A Modular Non-Inverting Buck-Boost DC-DC Converter

Abstract

DC-DC power converters with high voltage gain play a critical role in DC power collection topologies for offshore wind farms and their HVDC transmission systems. This paper proposes a modular DC-DC converter with high voltage gain based on a non-inverting buck-boost topology for high-power applications. The proposed converter consists of three non-inverting buck-boost modules connected as input-parallel and output series (IPOS). The reduced voltage stress on power devices, the increased voltage gain, and enhanced power conversion efficiency are all advantages of the proposed IPOS cascaded converters. However, IPOS cascaded DC-DC converters have a voltage balancing issue on the output side. The operation modes and the dynamic performance of the proposed converter are studied in both cases of identical and non-identical converter modules. Moreover, a novel state-space model for the proposed converter with non-identical modules and different control signals is developed. This model has been verified using the converter's switched model, and the result reveals that the developed model is accurate. Furthermore, output capacitors voltage balancing control scheme based on simple PI controllers for the proposed DC-DC converter is presented. The capacitor voltages are hence perfectly balanced. In addition, the presented controller system achieves a fast response with negligible oscillations and steady-state error. MATLAB/Simulink software package is used to simulate the proposed converter, investigate its operation, and examine the converter's dynamic behaviour.