Optimized Operation of Hydropower Plant with VSC HVDC Unit Connection

SUMMARY Among various renewable sources, hydropower is still the cheapest clean energy. As most of the new constructed hydropower plants are located at remote areas, HVDC lines are usually employed for hydropower transmission. In this paper, hydropower plant with VSC HVDC unit connection is proposed, in which the generator(s) of a hydropower station is connected to a voltage source converter (VSC) station directly and the power is transmitted by DC line. By using VSC HVDC unit connection, the hydraulic turbine realizes variable speed operation and thereby improves the hydraulic turbine efficiency substantially. In the paper, the progress of hydropower unit connection is reviewed and a typical configuration of hydropower plant with VSC HVDC station unit connection is introduced; the advantages of employing VSC HVDC unit connection technology are presented. A calculation model is established to calculate the maximum hydraulic turbine efficiency. Finally, the turbine efficiencies are compared between the variable speed operation of hydropower plant with VSC HVDC unit connection and fixed speed operation of a conventional hydropower plant; the power frequency variation range during variable speed operation is analyzed.