HVDC transmission overview

High voltage direct current transmission - A review, part I

“…Therefore, the utilization of HVDC links is usually higher than that for extra high voltage (EHV) AC transmission lowering the transmission cost per MWh. By eliminating loop flow, controllability frees up parallel transmission capacity for its intended purpose of serving intermediate load and providing an outlet for local generation [29].…”

“…Moreover, as the city power load is increasing, the capacity of grid need to be expanded, despite that the overhead AC lines have already occupied much transmission space. In a word, a new transmission approach is needed to solve these and other problems, the DC transmission, which is being used in several projects [30], [31]- [32], and [33]- [34]. Switching surges, for example, are the serious transient over voltages for the high voltage transmission lines.…”

“…Furthermore, the long distance AC lines usually require intermediate switching stations and reactive power compensation. This can increase the substation costs for AC transmission to the point where it is comparable to that for HVDC transmission [29].…”

Toward the Universal DC Distribution System

“…The adoption of HVDC lines for the transport of electrical energy over long distances is one example. The advantages of HVDC over HVAC are reported to be low-cost, decreased losses, and the absence of restrictions on long distance cables [3].…”

Modelling and Control for Bounded Synchronization in Multi-Terminal VSC-HVDC Transmission Networks

“…This guarantees grid access to renewable sources such as large-scale wind farms, hydro-electric facilities, or mine-mouth power plants in remote areas. In particular, the use of HVDC links in offshore wind farms improves voltage and frequency responses independently of the wind turbine type, and alleviates the effect of grid faults [3], [4].…”