| Magnetically-Saturated Controllable Reactor(MSCR)is an important electromagnetic equipment used for dynamic reactive power balance,voltage control and power quality improvement of power system.With more and more non-linear loads,impact loads and power fluctuations in the power supply access,which causes the grid reactive power and voltage fluctuations more and more frequent,so that the role of MSCR in stabilizing the grid voltage and regulating reactive power is more and more significant,and its modeling and calculation accuracy requirements are also higher and higher.Most of the existing MSCR models based on the magnetic circuit theory use the single value magnetization model,and the magnetic circuit topology ignores the influence of uneven flux distribution and magnetic flux leakage.This not only affects the study and development of MSCR,but also limits the overall level of power system simulation modeling.According to the complex and diverse structure of MSCR core,the core is in a large range of adjustable DC bias saturation nonlinear state,combined with the research status of core magnetization characteristics simulation and magnetic circuit topology determination,this dissertation focuses on the core nonlinear magnetization characteristics simulation,magnetic circuit topology division,magnetic circuit parameters determination and model solution.The main contents and achievements of this dissertation are as follows:(1)From the point of view of engineering application,this dissertation analyzes the influence of magnetic characteristics change caused by temperature change on the working current and magnetic saturation of MSCR,and analyzes the deviation between the calculated value and the measured value of hysteresis loop under different frequencies and magnitudes of magnetic density.The results show that the influence of temperature on the magnetization characteristics can be ignored,and the influence of the amplitude and frequency of the external excitation on the parameters of the magnetization characteristics model can be ignored.(2)In order to analyze the influence of hysteresis and eddy current effect on MSCR simulation results,a MSCR magnetization model considering core magnetic saturation,hysteresis and eddy current effect is proposed by combining dynamic J-A hysteresis model with MSCR equivalent core.By comparing with the results of MSCR magnetization model without considering hysteresis and eddy current effect,it is proved that it is necessary to take hysteresis and eddy current effect into account in MSCR modeling.(3)Based on the loss separation theory and the physical concept of resistance,the classical eddy current loss and abnormal eddy current loss are introduced into the hysteresis model of existing magnetic circuit section in the form of linear resistance and nonlinear resistance respectively,and an improved hysteresis equivalent model of iron core magnetic circuit section considering magnetic saturation,hysteresis and eddy current effect is proposed;At the same time,by defining the hysteresis loss coefficient,the hysteresis resistance calculation has a clear expression;In order to overcome the problem of large error in determining model parameters by engineering approximate calculation,a parameter determination method of step-by-step mixed mode is proposed by combining curve fitting with analytical calculation.The results show that the improved hysteresis equivalent model can significantly reduce the simulation error.Compared with the dynamic J-A hysteresis model from the aspects of calculation time,model structure and parameter determination,it shows the superiority and practicability of the improved core magnetic hysteresis model applied to the core magnetic circuit modeling.(4)Based on the segmented magnetic circuit method and the principle of flux tube,the equivalent magnetic circuit topology of core magnetic field is established,which is composed of uniform,corner and T-shaped magnetic sections;By combining the core magnetic circuit topology with the improved hysteresis equivalent model of core magnetic section,the equivalent models of three types of core magnetic section are established.Based on the magnetic field partition method and the principle of flux tube,the whole magnetic circuit topology of magnetic leakage field and the magnetic leakage topology of magnetic-valve are established,and the geometry and permeability calculation method of flux leakage tube are determined.Considering the frequency-dependent characteristics of winding resistance,the external circuit model of MSCR is established and coupled with magnetic circuit by gyrator.Although MSCR is taken as the research object in this dissertation,the magnetic circuit topology modeling method can be applied to the magnetic circuit and winding modeling of other electromagnetic equipment similar to MSCR.(5)In this dissertation,the trapezoidal method is used to discretize the external circuit,the magnetic circuit section and the magnetic leakage section of the core,The problem of large amount of calculation caused by nonlinear iteration is solved;Finally,the matrix equation of the electric-magnetic circuit model of MSCR is established by synthesizing the sub model into the total model.(6)Taking the MSCR prototype as an example,the modeling and solving method of the electric-magnetic circuit model is verified by comparing the calculated value of the electric-magnetic circuit model with the measured value and the calculated value of the 3D FEM.The results show that: the electric-magnetic circuit model can accurately simulate the changes of electric quantities such as current,reactive power and loss,and has the ability to analyze the magnetic field distribution and magnetic circuit parameter changes with less calculation time.It is also suitable for power system simulation analysis.This dissertation improves and perfects the MSCR modeling and simulation method based on magnetic circuit theory,and provides a new modeling and analysis method for electromagnetic equipment with similar structure to MSCR.It also provides support for improving power system simulation modeling method and optimizing power system network structure. |
