Többcsatornás Intelligens Villamos Energia Konvertáló Rendszerek = Multichannel Intelligent Electrical Energy Conversion Systems

Új, jövőbeli intelligens lakossági villamos elosztó rendszerre dolgoztunk ki javaslatot. A sokcsatornás egyen-egyen konverterek alkották az architektúra alapvető építő elemeit. Az újonnan fejlesztett ágens alapú, elosztott irányítás lehetővé tette az optimalizált teljesítmény áramlást a bemenő és a kimenő oldal között a konverter cellák ismétlődő be ill. kikapcsolásával. Ez egyrészt az átalakító rendszer hatásfokának javulását másrészt pedig a megbízhatóság javulását eredményezte. A konverter egységeknél kéthurkú, áram-feszültség szabályozást alkalmaztunk. A fogyasztói ágensek folyamatosan információt szolgáltattak a terhelés számára szükséges feszültségről és áramerősségről. Az intelligens ágenseket a gyakorlatban beágyazott szoftver algoritmusokat futtató mikrokontrollerekben valósítottuk meg. A rendszer megbízhatóságára és robusztusságára helyezve a hangsúlyt a működést és a párhuzamos konverterek decentralizált irányítását különböző meghibásodási eshetőségek figyelembe vételével vizsgáltuk. Sikerült olyan megoldást találni, amely a rendszer hatásfokát úgy növelte, hogy közben a megbízhatóság is javult. A számítógépes szimulációk és a laboratóriumi mérések megerősítették az elméleti eredményeket. | A new, future intelligent residential electrical distribution system was proposed. The multichannel dc-dc converters constituted the main building blocks of the architecture. The newly developed agent based, distributed control facilitated the optimized power-flow between the input and output side by recurring turn on and off converter cells. This resulted in increased overall efficiency as well as in improved reliability of the conversion system. Within the converter units double loop current-voltage control was applied. The consumer agents provided information continuously about the required voltage and current for the load. The intelligent agents were practically implemented by microcontrollers, running embedded software algorithms. Considering the system reliability and robustness the operation and decentralized control of parallel dc-dc converters working under faulty conditions were also investigated. The efficiency of the system could be increased while the system reliability was also improved. Computer simulations and laboratory tests confirmed the viability of the theoretical results

High frequency inverter-transformer-cycloconverter system for DC to AC (3-phase) power conversion

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.This thesis is concerned with a 3-phase multistage high frequency link DC to AC power conversion with a novel inverter-cycloconverter circuitry. The conversion system is composed of a high frequency PWM inverter, step-up high frequency transformer and cycloconverter with bidirectional switching devices. In first stage the DC voltage of the power source , say a submarine battery, is inverted to a system of 3-phase sinusoidally modulated I kHz alternative wave forms. For this purpose a suggested optimized PWM technique for 3-phase inverter operation is adopted, in which harmonic components up to 17 th ( 17 kHz) are eliminated from the inverter output voltages. In the second stage, for DC input isolation from AC output and also for a voltage transformation ( here stepping-up )a high frequency ( size reduced ) transformer is employed. Generalized high frequency operation, influence and side effects of the transformer on overall system design & performance is investigated. In the final stage the 1 kHz -to- 50 Hz conversion process is accomplished by a 3-phase cycloconverter. The proposed "nonlinear modulation strategy" for cycloconverter output voltage and associated harmonic analysis is demonstrated, in which the harmonic components up to 38th (1.9 kHz ) are eliminated from the conversion system output voltage. To assess the suggested functioning principles for the inverter & cycloconverter , the prototype conversion system was developed. Some design criteria and switching device selection are presented, together with different voltage & current wave forms of the prototype system under resistive & inductive load (induction motor) and their respective spectra

Space vector pulse-width modulation for multilevel inverters and solution to modulation dependent problems

Ph.DDOCTOR OF PHILOSOPH

Design of a static frequency converter suitable for aircraft power systems

Aircraft electrical systems use a three-phase, 400 HZ, AC Bus supplied by engine driven generators. In an effort to simplify and improve the production of AC power for aircraft and to eliminate the need for hydromechanical constant-speed drive (CSD), a number of systems have been devised for producing 400 HZ three-phase electric power using electronic circuitry. This has been made possible by some of the major advances in solid-state technology developed in recent years. One of these systems is a DC-Link converter, which has a variable input frequency but a constant output frequency. This offer a viable alternative to the CSD as means of providing a constant frequency power supply from an aircraft generator. The ease of replacement and repair, the reduction in servicing needs, and the ability to locate the components of the electrical systems through the aircraft all combine to bring about a considerable reduction in the maintenance time required. This thesis discusses aircraft generating systems, variable speed constant frequency systems (VSCF) and the principle of the static frequency converter. The operation and design of a 1 KVA three-phase PWM inverter and its associated control circuitry to produce 400 HZ AC is described in detail. Finally a design of a power harmonic filter is given

Iron losses in non-oriented steel subjected to matrix and DC-link converter supply : an experimental and analytical study on variable speed drives

A system approach to variable speed drives consisting of two low voltage induction motors (Y and A connection) fed by matrix and two-level DC-link converters is developed (chapter 7). The ratio of iron to copper winding losses is studied based on the induction motor equivalent circuit and constant V/f converter control. Electrical efficiency increased by up to 10% (partial load and low speed) in Y-connected motors fed by the matrix converter. While similar values of efficiency were observed in A-configured motors, up to 8% higher output power is extracted from the machines under two-level DC-link converter supply.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Modulation and Control Techniques for Performance Improvement of Micro Grid Tie Inverters

The concept of microgrids is a new building block of smart grid that acts as a single controllable entity which allows reliable interconnection of distributed energy resources and loads and provides alternative way of their integration into power system. Due to its specifics, microgrids require different control strategies and dynamics of regulation as compared to ones used in conventional utility grids. All types of power converters used in microgrid share commonalities which potentially affect high frequency modes of microgrid in same manner. There are numerous unique design requirements imposed on microgrid tie inverters, which are dictated by the nature of the microgrid system and bring major challenges that are reviewed and further analyzed in this work. This work introduces, performs a detailed study on, and implements nonconventional control and modulation techniques leading to performance improvement of microgrid tie inverters in respect to aforementioned challenges