Research Of Converter Transformer Core Material And The DC Bias

With China`s economic development,increasing demand for electricity,therefor our unique distribution of energy and demand imbalance,these lead to the country`s power transmission characteristics. The long-distance, high-capacity transport energy has become an inevitable choice. HVDC features just to meet these requirements, so in the future`s development of electric power, HVDC will become a new favorite. However, the rapid development of HVDC has led to a series highlighting problem, which is important problem is exacerbated by the DC bias magnetic phenomena. In addition, domestic converter transformer manufacturing over-reliance on imported silicon material, this situation is not conductive to long-term development of China`s power industry.Aiming at the problems of DC bias, this paper has done the following research work:First of all, it is a systematic study about the transmission transformer core material used in the case to understand the basic history of the development of the core material. Largely there are three processes of low carbon steel, silicon steel, soft magnetic amorphous alloy materials in the use of the core material. Low carbon steel belongs to the magnetic material in early stage, it has not seen. At present, what is the most use of steel in power transformer is the orientation silicon steel.Secondly, aiming at the phenomenon of transformer magnetic bias in HVDC system, it studied the mechanism of DC bias, generated hazards and existing solutions. The phenomenon of DC magnetic bias is geo-magnetically induced current generated by the solar storms, or DC transmission caused by the unbalance current. With the DC bias, transformer works in a non-linear state, then the transformer`s magnetizing current will include DC component. The existence of this DC component will have a negative effect on the normal operation of the transformer, such as the exciting current distortion, increasing the transformer core loss, local overheating caused by saturation of the iron core height and so on. The proposed solution has, transformer neutral series resistance, capacitance, or a variable power supply.Again, for large domestic transformer manufacturers Tianwei companies and ±800KV converter station east of Guangzhou were a study tour, and thus the converter transformer manufacture and use have a more intuitive understanding more specific. Through research, the current domestic DC transmission line, only two converter transformer cores using domestically-oriented silicon steel, which runs in the Xiluodu converter stations. It used ANSYS simulation software to build two-dimensional electromagnetic field circuit coupled model in Xiluodu ±500KVconverter transformer as a prototype. It changed the size of the DC voltage to get the excitation current and the core loss of transformer DC magnetic bias analog DC magnetic bias changes.Finally, changing the parameters of the core material in the existing simulation model, is mainly aimed at the Wuhan Iron 27QG110, 23QG90 and Nippon Steel 23ZH90. There are getting the excitation current, core loss and core operating point of the curve in the same simulation model, the same DC bias at transformer of different core material.