Power converter-based method for protecting three-phase power capacitor from harmonic destruction

Power capacitors are widely used for power factor correction in power systems. System harmonic currents and voltages have caused violent capacitor failures in recent years resulting in power interruptions. This paper proposes a new capacitor protection for resonant harmonic loads by applying a low capacity power converter to act as a virtual harmonic resistor to damp the resonance effect at the harmonic frequency and regenerates the real power back to the utility system at the fundamental frequency with minimum power loss. A three-phase prototype was developed and tested to verify the performance of the proposed method. The test results show the performance was as expected.