Efficiency evaluation of a DC transmission system based on voltage source converters

The efficiency of a VSC-HVDC transmission system used to transmit wind farm power to the network is investigated. The losses associated with the operation of the VSC-HVDC system are the conversion losses (conduction and switching losses) in converters and the transmission losses due to I²R (in the converter transformers, smoothing reactors, and DC cables). An analytical method based on the average and root mean square of the semiconductors´ current is used to estimate the conversion losses in the converters. The remaining power losses are evaluated using I²R. The results obtained using the analytical method are confirmed by the measured losses obtained from simulation studies.