Multiterminal DC grids: Operating analogies to AC power systems

Abstract

Nowadays, some Multi-terminal DC (MTDC) systems are in operation around the world. Soon, MTDC grids will be built and overlay the present AC grids. The main driver for the construction of such a grid is to facilitate large-scale integration of remote renewable energy sources to existing AC grids and to develop the energy market.This paper presents a comprehensive analogy between the control and operation aspects of the emerging MTDC grids to those of the traditional AC power grids. Similarities and difference between the two technologies are presented and highlighted. Based on the performed detailed overview, even though a three-layered control system, i.e., primary, secondary, and tertiary control layers is state-of-the-art in large-scale AC power systems, a two-layered control system will satisfy MTDC grids control and operation requirements. This paper also addresses some control and operational issues and limitations of MTDC grids.

Multi-terminal DC grids: challenges and prospects

“…Following successful research efforts, the Québec-New England HVDC Phase II was constructed and commissioned by ABB in 1990 as the first large multi-terminal HVDC system over the world [14]. It was based on LCC-HVDC technology and it was an extension of the existing two-terminal Québec-New England link into a five-terminal HVDC system, with a power rating of 2000 MW and a DC voltage rating of ±450 kV.…”

“…Apart from initiatives in Europe, there are other international projects that have been announced in recent years, which have developed several important HVDC installations around the world. Some project examples include ''Tres Amigas Super Station'', which will provide a connection between the three major U.S. transmission networks (Eastern, Western and Texas networks), and the new electricity ''superhighway'' between Xiangjiaba and Shanghai, carrying 6400 MW of electricity over more than 2000 km to supply 31 million people [14]. Table 1 summarizes some relevant MTDC systems worldwide.…”

“…Moreover, considering interoperability at the component low levels, for example, considering interchangeable DC circuit breakers from different manufacturers, there is a clear need for substantial further work on standardization. In addition, the development of grid codes for MTDS systems and, in particular, international codes are essential to inspire confidence to different grid operators for interconnecting each other through MTDC grids, which in turn will underpin MTDC grid development in the power industry [14].…”

“…A MTDC grid operating analogously to AC power systems permits the connection of power converters of different ratings, supplied by different vendors and considered for different applications. This idea is presented and discussed in detail in [14], where it is demonstrated that a two-layer control structure can achieve stable operation of the MTDC grid. As a step forward, the concept of AC/DC supergrid and its related challenges are discussed in [19].…”

Analysis on impacts of the shunt conductances in multi-terminal HVDC grids optimal power-flow

“…In recent years, extensive industrial and academic studies on MT-HVDC grids have been conducted [4,5]. Since 1951, there has been evidence of up to 180 predominant two-terminal point-to-point HVDC projects which have been implemented worldwide [6]. During the last decade, some HVDC systems have been extended with additional power converter stations to form the first operational MTDC systems.…”