Research On DC Conversion Technology Of Supercapacitor Energy Storage System

As a new kind of energy storage devices, supercapacitors have such a lot of advantages like large capacitance, fast charging/discharging performance, long service life and non-pollution to environment. Besides, supercapacitors have higher energy density than traditional electrostatic capacitors and higher power density than ordinary batteries. Therefore, supercapacitors have extensively perspective in the fields of distributed generation system, distribution network system, electric automobile and UPS. Research on the technology of supercapacitor energy storage is becoming the hot spot in recent years.Being enslaved to the breakdown voltage of electrolyte, the voltage of single supercapacitor is relatively low, therefore multiple supercapacitors constituting a serial-parallel structure are usually used as energy storage system. In the charging/discharging process, there is voltage imbalance among supercapacitors caused by their different properties, which will affect the system's discharge efficiency and energy utilization ratio, and even the service life of the supercapacitors. To solve this problem, an energy storage system based on supercapacitor array was designed and the voltage balance controlling strategy was proposed and to minimize the voltage imbalance and to achieve high efficiency and high energy utilization of the supercapacitors by recombining the serial-parallel structure via switches. Through theoretical analysis and experiment, the feasibility of the strategy was verified.It is not advised that supercapacitor discharges to load directly due to its continually declining voltage. A matched power converter between supercapacitor and load is usually preferred. Through the theoretical analysis of bidirectional DC/DC converter, this paper built the DC converter models of supercapacitor energy storage system. Different methods were used to control different power flows, which was also simulated through Matlab/Simulink. Bidirectional DC/DC converter can further improve the energy utilization ratio of supercapacitor, and has practical application value to supercapacitor energy storage system.