2020 | vol. 68 | nr. 2 | art. 1

A Bi-Directional DC/DC Converter for Battery-Supercapacitor Hybrid Energy Storage System

Baoge Zhang, Zhen Zhang, Donghao Wang, Ping Li, Yao Rong
Renewable energy sources (RES) (such as solar energy and wind energy) is the inevitable trend of power system development in the future, but its output power is intermittent and random, which brings new challenges to the safe and stable operation of power system. Energy storage technology is an effective way to solve the power quality of RES power generation and a key technology to ensure the safe and stable operation of power grid. Energy storage system (ESS) is mainly divided into the ESS with single energy storage element and hybrid energy storage system (HESS) with multiple energy storage elements. Because the ESS with single energy storage element has the disadvantages of the low energy density or low power density, the HESS is more widely used in the power grid. Among them, a bi-directional DC/DC converter is the most important part of the ESS, which is a vital medium for energy storage unit and output side to realize power transmission. The research background of this paper is battery-supercapacitor HESS. A bi-directional DC/DC converter for battery-supercapacitor HESS is proposed in accordance with the characteristics of topology redundancy and poor economy of the existing battery-supercapacitor HESS. The energy storage unit of the HESS consists of a battery and a supercapacitor. Because of the high energy density of the battery and the high power density of the supercapacitor, the battery is the main power supply and the supercapacitor is the auxiliary power supply. Meanwhile, the system adds the diode D with a selection switch function and the cold stand-by charging circuit of supercapacitor to ensure the performance of energy storage unit. The working principle and three working modes of the HESS (supercapacitor pre-charging cold stand-by mode, boost mode and buck mode) are analysed in detail. The validity of the topology is verified by building the simulation model in MATLAB/Simulink. The results show that the system has the advantages of low voltage stress of switching devices, not changing the voltage conversion ratio of bi-directional DC/DC converters, providing high current and improving the life of battery. This paper provides theoretical basis and simulation experimental basis for the study of bidirectional DC/DC converter with the characteristics of topology optimization and low voltage stress of switching devices. At the same time, it is helpful to promote a more efficient bi-directional DC/DC converter to be used in ESS and provide a feasible research basis for the safe and stable operation of energy storage technology in power system.
Keywords: hybrid energy storage system (HESS); energy storage unit; bi-directional DC/DC converter; voltage conversion ratio; voltage stress
To cite this article: Zhang B.G., Zhang Z., Wang D.H., Li P., Rong Y., “A Bidirectional DC/DC converter for battery-supercapacitor hybrid energy storage system”, in Electrotehnica, Electronica, Automatica (EEA), 2019, vol. 68, no.2, pp. 05-13, ISSN 1582-5175.