An Advanced Protection Scheme for Enabling an LVDC Last Mile Distribution Network

Abstract

Low voltage direct current (LVDC) distribution systems have the potential to support future realization of smart grids and enabling of increased penetration of distributed renewables, electric vehicles, and heat pumps. They do, however, present significant protection challenges that existing schemes based on dc fuses and conventional electro-mechanical circuit breakers cannot manage due to the nature of dc faults and slow device performance. Therefore, this paper presents an advanced protection scheme that addresses the outstanding challenges for protecting an LVDC last mile distribution network. The scheme takes advantage of advanced local measurements and communications that will be naturally integrated in smart grids, and the excellent level of controllability of solid state circuit breakers. It thus provides fast dc fault detection and interruption during dc transient periods, in addition to achieving fault limitation and fast reliable restoration. The introductory part of the paper quantifies the potential benefits of LVDC last mile distribution networks, and discusses the potential LVDC architectures that best utilize the existing plant. Based on the new LVDC architectures, a typical U.K. LV network is energized using dc and modeled, and is used as a case study for investigating the protection issues and evaluating the new protection scheme performance through simulation.

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“…However, this method temporarily de-energizes the entire network, which can create unnecessary outages. As a result, this scheme may not be suitable for local distribution networks and LVDC microgrids where a large number of sources and loads are connected to the system [156], [225], [230]. …”

“…An advanced protection scheme should have selfdiagnosing and self-healing capabilities to reduce damage caused by short circuit faults and to provide continuous power to loads, even during system faults [112], [156] [158]. The self-diagnosing capability of the system requires a well-designed protection scheme to be able to detect a fault very quickly and accurately locate the faulted area.…”

“…High voltage DC (HVDC) transmission lines have been increasingly used to provide a cost-effective solution for transferring power over long distances with enhanced power flow controllability [156].…”

“…At lower voltage and power levels, medium voltage DC (MVDC) and low voltage DC (LVDC) distribution systems can be effectively utilized in various systems, such as electric traction systems, telecommunication and data centers, and for shipboard and aircraft systems [112], [156].…”

“…Moreover, DC distribution systems have the potential to better support future smart grids in realizing a high penetration of distributed renewables and electric vehicles [156]. In order to protect DC systems from short circuit faults, various protection schemes have been developed for different applications and voltage levels.…”