Calculation of power losses for MMC-based VSC HVDC stations

VSC technology is now well established in HVDC and is, in many respects, complementary to the older Line Commutated Converter (LCC) technology. Many advantages have been claimed for VSC technology in HVDC, including the smaller site footprint. On the other hand, VSC HVDC stations have higher power losses than LCC stations. Although the relative advantages and disadvantages are well known within the industry, there have been very few attempts to quantify these factors on an objective basis. In part, this is because of the lack of applicable standards for determining the power losses of a VSC station. No equivalent of IEC 61803 is today available for VSC-HVDC, but now a draft IEC standard (IEC 62751) is in preparation, which will permit objective comparisons to be made between power losses of LCC and VSC stations.