The performance of solid state DC circuit breaker (SS-DCCB) is mainly determined by the on-state feature of power device. In this paper, an optimized low on-state voltage integrated gate commutated Thyristor (LO-IGCT) for SS-DCCB is developed. Firstly, the impacts of device parameters, including base length, carrier lifetime, emitter injection efficiencies, on on-state voltage are presented. And the boundary conditions raised by blocking voltage and controllable current requirement are analyzed. Based on that, a three-step Blocking-SOA-Emitter optimization routine is proposed. Then, the optimization methodology for doping profiles in different regions, especially in n- drift, n buffer, p+ base, n+ emitter and p+ emitter regions, is presented. The optimal values are derived with theoretical deduction or numerical calculation. After that, based the optimization result, samples of LO-IGCTs are fabricated and tested. The fabricated LO-IGCT sample shows a blocking voltage capability over 4500 V and an on-state voltage of 1.11 V at the current of 2000 A. The commercialized IGCT and IGBT optimized for high frequency applications exhibits 1.23 and 1.85 times the on-state voltage under same test configuration.

The hybrid line commutated converter (H-LCC) topology has been verified to reduce the commutation failure probability effectively, but the reverse blocking integrated gate commutated thyristor (RB-IGCT) that meets the requirements of this topology has not yet been developed. This study focuses on the optimal design of the RB-IGCT with high blocking voltage, large on-state current, and high turn-off capability. First, an emitter isolation (EI) structure is proposed to tune the low-level injection efficiency, and the forward leakage current can be reduced by 50% without degrading the on-state current. Then, a method for optimizing anode emitter is presented. A high-doped and shallow p+ emitter is preferred to control the current gain while ensuring a low on-state voltage. As to the turn-off capability, the corrugated p-base (CB) structure is used to independently improve the maximum controllable current (MCC). In addition to the corrugation amplitude, the effect of the corrugation width is verified by experiments. Finally, 8 kV RB-IGCT samples are fabricated and tested, which reach over 3 kA average on-state current and 5.5 kA MCC. This study not only provides a practical guidance to the design of the RB-IGCT but also promotes the development of the HVDC transmission system.

Explosion proof of power devices is important for the safe operation of high voltage direct current power transmission system based on modular multilevel converter (MMC-HVdc). Comparison of the main commercial power devices’ structures shows that the integrated gate commutated thyristor (IGCT) has the simplest housing structure, which is suitable for withstanding the extreme fault in the MMC-HVdc system. Explosion proof tests of IGCT are carried out with different distribution of destruction positions under the extreme failure in the MMC-HVdc system. The maximum surge current of IGCT is between 600 and 700 kA when 18 mF capacitor with 4500 V is discharged. IGCT with evenly distributed destruction positions shows excellent explosion proof, while IGCT with edge focusing destruction positions shows poor explosion proof. Further thermal analysis with simulation shows that IGCT's ceramic shell may suffer a huge transient thermal stress when the destruction positions focus on the edge areas. A designed gas pressure tolerance test shows that the gas pressure is in the safe area which IGCT can withstand under the extreme failure. This means that the thermal stress can be regarded as the main cause of IGCT's explosion phenomenon. Based on the explosion mechanism, an optimized IGCT with controlled punch-through design in the central area is proposed to avoid the edge area destruction under the extreme failure. And explosion proof experiment of optimized IGCT validates its excellent explosion proof under the extreme failure in the MMC-HVdc system.

Compared with IGBT, integrated gate commutated thyristor (IGCT) has lower on-state voltage, higher reliability, and lower manufacturing costs, thus making it more suitable for high-power high-voltage direct current (HVDC) applications. This paper focuses on the full-time junction temperature extraction of IGCTs for high-power applications. An electro-thermal model for IGCT is established. Nonlinear optimization and accuracy analysis of this model are performed, which proved that the model achieves good accuracy. On the basis of the electro-thermal model, junction temperature during switching-on, switching-off, and off-state is evaluated. The junction temperature during conduction is extracted based on the temperature-sensitive electrical parameter (TSEP) method. Combining these two schemes, a comprehensive method to extract full-time accurate junction temperature of IGCT for high-power application is proposed. An experimental platform of IGCT-based modular multilevel converters for HVDC applications is built, and power cycling experiments at different voltage and current ratings of up to 2.2 kV/1.5 kA were carried out. Results show the junction temperature profile over a long period. The junction temperatures of IGCT both in inverter and rectifier modes and under different power-loading conditions are compared with the proposed comprehensive method.

Modular multilevel converter (MMC) based on IGCT with high reliability, low cost and voltage drop is a promising choice for VSC-HVDC. This paper gives a comprehensive analysis, design and experiment of shoot-through faults in IGCT-MMC. Firstly, the designed structure of the sub-module based on IGCT (IGCT-SM) is introduced and an equivalent circuit is established with accurate estimation of the stray inductances. Then, the failure processes of IGCTs and diodes are discussed in detail. Meanwhile, the mechanical stress of the connecting copper bar is analyzed during shoot-through faults. After that, an experimental platform is built for performing the shoot-through faults. Both tests with switching action and without switching action are carried out under the DC-Link capacitor and voltage with 10 mF and 2.5 kV. The results show that though IGCT can't turn off the fault current, it can withstand the fault current. The whole structure maintains stable without any cracked housing package or copper bars under the surge current of 266 kA/0.40 ms. The 24 h short-circuit test under 3.15 kA shows that failed IGCT has an extremely low on-state voltage of no more than 1.2 V and is suitable for bypassing the faulty sub-module when a destroyed shoot-through fault occurs.

Integrated gate-commutated thyristor (IGCT) has low loss, low cost and high reliability in the application of modular multilevel converter (MMC). However, due to special turn-off process of IGCT, the commutation transient is very different for IGCT in MMC. This letter reveals a current oscillation phenomenon of MMC based on IGCT and fast recovery diode (FRD). Especially, this oscillation effect become apparent when the FRD with high surge current capability (HS-FRD) is employed in MMC because of high junction capacitance and high stray inductance, which will threaten the safe operation of the system. This letter analyzes current oscillation mechanism and gives the current oscillation modeling. In addition, through detailed tests under various stray inductances, the specific stray inductance range which can cause large current oscillation is obtained and an optimized inductance parameter of IGCT-MMC is proposed. The experiments show that the safe operation area of IGCT in MMC can be guaranteed maximally with the proposed optimized parameter.