ANALYSIS, DESIGN, AND LABORATORY EVALUATION OF A DISTRIBUTED UNIFIED POWER FLOW CONTROLLER CONCEPT

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

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

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

High power density dc-to-dc converters for aerospace applications

Three dc-to-dc converter topologies aimed at high-power high-frequency applications are introduced. Major system parasitics, namely, the leakage inductance of the transformer and the device output capacitance are efficiently utilized. Of the three circuits, the single-phase and three-phase versions of the dual active bridge topology demonstrate minimal stresses, better utilization of the transformer, bidirectional, and buck-boost modes of operation. All circuits operate at a constant switching frequency, thus simplifying design of the reactive elements. The power transfer characteristics and soft-switching regions on the Vout-Iout plane are identified. Two coaxial transformers with different cross-sections were built for a rating of 50 kVA. Based on the single-phase dual active bridge topology, a 50 kW, 50 kHz converter operating at an input voltage of 200 Vdc and an output voltage of 1600 Vdc was fabricated. Characteristics of current-fed output make the dual active bridge topologies amenable to paralleling and hence extension to megawatt power levels. Projections to a 1 MW system operating from a 500 Vdc input, at an output voltage of 10 kVdc and a switching frequency of 50 kHz, using MOS-controlled thyristors, coaxially wound transformers operating at three times the present current density with cooling, and multilayer ceramic capacitors, suggests an overall power density of 0.075 to 0.08 kg/kW and an overall efficiency of 96 percent

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

Low Power DC-DC Converters and a Low Quiescent Power High PSRR Class-D Audio Amplifier

High-performance DC-DC voltage converters and high-efficient class-D audio amplifiers are required to extend battery life and reduce cost in portable electronics. This dissertation focuses on new system architectures and design techniques to reduce area and minimize quiescent power while achieving high performance. Experimental results from prototype circuits to verify theory are shown. Firstly, basics on low drop-out (LDO) voltage regulators are provided. Demand for system-on-chip solutions has increased the interest in LDO voltage regulators that do not require a bulky off-chip capacitor to achieve stability, also called capacitor- less LDO (CL-LDO) regulators. Several architectures have been proposed; however, comparing these reported architectures proves difficult, as each has a distinct process technology and specifications. This dissertation compares CL-LDOs in a unified manner. Five CL-LDO regulator topologies were designed, fabricated, and tested under common design conditions. Secondly, fundamentals on DC-DC buck converters are presented and area reduction techniques for the external output filter, power stage, and compensator are proposed. A fully integrated buck converter using standard CMOS technology is presented. The external output filter has been fully-integrated by increasing the switching frequency up to 45 MHz. Moreover, a monolithic single-input dual-output buck converter is proposed. This architecture implements only three switches instead of the four switches used in conventional solutions, thus potentially reducing area in the power stage through proper design of the power switches. Lastly, a monolithic PWM voltage mode buck converter with compact Type-III compensation is proposed. This compensation scheme employs a combination of Gm-RC and Active-RC techniques to reduce the area of the compensator, while maintaining low quiescent power consumption and fast transient response. The proposed compensator reduces area by more than 45% when compared to an equivalent conventional Type-III compensator. Finally, basics on class-D audio amplifiers are presented and a clock-free current controlled class-D audio amplifier using integral sliding mode control is proposed. The proposed amplifier achieves up to 82 dB of power supply rejection ratio and a total harmonic distortion plus noise as low as 0.02%. The IC prototype’s controller consumes 30% less power than those featured in recently published works

Multiport power electronics circuitry for integration of renewable energy sources in low power applications : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering at Massey University, Palmerston North, New Zealand

The increasing demand for electricity and the global concern about environment has led energy planners and developers to explore and develop clean energy sources. Under such circumstances, renewable energy sources (RES) have emerged as an alternative source of energy generation. Immense development has been made in renewable energy fields and methods to harvest it. To replace conventional generation system, these renewable energy sources must be sustainable, reliable, stable, and efficient. But these sources have their own distinguished characteristics. Due to sporadic nature of renewable energy sources, the uninterrupted power availability cannot be guaranteed. Handling and integration of such diversified power sources is not a trivial process. It requires high degree of efficiency in power extraction, transformation, and utilization. These objectives can only be achieved with the use of highly efficient, reliable, secure and cost-effective power electronics interface. Power electronics devices have made tremendous developments in the recent past. Numerous single and multi-port converter topologies have been developed for processing and delivering the renewable energy. Various multiport converter topologies have been presented to integrate RES, however some limitations have been identified in these topologies in terms of efficiency, reliability, component count and size. Therefore, further research is required to develop a multiport interface and to address the highlighted issues. In this work, a multi-port power electronics circuitry for integration of multiple renewable energy sources is developed. The proposed circuitry assimilates different renewable sources to power up the load with different voltage levels while maintaining high power transfer efficiency and reliability with a simple and reliable control scheme. This research work presents a new multiport non-isolated DC-DC buck converter. The new topology accommodates two different energy sources at the input to power up a variable load. The power sources can be employed independently and concurrently. The converter also has a bidirectional port which houses a storage device like battery to store the surplus energy under light load conditions and can serve as an input source in case of absence of energy sources. The new presented circuitry is analytically examined to validate its effectiveness for multiport interface. System parameters are defined and the design of different components used, is presented. After successful mathematical interpretation, a simulation platform is developed in MATLAB/Simscape to conduct simulations studies to verify analytical results and to carry out stability analysis. In the final stage, a low power, low voltage prototype model is developed to authenticate the results obtained in simulation studies. The converter is tested under different operating modes and variable source and load conditions. The simulation and experimental results are compiled in terms of converter’s efficiency, reliability, stability. The results are presented to prove the presented topology as a highly reliable, stable and efficient multiport interface, with small size and minimum number of components, for integration of renewable energy sources

Switched Capacitor DC-DC Converter for Miniaturised Wearable Systems

Motivated by the demands of the integrated power system in the modern wearable electronics, this paper presents a new method of inductor-less switched-capacitor (SC) based DC-DC converter designed to produce two simultaneous boost and buck outputs by using a 4-phases logic switch mode regulation. While the existing SC converters missing their reconfigurability during needed spontaneous multi-outputs at the load ends, this work overcomes this limitation by being able to reconfigure higher gain mode at dual outputs. From an input voltage of 2.5 V, the proposed converter achieves step-up and step-down voltage conversions of 3.74 V and 1.233 V for Normal mode, and 4.872 V and 2.48 V for High mode, with the ripple variation of 20–60 mV. The proposed converter has been designed in a standard 0.35 μm CMOS technology and with conversion efficiencies up to 97–98% is in agreement with state-of-the-art SC converter designs. It produces the maximum load currents of 0.21 mA and 0.37 mA for Normal and High modes respectively. Due to the flexible gain accessibility and fast response time with only two clock cycles required for steady state outputs, this converter can be applicable for multi-function wearable devices, comprised of various integrated electronic modules

Morphing Switched-Capacitor Converters with Variable Conversion Ratio

High-voltage-gain and wide-input-range dc-dc converters are widely used in various electronics and industrial products such as portable devices, telecommunication, automotive, and aerospace systems. The two-stage converter is a widely adopted architecture for such applications, and it is proven to have a higher efficiency as compared with that of the single-stage converter. This paper presents a modular-cell-based morphing switched-capacitor (SC) converter for application as a front-end converter of the two-stage converter. The conversion ratio of this converter is flexible and variable and can be freely extended by increasing more SC modules. The varying conversion ratio is achieved through the morphing of the converter's structure corresponding to the amplitude of the input voltage. This converter is light and compact, and is highly efficient over a very wide range of input voltage and load conditions. Experimental work on a 25-W, 6-30-V input, 3.5-8.5-V output prototype, is performed. For a single SC module, the efficiency over the entire input voltage range is higher than 98%. Applied into the two-stage converter, the overall efficiency achievable over the entire operating range is 80% including the driver's loss