Normalization of Capacitor-Discharge I 2 t by Short-Circuit Fault in VSC-Based DC System.

In the voltage-source-converter-based dc system, the short-circuit current increases rapidly due to neighborhood dc-link capacitance. The protection system using a high-speed fuse has been applied in the industry to protect before the current freewheeling that ruins a semiconductor device. For proper protection system design, the capacitor-discharge I2t must be analyzed and set higher than the melting I2t of the fuse by securing sufficient capacitance. However, due to the implicit characteristics of the I2t function, it is difficult to calculate the required capacitance directly considering unknown fault resistance. In this article, the normalized I2t map of capacitor-discharge is presented as a calculation reference. After calculating the base values, the normalized I2t value can be calculated easily from the map without complicated formula. Since it is expressed as a function of the damping factor (half of the normalized resistance) and normalized capacitor's voltage, it helps I2t design with the range of fault resistance and voltage drop simultaneously. The proposed normalization and its result were verified through the experimental tests under various fault resistance. [ABSTRACT FROM AUTHOR]