基于固态变压器互联的主动配电网短路计算与保护研究

The project conceptually proposes to analyze the precise transfer mechanism of solid state transformer (SST) to the short-circuit current and identify the faults of different levels in SST internal components, and use these to support the protection of active distribution network integrated using SST. On the analysis methods, the research will study the coordination control and short-circuit current change law of SST during external faults, and the short-circuit transfer model from the source side to the fault side of SST can be established to determine the fault electrical constraints of SST coupling point in the hybrid AC and DC power grid, then the short-circuit current calculation method for active distribution networks integrated using SST will be proposed. Furthermore, the analytical redundant relation formulas among the internal fault transient characteristics of SST will be derived to obtain the analytical redundancy residual criterion and construct the fault detectability indicators for the rapid identification of SST internal component faults. On the application processes, the main protection principle of SST based on internal fault identification can be presented according to the discussion of protection ranges for different protection criterion combinations. Afterward, through defining the error criterion between characteristic function and measured data of short-circuit current transfer ratio, and combining with the time sequence similarity criterion of SST multiport instantaneous active power, the backup protection principle of SST and its setting modes coordinating with the driver circuit protection, the main protection of SST and the power grid protection will be proposed. As an intended outcome of this research, the protection and setting methods can be provided for the future distribution system based on SST as interconnection cores.

本项目在概念上提出解析固态变压器（SST）对短路电流的精细化传递机制、识别SST内部元件的不同程度故障，为基于SST互联的主动配电网保护创造条件。在分析方法上，研究外部故障时SST协调控制及短路电流变化规律，建立SST有源侧向故障侧的短路电流传递模型，进而确定交直流电网中SST联络点的故障电气约束，提出交直流主动配电网的短路计算方法；推导SST内部故障暂态特征量间的解析冗余关系式，构建解析冗余残差判据及其对元件故障的可检测性指标，快速识别SST内部元件故障。在应用途径上，探讨不同判据组合的保护范围量化方法，提出利用内部故障识别的SST主保护原理；定义短路电流传递比特征函数与测量数据的误差判据，再与SST多端口瞬时有功时序相似度判据相结合，提出SST后备保护原理及其与驱动电路保护、主保护和电网保护的配合方式。本项目最终期望达到为以SST为互联核心的未来配电系统保护和整定提供理论支持。

本项目在概念上提出解析固态变压器（SST）对短路电流的精细化传递机制、识别SST内部元件的不同程度故障，为基于SST互联的主动配电网保护创造条件。项目研究了电网故障时固态变压器（SST）的不脱网控制策略及运行性能指标解析，推导不脱网可控SST多端网络的故障电气量转移函数，建立了SST双端口短路电流传递模型，解决了SST流通受限短路电流传递机制难以解析的问题；研究了变流型电源在暂态和稳定阶段的短路电流计算模型，结合SST短路电流传递模型，提出了由SST互联的交直流主动配电网短路电流计算方法，实现了SST短路电流传递模型与传统短路电流计算的有机整合；分析了开关管等元件故障时SST内部故障电气量分布规律，由多频率变换和正负序分量计算提取SST暂态特征量，推导了不同特征量的解析关系式，提出了基于深度卷积神经网络的SST内部故障识别方法，实现了SST内部故障特征的快速检测及识别。项目的实施能够为高渗透分布式发电接入电网的短路计算和保护方案制定提供完善的理论基础和应用技术，为新能源发电的组网设计和运行控制提供重要的参考。