Basic topology and key devices of the five-terminal DC grid

Abstract

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.

Present and future multiterminal HVDC systems: current status and forthcoming developments

“…Among the islands of the Zhoushan archipelago, the larger and more power-consuming islands include the main island of Zhoushan, followed by the islands of Daishan, Qushan, Yangshan and Sijiao. To meet the increasing demands of the construction of new areas and development of different islands, the power load capacity will need to increase constantly [16].…”

“…The second stage is to build the five-terminal DC transmission system with DC breakers (successfully installed on December 29 th , 2016), so as to improve the fault clearance and recovery abilities as well as system availability, and conduct engineering inspections of the DC breakers under development. The third stage is to construct the five-terminal DC grid system [16]. [17] The five converters rated at ±200 kV in the Zhoushan DC grid are connected via modular multi-level voltage source converter (MMC-VSC) HVDC links to form a 5-terminal DC grid.…”

“…[17] The five converters rated at ±200 kV in the Zhoushan DC grid are connected via modular multi-level voltage source converter (MMC-VSC) HVDC links to form a 5-terminal DC grid. The converter stations used in this system incorporate symmetric monopole main wiring mode and the cables connect the converters with a total length of 140 km [16,18].…”

“…A full-bridge cascaded new-type topology of the hybrid circuit breaker was designed for this project, which comprises three parallel branches including the main branch, transfer branch, and energy-consuming branch [16]. These HVDC circuit breakers have rated voltage 200kV, rated current 2kA, short-circuit current breaking capacity 15kA, breaking time of 3ms and transient voltage 300kV [19].…”

Small-Scale HVDC Circuit Breaker

“…Substantial interest and research effort is thus currently invested into finding fast, reliable and efficient concepts for HVDC circuit breakers [5], with recent publication of several high power prototypes, for example [6], [7] and [8]. Several multiterminal systems have been developed, first implementing line commutated converters [9], [10], and recently with voltage source converters [11], [12], and although there are plans for system implementation of HVDC circuit breakers [13], little operational experience was gained. Requirement specifications and expected breaker-network interactions remain at a theoretical level.…”