Modeling and analysis of power quality compensation systems for current source inverter based induction furnace

With the developments in the power electronics technology, high-power converters have become available in many of industrial applications. High-power converters provide efficient electric energy utilizing and advance control of process in many of industrial applications. Besides the advantages of these power converters, they show nonlinear load characteristic which causes various power quality (PQ) problems in electric power systems.Induction steel scrap melting furnaces are one of the examples of industrial applications which use high power converters in power supplies. In high power induction furnaces, power supply is commonly formed from 12-pulse or higher pulse fully controlled rectifier, current source inverter and parallel resonant tank circuit. Besides the advantages of current source inverter based induction furnaces (CSI-IF) in melting process, CSI-IFs causes serious PQ problems such as; time varying harmonics and interharmonics. Moreover, when these high power furnaces are supplied from weak power systems, voltage fluctuations and flicker problems occur in the power system.In this thesis, the CSI-IF is modeled in PSCAD/EMTDC simulation program in order to investigate the time varying harmonics and interharmonics of CSI-IF and find solutions to these PQ problems. For the solution of PQ problems of CSI-IF, passive filtering and active filtering methods are investigated. In passive filtering methods; single tuned filter, C-type filter and broad band filter are designed for the PQ problems of CSI-IF. In active filtering methods, hybrid active power filters (HAPF) which use shunt active power filter (APF) - shunt passive filter topology and APF in series with shunt passive filters topology are designed for the PQ problems of CSI-IF. The compensation performances of these passive filters and HAPFs are investigated by modeling in PSCAD/EMTDC simulation program.