中频电炉由于是工频电源经整流逆变为中频，工作过程中对电网产生大量具有危害性的高次谐波，是电网负载中大谐波源之一。谐波会严重影响电网的安全运行，例如谐波电流在变压器中，产生附加高频涡流铁损，使变压器过热，降低了变压器的输出容量，使变压器的噪声增大，严重影响变压器的寿命；谐波电流的趋附效应使导线等截面变小，增加线路的损耗；谐波电压影响电网上其它各种电气设备不能正常工作，导致自动控制装置产生误动作，仪表计量不准确；谐波电压电流对附近的通讯设备正常运行产生干扰；谐波产生的暂时过电压和瞬态过电压使设备绝缘破坏，引发三相短路，烧毁变压器；谐波电压电流会引起公共电网中局部产生并联谐振和串联谐振，造成严重事故。在逆变过程中，首先由直流得到的是方波电源，方波相当于含有大量高次谐波的正弦波的叠加。虽然后级电路要进行滤波，但高次谐波并不能完全被滤除干净，这就是产生谐波的原因。
我们设计了5、7、11、13次单调谐滤波器，滤波补偿前，用户中频炉熔化阶段功率因数为0.91,滤波补偿装置投入后,大过补偿至容性0.98。滤波补偿装置投入运行后,电压总畸变率(THD值)为:2.02%。符合电能质量GB/T 14549-1993电压谐波（10KV）值4.0%以下的标准。5，7，11，13次谐波电流经滤波后，滤除率约为82∽84%，达到国标允许值。补偿滤波效果较佳.

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