Ultra-high power thyristor valves for HVDC in developing countries

In the last 3 years, HVDC technology has been extended to much higher voltages and currents than before, particularly for large back to back and interconnector schemes in rapidly developing countries such as China and Brazil. HVDC schemes are being built with voltage ratings as high as 800kV, with current ratings of up to 4500A today and 4750A planned in the near future. These increases of rating require advances in the design of thyristor valves. This paper describes recent developments in Alstom´s range of HVDC valves in order to accommodate these changes.