M.D. Noh, O-K. Oh, S. Kim, Y-W. Park
Chungnam National University, KR
DC/DC converter, SEPIC, fuel cell, feedback control
A single-ended primary-inductance converter (SEPIC)is a DC/DC converter that has a wide input range and is ideal for a fuel cell. The controller for a SEPIC is often designed heuristically without the consideration of the output requirements such as voltage ripple and the frequency bandwidth. In this paper, we develop a mathematical model of SEPIC using the state-space averaging technique. This model is cast into a disturbance-rejection problem, where the disturbance is the input voltage variation. The control input is the duty cycle variation from the nominal value. The output voltage is measured and used as the input for the controller. A 12-V 24-W SEPIC for a direct methanol fuel cell is designed. Then a feedback controller is designed to satisfy no more than 2% voltage ripple from DC to 40Hz when the input voltage swings from 8 to 24 V. Results from simulations and experiments show the disturbance rejection of more than 35 dB (less than 2% ripple) from DC to 50 Hz.