Fault Current Limiter With Large Capacity Based On Flux Compensation

Nowadays, fault current is increasing with the increasing of capacity in power system, and it is one of the serious problems, which must be solved. The thesis analyze the disadvantages and advantages of all kinds of fault current limiters after referring to strategies of fault current limiters all the world. Connected with technology of digital processing and power electronics, the new strategy, fault current limiters with large capacity based on flux compensation, is proposed in this thesis, at the same time, author introduced the working principle and characteristics of the whole device in detail.A new type fault current limiter based on flux compensation is introduced in this thesis. According to the transformer's equivalent circuit, the value of the current injected to the transformer's secondary winding is controlled, so that the value of transformer impedance in power system can be controlled. When there is a large fault current in power system, the transformer will present a high impedance to limit the fault current. In order to solve a fault current limiter with large capacity, we structure the transformer with multiple compensation windings. Multiple PWM inverters are connected with the multiple secondary winding.After analyzing the working principle, the author designed the whole system including the software system and the hard system such as Transformer, Rectifier, PWM inverter, and so on. Every part of the device must be designed according to the actual working condition.In order to make the device operate effectively, it is the key to accurately follow the current in power system. After comparing the hysteresis current control and PWM control with constant frequency, the author proposed the PWM control with constant frequency. The result of Simulink is very satisfied, and the research of the FCL based on flux compensation will play a very important role in the development of power system in the future.