Superimposed AC Signal Frequency Droop Assisted Scheme for Decentralized Power Management of Grid-Forming Controlled DC MGIncluding Multiple PMSG-WTs, DSs, and BESS Units

This paper presents an integrated control strategy for decentralized power management (PM) in a DC MG featuring PMSG-based wind turbines (WTs), droop-controlled dispatch able sources (DSs), and battery energy storage system (BESS). Inspired by frequency signalling methods used in AC micro grids, our approach introduces a corrective AC signal superimposed on the reference DC output voltages of the controllers. The frequency of this signal serves as a global coordination indicator, enabling the establishment of unified multi-part P/ω droop curves that facilitate effective PM across various sources while ensuring appropriate SOC management for BESS. Key findings include: (i) The drooping frequency of the AC signal relative to each source’s DC output power defines unified droop curves for decentralized PM and SOC control; (ii) DC-DC converters operate as controlled voltage sources in grid-forming mode, allowing autonomous transitions between power and voltage regulation states; and (iii) All generation and storage units contribute to generating the AC signal frequency, ensuring robust performance even with resource loss. This innovative control strategy enhances power balance within the MG while enabling regulated charging and discharging of BESS, demonstrating significant potential for improving the operational efficiency of DC micro grids.

Keywords: DC micro grid, PMSG-WTs, Battery, bi-directional converter, inverter.