Application Case of FGI SVG in a Large Electric Arc Furnace Steel Plant
Application Scenario and Core Issues
The core production equipment at a large special steel smelting base is an 80-ton AC electric arc furnace. During scrap steel melting, the furnace operating current is extremely unstable. It shows random, rapid, and wide-range fluctuations, making it a typical impact-type nonlinear load. This causes severe power quality issues in the plant's 10kV distribution system:
Severe Reactive Power Impact: During electrode short-circuit and arc ignition stages, the furnace instantaneously absorbs a large amount of reactive power. This causes the grid power factor to fluctuate violently between 0.5 and 0.9, with an average power factor of only 0.78.
Significant Voltage Fluctuation and Flicker: The sharp changes in reactive current cause frequent bus voltage fluctuations. This leads to noticeable "flickering" of workshop lighting, seriously affecting visual tasks and threatening the stable operation of other precision equipment like refining furnaces and continuous casters.
Serious Harmonic Pollution: The arc furnace load generates substantial harmonic currents, primarily in the 2nd to 7th orders. These harmonics cause transformers and cables to overheat, accelerating the aging of equipment insulation.
These problems directly result in high penalties from power factor adjustment fees. Furthermore, production stoppages and quality fluctuations caused by voltage instability create significant hidden production costs for the enterprise.
Solution and Implementation
Conventional solutions like Fixed Capacitor banks (FC) or Thyristor Switched Capacitors (TSC) could not address these issues. Their slow response time (in seconds) and inability for continuous adjustment could not keep up with the millisecond-level changes of the arc furnace, and even risked causing resonance. The steel plant ultimately chose the FGI SVG as the solution.
Based on fully-controlled IGBT power devices, the SVG acts like a "reactive current generator." Its core advantage lies in real-time detection of load current, enabling precise dynamic compensation. The project involved installing a set of FGI SVG devices in parallel on the plant's 10kV busbar. Key implementation features included:
Rapid Tracking: The SVG's control system monitors the arc furnace current in real-time. Its dynamic response speed is much faster than the rate of change in the furnace's operating conditions.
Dual-Function Management: While generating capacitive or inductive reactive power to balance the system's reactive demand, its Active Power Filter (APF) function simultaneously filters harmonic currents of specified orders.
Intelligent Operation: The device automatically and smoothly switches between reactive power compensation and harmonic filtering modes based on grid demand, enabling fully automatic, round-the-clock operation.
Operational Results
After the FGI SVG was put into operation, the plant's power quality improved fundamentally, with remarkable results:
Significant Improvement in Power Quality: The average power factor increased steadily from 0.78 to over 0.98, completely eliminating penalties from low power factor. Bus voltage fluctuation amplitude reduced by over 70%, and lighting flicker essentially disappeared. This provided a stable and reliable voltage environment for the entire production line. The content rates of major harmonic currents all met national standards, and abnormal heating issues in transformers and cables were resolved.
Direct and Notable Economic Benefits: The plant now avoids tens of thousands in monthly power factor adjustment fees. Reduced harmonics and stabilized voltage significantly lower losses and temperature rise in transmission and distribution equipment like transformers and cables, extending their service life and reducing maintenance costs. Improved power supply stability reduced unplanned stoppages in associated refining and continuous casting production lines due to voltage issues to zero, ensuring product output and quality.
Safe and Reliable System Operation: The FGI SVG itself operates with very low losses (<0.8%) and high efficiency. The equipment runs smoothly, eliminating the need for frequent switching operations required by traditional capacitor banks, thereby reducing the risk of switchgear failures.
The FGI high-voltage SVG is an ideal solution for power quality problems caused by impact-type, nonlinear loads like electric arc furnaces. It not only enables rapid dynamic reactive power compensation, stabilizes voltage, and improves power factor but also effectively suppresses harmonics, achieving "multiple benefits with one device." This investment recovers its cost in a short period through energy savings and reduced fees. More importantly, it ensures the long-term safety, stability, and efficiency of the enterprise's power supply system. It lays a solid energy foundation for continuous and automated production, offering comprehensive value far exceeding that of traditional compensation devices.
