Energy management strategy with two degrees of freedom for hybrid energy storage systems in islanded DC microgrids

作者：Zhang, Yuhan; Du, Guiping^*; Lei, Yanxiong

来源：IET Power Electronics, 2020, 13(14): 3171-3179.

DOI：10.1049/iet-pel.2020.0404

• secondary cells
• distributed power generation
• supercapacitors
• energy management systems
• power generation control
• electric current control
• hybrid energy storage systems
• islanded microgrids
• degrees of freedom
• transient process
• appropriate power distribution
• transient power fluctuations
• average power demand
• current stress
• isolated DC microgrids
• power-sharing mode
• battery-only mode
• EMS
• simplified DC microgrid
• islanded DC microgrids
• energy management strategy

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 frequencyf(c)and a charge/discharge coefficientk(b), according to the SC and battery state of charge (SOC), respectively. Thef(c)regulates SC current in the transient process and thek(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.