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This paper gives a comprehensive analysis and characterization of power loss of a high-power integrated gate-commutated thyristor (IGCT) in a modular multilevel converter (MMC) for a high voltage dc application. The practical scheme, power loss models, calculation methods, characterization of MMC based on IGCT are analyzed in detail. Especially, a comprehensive comparison of both half-bridge MMC (HB-MMC) and full-bridge MMC (FB-MMC) based on IGCT, press-pack insulated gate bipolar transistor (IGBT), module-type IGBT, press-pack injection enhanced gate transistor (IEGT), and module-type IEGT is analyzed in this paper. According to the study in this paper, the snubber power loss of MMC based on IGCT is far less than the conduction and switching power losses. Both the conduction and switching power losses of IGCT are always lower than that of press-pack and module-type IGBTs and IEGTs in MMC. The power loss of FB-MMC is higher than that of HB-MMC with the same transmission power because more switches are employed in FB-MMC. If taking diodes into account, the HB-MMC and FB-MMC based on IGCT can decrease power loss about 1.9%–49.3% and 8.3%–45.1% under different operation states, respectively. The study in this paper will provide a valuable reference and promote the application of IGCT in MMC.

This article proposes that a modular multilevel converter (MMC) based on the integrated-gate commutated thyristor (IGCT) is a promising solution for future highvoltage dc (HVdc) applications. The system-level scheme and technical issues of the IGCT MMC are proposed, and the commutation behaviors of the IGCT and the snubber circuit in the MMC are analyzed. On this basis, the optimal designs of the anode inductor, power supply system, valve series, and submodule structure are proposed, and a comprehensive experimental platform is built. Detailed experiments are conducted, including a double-pulse switching experiment, a back-to-back power cycling experiment, and an MMC operation experiment. Furthermore, the correctness and effectiveness of the proposed IGCT MMC solution are verified.

As power semiconductor devices are the key components of hybrid DC circuit breakers (HCBs), how to select suitable devices is critical for the whole HCB design. First, this paper compared the general characteristics of press pack insulated gate bipolar transistor (IGBT), injection-enhanced gate transistor (IEGT), and integrated gate commutated thyristor (IGCT). Then working conditions of devices were analyzed from the perspective of HCBs. According to these, vital features of devices including maximum turn-off current, on-state voltage, conduction ability, and robustness of power semiconductor devices were carefully analyzed and compared. Related experiments were implemented to compare maximum turn-off capability, and the 4.5 kV/3 kA IGBT/IEGT was able to turn off 19 and 22 kA respectively after 5-ms current conduction. Analysis and experiments indicated that IGCT was suitable for natural commutation low-voltage and low-current hybrid circuit breakers, due to its low on-state voltage and huge surge current conduction ability. Comparatively, IGBT and IEGT were more suitable for very high current interruption, and IEGT was the superior selection among available commercial devices. However, the interference should be considered in applications.

The automatic transfer switch can solve the problem of voltage drop and instantaneous power interruption, which is one of the most reliable and economical ways to improve the reliability and quality of the power supply. In view of the application demand of the important electric field, this paper puts forward the technology scheme of a compound automatic transfer switch based on forced current commutation, which is characterised by high reliability, fast switching and active and passive combined protection. First, the general technical scheme and working principle of the compound automatic transfer switch are introduced. Then, the simulation model of power distribution system with one master and one standby automatic transfer switch is established, and the system simulation is carried out to analyse the influence of the fault type on switching effect. Finally, the feasibility of the compound automatic transfer switch is verified by experiments, and its operational characteristics are obtained. It provides theoretical and technical basis for the product development and engineering application of the compound automatic transfer switch.