New Generation High Current Low Losses Thyristors for UHVDC Applications

New six-inch phase control thyristor(PCT)platform with enhanced current handling capability has been developed to enable an optimal design of converter valves for next generation Bulk power transmission.Silicon(Si)resistivity and wafer thickness of PCT are optimized to fulfil the demands laid on blocking capability while increasing the rated current.The parameters of electron irradiation are optimized for the best technology curve between the on-state voltage drop and reverse recovery charge.A narrow reverse recovery charge band has been identified for a safe voltage sharing in series connection with minimal demands on redundant PCT.Full utilisation of six-inch wafer and the optimized layout of cathode(snow-flake design)improves the on-state current ratings by nearly 20%compared to prior art thanks to the reduced on-state voltage by 10%.The on-state current rating for 7.2 kV device is up to 6.25 kA.The surge current capability increased by 30%and maximum surge current up to 63.5 kA is qualified for the 7.2 kV/6.25 kA device under the same test condition with improved packaging and reduced on-state voltage.Together with 30%lower value of circuit commutated recovery time,the new thyristor platform enables more efficient,powerful and stable converter valves for next generation ultra high voltage direct current transmission(UHVDC)systems with rated power beyond 10 GW.

New six-inch phase control thyristor（PCT） platform with enhanced current handling capability has been developed to enable an optimal design of converter valves for next generation Bulk power transmission.Sificon（Si） resistivity and wafer thickness of PCT are optimized to fulfil the demands laid on blocking capability while increasing the rated current.The parameters of electron irradiation are optimized for the best technology curve between the on-state voltage drop and reverse recovery eharge.A narrow reverse recovery charge band has been identified for a safe voltage sharing in series connection with minimal demands on redundant PCT.Full utilisation of six-inch wafer and the optimized layout of cathode（snow-flake design） improves the on-state current ratings by nearly 20% compared to prior art thanks to the reduced on-state voltage by 10%.The on-state current rating for 7.2 kV device is up to 6.25 kA.The surge current capability increased by 30% and maximum surge current up to 63.5 kA is qualified for the 7.2 kV/6.25 kA device under the same test condition with improved packaging and reduced on-state voltage.Together with 30% lower value of circuit commutated recovery time, the new thyristor platform enables more efficient, powerful and stable converter valves for next generation ultra high voltage direct current transmission（UHVDC） systems with rated power beyond 10 GW.