民用低压直流系统接地型式与短路保护研究

发布时间：2018-05-08 19:21

本文选题：低压直流系统 + 直流安全电压　；参考：《重庆大学》2014年硕士论文

【摘要】：节能环保的低压直流（low voltage direct current, LVDC）供电方式在民用建筑等常规领域具有很大的应用潜力，其安全保护问题的成功解决将成为LVDC系统向常规领域推广的关键所在。低压供电系统的安全主要体现为有合适的接地措施，并在故障时能保证电气设备及人身的安全。论文从LVDC系统接地型式、短路保护两方面展开研究，为LVDC系统的进一步推广提供一定的理论依据。低压系统接地型式的选择主要由系统电击防护性能与供电连续性决定，尤以电击防护性能为重点。安全电压限值是研究低压系统电击防护性能的基础，且直流电通过人体时的电击效应与交流电有着本质的差异。论文首先结合国际标准IEC60479-1，对比了直流电与交流电电击效应，给出了直流电的安全阈值曲线，分析了不同方向直流电通过人体时的安全电压限值。同时，，论文还对目前所能获得的直流电可能含有高频纹波的现象，讨论了直流纹波对人体电击效应的频率加权效应及影响。基于对直流安全电压的分析，论文探讨了理想直流源、单相桥式整流器两种直流供电电源系统各接地型式的电击防护性能。重点详细分析了基于直流微网、电压平衡器的直流双极供电系统的接地故障参数，利用Matlab/Simulink软件构建了DC±190V系统进行验证。在此基础上，讨论了各接地型式的供电连续性、电击防护性能与保护设备要求，与传统交流220V供电系统的对比表明，低压直流供电系统在电气安全方面有较明显的优势；直流TT系统在配备RCD的情况下，其供电连续性和电气安全性能可以得到很好兼顾，相较直流IT和直流TN系统而言，更适合作为该类含有电压平衡器的直流双极供电系统的接地型式，并给出了保证其电气安全的接地电阻取值范围及保护装置技术要求。针对LVDC系统的短路故障及保护配合问题，论文讨论了PWM控制的三相桥式整流器的短路故障，分别基于外特性曲线和开关函数模型，给出了两种简化短路模型。然后重点利用直流变换电源，搭建小型的直流供电网络，对线路短路、负载短路的故障参数分别进行测量，得到了LVDC系统短路电流的变化情况，并分析了各短路故障对直流供电电源的影响，测试了直流断路器与直流电源、直流负载自身保护的相互配合情况。
[Abstract]:Low-voltage DC low voltage direct current, LVDC) power supply mode with energy saving and environmental protection has great application potential in conventional fields such as civil buildings. The successful solution of its safety protection problem will become the key to popularize the LVDC system to the conventional field. The safety of low voltage power supply system is mainly reflected by proper grounding measures, and the safety of electrical equipment and personal can be guaranteed in the event of failure. In this paper, the grounding type and short circuit protection of LVDC system are studied, which provides a theoretical basis for the further popularization of LVDC system. The selection of grounding type of low voltage system is mainly determined by the system electric protection performance and the continuity of power supply, especially the electric shock protection performance. The safe voltage limit is the basis of studying the electric shock protection performance of low voltage system, and the electric shock effect of DC passing through the human body is essentially different from that of AC. Combining with the international standard IEC60479-1, this paper compares the electric shock effect between DC and AC, gives the safety threshold curve of DC, and analyzes the safe voltage limit when DC passes through human body in different directions. At the same time, the frequency weighting effect of DC ripple on human body is discussed. Based on the analysis of DC safe voltage, the paper discusses the protective performance of each grounding type of DC power supply system with ideal DC source and single-phase bridge rectifier. The grounding fault parameters of DC bipolar power supply system based on DC microgrid and voltage balancer are analyzed in detail, and the DC 卤190V system is constructed by Matlab/Simulink software. On this basis, the continuity of power supply, the protective performance of electric shock and the requirements of protective equipment are discussed. The comparison with the traditional AC 220V power supply system shows that the low-voltage DC power supply system has obvious advantages in electric safety. When DC TT system is equipped with RCD, its power supply continuity and electrical safety performance can be well taken into account, compared with DC IT and DC TN systems, It is more suitable to be the grounding type of DC bipolar power supply system with voltage balancer, and the range of grounding resistance and the technical requirements of protective device are given to ensure its electrical safety. Aiming at the problem of short circuit fault and protection coordination of LVDC system, this paper discusses the short circuit fault of three phase bridge rectifier controlled by PWM. Based on the external characteristic curve and switch function model, two simplified short circuit models are given. Then the DC power supply is used to build a small DC power supply network. The fault parameters of short circuit and load short circuit are measured, and the variation of short circuit current in LVDC system is obtained. The influence of each short-circuit fault on DC power supply is analyzed, and the mutual cooperation between DC circuit breaker and DC power supply, DC load self-protection is tested.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM862

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