A Control Strategy Based on Intermediate Bus Voltage Information for Wide-Range High-Efficiency Step-Up DC-DC Converters

With the increasing utilization of renewable energy generation, especially photovoltaic (PV) power generation, the technology for wide-range high-efficiency DC-DC converters is becoming increasingly important. This paper focuses on the control of high-efficiency step-up DC-DC converters with the multi-phase Boost and LLC (MPBLLC) converter. A control strategy based on intermediate bus voltage information is proposed to improve the efficiency over a wide input voltage range. The operation principle and the time domain model of the converter are analyzed first. Since the loss models in previous studies are not accurate and comprehensive enough, a loss modeling method for the variable voltage is proposed. It is based on the time domain analysis (TDA) and is available for a wide voltage range. By analyzing the level and influence factors of variables in the MPBLLC converter, a fast algorithm for loss modeling is also proposed. Further, the control strategy including the optimal bus voltage control is proposed for MPBLLC converter. Control modes are analyzed in detail. For the key part, four different control approaches are presented based on different variations of the intermediate bus voltage. Above all, the optimal bus voltage control is proposed based on the proposed variable bus loss model. Finally, a 500-W experimental prototype is built to verify the effectiveness of the proposed loss model and control strategy, which demonstrates good performance and high efficiency over a wide input voltage range.