Research On The Fault Analysis And Protection System Design Of Power Electronic Transformer

Electric power industry, as a basement of the global economic development, people have strong dependence on it because the driving functions in the industrial production and daily life. On the basis of the sustainable development of the global economy, the modern electric power industry goes forward to the direction of green and smart. Since the reform of energy structure recent years, the using rate of renewable energy in most countries in the world increasing and the concept of smart power grid gets promotion. The power transformer is the vital point of power system, it's development should comply with the times.Power Electronic Transformer (PET) is a new equipment which is in accordance with the trend of the smart grid. It combines power electric transformation with electromagnetic induction to convert the electrical energy. It is PET has many advantages such as small volume, light weight, environmental friendly etc. it has the function of voltage level conversion, electromagnetic isolation, and power transmission, and can also integrate and join up various distributed energy, adjust the quality of electric power to provide users with satisfied. In order to ensure the equipment and system functioning stable, it is necessary to design protection according to the characteristics of PET because of the differences of principle and structure of PET and traditional transformer.This paper first states the research background and the domestic and foreign development situation of power electronic transformer, makes a brief introduction of the basic principle and topology of PET and the applicable control strategy has selected. Then, according to the structure features of PET, the article analyzes the failure cause of main circuit and control system in PET, and choose the appropriate detect method to identify the fault. In order to deal with the fault of PET, this paper makes a verification of the feasibility of two redundant operation strategy by designing bridge arm redundancy strategy and bypass redundancy strategy and combined with simulation experiment. Also according to the operating environment of PET and combined with simulation model, this paper analyzed the influence of power grid fault in low and high voltage distribution network, including short circuit fault and open circuit fault to the PET. In the end, this paper designs a protection system according to the requirement of PET, and introduces applicable hardware protection circuit and software protection logic including voltage?current?temperature and humidity, and analyzed the operating strategy of PET.