**6. Conclusions**

A distributed cooperative control is proposed for multiple DC electric springs with the recently proposed topology in this paper. The novel DCES, which is composed of the DC/DC three port converter, bi-directional buck-boost converter, and battery system, can realize electrical isolation between the CL and the NCL and can also realize the traditional paralleled connection way of the electrical loads. The proposed distributed cooperative control composed of the primary control and the secondary control, can be used to realize the local voltage stability, power allocation of multiple DCESs and the consensus of DC-bus voltages and battery SOCs among multiple DCESs. The primary control is made up of the phased-shift control, decoupling control, adaptive droop control, and charging/discharging control. Furthermore, the secondary control consists of the voltage control

and SOC control. The proposed distributed cooperative control applied in multiple DCESs with the recently proposed topologies has been validated by the simulation results.

**Author Contributions:** Conceptualization, D.Z., Q.W. and M.C.; methodology, Q.W.; software, D.Z.; validation, D.Z., Q.W.; formal analysis, F.D.; investigation, D.Z.; resources, Q.W.; data curation, Q.W.; writing—original draft preparation, D.Z.; writing—review and editing, D.Z., Q.W., G.B.; visualization, F.D.; supervision, M.C.; project administration, Q.W.; funding acquisition, Q.W.

**Funding:** This work was supported by the Natural Science Foundation of Jiangsu Province under project BK20170675, and by the National Natural Science Foundation of China under project 51877040.

**Conflicts of Interest:** The authors declare no conflict of interest.
