Power converter based method for suppressing power capacitor harmonic current

The damage to power capacitors caused by harmonic pollution was very serious in recent years due to the wide spread of power electronic related, nonlinear loads. The violent failure of power capacitors may result in power interruption and even accidents in industry. In this paper, a novel converter based protection method is proposed for protecting the power capacitor from harmonic damage. A power converter, serially connected to the power capacitor, is used to generate the harmonic components of utility voltage in the proposed method. Hence, the harmonic voltage across the power capacitor is cancelled. It means that the voltage dropped in the power capacitor will be maintained as sinusoidal, despite the waveform distortion of the utility voltage; the current flowing through the power capacitor is then also sinusoidal. Therefore, the power capacitor will not be damaged by the harmonic. A prototype is developed and tested to verify the performance of the proposed method. The test results show that the proposed method has the expected performance.