Ultracapacitor based ride-through system for a DC load

Ultracapacitor is an emerging energy storage device suitable for high-power, short-term applications. In this paper, a ride-through system for a DC load based on the ultracapacitors and a current-reversible buck-boost converter is analyzed. Compared to an equivalent battery operated converter in the boost mode with continuous inductor current, the control to output transfer function of the ultracapacitor-based converter has an additional right half plane zero located very close to the origin. As a result, the achievable bandwidth of the controller is very low and a steady-state error prevails in the load voltage if the controller is designed to operate in the stable mode. However, if zero steady-state error in the load voltage is desired, it can be achieved by operating the system with some degree of instability during the short period of disturbance.