Voltage source converter (VSC)-based high-voltage direct current (HVDC) and multi-terminal (MT)/DC grid technologies are the new HVDC transmission technologies after ultra-high voltage alternative current (UHVAC) and UHVDC transmission technologies which have been widely used in China. The application of the new technologies has resulted in a rapid increase in the number of schemes in construction and planning worldwide. This has been stimulated by the greater level of functionality available from the VSC technology, which makes it suitable for a wide variety of applications. These include the integration of offshore wind farms, embedded links within AC networks and interconnectors, especially where the AC networks are relatively 'weak'. VSC technology has renewed interest in MT DC systems, which may ultimately lead to wide area DC grids. This study outlines the research and application on MT and DC grids in China with respect to VSC-HVDC key technologies and DC grid key technologies based on the presentation given in the International Workshop on Next Generation Power Equipment held on 23 September 2016 in Xian, China. The briefing details of the VSC-HVDC projects constructed and to be constructed in China are summarised in this study.

Due to their high controllability and flexibility, DC power grids have broad application prospects in the fields of networking of renewable energy and the power supply for oceanic archipelagos and future cities. This paper describes the system topology, control strategy, DC breaker configuration, and research, development and testing of converter valves and DC breaker equipment of the Zhoushan multi-terminal DC transmission system. Zhejiang Zhoushan has unique geographical and developmental features to demonstrate the irreplaceable technical advantages of a DC power grid for providing reliable power supply. The experience gained from the Zhoushan DC power grid project can offer valuable insights into the development and utilization of this technology worldwide.

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