电流差动保护在柔直接入的交流电网中适应性分析及改进措施研究

为适应新能源规模化接入电网,柔性直流输电技术应用日益广泛,我国电网已初步成为交直流混联电网。交流系统发生故障时,柔直系统提供短路电流的特征与传统同步发电机相比发生显著变化。首先分析故障特征的变化,柔直侧由于故障电流幅值受限,且负序阻抗无穷大,导致故障电流的幅值和相角与交流侧不同。分析了输电线路电流差动保护由于区内故障时两侧电流夹角增大,导致电流差动保护的动作量减少、制动量增加,导致灵敏度下降甚至拒动。在此基础上,提出了差动保护判据的改进方案:分别利用零序电流、负序电流和正序电流突变量构成辅助判据,提高区内接地故障和相间短路时电流差动保护的灵敏度,从而提高了差动保护在含柔直接入交流电网中动作的可靠性。最后,通过仿真验证了所提方案的可行性。

船舶岸电系统变电方案分析与设计

针对国内与国外岸电系统技术差距较大,尤其在船舶岸电系统变电方案设计方面研究较为落后的问题,研究船舶岸电系统最优电压等级计算方法,结合最优电压等级对比分析不同船舶岸电系统上船方式,提出合理的变电方案。

Study on Supply and Demand of Intelligent Home-based Aged Care in Shanghai

The 21st century is an era of aging population. With the accelerated aging of the population in our country, and the grim form of population aging, intelligent home-based care has become a concern for the elderly in the area of ？？care. This paper starts from the new concept of intelligent home-based care services and defines intelligent home care services. It also summarizes the current theoretical researches related to domestic research, which is of great significance for the investigation and research conducted in the later stage of research.