Ultracapacitor-based plug & play energy-recovery system for elevator retrofit

Vertical transportation is a promising field in terms of efficiency improvement opportunities. Several manufacturers are working on the development of new and efficient elevator lifts based on energy-recovery schemes. This paper is focused on the retrofit of already existing inverter-based non-efficient elevator actuators. This purpose is achieved through a) the connection of only two wires to the DC bus of the existing inverter, and b) a very simple but robust control based on several voltage hysteresis-bands. Simulation and experimental results show the validity of the approach.