Modeling, Analysis and Control of Hexagram Inverter for Three- Phase Induction Motor Drive

This paper presents the modeling, analysis and control of Hexagram inverter for three phase induction motor drive configuration. The Hexagram inverter can be used for both three phase and six phase applications. It has many advantages including reduced number of switches, modular structure leading to easy construction and maintenance, isolated dc buses. Besides, it has built-in fault redundancy due to the module interconnection. It has lowered dc energy storage requirement compared to that of cascaded H-bridge inverter. This eminent feature makes the system in high power applications. A simulation model of the Hexagram inverter fed three phase induction motor drive is developed in Matlab/Simulink environment. Simulation is carried out to study the drive performance at different operating conditions and the results are presented. Keywords: closed loop control, fault tolerant feature, hexagram inverter, three phase induction motor driv

Cascaded Converters For Integration And Management Of Grid Level Energy Storage Systems

ABSTRACT CASCADED CONVERTERS FOR INTEGRATION AND MANAGEMENT OF GRID-LEVEL ENERGY STORAGE SYSTEMS by ZUHAIR ALAAS December 2017 Advisor: Dr. Caisheng Wang Major: ELECTRICAL ENGINEERING Degree: Doctor of Philosophy This research work proposes two cascaded multilevel inverter structures for BESS. The gating and switching control of switching devices in both inverter typologies are done by using a phase-shifted PWM scheme. The first proposed isolated multilevel inverter is made up of three-phase six-switch inverter blocks with a reduced number of power components compared with traditional isolated CHB. The suggested isolated converter has only one battery string for three-phase system that can be used for high voltage and high power applications such as grid connected BESS and alternative energy systems. The isolated inverter enables dq frame based simple control and eliminates the issues of single-phase pulsating power, which can cause detrimental impacts on certain dc sources. Simulation studies have been carried out to compare the proposed isolated multi-level inverter with an H-bridge cascaded transformer inverter. The simulation results verified the performance of the isolated inverter. The second proposed topology is a Hierarchal Cascaded Multilevel Converter (HCMC) with phase to phase SOC balancing capability which also for high voltage and high power battery energy storage systems. The HCMC has a hybrid structure of half-bridge converters and H-bridge inverters and the voltage can be hierarchically cascaded to reach the desired value at the half-bridge and the H-bridge levels. The uniform SOC battery management is achieved by controlling the half-bridge converters that are connected to individual battery modules/cells. Simulation studies and experimental results have been carried on a large scale battery system under different operating conditions to verify the effectiveness of the proposed inverters. Moreover, this dissertation presents a new three-phase SOC equalizing circuit, called six-switch energy-level balancing circuit (SSBC), which can be used to realize uniform SOC operation for full utilization of the battery capacity in proposed HCMC or any CMI inverter while keeping balanced three-phase operation. A sinusoidal PWM modulation technique is used to control power transferring between phases. Simulation results have been carried out to verify the performance of the proposed SSBC circuit of uniform three-phase SOC balancing

Advances in Converter Control and Innovative Exploitation of Additional Degrees of Freedom for Multiphase Machines

Multiphase variable-speed drives and generation systems (systems with more than three phases) have become one of the mainstream research areas during the last decade. The main driving forces are the specific applications, predominantly related to the green agenda, such as electric and hybrid electric vehicles, locomotive traction, ship propulsion, ‘more-electric’ aircraft, remote offshore wind farms for electric energy generation, and general high-power industrial applications. As a result, produced body of significant work is substantial, making it impossible to review all the major developments in a single paper. This paper therefore surveys the recent progress in two specific areas associated with multiphase systems, namely power electronic supply control and innovative ways of using the additional degrees of freedom in multiphase machines for various non-traditional purposes

Enhanced decoupling current scheme with selective harmonic elimination pulse width modulation for cascaded multilevel inverter based static synchronous compensator

This dissertation is dedicated to a comprehensive study and performance analysis of the transformer-less Multilevel Cascaded H-bridge Inverter (MCHI) based STATic synchronous COMpensator (STATCOM). Among the shunt-connected Flexible AC Transmission System (FACTS) controllers, STATCOM has shown extensive feasibility and effectiveness in solving a wide range of power quality problems. By referring to the literature reviews, MCHI with separated DC capacitors is certainly the most versatile power inverter topology for STATCOM applications. However, due to the ill-defined transfer functions, complex control schemes and formulations were emerged to achieve a low-switching frequency high-bandwidth power control. As a result, adequate controller parameters were generally obtained by using trial and error method, which were practically ineffective and time-consuming. In this dissertation, the STATCOM is controlled to provide reactive power (VAR) compensation at the Point of Common Coupling (PCC) under different loading conditions. The goal of this work is to enhance the performance of the STATCOM with the associated proposed control scheme in achieving high dynamic response, improving transient performance, and producing high-quality output voltage waveform. To evaluate the superiority of the proposed control scheme, intensive simulation studies and numerous experiments are conducted accordingly, where a very good match between the simulation results and the experimental results is achieved in all cases and documented in this dissertation

Novel Single Phase Dc-Ac Inverter Topology With Enhanced Power Quality

Inverters are widely employed in many application such as photovoltaic (PV), uninterruptable power supply (UPS) etc for the conversion of direct current (DC) power to alternating current (AC) power. The key challenges in design and implementation of inverters are the realization of higher efficiency and good quality output power. To achieve these, this thesis presents a novel single phase DC-AC inverter topology with enhanced power quality. In this topology, a switch is connected at the lower arm of the full-bridge switches to control the output voltage across the full-bridge inverter. The switch at the lower arm of the full-bridge controls the output of full-bridge inverter by increasing or reducing the voltage level at the lower arm of the bridge. This switch of lower arm is controlled by a high frequency sinusoidal pulse width modulation (SPWM) switching signal. While the power switches of full-bridge inverter operate with square wave switching signal at a frequency of 50 Hz. The proposed topology produces a clean sinusoidal output waveform with low distortion and with minimum switching losses, thus yielding high quality output at high efficiency. Next, a random switching hybrid pulse width modulation (HPWM) inverter is developed in order to give a comparison between the proposed inverter and the random switching HPWM inverter. Both computer simulation and experiment were carried out to verify the performance of proposed topology. From the presented results, it is shown that proposed topology has superior performance compared to its conventional counterpart

Improving power transfer capability of SCIG based fixed speed WECS

Wind power generation is regarded as the most promising source of all renewable energy system. In this thesis, a concept to advance the knowledge in the possibility to improve the power transfer of the fixed speed Wind Energy Conversion System based on a Squirrel Cage Induction Generator is presented. The proposed system endeavour to increase power extracted from the wind energy system through the utilization of variable capacitors and tap changing transformer in tandem

An investigation of integrated woven electronic textiles (e-textiles) via design led processes

This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University LondonElectronic textiles (e­‐textiles) are created by the amalgamation of electronics and textiles, where electronics are integrated into or onto fabric substrates. Woven textiles are specifically considered in this thesis to integrate electronics into textiles' orthogonal architecture. This thesis investigates 'How can the weaving process be manipulated to make woven e-­textiles with integrated electronics?' The methodological approach taken is practice based research carried out via a technical materials approach and creative craft methods. An investigation of woven e-­textiles through design led practice and woven expertise is presented. Previously, woven e-­textiles have been investigated either via technical material approaches, (where the main emphasis remains on function) or via creative craft methods, (which emphasise experimental forms, manipulate integration methods and apply craft based knowledge). Both of these approaches have presented only limited investigation of unobtrusive integrated electronics in woven e-­textiles, and woven structures have not been fully utilised to support the integration. The research applies reflective practice through a design process model; this is based on the researcher's previous weaving expertise and designing methods. The work investigates how woven construction may be manipulated to develop novel integrated woven e-­textiles. It was found that five woven approaches were particularly of value for electronics integration. These were the use of double cloth, the integration of multiple functions into the textiles as part of the weaving, the use of complex weaving techniques to attach and integrate components, the use of inlay weft weaving and the manipulation of floats (free floating threads). The thesis makes original contributions to knowledge, including identification of key stages in the woven e-­textile design process, identification and application of advanced weaving techniques to facilitate integrated woven e-­textiles, and compilation of a systematic record of woven e-­‐textile techniques as a technical woven repository. Underpinning design principles that influence the developed e-­textile outcomes are identified. A range of woven e-­textile samples are designed and made. Three specific examples including an actuator ('RGB colour mixer'), a circuit ('corrugated pleat LED v2') and a soft module ('battery holder module v4'), are described in detail to illustrate their development using the e-­textile design process model. The knowledge gained has potential to be applied to industrial woven processes for e-­textiles.Brunel University EPSRC (DTA) bursar

Sistemas de conversão estatística aplicados em equipamentos com terminais a enrolamentos abertos ou em estrela.

Neste documento, s~ao propostas topologias de conversores que utilizam estruturas trifásicas, a três ou quatro fi os, alimentando equipamentos (motores ou transformadores) com terminais dispostos a enrolamentos abertos ou com conexão em estrela (Y ). Dentre os equipamentos mencionados tem-se: i) restaurador dinâmico de tensão (DVR), ii) ltro ativo de potência (APF) paralelo, iii) fi ltro ativo de potência (APF) série, iv) sistema de acionamento CA-CC-CA série/paralelo e v) sistema baseados em conversores com braços de dois e três-níveis. Para cada topologia estudada, são abordados os seguintes pontos: modelagem da con figuração, estratégias PWM, estratégia de controle. Também é realizado um estudo comparativo entre as topologias propostas e algumas convencionais, avaliando seus desempenhos atrav es de algumas guras de m erito as quais englobam distorções harmônicas das tensões e correntes, estimativa de perdas nos conversores e níveis de tensão no barramento CC. Resultados de simulação e experimentais são apresentados para fins de validação.This document reports studies on converter topologies applied in three-phase, four-wire or three-wire, systems feeding open-end winding (OEW) equipment or Wye-connected equipment. Such equipment are considered in this work as induction motors or transformers. The devices associated with these equipment are: i) dynamic voltage restorer (DVR), ii) Shunt Active Power Filter (Shunt-APF), iii) Series Active Power Filter (Series-FAP), iv) AC-DCAC series/parallel motor drive, v) Systems with converters based on two- and three-level leg connections. Each studied topology presents its con guration model, PWM strategy, control strategy. Comparative studies considering proposed and some conventional topologies are presented highlighting the harmonic distortion for the voltages and currents, semiconductor losses estimation, dc-link voltage ratings, etc. Simulation and Experimental results are presented for validation purposes. Keywords: Dynamic voltage restorer, shunt active power lter, series active power lter, ac-dc-ac motor drive system, series-connected conveters, parallel-connected converters, converters based on two- and three-level leg connections.Cape