Punna Srinivas and Udaya Bhasker Manthati
Bi-directional converter, battery, SC, HESS, PI controller
Due to the high penetration of renewable energy sources in dc microgrids, these microgrids are highly susceptible to fluctuations in power generation. To absorb these fluctuations, a hybrid energy storage system (HESS) consisting of the battery and the supercapacitor (SC) is used. The contrasting characteristics of battery and supercapacitors make them a perfect combination for HESS applications. The HESS is interfaced with a dc microgrid using a double-input bidirectional converter. This bidirectional converter not only provides decoupled control of battery and supercapacitor power but also provides energy exchange between the storage components within. This paper presents a converter modelling method for the double-input bidirectional converter. A controller was designed based on this for voltage regulation application for a dc microgrid. The modified operation of the converter made it possible to use the same controller for both HESS charging and discharging operation, thus making it a unified controller. The designed controller was better dc link voltage restoration to PV generation and load disturbance, the efficient power balance between the battery and the SC. The proposed modified operation of the bidirectional converter ensured a low equivalent series resistance (ESR) supercapacitor to be always within the desired range of state of charge (SOC). The operation of the modified converter and performance of the designed controller in voltage stability were validated with the experimental results.
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