The medium frequency electric furnace is one of the major harmonic sources in the power grid load, as it generates a large amount of harmful high-order harmonics during the operation of the power grid by rectifying and inverting the power supply into medium frequency. Harmonics can seriously affect the safe operation of the power grid, for example, harmonic currents in transformers can generate additional high-frequency eddy current iron losses, causing the transformer to overheat, reducing its output capacity, increasing its noise, and seriously affecting its lifespan; The convergence effect of harmonic current reduces the cross-sectional area of the conductor and increases the loss of the line; Harmonic voltage affects the normal operation of various electrical equipment on the power grid, leading to misoperation of automatic control devices and inaccurate instrument measurement; Harmonic voltage and current interfere with the normal operation of nearby communication equipment; The temporary and transient overvoltages generated by harmonics cause insulation damage to equipment, leading to three-phase short circuits and transformer burnout; Harmonic voltage and current can cause local parallel resonance and series resonance in the public power grid, leading to serious accidents. In the inverter process, the first source obtained from DC is a square wave power supply, which is equivalent to the superposition of sine waves containing a large number of high-order harmonics. Although the downstream circuit needs to be filtered, high-order harmonics cannot be completely removed, which is the reason for the generation of harmonics.
We designed single tuned filters for 5, 7, 11, and 13 times. Before filtering compensation, the power factor during the melting stage of the user's intermediate frequency furnace was 0.91. After the filtering compensation device was put into operation, the overcompensation reached a capacitance of 0.98. After the filtering compensation device is put into operation, the total voltage distortion rate (THD value) is 2.02%. Meets the standard of voltage harmonics (10KV) value below 4.0% in accordance with GB/T 14549-1993 for electrical energy quality. After filtering the 5th, 7th, 11th, and 13th harmonic currents, the filtering rate is about 82-84%, which meets the allowable value of the national standard. The compensatory filtering effect is better

The medium frequency electric furnace is one of the major harmonic sources in the power grid load, as it generates a large amount of harmful high-order harmonics during the operation of the power grid by rectifying and inverting the power supply into medium frequency. Harmonics can seriously affect the safe operation of the power grid, for example, harmonic currents in transformers can generate additional high-frequency eddy current iron losses, causing the transformer to overheat, reducing its output capacity, increasing its noise, and seriously affecting its lifespan; The convergence effect of harmonic current reduces the cross-sectional area of the conductor and increases the loss of the line; Harmonic voltage affects the normal operation of various electrical equipment on the power grid, leading to misoperation of automatic control devices and inaccurate instrument measurement; Harmonic voltage and current interfere with the normal operation of nearby communication equipment; The temporary and transient overvoltages generated by harmonics cause insulation damage to equipment, leading to three-phase short circuits and transformer burnout; Harmonic voltage and current can cause local parallel resonance and series resonance in the public power grid, leading to serious accidents. In the inverter process, the first source obtained from DC is a square wave power supply, which is equivalent to the superposition of sine waves containing a large number of high-order harmonics. Although the downstream circuit needs to be filtered, high-order harmonics cannot be completely removed, which is the reason for the generation of harmonics.
We designed single tuned filters for 5, 7, 11, and 13 times. Before filtering compensation, the power factor during the melting stage of the user's intermediate frequency furnace was 0.91. After the filtering compensation device was put into operation, the overcompensation reached a capacitance of 0.98. After the filtering compensation device is put into operation, the total voltage distortion rate (THD value) is 2.02%. Meets the standard of voltage harmonics (10KV) value below 4.0% in accordance with GB/T 14549-1993 for electrical energy quality. After filtering the 5th, 7th, 11th, and 13th harmonic currents, the filtering rate is about 82-84%, which meets the allowable value of the national standard. The compensatory filtering effect is better