of basic modules, is described and the steady-state operation analysis is presented. The ZVS of the proposed converter both in turn-on and turn-off instants are studied and their criteria are derived in detail. The simulation and measurement results are presented to verify the effectiveness of the proposed converter. View full abstract»

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  • 31. Multiple-input DC/DC converter topology for hybrid energy system

    Page(s): 1483 - 1501
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2347 KB)  

    In this study, a multiple-input non-isolated DC/DC converter topology is presented. The proposed multiple-input DC/DC converter is proficient for energy diversification from renewable and storage energy sources individually or simultaneously. It can be operated in buck, boost and buck-boost modes of operation with the capability of bidirectional power flow to achieve desired voltage level on either side. The development of small-signal modelling based on state-space averaging has been discussed. In addition, a power management control scheme for the proposed converter has also been presented. The proposed concept has been investigated through simulation using the MATLAB/Simulink environment and validated experimentally on a laboratory prototype using dSPACE 1103 real time digital controller. View full abstract»

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  • 32. Efficiency improvement on two-switch buck-boost converter with coupled inductor for high-voltage applications

    Page(s): 2846 - 2856
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1123 KB)

    With two controllable switches, the efficiency of the two-switch buck-boost converters can be optimised by adopting appropriate control schemes. Among the control schemes, when only one switch works at high frequency, losses of the converter can be reduced effectively, but the complicated control logic and compensation technique are needed for step-up/down smooth transitions; when both switches operate at high frequency, the efficiency of these converters are low for high-voltage applications because of the serious switching losses. In this study, the coupled inductor is introduced to reduce the switching losses of these converters for high-voltage application and an asynchronous control scheme is proposed to reduce the losses much more. Based on the designed prototype, theoretical calculation, experiment results and loss analysis are provided to compare the traditional converter adopting single-winding inductor and the proposed circuit with the coupled inductor. And the comparisons of the converter adopting coupled-inductor with the tradition synchronous control scheme and that with the proposed asynchronous control scheme are also presented. The analysis and experimental results show that the efficiency of the converter adopting coupled inductor with the proposed asynchronous control scheme is the highest one. Moreover, the smooth transitions between step-up and step-down are also guaranteed by the proposed asynchronous control scheme. View full abstract»

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  • 33. Single-harmonic active power line conditioner for harmonic distortion control in power networks

    Page(s): 2218 - 2226
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (498 KB)  

    In this contribution, a novel alternative concept and solution procedure for single-harmonic active power line conditioner (SHAPLC) planning is proposed to control voltage harmonic distortion in power networks. The development of the proposed solution concept, defined and detailed in this paper, is based on seeking a proper solution to practical situations, taking into account the particular harmonic distortion pattern and configuration of the power system in question. The location of the SHAPLC's, for each harmonic h of interest is determined through feasibility and sensitivity analysis. Once the best location for the SHAPLCs is known, the injection currents are determined by solving a non-linear programming algorithm. The usefulness and novelty of the SHAPLC planning methodology is illustrated with a case study, where results show its effectiveness to control the harmonic distortion in the power system. The solution procedure proposed in this contribution is aimed to achieve and assure individual harmonic distortion and total harmonic distortion indices meet recommended limits by Std-519 IEEE using SHAPLCs devices. According with revised literature, this goal has only been approached with certainty and sufficiency (not trial and error) by considering multiple injection currents at different harmonic frequencies from the selected bus. View full abstract»

    Open Access
  • 34. Magnetically coupled high-gain Y-source isolated DC/DC converter

    Page(s): 2817 - 2824
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1097 KB)

    A new form of magnetically coupled DC/DC converter is proposed for medium power applications (250 W to 2 kW), requiring a high-voltage gain, short inductive charging time and galvanic isolation. The proposed converter can be realised using a unique Y-source impedance network and a two-switch push-pull circuit with voltage-doubling rectification. The converter's voltage gain is presently not matched by any other converter operating at the same switch duty ratio. The converter also has more degrees of freedom in design for setting the desired gain than other converters, and hence can better meet the demands of many applications. The operating principles of the converter have been analysed mathematically, and are verified by both simulation and experiment. View full abstract»

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  • 35. High-voltage boost quasi-Z-source isolated DC/DC converter

    Page(s): 2387 - 2395
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1356 KB)  

    A high-voltage gain two-switch quasi-Z-source isolated DC/DC converter has been presented in this study. It consists of a quasi-Z-source network at its input, a push-pull square-wave inverter at its middle, and a voltage-doubler rectifier at its output. When coordinated appropriately, the new converter uses less switches, a smaller common duty cycle and less turns for the transformer when compared with existing topologies. Its size and weight are therefore smaller, whereas its efficiency is higher. It is therefore well-suited for applications, where a wide range of voltage gain is required like renewable energy systems, DC power supplies found in telecom, aerospace and electric vehicles. To demonstrate the performance of the proposed converter, a 400 V, 500 W prototype has been implemented in the laboratory. Efficiency of the prototype measured is found to vary from 89.0 to 97.4% when its input voltage changes from 44 to 82 V at full load. View full abstract»

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  • 36. Buck converter-based power supply design for low power light emitting diode lamp lighting

    Page(s): 946 - 956
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1299 KB)  

    This study deals with the analysis and implementation of an HPF (high power factor) single-stage, single switch buck converter-based power supply design for an LED (light emitting diode) lamp load of 13 W operated at the universal ac mains. In general purpose lighting applications, a buck converter is a good candidate for power factor correction with low component count and reduced cost. In low-power lighting, it is a tough task to control the THDi (total harmonic distortion) of ac mains current under the limits of strict international standards such as IEC-61000-3-2 with universal ac mains for class D equipments. In the proposed optocouplerless topology, HPF operation at input ac mains is achieved by operating the buck ac-dc converter in continuous conduction mode. The design, modelling and simulation of the proposed topology are executed using MATLAB-Simulink and sim-power system toolboxes. A prototype of the power supply for LED lamp is developed for multiple LEDs connected in series configuration. The efficiency of the proposed LED lamp driver is observed as 83.76% at rated voltage of 220 V and the THD of ac mains current less than 17.27% for a wide range of voltages of 90-270 V. View full abstract»

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  • 37. Modelling and control of a DC-DC quadratic boost converter with R2P2

    Page(s): 11 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (985 KB)  

    In the past years, the development of topologies with step-up capacities has been important to satisfy the new requirement of renewable source energy. This study presents a quadratic boost converter based on the reduced redundant power processing (R2P2) principle, well as the controller design methodology using current-programmed control to satisfy the specifications of output voltage regulation. Non-linear and linear models are developed; the latter exhibits fourth-order characteristic dynamics with complex right-half plane zeros. In the proposed control scheme, the current of the switch is used for feedback purposes. When the current loop is implemented, the fourth-order dynamics are changed to a dominant first order, which simplifies the controller design of outer loop. For this loop, a conventional controller is designed. At the end, experimental results are given for a 23 W quadratic boost converter, where open-loop and closed-loop responses are compared. View full abstract»

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  • 38. Effective space vector modulation switching sequence for three phase Z source inverters

    Page(s): 2695 - 2703
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1020 KB)

    A new approach in the PWM technique is proposed through proper choice of active vectors and placement of a shoot through (ST) states for three phase Z source inverter (ZSI). Compared to the existing modulation method, the power conversion interval is maximum in this technique which improves the output voltage at higher modulation indices. Also with the inclusion of ST states, the number of switching is less avoiding the switching losses. The switching is performed at higher operating frequency which reduces the voltage stress and the size of LC components. In each sector, the ST interval is properly selected to improve the bus utilisation thus increases the voltage gain of ZSI. Furthermore, the analysis is performed by deriving the expression for the RMS flux ripple over a sub-cycle and evaluated in terms of switching instants which facilitates immediate comparison for all the presented methods. The proposed method is verified through the simulation and experimental results. View full abstract»

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  • 39. High step-up interleaved converter with soft-switching using a single auxiliary switch for a fuel cell system

    Page(s): 2704 - 2716
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1368 KB)

    This study aims to develop a soft-switching interleaved converter with a high-voltage conversion ratio using a single auxiliary switch. As a step-up voltage converter, it performs zero voltage switching and zero current switching operations on main switches by means of the manipulation of the single auxiliary switch. In this manner, both the switching loss and switching stress of main switches can be reduced, giving rise to an improvement in the conversion efficiency. Placed in parallel with a converter available, merely a single resonant branch is employed in the proposed soft-switching mechanism, a simple and elegant way to reach the goal. This proposal is further applied to a fuel cell system as a high performance DC voltage booster so as to drive a high-voltage DC load. PSIM simulations are conducted and subsequent experimental validation is presented at the end of this work. View full abstract»

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  • 40. Single DC source three-phase multilevel inverter using reduced number of switches

    Page(s): 775 - 783
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (974 KB)  

    A novel pulse-width modulation-less three-phase multilevel DC-AC inverter using only one DC source is presented in this study. The proposed approach enables multilevel output to be realised by a few cascaded H-bridges and a three-leg inverter using minimum number of power switches. As an illustration, a 19-level three-phase inverter has been implemented based on cascading four H-bridges and a three-leg inverter. Switching strategy has been derived for the proposed inverter such that a three-phase power system with 19 output levels can be realised with proper capacitor voltage regulation and a single energy source. Only 22 power switches instead of 108 are required to achieve the objective. Experimental results are included to demonstrate the outstanding performance of the proposed inverter. Although only 50 Hz results are presented, the proposed inverter could be applied in aircraft systems by only changing the switching frequency. View full abstract»

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  • 41. Bidirectional control of a dual active bridge DC-DC converter for aerospace applications

    Page(s): 1104 - 1118
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (2131 KB)  

    This study presents a novel controller for bidirectional control of a dual active bridge (DAB) DC-DC converter. The proposed controller uses the high-frequency AC-link current of the DAB DC-DC converter as a control parameter so that the dynamic power and regeneration demands of advanced aircraft electric loads can be met using ultracapacitors. A model of the proposed current control technique has been developed and simulations of a 540-V/20-kW prototype show that the proposed control system exhibits good static and dynamic performance during bidirectional operation. The same control technique can control the DAB converter operating in quasi-square-wave mode under low loads. The results obtained from the model under various voltages, currents and power transients verify converter operation and validate the proposed controller performance during bidirectional power transfer. View full abstract»

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  • 42. High-efficiency bidirectional dc-dc converter with high-voltage gain

    Page(s): 173 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1415 KB)  

    The aim of this study is to develop a high-efficiency bidirectional dc-dc converter for a power storage system. The proposed converter can boost the voltage of an energy-storage module (e.g. battery) to a high-voltage-side dc bus for the load demand. When the high-voltage-side dc bus has excess energy, this energy-storage module can be charged by the dc bus. In this study, a coupled-inductor bidirectional converter scheme utilises only three power switches with the properties of voltage clamping, synchronous rectification and soft switching. As a result, the objectives of high-voltage gain, high-efficiency power conversion and bidirectional power control can be achieved. Some experimental results via a 48/360 V kW-level prototype are given to verify the effectiveness of the proposed converter in practical applications. View full abstract»

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  • 43. Rapid prototyping of power electronics converters for photovoltaic system application using Xilinx System Generator

    Page(s): 2269 - 2278
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1299 KB)  

    The aim of this study is to develop a research platform for rapid prototyping of the power electronics converters for solar photovoltaic (PV) system applications. This study describes the field-programmable gate array (FPGA)-based hardware-in-the-loop (HIL) simulation of voltage source inverter (VSI) used for PV system power conversion. The PV system and inverter models are realised in simulation as part of the HIL to test the real-time functionality of the FPGA controller. The generation of switching control signals for the VSI and its interface with the PV system is developed through the Xilinx System Generator (XSG) domain. The XSG automatically generates the VHSIC hardware description language (VHDL) code using hardware description language co-simulation for generation of gating signal for modulation of the VSI. To validate the proposed approach, the sinusoidal pulse-width modulation using bipolar and unipolar switching schemes and current control method have been tested for the PV supported VSI. The proposed approach of the rapid prototype model has been designed and implemented in the laboratory through XSG and MATLAB/SIMULINK interface. Performance comparison between the software simulation and real-time HIL simulation has been demonstrated. View full abstract»

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  • 44. Reduced sensor configuration of brushless DC motor drive using a power factor correction-based modified-zeta converter

    Page(s): 2322 - 2335
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1608 KB)  

    This study deals with the design and development of a power factor (PF) correction-based modified-zeta converter fed brushless DC (BLDC) motor drive. A single-phase supply followed by a diode bridge rectifier and a modified-zeta converter operating in discontinuous inductor current mode (DICM) is used to feed a voltage source inverter (VSI) driving a BLDC motor. The modified-zeta converter operating in DICM acts as an inherent PF pre-regulator. A single-voltage sensor is used for the DC-link voltage control, which is used to control the speed of the BLDC motor. This facilitates the operation of VSI in fundamental frequency switching for reducing the switching losses in VSI. The proposed BLDC motor drive is designed and its performance is simulated in MATLAB/Simulink environment for achieving an improved power quality at AC mains for wide range of speed control. The obtained power quality indices are under the recommended limits of international power quality standard IEC 61000-3-2. Finally, the performance of the proposed drive is validated with test results obtained on a developed prototype of the proposed BLDC motor drive. View full abstract»

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  • 45. Real-time control of shunt active power filter under distorted grid voltage and unbalanced load condition using self-tuning filter

    Page(s): 1895 - 1905
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1336 KB)  

    In this paper, an alternative control method is proposed to improve the harmonic suppression efficiency of the active power filter in a distorted and an unbalanced power system to compensate for the perturbations caused by the unbalanced non-linear loads. The proposed method uses a self-tuning filter (STF) to process the grid voltage in order to provide a uniform reference voltage to obtain the correct angular position of the phase locked loop. Moreover, the required compensation currents are obtained by implementing another STF in the transformed set of currents in order to separate the fundamental and the harmonic currents. This allows the calculation of a precise reference current for the unbalanced, the non-linear and the variable load conditions. The proposed control method gives an adequate compensating current reference even for a non-ideal voltage and unbalanced current conditions. The real-time control of the filter under the distorted and the unbalanced power system is developed in an RT-LAB real-time platform. The results obtained in the software-in-the-loop configuration are presented to verify the effectiveness of the proposed control technique. View full abstract»

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  • 46. FPGA-based real time incremental conductance maximum power point tracking controller for photovoltaic systems

    Page(s): 1294 - 1304
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1012 KB)  

    Maximum power point tracking (MPPT) is an important issue in photovoltaic (PV) systems. Hence, we need to design an efficient and cost-effective system which is able to transfer the maximum power received from PV cell to the load. This study describes the hardware implementation of a real time incremental conductance (INC) MPPT algorithm for a PV module. According to the PV dynamic model, a criterion is presented that by modifying the original algorithm, an adaptive variable step size INC algorithm is realised and efficiently is implemented on XILINX XC3S400 field programmable gate array (FPGA). At first, the PV model characteristics and the proposed algorithm with the mathematical equations are modelled and simulated using `MATLAB/Simulink-system generator' environment; then the system performance is examined. It is worth that some solutions are proposed to simplify the system based on the design constraints for hardware implementation of digital controller on FPGA. The optimised design of hardware architecture and the high processing speed of FPGA have enhanced the performance of digital controller in designed MPPT system. The experimental results show the proposed method provides a good tracking speed and also mitigation of fluctuation output power. View full abstract»

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  • 47. High step-up passive absorption circuit used in non-isolated high step-up converter

    Page(s): 1945 - 1953
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (828 KB)  

    To obtain a high step-up gain with high efficiency in distributed power sources application, such as photovoltaic (PV) and fuel cells, a passive absorption circuit with voltage step-up character is inserted in the interleaved flyback-forward converter for leakage energy recycle and voltage gain extension. By applying the high step-up passive-clamp circuit, the voltage spike on the metal-oxide semiconductor field-effect transistor is clamped and the energy stored inside the leakage inductance of the coupled inductor can be recycled to get high-output voltage. Moreover, it offers another design freedom to obtain higher voltage-conversion ratio. The operational principle and characteristics of the improved flyback-forward converter are presented, and verified experimentally with a 500 W prototype converter. The proposed high step-up passive-clamp can be widely used in high step-up DC-DC converter applications, and a new high step-up topology is deduced to illustrate the theoretical analysis. View full abstract»

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  • 48. Non-isolated multi-input–single-output DC/DC converter for photovoltaic power generation systems

    Page(s): 2806 - 2816
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (891 KB)

    A new multi-input non-isolated DC/DC converter with high-voltage transfer gain is proposed in this study. The presented converter consists of the conventional buck-boost and boost converters. All the stages except the last stage are buck-boost converters. The last stage is the conventional boost converter. The proposed multi-input high-voltage gain converter benefits from various advantages such as reduced semiconductor current stress, no limitation for switching duty cycle and wide control range of different input powers. The presented converter can even operate when one or some power input fail to provide energy to the load. The steady-state operation and dynamic modelling of the suggested converter are analysed thoroughly. Experimental results are also provided to verify the feasibility of the presented converter. View full abstract»

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  • 49. Induction motor control based on approximate stator flux

    Page(s): 2765 - 2777
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1387 KB)

    In this study, a novel sensorless method for the induction motor control is proposed. In this method, magnitude and rotational speed of approximate stator flux vector are controlled. In the proposed approximate stator flux control (ASFC) method, utilisation of the mechanical sensors and current transducers is not required. Therefore implementation cost of ASFC is comparable with that of conventional v/f control method. In ASFC, in linear modulation range, to control rotating field speed and stator flux modulus, desired voltage vector components in line with and perpendicular to the stator flux vector are calculated. Based on these two components, three-phase voltages are applied to three-phase inverter using pulse-width modulation strategy. In addition, in overmodulation range, a switching-table-based approach is presented to control the rotating field speed by adjusting the stator flux modulus. The relationship between the stator flux modulus and rotating field speed is derived and it is shown that average switching frequency is calculable and under control. Through simulations and experiments, ASFC method is compared with v/f method in terms of motor behaviour in starting and steady-state operation. Also, correctness of presented formulas is validated by simulations and experimental results. View full abstract»

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  • 50. Speed sensorless control of a six-phase induction motor drive using backstepping control

    Page(s): 114 - 123
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (940 KB)  

    In this study, a direct torque and flux control is described for a six-phase asymmetrical speed and voltage sensorless induction machine (IM) drive, based on non-linear backstepping control approach. First, the decoupled torque and flux controllers are developed based on Lyapunov theory, using the machine two axis equations in the stationary reference frame. In this control scheme, the actual stator voltages are determined from dc-link voltage using the switching pattern of the space vector pulse-width modulation inverter. Then, for a given motor load torque and rotor speed, a so-called fast search method is used to maximise the motor efficiency. According to this method, the rotor reference flux is decreased in the small steps, until the average of real input power to the motor reaches to a minimum value. In addition, a model reference adaptive system-based observer is employed for online estimating of the rotor speed. Finally, the feasibility of the proposed control scheme is verified by simulation and experimental results. 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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