Energy Management Strategy for Supercapacitor Storage Using a Nonlinear Virtual Impedance

Abstract

This paper proposes a new energy management strategy (EMS) used for charging and discharging a supercapacitor (SC). The method is based on a nonlinear impedance and resembles the droop control applied in microgrid structures. The droop control has the advantage of being decentralized so the proposed EMS also benefits this characteristic. Usually a tradeoff must be made between voltage regulation and load sharing for the droop control and a nonlinear resistor is often used to minimize this tradeoff. For charging and discharging a SC in droop controlled microgrids, a virtual impedance with an RC characteristic is usually used. The proposed method was created by merging together the two strategies, the nonlinear resistor and the virtual capacitive impedance, in order to benefit from the advantages provided by both methods. An overview of the most common strategies is also presented in this paper.