Design and Control of Distributed Power Flow Controller

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Title: Design and Control of Distributed Power Flow Controller
Author: Song, Wenchao
Advisors: Alex Huang, Committee Chair
Subhashish Bhattacharya, Committee Member
Mesut Baran, Committee Member
Fen Wu, Committee Member
Abstract: 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 ($15–25 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.
Date: 2010-04-22
Degree: PhD
Discipline: Electrical Engineering

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