HVDC is harder than AC transmission, but isn't it a solved problem? "In July 2016, ABB Group received a contract in China to build an ultrahigh-voltage direct-

HVDC is harder than AC transmission, but isn't it a solved problem? "In July 2016, ABB Group received a contract in China to build an ultrahigh-voltage direct-current (UHVDC) land link with a 1100 kV voltage, a 3,000 km (1,900 mi) length and 12 GW of power, setting world records for highest voltage, longest distance, and largest transmission capacity." (From https://en.wikipedia.org/wiki/High-voltage_direct_current https://en.wikipedia.org/wiki/High-voltage_direct_current)