High Power Density Medium-Voltage Converter Integration via Electric Field Management

SiC-based converters can achieve much higher voltage rating and power density than Si- based ones. Therefore, electric field (E-field) intensity inside SiC-based converters can become significantly high and initial partial discharges, especially along the exposed metal or insulator to air interfaces. To achieve discharge free by design, E-field intensity and insulation space in air need be carefully analyzed and well managed. Due to the complicated structure of power converters, sharp edges and corners cannot be fully avoided. Thus, E-field management should be considered for such critical regions, in order to make the E-field distribution more uniform and shrink the insulation size. In this article, by using the self-made medium-voltage power electronics building block (PEBB) as an example, critical regions for insulation design are identified. Then focusing on the region between the cooling system and the heatsink, the influence on E-field distribution with different guard rings’ shape, size, and location, is demonstrated. Following the simulation analysis and design comparison, six guard rings are fabricated and experimentally verified. Therefore, a methodology about E-field management for power converters is provided in this article, including critical region analysis, design comparison, guard ring fabrication, and experimental verification.