In this study, a novel energy management strategy (EMS) with two degrees of freedom is proposed for hybrid energy storage systems consisting of supercapacitor (SC) and battery in islanded microgrids. The proposal introduces two degrees of freedom including an adaptive high-pass filter cut-off frequency f _c and a charge/discharge coefficient k _b , according to the SC and battery state of charge (SOC), respectively. The f _c regulates SC current in the transient process and the k _b controls battery current in the steady-state. Therefore, appropriate power distribution that the SC suppresses the transient power fluctuations while the battery supports average power demand is realised, over-charging, and over-discharging are avoided and the current stress of the battery during the shut-down process is reduced. Moreover, three operation modes for isolated DC microgrids, comprising power-sharing mode, battery-only mode, and extreme mode are demonstrated. Hence, the DC microgrid can remain stable for the whole time, achieve seamless transitions from the power-sharing mode to the two others, and provide faster SOC recovery of the SC. The effectiveness of the proposed EMS is validated by experimental studies with a prototype of the simplified DC microgrid.

中文翻译：

---

具有两个自由度的岛状DC微电网混合储能系统的能量管理策略

在这项研究中，提出了一种具有两个自由度的新型能源管理策略（EMS），用于岛状微电网中由超级电容器（SC）和电池组成的混合储能系统。该提案引入了两个自由度，包括自适应高通滤波器的截止频率F _c和充放电系数ķ _b ，分别根据SC和电池的充电状态（SOC）。的F _c调节瞬态过程中的SC电流，并且ķ _b控制稳态下的电池电流。因此，实现了在电池支持平均功率需求的同时SC抑制瞬态功率波动的适当功率分配，避免了过度充电和过度放电，并且减少了关闭过程中电池的电流应力。此外，还演示了隔离直流微电网的三种工作模式，包括功率共享模式，仅电池模式和极限模式。因此，DC微电网可以在整个时间内保持稳定，实现从功率共享模式到其他两种模式的无缝过渡，并提供更快的SC SOC恢复。通过简化直流微电网原型的实验研究验证了所提出的EMS的有效性。