The Study Of Transformer Saturation Model For Electro Magnetic Transient Simulation

"Electric power is the vanguard of economic development", powerful electric power industry is an important guarantee of the rapid development of China'market economy. With the implementation of national network, the requirements on the power network's safe and stable operation are increasing. Transformation link of power network operation is accomplished mainly by the transformer. Therefore the operation state of transformers directly affects the reliability of the power network. So the study of the transient simulation of transformers has important significance.Numerical simulation for power system is an important research and analysis method for the power system development and practical operation. With fast development of power system, higher requirements are set for system simulation. It is one of the hot topics to study and develop system simulators with higher precision and fast calculation speed.The content of the thesis focuses on the study of the transformer electromagnetic transient simulation. The contribution of the thesis is listed as follows: First of all, the principle and properties of transformers are thoroughly explored. On the basis of that, the classical model and the unified magnetic equivalent circuit model of transformers are summarized and derived. The classical model is divided into ideal transformer model and the model basing on controlled source principle. The unified magnetic equivalent circuit model is divided into the magnetic equivalent circuit model basing on the electric circuit principle and UMEC model.Secondly, on the basis of the above model, the transformer saturation properties are studied in detail. When the transformer encounters the transient conditions such as no-load closing and short circuit fault, the saturation may occur. This paper presents the model considering on permeance non-linear. The idea is piecewise linear of no-load test curve combined with UMEC. The UMEC model is used to expressed the relationship and interaction of transformer internal each part. Piecewise linear of no-load test curve is used to simulate approximately the transformer magnetic circuit saturation. This model makes full use of the advantages of the UMEC model such as without the wingding turns, core cross-sectional area and length of iron core, the proportion relation of permeance of iron core and yoke. Meanwhile, the model overcomes the disadvantage of the piecewise linear method basing on the no-load test curve considering only the permeance nonlinear of excitation branch. Therefore, the model has higher precision.Finally, with the help of the object-oriented programming technology and Visual C++6.0, the transformer electromagnetic transient simulation software is developed. The transformer is placed at a system. The transformer electromagnetic transient simulation software is designed and implemented. The components of power network are designed as different categories in accordance with their respective abstract characteristics, and each component treated as a concrete example of the corresponding category, including: transformer class, power class, load class, etc. This makes the structure of system clear and concise; meanwhile, maintaining and expansion for the system are very convenient, such as: just only compiling the components related to the specific model classes finishes the adding of the new types of components.The results of the example demonstrate the correctness and effectness of the system developed. The achievement gained of the thesis lays a solid foundation for the further research and developing of transformer electromagnetic transient simulation of power system.