Distributed Secondary Control Strategy For The Islanded DC Microgrid Based On Virtual DC Machine Control

The virtual DC machine (VDCM) control can integrate characteristics of the DC machine into an energy storage converter to provide damping and inertia support for the DC microgrid. However, on the one hand, the droop characteristics of the VDCM inevitably lead to steady-state voltage deviations. On the other hand, the difference in the state of charge (SOC) of the energy storage unit (ESU) is not taken into account, making it difficult to achieve SOC balance among the ESUs. To address these challenges, firstly, a hierarchical control architecture for an islanded DC microgrid based on the VDCM is presented. Secondly, to obtain the system average voltage and the average SOC of the ESUs, a distributed voltage observer and SOC observer based on the dynamic consensus algorithm are presented. Thirdly, the secondary voltage controller and SOC controller are proposed, which are implemented by introducing voltage compensation and power compensation into the VDCM. Finally, a simulation platform is established. The simulation results show that the proposed method can realize voltage regulation and SOC balance under various communication topologies. Specifically, under the ring communication topology, the secondary control objectives can still be realized even in the event of communication failures or converter failures.