Protecting the Future Electric Power Systems

直流电网是一种新兴的电力系统，具有显著的潜在效益。高压直流（HVDC）电网提高了大容量输电系统的可靠性和效率，也促进了大规模可再生发电系统的电网整合。中压和低压直流电网以及直流微电网促进了分布式能源的整合。然而，未解决的保护问题限制了直流电网的利用。现有的保护系统（继电器）不能完全保护直流电网免受故障（短路）和干扰的不利影响。 拟议的研究计划的长期目标是通过开发高速，可靠，鲁棒和选择性的保护策略，以确保在未来的电力系统中的直流电网的安全运行。在短期内，拟议的研究计划将解决HVDC电网和DC微电网的主要保护问题，如下所述。 目前还没有用于网状HVDC电网中的传输线路的故障保护的商业上可用的技术。将制定保护策略，以便在HVDC电网中实现及时可靠的故障检测和定位（故障线路的识别）。所提出的保护策略将适用于具有不同配置、接地类型和换流器技术的HVDC电网。此外，还将开发广域系统保护方案（SPS），通过检测和抵消可能导致连锁停电的线路过载条件来保护HVDC电网的完整性。2)直流微电网保护 现有的保护策略不能满足直流微电网应用对速度和可靠性的要求。拟议的研究计划将开发一种保护策略，用于直流微网馈线的高速可靠故障保护。此外，将开发SPS以保护DC微电网的完整性免受电压崩溃。在并网和孤岛运行模式下，SPS将能够及时采取补救措施，以抵消可能导致电压崩溃的干扰。 拟议的研究计划将推进HVDC电网和DC微电网保护的最新技术，从而：1）导致第一个继电器的开发和商业化，以保护这些DC电网免受故障和系统范围的干扰;2）促进大容量电力的长距离传输，具有更高的可靠性和效率，在包括加拿大在内的大国; 3）通过防止广泛的灾难性故障来改善现代化电网的动态和稳定性，例如，2003年加拿大和美国的大停电; 4）增加可再生能源系统在加拿大配电系统中的渗透。

Direct Current (DC) grids are emerging electric power systems with remarkable potential benefits. The High-Voltage DC (HVDC) grid improves reliability and efficiency of bulk power transmission systems and also facilitates grid integration of large-scale renewable generation systems. The medium-voltage and low-voltage DC grids and the DC microgrid facilitate integration of distributed energy resources. However, unresolved protection issues have constrained utilization of DC grids. The existing protection systems (relays) do not fully protect DC grids against adverse effects of faults (short-circuits) and disturbances. The long-term objective of the proposed research program is to ensure secure operation of DC grids in the future electric power systems by developing high-speed, reliable, robust, and selective protection strategies. In the short-term, the proposed research program will address the main protection issues of the HVDC grid and the DC microgrid, as explained below.1) HVDC Grid Protection Currently there is no commercially available technology for fault protection of transmission lines in the meshed HVDC grid. A protection strategy will be developed to enable timely and reliable fault detection and location (identification of the faulted line) in the HVDC grid. The proposed protection strategy will be applicable to HVDC grids with different configurations, grounding types, and converter technologies. In addition, a wide-area System Protection Scheme (SPS) will be developed to protect integrity of the HVDC grid by detecting and counteracting line overloading conditions that can lead to cascading outages. 2) DC Microgrid Protection The existing protection strategies do not meet the speed and reliability requirements for DC microgrid applications. The proposed research program will develop a protection strategy for high-speed and reliable fault protection of DC microgrid feeders. Besides, a SPS will be developed to protect integrity of the DC microgrid against voltage collapse. The SPS will be capable of taking timely remedial actions to counteract the disturbances that can lead to voltage collapse, under both grid-connected and islanded operation modes. The proposed research program will advance the state-of-the-art in protection of the HVDC grid and the DC microgrid, and thereby:1) lead to development and commercialization of the first relays to protect these DC grid against faults and system-wide disturbances;2) facilitate long-distance transmission of bulk power with higher reliability and efficiency, in large countries including Canada; 3) improve dynamics and stability of the modernized power grid by preventing widespread catastrophic failures, e.g., the blackout of 2003 in Canada and USA; and 4) increase penetration of renewable energy systems into Canadian distribution systems.