Translated Abstract
With the rapid development of the society in recent years, the structure and characteristics of the power system has changed dramatically. Due to the single function and other obvious deficiencies, which can’t meet the demands of the power system, Solid State Transformer (SST) emerges at the moment. Solid State Transformer (SST) is a new type of power electronic device. Besides traditional functions of power transformers, SST has following advantages, including reduction of volume and weight of the device, and it is also friendly to the environment; It can regulate the primary and secondary voltage with high degree of controllability; It can also provide DC interface for distributed generation technology and DC load. With the advantages above, SST can solve many problems of the power system.
Firstly, this thesis introduced the research background, SST working principle, development history and current research situation of SST, then classify SST structure into several topologies according to the different times of power conversion, and analyzed the advantages and disadvantages of different topological structure. Secondly, this thesis analyzes the key part of the SST sub-module of the main circuit--High Frequency Isolated DC/DC converter and DC/AC converter. furthermore analysis of the DAB circuit working principle and its realization of soft switching conditions is discussed,so is the analysis of the working principle of the DC/AC converter. In addition, according to the design index of the system, design of 1MW 10kV module cascaded SST is proposed. Design of DAB circuit based SiC MOSFET and full bridge Inverter circuit based IGBT including components selection and loss calculation are also given. MATLAB/Simulink software is used to do the simulation study of SST sub-module circuit. Then, according to the requirements of SiC MOSFET and IGBT device characteristics, a drive circuit is designed respectively for SiC MOSFET and IGBT.
At the end of this thesis, a input DC voltage 820V, power 27.78kW, DAB switch frequency 20kHz, inverter switch frequency of 450Hz SST sub module experiment platform is built to test the circuit basic functions and rationality of the circuit design. At the same time, the efficiency curve of different power is measured by the power analyzer, and the requirement of design index is achieved. The maximum efficiency can reach 97.6%.
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