PWM-Current Source Converter Based on IGCT-in-Series for DC Buck and Constant-Current Application: Topology, Design, and Experiment

Abstract

PWM-current source converter (CSC) based on IGCT-in-series has the advantages in efficiency, reliability, cost, and controllability. It is a promising choice to replace silicon-controlled rectifier in dc buck and constant-current application, as well as to use in power transmission. This article firstly presents the series-IGCT-based CSC topology according to the IGCT device and CSC operation characteristics. On the basis of traditional CSC topology, di/dt-limitation inductor, absorption circuit and voltage sharing circuit are set. Secondly, the commutation process of series-IGCT-based CSC in each stage of one ac period is analyzed to obtain the coupling model between overvoltage on device and converter parameters. Furthermore, a prototype of 10kV, 1kA series-IGCT-based CSC for transmission line deicing is designed in both parameter and structure. Finally, pulse switching and power-cycling experiments of implemented prototype are carried out. The results verify that with designed parameters, overvoltage on devices is within a save range, and voltage unevenness among six units in series can be limited to 6.5%. Moreover, the prototype shows stability and reliability during long-term power-cycle operation, definitely verifying the feasibility of proposed series-IGCT-based CSC. Compared with IGBT, loss power of IGCT scheme is more than 10% lower, and reach the efficiency of 98.7%.