Decentralized Multilayer Master-Slave Control Strategy for Power Management in Autonomous DC Microgrid Clusters

DC microgrid clusters are effective solutions for integrating multiple autonomous subgrids at the same and different voltage levels. In such a system, global power management is an essential concern, but it is always degraded by system structures and line impedances of distributed generation units (DGUs). To solve this problem, a decentralized multilayer master-slave control strategy is proposed. In the selected master DGU, an ac signal is injected into the output voltage, and power information is carried by its frequency and consequently broadcast to other slave DGUs via power lines. In slave DGUs, the output power is regulated to track the demodulated power information, which generates voltage offset to realize power sharing in a single subgrid. The interlinking converter is exploited for interconnection between two subgrids, it is also used to transmit the broadcast power information from one subgrid to another one, which therefore ensures global power management throughout the dc microgrid cluster. All the control algorithms rely on only local measurement, and information transmission is implemented via existing power lines, no dedicated communication network is required. The effectiveness of the proposed strategy is validated by hardware-in- loop and experimental results.