Magnetization Curve Fitting And Application Of Magnetic-valve Controllable Reactor

With the continuous improvement of voltage grade, the demand of power grid for reactive power is increasing gradually. Magnetic-valve controllable reactor(MCR) is a kind of electromagnetic equipment which can control the saturation of magnetic valve to output reactive power, and it has a great application future because of a series of advantages, such as wide application range, low maintenance cost, smooth adjustment reactive power. Magnetization characteristic is the basis of theoretical research and engineering design for all electromagnetic equipments, so it plays an important role in MCR. However, the appearance of magnetic valve changes structure of the iron core, which makes the solving steps of magnetization characteristic of MCR become fitting magnetization curve of the ferromagnetic material at first, and then deducing formulas according to shape function of the magnetic valve. And in order to reduce the harmonic, scholars have studied the magnetic valve with different shapes in recent years. So the thesis proposes fitting functions which are suitable for deducing the magnetization characteristic Firstly, and then magnetization characteristics are solved based on MCR with different magnetic valves, current characteristics are analyzed using the magnetization characteristics at last. The specific research process is as follows:Firstly, the working principle of MCR is explained from the aspect of DC excitation changing magnetic permeability, and the equivalent circuit is gotten by analyzing the working process in detail. In order to verify the correctness of theoretical analysis, the simulation model is constructed based on the equivalent circuit in MATLAB and the working current is analyzed by an example.Secondly, the general formulas of magnetization characteristic of MCR are gotten by equivalent section of the iron core, and the ideal small slope which is a most simple fitting function of magnetization curve of the ferromagnetic material is applied to solving magnetization characteristics of MCR with different magnetic valves. Then the effective values or mean value and instantaneous expressions of working current, control current and winding currents are deduced based on the magnetization characteristics, which provide a calculation method for the application of different fitting functions.Furthermore, the fitting methods and achieving tools for magnetization curve are analyzed, and fitting effects of the existing fitting functions are compared from approximation level and residual error. At the same time, logarithmic fitting function which has high fitting precision is proposed by observation and analysis. Two fitting functions are proposed according to structure and work attributes of MCR, and they are compared with the ideal small slope fitting function to illustrate the necessity of extended research.Finally, the two fitting functions proposed are applied to solving magnetization characteristics of single-stage MCR and two-stage MCR. Then current characteristics are analyzed based on the two magnetization characteristics of single-stage MCR and are compared with the ideal small slope fitting function, the results show that the current characteristics based on the fitting functions proposed are more in line with the actual operation of MCR.