Abstract
Aiming at the demand for medium- and high-voltage port access capability in energy router, this study proposes a quad-port DC/DC converter topology scheme based on modular multilevel converter (QP-M2DC). Compared with the traditional multiterminal energy routing converter, it has the advantages of high modularity, strong flexibility, and high power density. In addition, for the modular structure on the medium- and high-voltage sides, this study proposes a narrow phase-shift cyclic modulation strategy, which reduces the system need for voltage balance control and simplifies the overall system control. This study comprehensively introduces and analyses the QP-M2DC topology, working principle, high-frequency link equivalent, and power characteristics, then establishes an equivalent model of system control, and proposes a control scheme for a multiterminal energy routing converter. Finally, a simulation model of the system is established through PLECS, and the simulation results show that in such a narrow phase-shift modulation strategy, the proposed topology can have stable operation in a variety of patterns, reduce the capacitance, and achieve better voltage balance at the same time. The experimental results show the converter efficiency of up to 97.8%. It further shows the superiority of the proposed topology structure and the correctness and effectiveness of the proposed control schemes.
Highlights
With the development of microgrid technology, medium- and high-voltage DC microgrid (DCMG) has become the main research hotspots
Due to the diversification of its usage scenarios, multi-bus power distribution structure is required, and its interface types can be a variety of distributed energy sources, energy storage systems, AC and DC loads, etc. [2]. erefore, in the DCMG energy management system, as an important part of the electrical energy router, it can control the bidirectional flow of energy and realize the voltage conversion and electrical isolation between the medium-voltage direct current (MVDC) and the low-voltage direct current (LVDC). e core device for plug and play is the DC transformer (DCT)
Based on the above analysis, this study proposes a topology scheme of quad-port DC/DC converter based on modular multilevel structure to realize the multiterminal power routing transformation with medium- and high-voltage port access in the DCMG multi-bus distribution application. is topology integrates the advantages of modular multilevel converter (MMC) and traditional dual active bridge (DAB), with a high-voltage working level and flexible modular design
Summary
With the development of microgrid technology, medium- and high-voltage DC microgrid (DCMG) has become the main research hotspots now. Erefore, to improve the power capacity and voltage level of DCT, the structure of input series and output parallel based on DAB is a common scheme for DCT to connect MVDC and LVDC [9] Based on the above analysis, this study proposes a topology scheme of quad-port DC/DC converter based on modular multilevel structure to realize the multiterminal power routing transformation with medium- and high-voltage port access in the DCMG multi-bus distribution application. The topological structure, working principle, equivalent analysis of high-frequency link (HFL), and power transfer characteristics of QP-M2DC are comprehensively introduced and analysed, the equivalent model of system control is established, and a control scheme of multiterminal energy routing converter is proposed. An experimental platform is set up, and the maximum efficiency of the proposed scheme can reach 97.8%, which further verifies the superiority of the scheme
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