A 10kV/400V SiC based DC-DC Converter with Input-Series-Output-Parallel Configuration and Three-Loop Control

There is a continuous demand for high power, high frequency, high reliability dc-dc converters in various applications such as medium voltage dc (MVDC) distribution systems, energy storage and electrical vehicle charging facilities. Hence, the input-series-output-parallel (ISOP) dc-dc converter has been widely researched. However, there are a number of challenges with the increase of the input voltage, such as the requirement of high-voltage-isolated and compact high frequency transformers, high reliability and isolated control systems between the high-voltage input side and the low-voltage output side, components selection and design to realize the high efficiency, reliable and effective thermal management, and modular structure design. Therefore, in this article, a 10kV/400V ISOP dc-dc converter with eleven dual active bridge (DAB) sub-converters (SCs) based on SiC MOSFETs has been designed to address these challenges, which can satisfy the pursuit for high frequency, high reliability and high efficiency as well as the demand for high voltage isolation and modular structure design. Firstly, the hardware design is presented, which includes the design of the gate driver circuit, high frequency transformer, thermal management, modular structure and the whole prototype. Hence, a high efficiency (97.8%) and large voltage conversion ratio (10kV/400V) ISOP-DAB converter has been achieved in this article. Secondly, a decoupled three-loop control (DTLC) based on the master-slave control architecture (MSCA) has been proposed, which integrates the input voltage sharing control (IVSC) loop, output voltage control (OVC) loop and output current control (OCC) loop. Therefore, effective power sharing, stable output voltage control and flexible output current regulation can be achieved with fast dynamic response. The improved hardware design and the DTLC based on the MSCA have been verified by simulation and experimental results.