| dc.description.abstract | High Voltage Direct Current (HVDC) transmission systems continue to be an excellent
asset in modern power systems, mainly for their ability to overcome the problems of AC
transmission, such as the interconnection of asynchronous grids, stability of long
transmission lines, and use of long cables for power transmission.
In the past 20 years, Voltage Source Converter (VSC)-HVDC transmission systems were
developed and installed in many projects, thereby adding more operational benefits to DC
transmission option, such as high controllability, ability to supply weak networks, and
reduced converter reactive power demand. Nevertheless, VSC-HVDC transmission suffers
from the disadvantages of high losses and cost.
In this research, a hybrid HVDC employing a Line Commutated Converter (LCC) as
rectifier and a VSC as inverter is used to supply a passive network through a DC cable. The
hybrid system is best suited for unidirectional power transmission scenarios, such as power
transmission to islands and remote load centers, where the construction of new transmission
lines is prohibitively expensive. Control modes for the rectifier and inverter are selected and
implemented using Proportional Integral (PI) controllers. Special control schemes are
developed for abnormal operating conditions such as starting at light load and recovering
from AC network faults. The system performance under steady state and transient conditions
is investigated by EMTP-RV simulations. The results show the feasibility of the hybrid
system. | en |
