Research And Application Of Fast Algorithms For Electromagnetic Field Problems With Complex Wire Structures

The analysis of large grounding grids, radio interference of the transmission line and the electromagnetic environment of high voltage direct current (HVDC) converter station are paying much attention as their importance to the EMC problem. All of these problems can be treat as the electromagnetic field problems which have much conductor wires and the complex medium round them to be considered. And usually, many responses for different frequencies must be computed for these problems. Supported by the projects of Natural Science Foundation (50577019), in this thesis, the fast method to solve the problems above are researched and applied practical. Our methods are verified by comparing with the results tested and computed by other methods. The main innovative achievements are as follows:1. A fast approach to compute the magnetic field induced by the conductor under the ground at lower frequency is presented. As the leak currents in the soil are considered, the magnetic field obtained by this method is more accurate than the traditional moment method and also faster than the finite element method.2. A wire integral equation for imperfect conductor is set up. Using triangle basic function and galerkin method, combining the complex image method and integral transform method, the integral equation is solved fast by the moment method with the uniform lossy ground is considered.3. An approach for analysis of the radio interference level induced by EVAC transmission line is presented. And the protecting distance of the transmission line for the shortwave radio station is obtained which is practical for the EVAC project.4. A fast parallel method for analysis of large scale problems is developed based on the moment method and shows good speedup in a PC cluster built with multi-core CPU system.5. A self-adaptive MBPE method is presented. Combined with the parallel computing method, this method is very efficient for the large scale problem which many responses at different frequencies are needed.6. An antenna model for the valve hall in the HVDC converter station is setup to analyze its EM interference. Based on the results, the shielding effectiveness needed for the valve hall is represent and the useful shielding measures are given.