Study On Harmonic Suppression And Reactive Power Compensation Of Large-Capacity Mid-Frenquency Furnace System

With the development of the economy in china, the steel industry is growing rapidly.More and more Mid-frenquency furnaces of big capacity for steel-making are invested to the industry. The excessive electricity harmonics and low power factor was caused by variable flow and variable frequency, which have a negative impact on power quality. Therefore, Studying on harmonic suppression and power factor improvement of Mid-frenquency furnace system is necessary.In this paper, parallel resonant intermediate frequency induction furnace system was described, including circuit structure and principles.And harmonic currents and reactive power generated by the furnace was analyzed.The method of large capacity of intermediate frequency furnace harmonic control and the power factor improvement was put forward.Firstly, Double rectifier series technology was applied to suppress harmonics of the electric furnace. The inverter output voltage was increased, and the induction coil current loss was reduced effectively. The power factor of electric furnace was improved in some extent. And then based on the analysis of the power control method of intermediate frequency furnace which causes low power factor of net side, the power control method of parallel resonant intermediate frequency electric furnace was improved and the specific control circuit was given.Secondly, For the high content of harmonic working current and low power factor, the reactive compensation on transformer high voltage side was proposed. The real test show good effect for the harmonic prevention.Productivity efficiency and equipment's reliability are improved, and lots of cost can be saved for adopting the compensation technology. Finally, we give a short summary of the paper.