Distributed Cooperative Control and Stability Analysis of Multiple DC Electric Springs in a DC Microgrid

TLDR

DC electric springs have been proposed to improve voltage regulation and power quality in DC microgrids. The study establishes a distributed cooperative control framework for multiple DC electric springs in a DC microgrid and analyzes its small‑signal stability. The framework uses a primary droop controller and a secondary consensus algorithm that regulates bus voltage and balances state‑of‑charge, and a small‑signal model of four DC electric springs is developed to analyze stability via eigenvalue sensitivity to communication weight. The cooperative control achieves bus‑voltage consensus and SOC balance using only neighbor‑to‑neighbor communication, and its effectiveness is confirmed by simulation and experimental studies in an islanded DC microgrid.

Abstract

Recently, dc electric springs (dc-ESs) have been proposed to realize voltage regulation and power quality improvement in dc microgrids. This paper establishes a distributed cooperative control framework for multiple dc-ESs in a dc microgrid and presents the small-signal stability analysis of the system. The primary level implements a droop control to coordinate the operations of multiple dc-ESs. The secondary control is based on a consensus algorithm to regulate the dc-bus voltage reference, incorporating the state-of-charge (SOC) balance among dc-ESs. With the design, the cooperative control can achieve average dc-bus voltage consensus and maintain SOC balance among different dc-ESs using only neighbor-to-neighbor information. Furthermore, a small-signal model of a four dc-ESs system with the primary and secondary controllers is developed. The eigenvalue analysis is presented to show the effect of the communication weight on system stability. Finally, the effectiveness of the proposed control scheme and the small-signal model is verified in an islanded dc microgrid under different scenarios through simulation and experimental studies.