A Shunt Capacitor Equipped with a Series Inverter for Compensating Harmonics along with Existing Equipment

Abstract

This paper proposes a novel control method for the shunt capacitor equipped with a series inverter (ISC) in order to use with existing shunt capacitors in parallel. The proposed method controls the equivalent impedance of the ISC in the normal operation range to be equal to the conventional shunt capacitors equipped with a series inductor (LSC). The control increases the impedance to enhance its harmonic compatibility when the harmonic voltage increases beyond the normal operation range. Simulation results verify that the proposed ISC can compensate harmonic current together with the existing 6% LSC. In addition, the ISC can avoid its overcurrent even if it is used with the resonant condition by the existing shunt capacitor. This paper also investigates the circuit design for satisfying both harmonic compensation effect of the 6% LSC and the harmonic compatibility of the 13% LSC. The required dc voltage in the series inverter is 13% of the rated line-to-lime voltage. Thus, the capacity of the series inverter is much smaller than the total compensation capacity of the shunt capacitor.