Standards Development

Scope

This technical specification provides guidelines for the planning and design of direct current (DC) or hybrid microgrids connected or not connected to low-voltage (LV) or medium-voltage (MV) alternating current (AC) systems, including load and generation forecasting, voltage level selection, topologies, equipment selection, protection system, monitoring, communication, metering, DER and load connection, and interface to AC systems (if any). DC or hybrid microgrids can be based on MV and LV distribution.

This technical specification is applicable to various DC or hybrid microgrids, including those used in industrial parks, buildings, EV charging stations, data centers, islands, remote areas, etc.

DC systems used for railway applications are excluded from this document.

Purpose

This proposal is to relaunch the ongoing project IEC TS 63354 following the SMB Decision 176/8 60. The project was approved in 2020-07 with the original title of Guideline for the planning and design of the decentralized direct current distribution systems (8B/61/NP, 8B/67/RVN). Responding to the fact that the DC technologies on LV and MV level are in still rapid development and DC and AC/DC hybrid microgrids are typical applications at this stage, the title and scope were changed to Guideline for the plann ing and design of direct current or hybrid microgrids (8B/205/Q, 8B/206/RQ) in 2024 -02.

The project covers a wide range of topics, including prediction, voltage levels, grid topology, protection, grounding, user access, and other aspects. Some of these topics need to be handled in collaboration with work in other committees and WGs, for examp le LV and MV DC voltage levels in TC 8/JWG 9, DC protection in TC 95, prosumer side LV DC in TC 64, etc. The complexity of the topics, changes in scope and title, and the collaboration with other TCs/WGs caused significant longer working period than the or iginal plan.

Since the approval of the project, LV and MV DC technologies and implementations keep developing rapidly around the world, for example the MVDC Tie Pilot and AC/DC Hybrid Distribution grid Projects in Korea, MVDC Distribution interconnecting MV/LV project in Japan, Eagle Pass Tie Project and Mackinac Project in the USA, the Hällsjön and Grängesberg project in Sweden, Tjaereborg Project in Denmark, Angle -DC project, Nottingham University in the UK, FEN Research Campus MVDC Grid in Germany, Vindhyachal Projec t in India, Beichen AC/DC project, Guangzhou University Project and many projects in China. These projects show a variety of expectations for MV/LV DC technologies, including capacity increase for offshore wind power in island areas, improvement of conventional ac system applying for AC/DC hybrid and MV/LV DC grid, integration of renewable energy sources, power supply to the rapid growth of DC loads such as electric vehicles (EV), data centres, battery storage systems etc. These applications cover various s cenarios such as offshore wind/tidal/wave energy base, island DC power supply systems, DC systems in residential area, industrial parks, campuses, data centres, EV charging stations, as well as urban distribution systems. Many of these projects are DC or hybrid microgrids, as an early stage of a larger DC system, pilots, or permanent microgrids, which can be isolated DC systems, or with connection to AC systems via one or multiple connection points, or embedded as a whole through a single bus.

DC microgrid technology distinguishes from AC in terms of technical principle, equipment and control mode. Compared to AC systems, the DC systems have more diversified structures, power electronic devices, control and operation modes. For example, in DC system design, it needs to decide the voltage polarity configuration (monopolar or bipolar), according to the reliability requirement of load and budget, which is not included in AC system.

This project can serve the industry by providing references and methods for the selection of voltage levels, design of grid layout, selection and sizing of DC components, configuration of protection, control and metering systems, connection of DER and DC load, as well as interfacing AC systems, etc.

SC 8B/WG 5 have invested significant expert resources and efforts in this project. So far, WG 5 has held 16 meetings, developed five versions working drafts, circulated 1st CD in July 2024. WG 5 has resolved over 200 comments from the 1st CD circulation and the 2nd CD will soon be circulated. Relevant work including DC voltage levels in TC 8 and protection in TC 95 and converter specifications in TC 22 are also made remarkable progress and could help WG 5 to accelerate the work. Considering the global trend towards energy transition and the development of DC technologies and applications, the value and importance of this project are even more prominent.