A Novel Fourth-Order Buck-Boost Converter

The paper presents a novel fourth-order Buck-Boost converter with coupled inductors, one MOSFET transistor, three diodes, 2 capacitors and a separate inductor. The advantage of the proposed converter compared with the classical one is that it employs two degrees of freedom and for the same duty cycle provides a substantial higher output voltage. The dc and ac analyses are performed, and the design equations are provided. First, in order to test the functionality of the converter and to confirm the theoretical analysis, the fourthorder Buck-Boost converter is first subjected to simulation and then verified by practical experiments in open loop. In the last part, a state space model is provided for calculating the control to output transfer function. As the converter is of fourth order an approximation is used for reducing the control to output function order to two. The approximated transfer function has 99.34% approximation and contains a zero and two poles. Based on it a controller is designed and finally the theoretical considerations in closed loop operation are verified through simulations.