Browsing by Author "Mesut Baran, Committee Member"

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Advanced Modulation, Control and Application for Multilevel Inverters
(2009-11-13) Liu, Yu; Alex Huang, Committee Chair; Hoon Hong, Committee Member; Subhashish Bhattacharya, Committee Member; Mesut Baran, Committee Member
LIU, YU. Advanced Modulation, Control and Application for Multilevel Inverters. (Under the direction of Alex Huang.) The purpose of the research has been to develop advanced modulation, control and application for multilevel inverters. A new series of modulations has been proposed to achieve minimal THD (Total Harmonic Distortion) for multilevel inverters. The first minimal THD modulation is a real-time algorithm used to calculate optimal values of switching angles for given DC voltages and a modulation index. The second one is an algorithm used to calculate optimal values of DC voltages and switching angles for a given modulation index. The third one used an algorithm to calculate optimal values of DC voltages, switching angles and a modulation index. Another new optimal combination modulation strategy has been proposed for the 10 MVA 5-level cascade multilevel inverter based STATCOM (Static Synchronous Compensator) system. In this thesis, I also proposed several advanced controls for cascade multilevel inverters to be used in STATCOM applications. A new feedback control strategy for balancing individual DC capacitor voltages is proposed. The key part of the control strategy is a compensator used to cancel the variable parts in the model. I have also proposed the solutions for enhancing ride-through capability of the STATCOM during faults conditions.
Design and Control of a Cascaded H-Bridge Converter based Solid State Transformer (SST).
(2010-08-06) Zhao, Tiefu; Alex Huang, Committee Chair; Mo-Yuen Chow, Committee Member; Mesut Baran, Committee Member; Subhashish Bhattacharya, Committee Member; Fen Wu, Committee Member
Design and Control of Distributed Power Flow Controller
(2010-04-22) Song, Wenchao; Alex Huang, Committee Chair; Subhashish Bhattacharya, Committee Member; Mesut Baran, Committee Member; Fen Wu, Committee Member
Electricity is the one important energy form used in industrial, commercial, and residential areas. The power transmission system is essential for the power utility system to transmit electricity. Now the transmission lines in the modern interconnected power system are heavily loaded to meet the growing demands. The aggregate demand for electricity has grown by about 25% over the last decade and is expected to grow no less than 20% for the next decade. At the same time, however, the annual investment in transmission facilities has declined, leading directly to severe power congestion in the transmission lines. Construction of new transmission facilities could alleviate congestions, but it is cost-prohibitive and time-consuming. The way of using passive components and Flexible AC Transmission System (FACTS) to manage the power flow on transmission lines is efficient but not very effective. While low-cost ($15â€“25 per kVar as for static capacitors) and easy-to-use, passive components are inadaptable and slow for control purpose. The FACTS devices can control the power flow on transmission lines with flexible control and fast response through the use of large power converters (10-300 MW), but high expenses, typically exceeding $100 per kVA, together with reliability concerns constitute substantial obstacles for the widespread application of FACTS. Recently ETO Light modular voltage source converter (VSC) has been developed. It has lower cost, higher reliability and high power density and can be completely housed in an enclosure without additional user intervention. Accordingly, ETO Light converter has the potential to widely spread the use of the modular voltage source converter in FACTS applications and other high power industry applications. This dissertation introduces a new concept of distributed power flow controller (DPFC) based on the development of ETO Light converter. Unlike the conventional lumped high rating (10-300MVA) series compensation converter, the proposed distributed power flow controller uses multiple scaled-down (1-2MVA) single-phase power converters to dynamically control the impedance of the power transmission line, thus control the active power flow. The power density is enhanced and the cost is reduced by applying the ETO Light converter. The distributed power flow controller has the self-power, self-protection and self-control functions. It only accepts the command from external system level controller, and then injects compensating voltage to control the current and active power flow through the power transmission line. The standard modular design of DPFC enables the high reliability, short design cycle and the easy installation/maintenance of power converter. This dissertation demonstrates the principles of the modular distributed power flow controller based on the ETO light converter. The modeling and controller design are proposed and verified by the simulation and experimental results. The applications in the transmission system, distribution system and demand side management are proposed and verified by simulation. The fault tolerant design for DPFC are discussed and presented and verified by the simulation and experimental results. The research work for the design and control of DPFC sheds the light for the practical intelligent and distributed high power converter applications in the power grid.
Design Considerations of High Voltage and High Frequency Transformer for Solid State Transformer Application
(2009-08-28) Baek, Seunghun; Mesut Baran, Committee Member; Alex Huang, Committee Member; Subhashish Bhattacharya, Committee Chair
Design, Control and Characteristics of Multilevel Active NPC Converters for High Power Applications.
(2010-08-31) Li, Jun; Alex Huang, Committee Chair; Subhashish Bhattacharya, Committee Chair; Srdjan Lukic, Committee Member; Mesut Baran, Committee Member; Peng Ning, Committee Member
Distributed Modular Controller Architecture for High Power Converter Applications
(2005-12-28) Liu, Wei; Alex Q. Huang, Committee Chair; Mesut Baran, Committee Member; Maysam Ghovanloo, Committee Member
Modular converter is of particular interest in high power applications in order to achieve higher level of flexibility, expandability and reliability. Power electronics building block(PEBB) and H-bridge building block(HBBB) are typical modular blocks proposed for this applications. However, for converters based on the modular converter concept, the conventional controller is still not modular. The controller typically only has one single central control unit. The central controller has direct connections with each modular converter. When the controller and the power converters are placed close to each other, there will not be problem to do so despite a lot of wire connections. For high voltage and power rating converters, it is true that the power converters will consist of many modular blocks and these blocks will be placed at some distance from the controller. In this case, digital switch signals must be sent to the converters via optical fiber to improve reliability. However, the required fiber connections are too many that increase the risk of fault. Moreover, the analog signals from the sensors such as the voltage and current are usually sending back to the central controller through analog wire connections that has low electromagnetic interference (EMI) susceptibility. To solve the problems mentioned above for a high power converter system that may have multiple modular converter units, a modular controller architecture is needed and this concept is starting to be accepted specially if the system is constructed with modular converters. In this thesis, the proposed modular controller architecture includes a central controller and distributed local controllers. Each modular converter is accompanying with a local controller. The central controller performs the main control loop calculation and then sends the control commands to the local controllers. The central controller and the local controllers are communicated based on defined protocol via optical fibers. Then, the local controllers decode the command and generate the gate signals to the converter. Also, the local controllers have the function to convert analog information to digital such as voltages and currents and then feed back them to the central controller via optical fibers. The communication between the central controller and each local controller requires only two optical fibers. This largely increases the system reliability and also the flexibility to expand the system to higher power rating.
Investigation of High Temperature Operation Emitter Turn Off Thyristor (ETO) and Electro Thermal Design of Heatpipe Based High Power Voltage Source Converter Using ETO
(2006-08-21) Tewari, Karan; Mesut Baran, Committee Member; Alex Q Huang, Committee Chair; Subhashish Bhattacharya, Committee Co-Chair
The Emitter Turn Off Thyristor (ETO) is an emerging high power device that can be considered as a Mosfet-GTO hybrid. It is very suitable for high power applications due to many of its significant advantages in terms of usability and performance benefits. It combines the advantages of simplified control and improved switching performance. This thesis is focused on firstly investigating the loss characteristics of the ETO with variation in operating junction temperature. The switching loss, leakage loss and conduction loss of the ETO are recorded as a function of junction temperature in order to gain a better understanding of the thermal performance. Switching loss and conduction loss are found to have a linear dependence on temperature, whereas leakage loss is dependent exponentially on junction temperature. An effort is made in order to understand what limits the operation of semiconductor devices beyond a certain temperature limit. All this is then combined to develop a closed loop thermal model which is used to study the thermal stability. Thermal instability at high temperatures is caused primarily by the large leakage current, which rises exponentially with rise in temperature. Thermal stability can be maintained as long as the change rate of losses remains low enough such that the losses can be carried out of the switching junction of the device by means of the thermal conductance. This condition and the loss characteristics were used to predict the high temperature operating limit of the ETO. It is seen that due to the excellent loss characteristics of the device and due to the low thermal resistance from the junction to ambient, that the ETO should be capable of operating at temperatures well above 160 Degrees Celsius. Tests are done on the ETO in order to corroborate this theory and calculations Multilevel converters have become an important technology in high-power applications, especially for Flexible AC transmission system (FACTS) applications. In this thesis, a high power (megawatt range) modular Voltage Source Converter (VSC), using the newly developed Emitter turn-off (ETO) Thyristor, is proposed and a design methodology is developed for the various parameters of such a system. One of the main constraints in the design of such a system is essentially the design of the cooling system to carry the large heat generated by the various components such as switches, diodes and passives. Heat pipe based cooling system is very attractive for very high power applications. The hardware configuration, thermal calculation as well as component selection and design are presented in this thesis. Based on the electrical configuration of the new VSC, loss calculations are done for Statcom operation under different operation modes for components such as ETO and diodes, and the heat removal capability that is required from the heat pipes is determined. 3D Finite Element simulations are done on ANSYS software to understand the working and the selection of heat pipes. Electro-thermal simulations are done using thermal resistances of various components of the VSC including the thermal resistance of heat pipes obtained from tests.
Transient Performance Improvement Circuit (TPIC)s for DC-DC Converter Applications.
(2010-04-29) Keun Lim, Sung; Alex Huang, Committee Chair; Subhashish Bhattacharya, Committee Member; Tamara Young, Committee Member; Mesut Baran, Committee Member; Srdjan Lukic, Committee Member