Control and Design of a High voltage Solid State Transformer and its Integration with Renewable Energy Resources and Microgrid System by Xu She -Faculty of North Carolina State University

Control and Design of a High voltage Solid State Transformer and its Integration with Renewable Energy Resources and Microgrid System

by Xu She

 A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Electric Engineering-2013 

 BIOGRAPHY Xu She was born in Hunan, China. He received the B.S. degree in electrical engineering (major) and B.A. degree in English (minor), with honor from Huazhong University of Science and Technology, China, in 2007. He received his M.S. degree majored in power electronics and motor drive with honor from the same university in 2009. He started to pursue his Ph.D. degree in North Carolina State University in 2009. From August 2009 to July 2010, he has been working on the modeling of the green energy hub and DC microgrid project. Since August 2010, he has been working on the solid state transformer project. He was the team leader of Solid State Transformer (SST) group and Medium Voltage DC (MVDC) transmission group at Future Renewable Electric Energy Delivery and Management (FREEDM) Systems Center. From May to August 2012, he was an intern with high power conversion systems laboratory at GE global research center, US, conducting research on next generation high voltage dc transmission (HVDC) system. His research interests are high power/voltage converters and their industrial applications, and renewable energy resources integration. His role in the first job will be a research engineer (lead professional career band) in high power conversion systems laboratory at GE global research center.

 Chapter

 1 Introduction

1.1 The distribution transformer 1.1.1 Introduction of the distribution transformer Power generation, transmission, and distribution are the three main constituents of the modern power system, in which the transformer plays a most critical role [1]. Transformers enable high efficiency and long distance power transmission by boosting the voltage to a higher one in the generation side with the so called power transformer. In the distribution system side, this high voltage is stepped down for industrial, commercial, and residential use with the so called distribution transformer. The distribution transformer provides final voltage transformation to the end users in the distribution system, which usually with voltage level less than 34.5kV at high voltage side. At the low voltage side, 120/240V split single phase system and 480V three phase systems are usually adopted in the US. The distribution transformer can be classified from different perspective of view. According to the phase number, it can be classified into three phase transformer and single phase transformer. According to the installation method, it can be classified into pole mounted transformer and pad mounted transformer. The pad mounted transformers are installed for the distribution system with lines located at ground level or underground. While the pole mounted transformers are mounted on a utility pole. According to the insulation medium, it can be classified into liquid-immersed transformer and dry type transformer. The distribution transformers are widely used in various applications, such as renewable energy resources integration, high power charge station, traction system, reactive power compensator, active power filter, and etc., as shown in Figure 1-1[2][3]. It functions as a passive interface between the distribution system and the low voltage loads/sources. Therefore, the voltage quality of the grid cannot be guaranteed if no additionally devices are installed.

LINK:
https://repository.lib.ncsu.edu/bitstream/handle/1840.16/9027/etd.pdf?sequence=1&isAllowed=y