Investigation of Nonlinear Droop Control in DC Power Distribution Systems: Load Sharing, Voltage Regulation, Efficiency, and Stability

Fang Chen*, Rolando Burgos, Dushan Boroyevich, Juan C. Vasquez, Josep M. Guerrero

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

80 Citations (Scopus)
314 Downloads (Pure)

Abstract

Linear droop faces the design tradeoff between voltage regulation and load sharing due to cable resistances and sensing errors. Using a larger droop resistance improves load sharing, but requires a wider droop voltage range. In the nonlinear droop, droop resistance is a function of the converter's output current, and its value increases when the output current increases. As a result, the impacts from sensors and cables are reduced. In this paper, the design of nonlinear droop in dc power distribution systems is studied with special emphasis on load sharing, voltage regulation, system efficiency, and stability. After discussing the piecewise linear and nonlinear droop control, a generic polynomial expression is presented to unify different droop equations. The impact of droop on dc system efficiency is analyzed by evaluating cable and power converter losses. The converter's output impedance using nonlinear droop is modeled to analyze the system stability with constant power loads. The selection and design guidelines of nonlinear droop are summarized, considering both the static performance and interaction with load systems. The analysis is verified in 400-V multi-source dc systems. The nonlinear droop is fully distributed as it only needs local information.

Original languageEnglish
Article number8616804
JournalIEEE Transactions on Power Electronics
Volume34
Issue number10
Pages (from-to)9407-9421
Number of pages15
ISSN0885-8993
DOIs
Publication statusPublished - 1 Oct 2019

Keywords

  • Constant power load (CPL)
  • current sharing
  • dc microgrids
  • droop
  • efficiency
  • nonlinear
  • stability
  • voltage regulation

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