Research on The Current Flow Mechanism of Press-Pack IGBT under Short Circuit Condition in VSC-HVDC System

In this paper, we studied the current flow mechanism of PPI (Press-Pack IGBT) module under short-circuit condition in VSC-HVDC application. Through the anatomical analysis of PPI modules tested in different current duration, the change process of the faulty chip and packaging materials was observed. The concept of “heat infection” between subunits in a faulty PPI module was proposed, which means the remaining good chips fail due to heat transmission from the faulty chip. Combining the experimental result and simulation analysis, we find that explosion-proof ability is the primary condition for a failed PPI module to have long-term flow capability under short circuit condition. Meanwhile, the selection of packaging materials and the thickness of the bypass structure must be fully considered, in order to avoid heat concentration and fusing of internal materials.