A Shared Resonance Damping Scheme for Multiple Switchable Capacitors

An effective measure to mitigate a shunt capacitor caused harmonic resonance is to add a C-type damping unit in series with the capacitor. If there are multiple switchable capacitors, each of them requires a C-type damping unit. The cost and space requirement for implementing these changes, therefore, increase with the number of switchable capacitors. In view of this disadvantage, a scheme that allows multiple switchable capacitors to share a common damping unit is proposed in this paper. The damping unit is designed in such a way that it will provide adequate damping for all possible on/off combinations of the capacitors involved. In addition and proven methodically, the design method can further guarantee resonance free for all possible network impedance conditions. Performance and usefulness of the proposed scheme has been demonstrated through comparative studies on actual capacitor application cases.