High Efficiency DC/DC Buck-Boost Converters for High Power DC System Using Adaptive Control

In this paper presents new topologies Multilevel DC-DC buck-boost converter which consists of an inductor based boost circuit and a switched capacitor circuit has high voltage gain and flexible output voltage. Operation of these switching devices causes inherently nonlinear characteristic to the DC-DC Converters include buck-boost converter. It is suitable for a low voltage power source such as fuel cells. However, in high switching frequency, multilevel DC-DC buck-boost converter's power conversion efficiency is reduced by switching loss. Against the problem, this paper proposes an five level soft-switching multilevel DC-DC converter. Proposed system consists of development of fuzzy logic controller for generating control PWM pulses of required duty cycle foe MOSFET of the buck-boost converter to maintain the constant output voltage. Duty cycle of the converter is adjusted continuously to obtain required output voltage. However, implementations of this control method to nonlinear system like buck-boost converters will suffer from dynamic response for the converter output. To achieve a stable and fast response, nonlinear controller were applied to control buck-boost converters. The efficiency of the proposed converter is improved compared with the conventional soft switching converter in high boost ratio. The operation of the proposed converter has been confirmed by circuit experiments and simulations by using MATLAB Simulink.