A large amount of plant asynchronous electrical equipment, the reactive power loss changes, instability, such as the use of large welding industry, a rapid or fast load reactive power change, the three-phase unbalanced load and sometimes harmonics and other features. Automobile factories, motorcycle factories, spot welding, seam welding load changes, welding machine is extremely fast, and triggered a large number of reactive power, while reducing the total voltage value, will result in poor quality welding and soldering impact production efficiency. Our research and development of SCL-DH dynamic compensation filter device not only can improve the quality of welding current stability, eliminating flicker, and can take full advantage of existing equipment, reduce basic expenses.