Investigation and mitigation of harmonic amplification problems caused by single-tuned filters

This paper investigates the harmonic amplification problems in a plastic plant and the appropriate mitigation methods. Four single-tuned filters (LC filters) were installed to eliminate the harmonic currents from three 6-pulse rectifiers. However, after the capacitance reduction of some filter capacitors, the driving point impedance at the frequency of 8(th) order harmonic increased severely and the harmonic current of this order was amplified. There were many failures about the capacitors of filters. Field measurements and computer simulations are used to verify the disturbance problems. Finally, two high-pass damped filters are recommended to replace the original single-tuned filters. The amplification problems at some even-order harmonics can be avoided.