面向中压直流配电网的大容量新能源发电接入系统组成机理和运行控制研究

AC/DC hybrid distribution networks and large-scale distributed grid-connected renewable generation are the two key challenges for the development of smart grid. Photovoltaic-energy storage system is an important technical development path to deal with these challenges. In this project, the large-capacity renewable generation system integrated into the medium voltage DC distribution network will be investigated by using the priority-based power flow optimization in terms of configuration, topology, operation mechanism and control strategy. The “Virtual DC machine” based grid-connected control strategy of the renewable generation system, the all voltage source mode based distributed control strategy of DC/DC converters with series-connected outputs, the maximum efficiency point tracking (MEPT) control strategy for the two-stage photovoltaic converters, a novel topology of the photovoltaic converter based on LC resonant circuits and distributed boost circuits will be proposed in this project. The final target of this project is to reveal the optimization principles of power flow in the large-capacity renewable generation systems, and to propose a novel solution of the photovoltaic generation integrated into the medium voltage DC distribution network with high performance, high efficiency, high reliability, high stability, flexible control, perfect protection and good extendibility. Based on the above works, the researches on the theory and technology in the field of “Renewable generation integrated into DC distribution network” will be promoted to a higher level.

交直流混合配电网和大规模分布式新能源并网是智能电网发展进程中的两项重大挑战，而面向中压直流配电网的光伏-储能系统正是应对上述挑战的重要技术发展途径。本项目以接入中压直流配电网的大容量新能源发电系统为研究对象，以基于分级管理的功率流优化为基本思路，从组成结构、电路方案、运行机制和控制策略四个方面开展研究，拟提出具有“虚拟直流电机”特性的新能源发电系统并网控制策略，输出串联DC/DC变换器的全电压源模式分布式控制策略，两级光伏发电变换电路的最大效率点跟踪（MEPT）控制策略，基于LC谐振电路和分布式升压电路协同运行的新型光伏发电变换器电路方案。最终目标是揭示大容量新能源发电系统中功率流的优化机理，提出并实现一整套高性能、高效率、高可靠性、高稳定性且控制灵活、保护完善、易于扩展的光伏发电接入中压直流配电网解决方案，使“新能源发电接入直流配电网”这一重要领域的理论研究与技术水平提升到一个新的高度。

交直流混合配电网和大规模分布式新能源并网是智能电网发展进程中的两项重大挑战 ，而面向中压直流配电网的光伏-储能系统正是应对上述挑战的重要技术发展途径。本项目以接入中压直流配电网的大容量新能源发电系统为研究对象，以基于分级管理的功率流优化为基本思路，从组成结构、电路方案、运行机制和控制策略四个方面开展了深入研究，取得了一系列重要的创新成果：1）针对面向中压直流配电网的光伏接入系统，提出了两级式系统架构，第一级采用差分功率处理电路，实现组串/组件级MPPT，第二级采用输入并联输出串联（IPOS）结构实现高效的高升压比变换；2）提出了新型隔离型DC/DC变换电路，前级采用交错并联Boost电路，主要实现MPPT，而后级采用全桥谐振LLC拓扑，主要实现软开关高升压比变换；3）提出了基于“虚拟直流电机”的光伏-储能系统跨模块协同控制策略，提升了并网运行的稳定性；4）提出了隔离型DC/DC变换电路和差分功率处理电路的效率优化方法，改善了系统综合效率；5）提出了一种基于模块化三端口变换器（TPC）的新型光伏中压直流接入系统架构及其控制策略，同时实现了分布式光伏MPPT和模块输出侧均压。项目成果揭示了大容量新能源发电系统中功率流的优化机理，提出并实现了一整套高性能、高效率、高可靠性、高稳定性且控制灵活、保护完善、易于扩展的光伏发电接入中压直流配电网解决方案，提升了“新能源发电接入直流配电网”这一重要领域的理论与技术水平。

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