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Article

Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices

Department of Electrical and Computer Engineering, University of Patras, 26504 Patras, Greece
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Author to whom correspondence should be addressed.
Academic Editor: Enrico Sciubba
Energies 2017, 10(4), 433; https://doi.org/10.3390/en10040433
Received: 30 September 2016 / Revised: 11 January 2017 / Accepted: 16 March 2017 / Published: 27 March 2017
(This article belongs to the Special Issue Microgrids 2016)
Direct current (DC) distribution systems and DC microgrids are becoming a reliable and efficient alternative energy system, compatible with the DC nature of most of the distributed energy resources (DERs), storage devices and loads. The challenging problem of redesigning an autonomous DC-grid system in view of using energy storage devices to balance the power produced and absorbed, by applying simple decentralized controllers on the electronic power interfaces, is investigated in this paper. To this end, a complete nonlinear DC-grid model has been deployed that includes different DC-DERs, two controlled parallel battery branches, and different varying DC loads. Since many loads in modern distribution systems are connected through power converters, both constant power loads and simple resistive loads are considered in parallel. Within this system, suitable cascaded controllers on the DC/DC power converter interfaces to the battery branches are proposed, in a manner that ensures stability and charge sharing between the two branches at the desired ratio. To achieve this task, inner-loop current controllers are combined with outer-loop voltage, droop-based controllers. The proportional-integral (PI) inner-loop current controllers include damping terms and are fully independent from the system parameters. The controller scheme is incorporated into the system model and a globally valid nonlinear stability analysis is conducted; this differs from small-signal linear methods that are valid only for specific systems, usually via eigenvalue investigations. In the present study, under the virtual cost of applying advanced Lyapunov techniques on the entire nonlinear system, a rigorous analysis is formulated to prove stability and convergence to the desired operation, regardless of the particular system characteristics. The theoretical results are evaluated by detailed simulations, with the system performance being very satisfactory. View Full-Text
Keywords: DC distribution systems; DC microgrids; stability analysis; droop control; DC/DC converters; storage devices DC distribution systems; DC microgrids; stability analysis; droop control; DC/DC converters; storage devices
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MDPI and ACS Style

Makrygiorgou, D.I.; Alexandridis, A.T. Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices. Energies 2017, 10, 433. https://doi.org/10.3390/en10040433

AMA Style

Makrygiorgou DI, Alexandridis AT. Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices. Energies. 2017; 10(4):433. https://doi.org/10.3390/en10040433

Chicago/Turabian Style

Makrygiorgou, Despoina I., and Antonio T. Alexandridis 2017. "Stability Analysis of DC Distribution Systems with Droop-Based Charge Sharing on Energy Storage Devices" Energies 10, no. 4: 433. https://doi.org/10.3390/en10040433

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