Abstract
DC bus voltage signaling (DBS) and droop control are frequently employed in DC nano and microgrids with distributed energy resources (DERs) operating in a decentralized way. This approach is effective in enforcing the desired contributions of power sources and energy storage systems (ESSs) in steady-state conditions. The use of supercapacitors (SCs) along with batteries in a hybrid energy storage system (HESS) can mitigate the impact of high and fast current variations on the losses and lifetime of the battery units. However, by controlling the HESS as a single unit, one forfeits the potential contribution of the SC and its high power capabilities to dynamically improve voltage regulation in a DC nanogrid. This paper discusses an approach where the SC interface is controlled independently from the battery interface, with a small droop factor and a high pass filter (HPF), to produce high and short current pulses and smooth DC bus voltage variations due to sudden power imbalances in the DC nanogrid. Experimental results are presented to show that, unlike in a conventional HESS, the SC unit can be used to improve the dynamic voltage regulation of the DC nanogrid and, indirectly, mitigate the high and fast current variations in the battery.
Highlights
Due to environmental issues and the shortage of fossil fuel, the participation of renewable energy sources (RESs) in the power system is expected and desired to increase
In order to test this feature, the solar converter operates in power demanded from the DC nanogrid varies between no-load and full-load
DC nanogrid with a RES, twoenergy energy storage and a variable load load was assembled in the in
Summary
Due to environmental issues and the shortage of fossil fuel, the participation of renewable energy sources (RESs) in the power system is expected and desired to increase. DC bus signaling (DBS) and droop control are frequently employed in DC nano and microgrids with various DERs operating in a decentralized way [12] They are based on locally measured variables, such as DC bus voltage, and provide an effective means for setting power sharing among parallel units in steady-state conditions. The threshold voltage is used for energy management and can be updated by a supervisory controller employing low bandwidth communication, but is not essential for system operation Disregarding the latter, for high reliability, and assuming that he SC and battery are not co-located, the SC unit should present a droop factor lower than that of the battery’s to be able to contribute more to dynamic voltage regulation. Simulation and experimental results are presented to show that this approach can provide an improvement in the dynamic regulation of the DC nanogrid voltage as well as mitigate the fast current components in the battery unit
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