How does the harmonic suppression strategy of electromagnetic heating furnace reduce pollution to the power grid?
Release Time : 2025-10-15
Electromagnetic heating furnaces are widely used in industrial heating applications. However, the harmonic currents generated during their operation can pollute the power grid, affect power quality, and potentially interfere with other electrical equipment. To address this issue, a systematic harmonic suppression strategy must be developed based on the harmonic generation mechanism and the operating characteristics of electromagnetic heating furnaces to reduce grid pollution.
Harmonics in electromagnetic heating furnaces primarily originate from their power electronics conversion process. A rectifier converts AC power to DC, which is then converted to high-frequency AC by an inverter to supply the heating coil. During the rectification process, nonlinear components distort the current waveform, generating a large number of low-order harmonics. Switching in the inverter stage can introduce higher-order harmonics. Once these harmonic currents are injected into the power grid, they can cause voltage fluctuations, waveform distortion, and even lead to equipment malfunction or damage. Therefore, harmonic suppression must address the two key stages of rectification and inversion.
Source control is the primary strategy for harmonic suppression. By optimizing the rectifier circuit design, multi-pulse rectification technology, such as 12-pulse or 24-pulse rectification, can be adopted to reduce harmonic content by increasing the number of rectification phases. Furthermore, selecting low-harmonic rectification devices, such as IGBT modules, instead of traditional thyristors, can reduce harmonic generation during the switching process. Furthermore, optimizing the inverter's PWM modulation strategy and adopting space vector modulation or specific harmonic cancellation technology can reduce high-order harmonic output in the inverter stage. These measures address harmonic pollution at the source.
Passive filtering is a common method for harmonic suppression. Installing a passive filter, such as a single-tuned filter or high-pass filter, on the power supply side or low-voltage side of the transformer in an electromagnetic heating furnace can specifically filter out harmonics of specific frequencies. Passive filters utilize the LC resonance principle to create a low-impedance path for harmonics of a specific frequency, thereby directing the harmonic current into the filter for dissipation. While this approach offers advantages in terms of simplicity and cost, it requires customized parameters based on the harmonic characteristics of the power grid, and filtering effectiveness may decrease as harmonic frequencies vary. Therefore, regular monitoring of grid harmonics and adjustment of filter parameters are necessary to maintain effectiveness.
Active filtering technology offers a more flexible solution for harmonic suppression. Active power filters monitor harmonic currents in the grid in real time and generate compensating currents of equal amplitude and opposite phase, thereby canceling out the harmonics. This technology dynamically tracks harmonic changes, effectively compensating for harmonics with fluctuating frequency and amplitude, and its compensation characteristics are unaffected by grid impedance. Connecting active filters in parallel with electromagnetic heating furnace systems can significantly reduce harmonic currents injected into the grid, ensuring that the total harmonic distortion (THD) meets national standards. Furthermore, active filters provide overvoltage protection, suppressing spikes and overvoltage shocks to equipment.
Hybrid filtering combines the advantages of passive and active filtering. Given the harmonic characteristics of electromagnetic heating furnaces, passive filters can be used in the low-order harmonic range, where harmonic content is high, to reduce equipment costs. Active filters can be used to precisely compensate for higher-order harmonics or dynamically changing harmonics. This solution ensures effective filtering while controlling overall costs, making it suitable for industrial scenarios with high power quality requirements. During implementation, the capacity ratio of passive and active filters should be appropriately allocated based on harmonic detection results.
System-level optimization is a complementary measure for harmonic suppression. Increasing transformer capacity can relatively reduce the impact of harmonic currents on the power grid; connecting reactors in series with capacitor banks can prevent capacitors from amplifying harmonics. Optimizing the power supply system layout of the electromagnetic heating furnace to avoid sharing the same busbar with other sensitive equipment can reduce harmonic propagation. Furthermore, strengthening equipment maintenance to ensure efficient coupling between coils and cookware and avoid harmonic increases due to load mismatch are also key aspects of system optimization.
Harmonic suppression must be integrated throughout the entire design, installation, and operation cycle of the electromagnetic heating furnace. From circuit topology optimization to filter device selection, from source control to dynamic compensation, comprehensive consideration must be given to technical feasibility, economic efficiency, and long-term stability. By implementing the above strategies, the harmonic pollution of the electromagnetic heating furnace to the power grid can be effectively reduced, the quality of electric energy can be improved, and the safe and efficient operation of industrial production can be guaranteed.