Power Frequency Magnetic Field Coupling Mechanism And Its Suppression Measures

In this paper, the calculation and analysis on the power frequency magnetic field are illustrated. The main work is as follows:Based on the structural stability analysis of the voltage source inverter with IGBT in series,the single-phase inverter model was established by Ansys,and then the finite element method is used to calculate the force between valve sections of the converter with the existing design capacity in various working conditions; Based on those results, the distance between valve sections was modified and the force in each case was calculated for the purpose of obtaining the optimum distance in which the electromotive force has the minimum value. Considering mechanical vibration and possible resonance, the natural frequency of a single valve section was calculated, and frequency components of the valve section current waveform were analyzed through Fourier transform; By comparing, it results that the electromotive power caused by the current will not cause resonance of the valve section. This part proposed measures through simulation and calculation related to optimize the design of the inverter to prevent mechanical damage which is due to the electromotive power exceeding the designing threshold.As the problem that the power frequency magnetic field of the SVC air-core reactor beyond the standards in Chuxiong converter station of China Southern Power Grid, magnetic vector potential distribution of the power frequency magnetic field around the air-core reactor was replicate,and then the calculation of the inducted current in the closed-loop conductor. Firstly, the calculation principle of the inducted current in the closed-loop conductor was analyzed, the calculated model of the conductor system around the reactor was established based on the parameter extracting algorithm of the complicated conductor system.By numerical integration of the magnetic vector potential through the conductor, the inducted voltage in each conductor elements was obtained and equipped to its voltage source. And then, based on the accomplished calculation model and equivalent voltage source, the inducted current in each conductor elements was obtained by solving matrix equation. Finally, the above proposed calculation method was verified by applying it to the test model. Suppression method was researched to reduce the inducted current around the reactor. It resulted that the choice of suppression methods would depend on shielding measures due to its effect on magnetic field distribution.