Showing papers on "Power factor published in 2012"

Power Electronics Converters for Wind Turbine Systems

Abstract: The steady growth of installed wind power together with the upscaling of the single wind turbine power capability has pushed the research and development of power converters toward full-scale power conversion, lowered cost pr kW, increased power density, and also the need for higher reliability. In this paper, power converter technologies are reviewed with focus on existing ones and on those that have potential for higher power but which have not been yet adopted due to the important risk associated with the high-power industry. The power converters are classified into single- and multicell topologies, in the latter case with attention to series connection and parallel connection either electrical or magnetic ones (multiphase/windings machines/transformers). It is concluded that as the power level increases in wind turbines, medium-voltage power converters will be a dominant power converter configuration, but continuously cost and reliability are important issues to be addressed.

Energy Scavenging for Wireless Sensor Networks: with Special Focus on Vibrations

Abstract: 1 Introduction.- 1. Energy Storage.- 2. Power Distribution.- 3. Power scavenging.- 4. Summary of potential power sources.- 5. Overview of Vibration-to-Electricity Conversion Research.- 2 Vibration Sources and Conversion Model.- 1. Types of Vibrations Considered.- 2. Characteristics of Vibrations Measured.- 3. Generic Vibration-to-Electricity Conversion Model.- 4. Efficiency of Vibration-to-Electricity Conversion.- 3 Comparison of Methods.- 1. Electromagnetic (Inductive) Power Conversion.- 2. Electrostatic (Capacitive) Power Conversion.- 3. Piezoelectric Power Conversion.- 4. Comparison of Energy Density of Converters.- 5. Summary of Conversion Mechanisms.- 4 Piezoelectric Converter Design.- 1. Basic Design Configuration.- 2. Material Selection.- 3. Analytical Model for Piezoelectric Generators.- 4. Discussion of Analytical Model for Piezoelectric Generators.- 5. Initial Prototype and Model Verification.- 6. Design Optimization.- 7. Analytical Model Adjusted for a Capacitive Load.- 8. Discussion of Analytical Model Changes for Capacitive Load.- 9. Optimization for a Capacitive Load.- 10. Conclusions.- 5 Piezoelectric Converter Test Results.- 1. Implementation of Optimized Converters.- 2. Resistive load tests.- 3. Discussion of resistive load tests.- 4. Capacitive load tests.- 5. Discussion of capacitive load test.- 6. Results from testing with a custom designed RF transceiver.- 7. Discussion of results from custom RF transceiver test.- 8. Results from test of complete wireless sensor node.- 9. Discussion of results from complete wireless sensor node.- 10. Conclusions.- 6 Electrostatic Converter Design.- 1. Explanation of concept and principle of operation.- 2. Electrostatic Conversion Model.- 3. Exploration of design concepts and device specific models.- 4. Comparison of design concepts.- 5. Design Optimization.- 6. Flexure design.- 7. Discussion of design and conclusions.- 7 Fabrication of Electrostatic Converters.- 1. Choice of process and wafer technology.- 2. Basic process flow.- 3. Specific processes used.- 4. Conclusions.- 8 Electrostatic Converter Test Results.- 1. Macro-scale prototype and results.- 2. Results from fluidic self-assembly process prototypes.- 3. Results from integrated process prototypes.- 4. Results from simplified custom process prototypes.- 5. Discussion of Results and Conclusions.- 9 Conclusions.- 1. Justification for focus on vibrations as a power source.- 2. Piezoelectric vibration to electricity converters.- 3. Design considerations for piezoelectric converters.- 4. Electrostatic vibration to electricity converters.- 5. Design considerations for electrostatic converters.- 6. Summary of conclusions.- 7. Recommendations for future work.- Acknowledgments.- Appendix A: Analytical Model of a Piezoelectric Generator.- 1. Geometric terms for bimorph mounted as a cantilever.- 2. Basic dynamic model of piezoelectric generator.- 3. Expressions of interest from basic dynamic model.- 4. Alterations to the basic dynamic model.- Appendix B: Analytical Model of an Electrostatic Generator.- 1. Derivation of electrical and geometric expressions.- 2. Derivation of mechanical dynamics and electrostatic forces.- 3. Simulation of the in-plane gap closing converter.- References.

Adaptive VAR Control for Distribution Circuits With Photovoltaic Generators

Abstract: We show how an adaptive control algorithm can improve the performance of distributed reactive power control in a radial distribution circuit with a high penetration of photovoltaic (PV) cells. The adaptive algorithm is designed to balance the need for power quality (voltage regulation) with the desire to minimize power loss. The adaptation law determines whether the objective function minimizes power losses or voltage regulation based on whether the voltage at each node remains close enough to the voltage at the substation. The reactive power is controlled through the inverter on the PV cells. The control signals are determined based on local instantaneous measurements of the real and reactive power at each node. We use the example of a single branch radial distribution circuit to demonstrate the ability of the adaptive scheme to effectively reduce voltage variations while simultaneously minimizing the power loss in the studied cases. Simulations verify that the adaptive schemes compares favorably with local and global schemes previously reported in the literature.

Optimal inverter VAR control in distribution systems with high PV penetration

Abstract: The intent of the study detailed in this paper is to demonstrate the benefits of inverter var control on a fast timescale to mitigate rapid and large voltage fluctuations due to the high penetration of photovoltaic generation and the resulting reverse power flow. Our approach is to formulate the volt/var control as a radial optimal power flow (OPF) problem to minimize line losses and energy consumption, subject to constraints on voltage magnitudes. An efficient solution to the radial OPF problem is presented and used to study the structure of optimal inverter var injection and the net benefits, taking into account the additional cost of inverter losses when operating at non-unity power factor. This paper will illustrate how, depending on the circuit topology and its loading condition, the inverter's optimal reactive power injection is not necessarily monotone with respect to their real power output. The results are demonstrated on a distribution feeder on the Southern California Edison system that has a very light load and a 5 MW photovoltaic (PV) system installed away from the substation.

Large Signal Stability Analysis Tools in DC Power Systems With Constant Power Loads and Variable Power Loads—A Review

Abstract: Electric motor drives and power electronic converters have become increasingly common in advanced power systems. Passive LC filters are used in these systems to reduce the power ripples. These filters are usually poorly damped for reducing the losses as well as the size/weight and the cost of the system. This leads to instability phenomena if the load power exceeds a power limit depending on the filter parameters. The purpose of this paper is to present tools allowing large signal stability analysis of a dc power system. These tools allow estimation of the domain of attraction of the system operating point. It will be shown that this large signal stability analysis gives useful hints on the design of the system to optimize the stability criteria for constant and variable power loads. The impact of the load dynamics on stability is also studied. An electric drive connected to a dc power supply through a poorly damped LC filter is used as a case study. The simulations and the experimentations confirm the analytical results.

Analysis and Design of the Integrated Double Buck–Boost Converter as a High-Power-Factor Driver for Power-LED Lamps

Abstract: In this paper, an integrated double buck-boost (IDBB) converter is proposed as a high-power-factor offline power supply for power-LED lamps. The IDBB converter features just one controlled switch and two inductors and is able to supply a solid-state lamp from the mains, providing high power factor and good efficiency. In this paper, the IDBB converter is analyzed, and a design methodology is proposed. It is demonstrated that, with a careful design of the converter, the filter capacitances can be made small enough so that film capacitors may be used. In this way, the converter mean time between failures can be made as high as that of the solid-state lamp. A design example for a 70-W converter supplied from a 230 V/50 Hz mains for street lighting applications is shown. Finally, experimental results from a laboratory prototype are also presented.

Power transmission system

Abstract: Provided is a power transmission system that can prevent a plunge in power transmission efficiency even when there is a positional shift of a power reception antenna with respect to a power transmission antenna. A power transmission system 100 of the present invention is characterized by including: a power transmission antenna 105 that includes a wound power transmission coil that is placed on the ground; and a power reception antenna 201 that is disposed in such a way as to face the power transmission antenna 105 , includes a wound power reception coil, and receives electric energy from the power transmission antenna 105 via an electromagnetic field, wherein an area (S 1 ) of a first projection plane that is formed by the power transmission coil in a vertical direction with respect to a horizontal plane is larger than an area (S 2 ) of a second projection plane that is formed by the power reception coil in the vertical direction with respect to the horizontal plane.

Efficiency Analysis of Drive Train Topologies Applied to Electric/Hybrid Vehicles

Abstract: One of the most important research topics in drive train topologies applied to electric/hybrid vehicles is the efficiency analysis of the power train components, including the global drive efficiency. In this paper, two basic traction electric drive systems of electric/hybrid vehicles are presented and evaluated, with a special focus on the efficiency analysis. The first topology comprises a traditional pulsewidth-modulation (PWM) battery-powered inverter, whereas in the second topology, the battery is connected to a bidirectional dc-dc converter, which supplies the inverter. Furthermore, a variable-voltage control technique applied to this second topology is presented, which allows for the improvement of the drive overall performance. Some simulation results are presented, considering both topologies and a permanent-magnet synchronous motor (PMSM). An even more detailed analysis is performed through the experimental validation. Particular attention is given to the evaluation of the main drive components efficiency, including the global drive efficiency, presented in the form of efficiency maps. Other parameters such as motor voltage distortion and power factor are also considered. In addition, the comparison of the two topologies takes into account the drive operation under the motoring and regenerative-braking modes.

Evaluation and Efficiency Comparison of Front End AC-DC Plug-in Hybrid Charger Topologies

Abstract: As a key component of a plug-in hybrid electric vehicle (PHEV) charger system, the front-end ac-dc converter must achieve high efficiency and power density. This paper presents a topology survey evaluating topologies for use in front end ac-dc converters for PHEV battery chargers. The topology survey is focused on several boost power factor corrected converters, which offer high efficiency, high power factor, high density, and low cost. Experimental results are presented and interpreted for five prototype converters, converting universal ac input voltage to 400 V dc. The results demonstrate that the phase shifted semi-bridgeless PFC boost converter is ideally suited for automotive level I residential charging applications in North America, where the typical supply is limited to 120 V and 1.44 kVA or 1.92 kVA. For automotive level II residential charging applications in North America and Europe the bridgeless interleaved PFC boost converter is an ideal topology candidate for typical supplies of 240 V, with power levels of 3.3 kW, 5 kW, and 6.6 kW.

Elimination of an Electrolytic Capacitor in AC/DC Light-Emitting Diode (LED) Driver With High Input Power Factor and Constant Output Current

Abstract: While LEDs enjoy relatively long lifetime up to 10 years, the lifetime of traditional LED drivers using electrolytic capacitor as storage element is limited to typically less than 5 years. In this paper, an ac/dc LED driver without electrolytic capacitor is studied. Compared with other methods to eliminate electrolytic capacitor, the proposed driver has the advantages of almost unity input power factor and constant output current for LEDs. The operation principle, detailed design procedure of the main circuit, and control strategy are presented. The feasibility of the proposed converter has been successfully verified by experiments.

Effective Capacitive Power Transfer

Abstract: Capacitive power transfer (CPT) systems have up to date been used for very low power delivery due to a number of limitations. A fundamental treatment of the problem is carried out and a CPT system is presented that achieves many times higher power throughput into low-impedance loads than traditional systems with the same interface capacitance and frequency of operation and with reasonable ratings for the switching devices. The development and analysis of the system is based well on the parameters of the capacitive interface and a design procedure is provided. The validity of the concept has been verified by an experimental CPT system that delivered more than 25W through a combined interface capacitance of 100 pF, at an operating frequency of only 1 MHz, with efficiency exceeding 80%.

Grid-Connected Boost-Half-Bridge Photovoltaic Microinverter System Using Repetitive Current Control and Maximum Power Point Tracking

Abstract: This paper presents a novel grid-connected boost-half-bridge photovoltaic (PV) microinverter system and its control implementations. In order to achieve low cost, easy control, high efficiency, and high reliability, a boost-half-bridge dc-dc converter using minimal devices is introduced to interface the low-voltage PV module. A full-bridge pulsewidth-modulated inverter is cascaded and injects synchronized sinusoidal current to the grid. Moreover, a plug-in repetitive current controller based on a fourth-order linear-phase IIR filter is proposed to regulate the grid current. High power factor and very low total harmonic distortions are guaranteed under both heavy load and light load conditions. Dynamic stiffness is achieved when load or solar irradiance is changing rapidly. In addition, the dynamic behavior of the boost-half-bridge dc-dc converter is analyzed; a customized maximum power point tracking (MPPT) method, which generates a ramp-changed PV voltage reference is developed accordingly. Variable step size is adopted such that fast tracking speed and high MPPT efficiency are both obtained. A 210 W prototype was fabricated and tested. Simulation and experimental results are provided to verify the validity and performance of the circuit operations, current control, and MPPT algorithm.

Tunable wireless power architectures

Abstract: Described herein are improved configurations for a wireless power transfer. The parameters of components of the wireless energy transfer system are adjusted to control the power delivered to the load at the device. The power output of the source amplifier is controlled to maintain a substantially 50% duty cycle at the rectifier of the device.

New Efficient Bridgeless Cuk Rectifiers for PFC Applications

Abstract: Three new bridgeless single-phase ac-dc power factor correction (PFC) rectifiers based on Cuk topology are proposed. The absence of an input diode bridge and the presence of only two semiconductor switches in the current flowing path during each interval of the switching cycle result in less conduction losses and an improved thermal management compared to the conventional Cuk PFC rectifier. The proposed topologies are designed to work in discontinuous conduction mode (DCM) to achieve almost a unity power factor and low total harmonic distortion of the input current. The DCM operation gives additional advantages such as zero-current turn-ON in the power switches, zero-current turn-OFF in the output diode, and simple control circuitry. Performance comparisons between the proposed and conventional Cuk PFC rectifiers are performed based on circuit simulations. Experimental results for a 150 W/48 Vdc at 100 Vrms line voltage to evaluate the performance of the proposed bridgeless PFC rectifiers are provided.

Analysis and Evaluation of DC-Link Capacitors for High-Power-Density Electric Vehicle Drive Systems

Abstract: In electric vehicle (EV) inverter systems, direct-current-link capacitors, which are bulky, heavy, and susceptible to degradation from self heating, can become a critical obstacle to high power density. This paper presents a comprehensive method for the analysis and comparative evaluation of dc-link capacitor applications to minimize the volume, mass, and capacitance. Models of equivalent series resistance that are valid over a range of frequency and operating temperature are derived and experimentally validated. The root-mean-square values and frequency spectra of the capacitor current are analyzed with respect to three modulation strategies and various operating conditions over practical ranges of load power factor and modulation index in EV drive systems. The modeling and analysis also consider the self-heating process and resulting core temperature of the dc-link capacitors, which impacts their lifetimes. Based on an 80-kW permanent-magnet (PM) motor drive system, the application of electrolytic capacitors and film capacitors has been evaluated by both simulation and experimental tests. The inverter power density is improved from 2.99 kW/L to 13.3 kW/L, without sacrificing the system performance in terms of power loss, core temperature, and lifetime.

Wireless power transmission system using solar cell module

Abstract: A wireless power transmission system includes a charging and path controller configured to supply, to a battery module, power generated by a solar cell module, or power generated by an alternating current-to-direct current (AC/DC) converter, based on a control signal; a power converter configured to receive power from the battery module and generate a supply power to be supplied to a target device from power received from the battery module using a resonant frequency; a source resonator configured to receive the supply power from the power converter and transmit the supply power received from the power converter to the target device; and a control/communication unit configured to generate the control signal of the charging and path controller based on an amount of the power generated by the solar cell module and an amount of power that can be output from the battery module.

Power-Extraction Circuits for Piezoelectric Energy Harvesters in Miniature and Low-Power Applications

Abstract: When a piezoelectric energy harvester is connected to a simple load circuit, the damping force which the piezoelectric element is able to generate is often below the optimal value to maximize electrical power generation Circuits that aim to increase the power output of a piezoelectric energy harvester do so by modifying the voltage onto which the piezoelectric current source drives its charge This paper presents a systematic analysis and comparison of all the principal types of power extraction circuit that allow this damping force to be increased, under both ideal and realistic constraints Particular emphasis is placed on low-amplitude operation A circuit called single-supply prebiasing is shown to harvest more power than previous approaches Most of the analyzed circuits able to increase the power output do so by synchronously inverting or charging the piezoelectric capacitance through an inductor For inductor Q factors greater than around only 2, the single-supply prebiasing circuit has the highest power density of the analyzed circuits The absence of diodes in conduction paths, achievable with a minimum number of synchronous rectifiers, means that the input excitation amplitude is not required to overcome a minimum value before power can be extracted, making it particularly suitable for microscale applications or those with a wide variation in amplitude

Transformerless Split-Inductor Neutral Point Clamped Three-Level PV Grid-Connected Inverter

Abstract: Characterized by low leakage current and low voltage stress of the power device, a neutral point clamped three-level inverter (NPCTLI) is suitable for a transformerless photovoltaic (PV) grid-connected system. Unfortunately, the shoot-through problem of bridge legs still exists in an NPCTLI, so its operation reliability is degraded. An improved three-level grid-connected inverter is proposed based on the NPCTLI and the dual-buck half-bridge inverter (DBHBI), and which avoids the shoot-through problem. The proposed topology guarantees no switching-frequency common-mode voltage and no shoot-through risk. Furthermore, the freewheeling diode of bridge legs of the DBHBI can be removed taking into consideration the unity power factor of grid current, and a straightforward topology is thus derived. The new topology is referred to as split-inductor NPCTLI (SI-NPCTLI). The operation mode, common-mode characteristic, and control strategy are analyzed. Finally, both the simulation and the experimental results of a 1-kW SI-NPCTLI prototype verify the analysis.

Wireless power transfer device and wireless power transfer method

Abstract: A wireless power transfer device including: a power transmitter 1 including a power transmission resonator composed of a power transmission coil and a resonant capacitance; and a power receiver including a power receiving resonator composed of a power receiving coil and a resonant capacitance. The wireless power transfer device further includes a power-transmission auxiliary device including an auxiliary resonator composed of an auxiliary coil and a resonant capacitance. The power-transmission auxiliary device and the power transmitter are configured to be disposed so as to face each other, forming a power receiving space for disposing the power receiving coil between the power transmission coil and the auxiliary coil. An efficient power transfer can be performed without providing an adjusting circuit in the power receiver even when the power receiving coil is not appropriately disposed with respect to the power transmission coil.

Single-Stage, Universal-Input AC/DC LED Driver With Current-Controlled Variable PFC Boost Inductor

Abstract: This paper presents a single-stage flyback power-factor-correction (PFC) circuit with a variable boost inductance for high-brightness LED applications for the universal input voltage (90-270 Vrms). The proposed circuit overcomes the limitations of the conventional single-stage PFC flyback with a constant boost inductance that cannot be designed to achieve a practical maximum bulk-capacitor voltage level (i.e., less than 450 V) at high line while meeting required line-current harmonic specifications at low line. According to the proposed method for achieving variable boost inductance, the boost inductance has a constant high value at high line, while at low line it is reduced proportionally to the load current, so that the IEC 61000-3-2 class C and corresponding Japanese JIS C 61000-3-2 class C line-current harmonic limits are satisfied. The proposed single-stage PFC flyback LED driver with the variable boost inductor is experimentally verified on a 24-V/91-W prototype circuit.

A Novel Valley-Fill SEPIC-Derived Power Supply Without Electrolytic Capacitor for LED Lighting Application

Abstract: The high-brightness white-light-emitting diode (LED) has attracted a lot of attention for its high efficacy, simple to drive, environmentally friendly, long lifespan, and compact size. The power supply for LED also requires long life, while maintaining high efficiency, high power factor, and low cost. However, a typical power supply design employs an electrolytic capacitor as the storage capacitor, which is not only bulky, but also with a short lifespan, thus hampering performance improvement of the entire LED lighting system. In this paper, a novel power factor correction (PFC) topology is proposed by inserting the valley-fill circuit in the single-ended primary inductance converter (SEPIC)-derived converter, which can reduce the voltage stress of the storage capacitor and output diode under the same power factor condition. This valley-fill SEPIC-derived topology is, then, proposed for LED lighting applications. By allowing a relatively large voltage ripple in the PFC design and operating in the discontinuous conduction mode (DCM), the proposed PFC topology is able to eliminate the electrolytic capacitor, while maintaining high power factor and high efficiency. Under the electrolytic capacitor-less condition, the proposed PFC circuit can reduce the capacitance of the storage capacitor to half for the same power factor and output voltage ripple as comparing to its original circuit. To further increase the efficiency of LED driver proposal, a twin-bus buck converter is introduced and employed as the second-stage current regulator with the PWM dimming function. The basic operating principle and analysis will be described in detail. A 50-W prototype has been built and tested in the laboratory, and the experimental results under universal input-voltage operation are presented to verify the effectiveness and advantages of the proposal.

A Five-Level Inverter Topology with Single-DC Supply by Cascading a Flying Capacitor Inverter and an H-Bridge

Abstract: In this paper, a new three-phase, five-level inverter topology with a single-dc source is presented. The proposed topology is obtained by cascading a three-level flying capacitor inverter with a flying H-bridge power cell in each phase. This topology has redundant switching states for generating different pole voltages. By selecting appropriate switching states, the capacitor voltages can be balanced instantaneously (as compared to the fundamental) in any direction of the current, irrespective of the load power factor. Another important feature of this topology is that if any H-bridge fails, it can be bypassed and the configuration can still operate as a three-level inverter at its full power rating. This feature improves the reliability of the circuit. A 3-kW induction motor is run with the proposed topology for the full modulation range. The effectiveness of the capacitor balancing algorithm is tested for the full range of speed and during the sudden acceleration of the motor.

A Novel Single-Stage High-Power-Factor AC-to-DC LED Driving Circuit With Leakage Inductance Energy Recycling

Abstract: This paper proposes a novel single-stage ac-to-dc light-emitting-diode (LED) driver circuit. A buck-boost power factor (PF) corrector is integrated with a flyback converter. A recycling path is built to recover the inductive leakage energy. In this way, the presented circuit can provide not only high PF and low total harmonic distortion but also high conversion efficiency and low switching voltage spikes. Above 0.95 PF and 90% efficiency are obtained from an 8-W LED lamp driver prototype.

Towards a 99% Efficient Three-Phase Buck-Type PFC Rectifier for 400-V DC Distribution Systems

Abstract: In telecom applications, the vision for a total power conversion efficiency from the mains to the output of point-of-load (PoL) converters of 95% demands optimization of every conversion step, i.e., the power factor correction (PFC) rectifier front-end should show an outstanding efficiency in the range of 99%. For recently discussed 400-V dc distribution bus voltages, a buck-type PFC rectifier is a logical solution. In this paper, an efficiency-optimized, 98.8% efficient, 5-kW three-phase buck-type PFC rectifier with 400-V output is presented. Methods for calculating losses of all components are described and are used to optimize the converter design for efficiency at full load. Special attention is paid to semiconductor losses, which are shown to be dominant, with the parasitic device capacitance losses being a significant component. The calculation of these parasitic capacitance losses is treated in detail, and the charge-balance approach used is verified. A prototype of the proposed rectifier is constructed which verifies the accuracy of the models used for loss calculation and optimization.

A Robust Adaptive Control Strategy of Active Power Filters for Power-Factor Correction, Harmonic Compensation, and Balancing of Nonlinear Loads

Abstract: This paper introduces a robust adaptive control strategy of shunt active power filters (SAPF) for power-factor correction, harmonic compensation, and balancing of nonlinear loads. The proposed control scheme is implemented without load harmonic detection. The compensation constraints are obtained by regulating indirectly the currents of the power mains. The reference currents of are generated by the dc-link voltage controller based on the active power balance of system. They are aligned to the phase angle of the power mains voltage vector, by using a phase-locked loop system. The current control strategy is implemented by an adaptive pole-placement control strategy integrated to a variable structure control scheme. This control scheme uses the internal model principle of reference currents for achieving the zero steady-state tracking error. Experimental results are shown for determining the effectiveness of an -proposed control system.

Operation and Control of a Hybrid Seven-Level Converter

Abstract: This paper introduces a novel hybrid seven-level converter that is based on the upgrade of the five-level active neutral-point-clamped converter concept and is suitable for high-power applications. The paper provides a comprehensive analysis for the operation of the converter. Based on the analysis, a space vector modulation (SVM)-based switching strategy that takes advantage of redundant switching vectors of the SVM strategy to counteract the voltage drift phenomenon of the proposed converter is proposed. The limit to the range of operation of the seven-level converter based on the proposed SVM strategy is also presented. It is shown that the ability to stabilize the dc-link capacitor voltages and the per-phase flying capacitors is a function of the converter operating indices, i.e., the load power factor and modulation index. The salient feature of the proposed SVM-based control strategy is that it enables proper operation of the converter with no requirements for additional controls or auxiliary power circuitry, within the specified range of operation. Performance of a converter under various operating conditions, based on the proposed SVM strategy, in the MATLAB/Simulink environment, is evaluated and experimentally demonstrated.

A large air gap 3 kW wireless power transfer system for electric vehicles

Abstract: A wireless power transfer system for electric vehicles is required to have high efficiency, a large air gap, and good tolerance for misalignment in the lateral direction and to be compact and lightweight. A new 3 kW transformer has been developed to satisfy these criteria using a novel H-shaped core and split primary capacitors. The design procedure based on the coupling factor k, the winding's Q, and the core loss is described. An efficiency of 90% was achieved across a 200 mm air gap.

Integrated circuit wireless communication unit and method for providing a power supply

Abstract: An integrated circuit is described for providing a power supply to a radio frequency (RF) power amplifier (PA). The integrated circuit includes a low-frequency power supply path including a switching regulator and a high-frequency power supply path arranged to regulate an output voltage of a combined power supply at an output port of the integrated circuit for coupling to a load. The combined power supply is provided by the low-frequency power supply path and high-frequency power supply path. The high-frequency power supply path includes: an amplifier including a voltage feedback and arranged to drive a power supply signal on the high-frequency power supply path; and a capacitor operably coupled to the output of the amplifier and arranged to perform dc level shifting of the power supply signal.

Design of a Soft-Switching Asymmetrical Half-Bridge Converter as Second Stage of an LED Driver for Street Lighting Application

Abstract: High-brightness LEDs are considered remarkable lighting devices due to their high reliability, chromatic variety, and increasing efficiency. As a result, a high number of solutions for supplying LED strings are emerging. One-stage solutions are cost-effective, but their efficiency is low because they have to fulfill several purposes with only one converter: power factor correction (PFC), galvanic isolation (in some cases), and current regulation. Two-stage and three-stage solutions have higher efficiency because each stage is optimized for only one or two tasks and they are the preferred options when supplying several strings at the same time. In this paper, a two-stage solution is proposed. The first stage is the well-known PFC boost converter. The second stage, on which this paper is focused, is the asymmetrical half bridge (AHB). Its design has been optimized based on the needs and characteristics of LED-based street lighting applications. The proposed transformer design (with asymmetrical secondary windings) minimizes the conduction losses while the model of the converter during the dead times optimizes their duration, reducing switching losses in the MOSFETs and diodes. Experimental results obtained with a 40-W prototype show an efficiency as high as 94.5% for this second stage and validate the proposed design procedure and model.

A ZVS Interleaved Boost AC/DC Converter Used in Plug-in Electric Vehicles

Abstract: This paper presents a novel, yet simple zero-voltage switching (ZVS) interleaved boost power factor correction (PFC) ac/dc converter used to charge the traction battery of an electric vehicle from the utility mains. The proposed opology consists of a passive auxiliary circuit, placed between two phases of the interleaved front-end boost PFC converter, which provides enough current to charge and discharge the MOSFETs' output capacitors during turn-ON times. Therefore, the MOSFETs are turned ON at zero voltage. The proposed converter maintains ZVS for the universal input voltage (85 to 265 Vrms), which includes a very wide range of duty ratios (0.07-1). In addition, the control system optimizes the amount of reactive current required to guarantee ZVS during the line cycle for different load conditions. This optimization is crucial in this application since the converter may work at very light loads for a long period of time. Experimental results from a 3 kW ac/dc converter are presented in the paper to evaluate the performance of the proposed converter. The results show a considerable increase in efficiency and superior performance of the proposed converter compared to the conventional hard-switched interleaved boost PFC converter.