Electromagnetic Analysis Of Controllable Reactor Of Transformer Type Based On FEM

CRT(Controllable Reactor of Transformer Type) is a novel controllable reactor, whichcan adjust a wide range of inductive reactive power output quickly and smoothly, and canreduce the harmonic to the required level by set a reasonable power-step number. These adva-ntages make it to meet the requirements of compensating the reactive power and controllingvoltage stability of grid. Therefore, there are a growing number of domestic and foreign scho-lars who have carried out in-depth research with CRT.In this thesis, CRT is considered as the main object of study. Some basic theoreticalissues of CRT are analyzed in the research, such as equivalent circuit of CRT, operatingcharacteristics, harmonic analysis and calculation of power-step number. The electromagneticfield distribution and the core flux distribution of CRT are analyzed by means of FEM(finiteelement method). In this way the current of control winding when CRT running at rated loadis obtained. The impedance parameters of CRT are also calculated. This study providespractical information for structure optimize of the CRT and a more in-depth study on thefollow-up.The first part introduces the basic working principle of CRT. The polygon equivalentcircuit model, the keystone equivalent circuit model and the ray-shaped equivalent circuitmodel of CRT are established according to its structure. This part also analyzes the harmoniccharacteristics, the control characteristics, active consumption and response time of CRT. Therelationship between harmonic coefficients and power-step number and the expression ofcontrol characteristic (relationship between thyristor firing angle and current) is obtained.Then the calculation method of active consumption is given. Finally, the transition process ofCRT is analyzed by using matlab simulation. Through the analysis of these properties of CRT,the conclusion is draw that there are many advantages of CRT for the small harmonic and thefast response. Thus, a comprehensive understanding of CRT is obtained.Since the power-step number of CRT is closely linked to the harmonic, the second partanalyzes the harmonic of CRT in depth. According to the standard of harmonic, three kinds ofdefinitions of harmonic coefficient are given. According to the three definitions the relationalexpressions of the relationship between harmonic coefficient and their power-step number arederived. The results of numerical examples are compared and analyzed which show that underthe premise of meeting the harmonic current limiting requirements, the calculation method inthe existing literature of harmonic calculation of CRT leads to too many power-step number.For this reason we use the new method to reduce the power-step number of CRT from five totwo. This method can greatly simplify the structure and control of CRT, and also can reducethe cost of manufacturing. The third part describes the general method of FEM for calculating the electromagneticfield. The finite element mathematical model of CRT is given. This chapter introduces theANSYS finite element software and its usage in electromagnetic field analysis in two-dime-nsion. The use method and general steps of finite element analysis is also described. Finally,the analysis steps of field circuit coupled method used in the electromagnetic field distributionof CRT are introduced.The forth part uses ANSYS as the simulation platform which establishes the solid modelof6winding CRT by using the field circuit coupled FEM. The harmonic magnetic field ofCRT is analyzed. The results show that at rated load, the magnetic field of CRT mainlydistributes between working winding and control winding and their respective amount ofspace. There is almost no flux passing through the core. On this basis, we use ANSYSpostprocessing function to get the flux passing through the core and windings, so the currentdistribution of each control winding is also obtained. Finally, the principle of the magneticenergy method for inductance calculation is introduced. According to the magnetic energymethod, the mut-ual impedance matrix and short circuit impedance matrix of CRT arecalculated by using APDL language.