Research and application on multi‐terminal and DC grids based on VSC‐HVDC technology in China

Abstract

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.

Dynamics and Stability of Meshed Multiterminal HVDC Networks

“…where, v eq = (v eq,ua , v eq,ub , v eq,uc , v eq,la , v eq,lb , v eq,lc ) T , v eq ∈ R 6×1 is the equivalent vector of aggregated submodule capacitor voltage at each phase, i = (i ua , i ub , i uc , i la , i lb , i lc ) T is the arm current per phase, the subindices are used for the {u, l} upper and lower arms, respectively and the sub- The model in (1) represents the voltage of the upper arm loops,…”

“…MT-HVDC increase the efficiency of the power transfer over long distances compared to HVAC solutions and the reliability of the power supply compared to point-to-point interconnection. Moreover, the use of the Voltage Source Converter (VSC) technology, with independent control of active and reactive power at the AC terminals is considered and advantage to support weak power systems [1]. The deployment of large interconnected HVDC grids requires specific power system analyses, similar to those traditionally applied to AC power systems, which however need to the adapted to describe the specific components and operation of MT-HVDC grids.…”

Design and Experimental Tests of a Superconducting Hybrid DC Circuit Breaker

“…Fast operating DC circuit breakers therefore are acritical technology for manag- ing faults in DC grids. DC circuit breakers are required to detect and clear the fault within 2-5 milliseconds [4,5]. A DC circuit breaker using a superconductor for current limiting has been proposed and experimently investigated [6,7].…”

Electromechanical Transient Modeling of Line Commutated Converter-Modular Multilevel Converter-Based Hybrid Multi-Terminal High Voltage Direct Current Transmission Systems

“…In recent years, the hybrid HVDC systems have drawn more and more attention both from academic and industrial fields because of the combined advantages of LCC and VSC (especially the MMC) [2][3][4][5][6][7][8][9][10][11][12][13][14]. Previous studies about hybrid HVDC systems mainly focused on electromagnetic transient modeling [4][5][6][7], control protection strategies [8][9][10] and harmonic analyses [11,12], which are mainly based on the electromagnetic transient simulation platform.…”