A new capacitance estimation method of supercapacitor bank using a bank impedance and current injection

This paper proposes a capacitance estimation method of the supercapacitor bank in the supercapacitor energy storage system (SCESS). To diagnose a deterioration, the capacitance of the supercapacitor bank is estimated by using a current injection. The injected current causes an AC ripple voltage and AC ripple current in the supercapacitor bank, which are extracted by using the proposed signal processing method. The proposed method provides an accurate value of the capacitance for reliability and durability of the supercapacitor energy storage system. Usefulness of the proposed estimation method is verified through simulation and experiment with a prototype of a 10kW SCESS. Experimental results shows that the maximum estimation error rate is less than 3% at both 2.25F and 2.57F capacitance bank.