Numerical Simulation And Verification Of Stray-Field Loss Of Transformer Structure Under Magnetic Bias And Harmonic Excitation

Due to the rapid development and wide application of High-Voltage Direct Current transmission system in China,the transmission and transformation equipment in the power system often works under magnetic bias and harmonic excitation.As the key electrical equipment in the system,the loss distribution of the transformer is one of the most important concerns in the design process,and the hybrid excitation of the magnetic bias and harmonics aggravates the irrationality of the leakage magnetic field and stray-field loss distribution of the transformer.As a result,the risk of partial overheating and operation failure of the equipment also increases,and the research on the loss of the structural parts is facing more severe challenges.Studying the distribution of magnetic field and loss in transformer structural components under the conditions of magnetic bias and harmonic excitation,effective measures can be taken during the design of the transformer to reduce the stray-field losses,which has important theoretical value for the safe and stable operation of the power grid,product design and structural optimization of the transformer.Funded by the National Natural Science Foundation of China(51 777073)and the National Key Research and Development Program(2017YFB0902703),this paper is based on the TEAM P21 benchmark model in-depth numerical simulation and analysis of the stray-field loss of structural parts in the transformer under the conditions of bias and harmonic excitation.Experimental verification method.Considering the difference of the eddy current loss of the coil under no-load and load conditions,an improved method for determining the stray-field loss of structural parts based on experiments is proposed.Build a silicon steel laminated magnetic and loss characteristic measurement system,propose a core loss model that can consider the influence of the bias magnetic field,and use it to calculate the stray-field loss of laminated magnetic components under the excitation of a three-dimensional leakage magnetic field.With the help of simulation and experimental results of magnetic field and loss,the effectiveness of the method in this paper is verified.Based on the simulation and measurement results,the influence of the DC bias magnetic field on the stray-field loss is analyzed,and the distribution of the additional loss in the laminated magnetic conductive member under AC and DC hybrid excitation and its influence on the stray-field loss are obtained.Based on engineering requirements,the benchmark model is upgraded and improved,and the influence of excitation frequency on the conductivity of the material is analyzed through the measurement and calculation results.Finally,the upgraded model is used to in-depth study the change law of the leakage magnetic field and loss of the copper plate under the action of magnetic bias and harmonics.