Energy oscillation suppression method for hybrid energy storage in isolated DC microgrid

In isolated DC microgrids, sudden load changes can cause DC voltage fluctuations. Hybrid energy storage systems composed of high-power-density flywheels and high-energy-density batteries can maintain voltage stability. However, due to differences in dynamic response speed characteristics, energy cycling oscillation occur at the end of voltage fluctuation transients between the flywheel and the energy storage system, reducing system stability, causing energy waste, and even leading to instability. This paper proposes a control method to suppress energy oscillation in flywheelbattery hybrid energy storage systems. Utilizing DC bus voltage information, the method dynamically controls the virtual capacitor parameters in the hybrid energy storage droop control to allocate the power borne by each energy storage unit. This ensures accurate power allocation during transient processes, thereby suppressing energy exchange between hybrid energy storage units and achieving stable voltage control even without communication. Simulation experiments verify the effectiveness and superiority of the proposed control method.