HA 컨버터를 응용한 AC-DC 및 DC-AC 전력 변환

학위논문 (박사)-- 서울대학교 대학원 : 전기공학부, 2013. 2. 조보형.This dissertation proposes a new topology H-bridge converter with additional switch legs (HA converter). The proposed topology has simple circuit structure with expandability and flexibility. With six semiconductor devices and single inductor, the topology is capable of operating as buck, boost, and buck-boost converter. Theoretically, it demonstrates low common mode current and electromagnetic interference (EMI) by solidly connecting grounds of input and output terminals. The proposed topology is advantageous not only in grid-connected power conversion application but also in stand-alone power system such as electric vehicle, because these systems include large parasitic capacitances and are prone to high common mode EMI due to the wide mechanical structure of the conductor. Among many offspring circuits of the HA converter, a boost-buck-boost (B3) rectifier for off-line power supply with active power factor correction and a buck-buck-boost (B3) inverter for grid-connected photovoltaic system are proposed as two practical examples. Principle of operations, dedicated control algorithms, and filters for the new circuits are analyzed and designed in detail. Experimental results based on the laboratory prototype hardware prove that the proposed circuits outperform their conventional counterparts by showing low common mode noise and comparable efficiency.Abstract............................i Contents...........................ii List of Figures....................iv List of Tables......................x 1. Introduction.....................1 1.1. Motivations and Backgrounds....1 1.2. Objectives.....................2 1.3. Dissertation Outlines..........4 2. H-bridge Converter with Additional Switch Legs (HA Converter)......................7 2.1. Review of Common Mode EMI......7 2.1.1. In Off-line AC-DC Rectifier.11 2.1.2. In Grid-connected DC-AC PV Inverter...........................16 2.2. Topology Derivation...........24 2.2.1. Dual H-bridges..............29 2.2.2. HA Converter................31 2.3. Feature of HA Converter.......34 3. B3 Rectifier for AC-DC Conversion.........................40 3.1. Advantage of B3 Rectifier.....40 3.2. Operation.....................43 3.3. Control.......................45 3.3.1. Power Imbalance in a Line Cycle..............................47 3.3.2. Inductor Current Reference Calculation........................51 3.3.3. Compensator Design..........56 3.4. Differential Input Filter Design.............................67 3.5. Experiments...................75 3.5.1. Implementations.............75 3.5.2. Results and Discussions.....81 4. B3 Inverter for DC-AC Conversion.........................88 4.1. Advantage of B3 Inverter...........................88 4.2. Operation.....................91 4.3. Control.......................93 4.3.1. Inductor Current Reference Calculation........................93 4.3.2. Compensator Design..........98 4.4. Differential Output Filter Design............................104 4.5. Experiments..................111 4.5.1. Implementations............111 4.5.2. Results and Discussions....117 5. Flexibility of HA Converter.........................125 6. Conclusion and Further Works...134 Appendix..........................137 A.1. Correction Factor of B3 Rectifier in Small Signal Model.............................137 A.2. Input Impedances of Boost and Buck-boost Converter.........................139 A.3. Loss Estimation of B3 Rectifier Switches..........................144 A.4. H5 and HERIC Inverter Operations........................153 References........................160 국문 초록.........................168 감사의 글.........................169Docto

A SINGLE-PHASE DUAL-OUTPUT AC-DC CONVERTER WITH HIGH QUALITY INPUT WAVEFORMS

A single-phase, buck-boost based, dual-output AC-DC converter is studied in this thesis. The converter has two DC outputs with opposite polarities, which share the same ground with the input power line. The power stage performance, including the input filter, is studied and procedure to select power components is given. The circuit model is analyzed to develop appropriate control. Zerocrossing distortion of the source input current is addressed and a solution is proposed. Experimental results are satisfactory in that a high power factor line current results for steady-state operation

Study of Input Power Factor Correction in Single Phase AC-DC Circuit Using Parallel Boost Converter

An ac to dc converter is t h e m o s t i m p o r t a n t p a r t o f any power supply unit used in the all- electronic equipments that forms a considerable part of load on the utility. Power electronic equipments are increasingly being used for power conversion, thereby injecting lower order harmonics into the utility. As a result, the total harmonic distortion is high and input power factor is poor. Thus, power factor correction schemes are implemented so as to make the power factor unity thereby leading to low input current distortion. Amongst the several techniques used for PFC, high frequency active PFC is used to get better power factor but it has drawbacks that includes additional losses, thus reducing the overall efficiency, increase in EMI. The efficiency is improved by reducing the losses using soft switching techniques such as ZVS and ZCS. Boost converter is preferred because input current does not have cross-over distortion and it is continuous. In this project, a control technique for boost converter is proposed. This is based on hysteresis-control scheme in which two sinusoidal current references are generated namely IP,ref, IV,ref, such that one is for the peak and the other is for the valley of the inductor current. In this control technique, when the inductor current goes below the lower reference IV,ref the switch is turned on and is turned off when the inductor current goes above the upper reference IP,ref, thereby giving rise to a variable frequency control. To avoid too high switching frequency, the switch should be kept open near the zero crossing of the line voltage so introducing dead times in the line current. Thus, we can say that by using hysteresis controlled boost converter PFC , power factor of an AC-DC converter can be increased

Single-stage ac–dc buck–boost converter for medium-voltage high-power applications

This study proposes three topologies based on single-stage three-phase ac-dc buck-boost converters suitable for medium-voltage high-power applications. The first two topologies are based on a dual three-phase buck-boost converter, with a three-winding phase-shifted transformer to achieve sinusoidal input currents, with relatively small ac filters. The limitation of these two topologies is the switching devices are exposed either to a high voltage beyond that tolerable by a single device. The third topology is based on three single-phase buck-boost converters; with their dc output terminals connected in series to generate high voltage. By using this approach, voltage stresses on the switching devices are greatly reduced, and sinusoidal input currents with nearly unity power factor is achieved over the entire operating range when using small ac filters. Analysis, PSCAD/EMTDC simulations and experimentation are used to assess the feasibility of the proposed topologies during normal operation. Major findings of this study are discussed and summarised as a comparison between the three topologies

Single-Stage Led Drivers Based On Integrated Bcm Boost And Llc Converters For Street Lighting

Electrical lighting has been an important technology to modern society. Given the increasing concerns about environmental and energy saving issues, light-emitting-diode (LED) has become the research focus due to the features of mercury elimination and high energy efficiency compared to conventional lamps. Performance aspects of LED lighting are related with LED driver, thus an appropriate converter should be designed to power up the LEDs with good input power factor and high efficiency. To achieve these elements, single-stage alternating current to direct current (AC-DC) converter with power factor correction (PFC) is proposed as LED driver for application in street lighting. In this topology, a pair of boost circuits which share a single inductor are combined as a PFC stage and then integrated with half-bridge LLC resonant converter. Three kinds of rectifier circuits are proposed for the secondary-side rectification; full-wave bridge rectifier, full-wave voltage doubler rectifier and dual half-wave rectifiers. All rectifier circuits have their own advantages and remove the requirement of center-tapped transformer in circuit design. The power switches are driven by a high-voltage resonant controller IC L6598 with nearly 0.5 duty cycle and a small dead time. All proposed LED drivers have been tested in the laboratory for supplying 12 high-power LEDs from ac input voltage of 240-V. From the comparison results, LED driver using full-wave voltage doubler rectifier has shown the best performances, followed by LED driver using full-wave bridge rectifier and then LED driver using dual half-wave rectifiers. The highest power factor measured is almost unity at 0.99, the lowest total harmonic distortion (THD) is 13.8%, the highest efficiency is 93.39% and the lowest bus voltage is 330-V. The power factor correction was successfully achieved and high conversion efficiency was obtained due to soft-switching characteristics of the LED driver. The voltage stress on bus capacitor is considerably reduced to 1.36 times of the input-peak-voltage. The dimming capability was also accomplished. Lastly, the minimization of storage capacitance was successful with an acceptable range of output current ripple for flicker-less LED lighting

Low Voltage Regulator Modules and Single Stage Front-end Converters

Evolution in microprocessor technology poses new challenges for supplying power to these devices. To meet demands for faster and more efficient data processing, modem microprocessors are being designed with lower voltage implementations. More devices will be packed on a single processor chip and the processors will operate at higher frequencies, exceeding 1GHz. New high-performance microprocessors may require from 40 to 80 watts of power for the CPU alone. Load current must be supplied with up to 30A/µs slew rate while keeping the output voltage within tight regulation and response time tolerances. Therefore, special power supplies and Voltage Regulator Modules (VRMs) are needed to provide lower voltage with higher current and fast response. In the part one (chapter 2,3,4) of this dissertation, several low-voltage high-current VRM technologies are proposed for future generation microprocessors and ICs. The developed VRMs with these new technologies have advantages over conventional ones in terms of efficiency, transient response and cost. In most cases, the VRMs draw currents from DC bus for which front-end converters are used as a DC source. As the use of AC/DC frond-end converters continues to increase, more distorted mains current is drawn from the line, resulting in lower power factor and high total harmonic distortion. As a branch of active Power factor correction (PFC) techniques, the single-stage technique receives particular attention because of its low cost implementation. Moreover, with continuously demands for even higher power density, switching mode power supply operating at high-frequency is required because at high switching frequency, the size and weight of circuit components can be remarkably reduced. To boost the switching frequency, the soft-switching technique was introduced to alleviate the switching losses. The part two (chapter 5,6) of the dissertation presents several topologies for this front-end application. The design considerations, simulation results and experimental verification are discussed

A Control Scheme for an AC-DC Single-Stage Buck-Boost PFC Converter with Improved Output Ripple Reduction

AC-DC power factor correction (PFC) single-stage converters are attractive because of their cost and their simplicity. In these converters, both PFC and power conversion are done at the same time using a single converter that regulates the output. Since they have only a single controller, these converters operate with an intermediate transformer primary-side DC bus voltage that is unregulated and is dependent on the converters’ operating conditions and component values. This means that the DC bus voltage can vary significantly as line and load conditions are changed. Such a variable DC bus voltage makes it difficult to optimally design the converter transformer as well as the DC bus capacitor. One previously proposed single-stage AC-DC converter, the Single-Stage Buck-Boost Direct Energy Transfer (SSBBDET) converter has a clamping mechanism that can clamp the DC bus voltage to a pre-set limit. The clamping mechanism, however, superimposes a low frequency 120 Hz AC component on the output DC voltage so that some means must be taken to reduce this component. These means, however, make the converter transient slow and sluggish. The main objective of this thesis is to minimize the 120 Hz output ripple component and to improve the dynamic response of the SSBBDET converter by using a new control scheme. In the thesis, the operation of the SSBBDET converter is reviewed and the proposed control method is introduced and explained in detail. Key design considerations for the design of the converter controller are discussed and the converter’s ability to operate with fixed DC bus voltage, low output ripple and fast dynamic response is confirmed with experimental results obtained from a prototype converter

Survey on Photo-Voltaic Powered Interleaved Converter System

Renewable energy is the best solution to meet the growing demand for energy in the country. The solar energy is considered as the most promising energy by the researchers due to its abundant availability, eco-friendly nature, long lasting nature, wide range of application and above all it is a maintenance free system. The energy absorbed by the earth can satisfy 15000 times of today’s total energy demand and its hundred times more than that our conventional energy like coal and other fossil fuels. Though, there are overwhelming advantages in solar energy, It has few drawbacks as well such as its low conversion ratio, inconsistent supply of energy due to variation in the sun light, less efficiency due to ripples in the converter, time dependent and, above all, high capitation cost. These aforementioned flaws have been addressed by the researchers in order to extract maximum energy and attain hundred percentage benefits of this heavenly resource. So, this chapter presents a comprehensive investigation based on photo voltaic (PV) system requirements with the following constraints such as system efficiency, system gain, dynamic response, switching losses are investigated. The overview exhibits and identifies the requirements of a best PV power generation system