Design And Research On Harmonic Elimination System Of 15mW Intermediate Frequency Power Supply

In today’s rapid economic development, large-scale casting manufacturing enterprises as a national main industry has a the rapid development, more and more medium frequency power supply are used in the production and life. As the intermediate frequency power supply is nonlinear load, it brings a series of electric energy problems because of the unbalance of the rectifier capacity. In the process of intermediate frequency power supply rectifying and inverting, it will produce the harmonic, which will result in the harmonic loss. Therefore, it is very necessary to study the harmonic suppression of large intermediate frequency electric furnace. With the increasing demand of power supply enterprises to the Internet, the research on the technology and equipment of eliminating harmonics to improve the power quality has become a hot issue in the current research.This paper analyzes the structure and operation principle of the main circuit of the large capacity parallel resonant intermediate frequency power supply, and studies the causes and characteristics of the harmonic generation of the 15000 kW intermediate frequency electric furnace. We study passive and active harmonic elimination methods.Finally, we give a short summary of the paper. We put out the relationship between the rectifier and transformer harmonic phase, and analyzes the principle of each phase input current balance and harmonic cancellation. The main work of this design is as follows:(1) The circuit structure and working principle of the parallel resonant intermediate frequency induction furnace system are analyzed. The causes and characteristics of harmonic generation in intermediate frequency electric furnace are analyzed. Analysis of the influence of the commutation process and the capacity of the power grid on harmonic wave, and the effect of leakage reactance on harmonic wave is analyzed.(2) Next, the harmonic elimination method for large capacity intermediate frequency electric furnace system is given. The principle of passive filter, multi phase rectifier and transformer phase shifting based on harmonic elimination are analyzed in theory.(3) According to the theoretical derivation and the phase diagram analysis of the intermediate frequency power system harmonic suppression method: by increasing the medium frequency power supply phase number and pulse number to reduce the harmonic in large capacity rectifier power supply is the most effective method, and through specific simulation verify the control method have good harmonic suppression effect.By using phase shift technology based on rectifier transformer, harmonic generation of intermediatefrequency power supply can be reduced, which can effectively control the harmonic pollution of power grid. Based on the idea of control harmonic, the paper analyzes the effect of the 12 pulse and 24 pulse transformer phase shift technology on the harmonic suppression, and the results have reached the expected goal.(4) The passive filter reactive power compensation device is analyzed. Each phase current asymmetry is the main reason for the high capacity medium frequency power supply. First of all, through the control circuit is provided with a current feedback control to ensure balanced input currents, which can not only ensure the input transformer uniform power allocation and symmetry elimination of low order harmonics. Uncancelled harmonic at high voltage side of the passive filter can eliminate specific high harmonics. In high voltage side of the transformer filter compensation method is using the transformer leakage reactance in series current limiting inductance, to further reduce the harmonic upload, and also can improve the parallel resonant power supply system power factor, saving the cost of production.Finally, an overview of the research work of this paper is made.