Measurement And Calculation Of Magnetization Properties Of Electrical Steel Under Interharmonics Excitation

Electrical power systems quality has always been one of the important research topics in power system.With the application of UHV DC transmission and Flexible Alternating Current Transmission Systems(FACTS),the massive construction of wind turbines and the extensively use of power electronics in coal and other industrial sectors,the problem of interharmonics in power system is paid more and more attention by researchers.On the basis of fully study of the generation mechanism of interharmonic,the interharmonic frequencies generated by each interharmonic source and the measurement method of magnetic material properties,the loss and magnetization characteristics of electrical steel sheets and laminated core under interharmonic excitation are systematically studied.Based on the improved circuit-magnetic circuit coupling model,the exciting currents of electrical steel sheets under interharmonics condition are calculated and analyzed.(1)Based on the national standard GB/T 3655-2008,an electric steel measurement platform which can produce arbitrary waveform excitation is built.The amplitude and frequency of each component in the excitation can be controlled,which provides the foundation for the research.The magnetic characteristics,loss characteristics and excitation characteristics of electrical steel sheets under different interharmonic excitation were experimentally studied based on the platform.The effects of interharmonic frequency and amplitude on the magnetization and loss characteristics of electrical steel sheet are researched.(2)In order to study the effect of interharmonics on the actual transformers,a laminated core model was designed and manufactured according to the standard process of the actual transformer core.The magnetic characteristics and loss characteristics of laminated core under interharmonic excitation are analyzed and contrasted with steel sheets.(3)A new equivalent model of single-phase transformer considering hysteresis is proposed.The calculation results of Epstein frame under sinusoidal excitation agree well with the experimental results,which prove the accuracy of the calculation model.Compared with the existing simulation methods,this model improves the calculation speed and accuracy.Finally,the excitation current of Epstein frame under interharmonic excitation is simulated.