Enhanced Over-current Capability and Extended SOA of Power Modules Utilizing Phase Change Material

In a micro grid sourced by converters, to drive the protection relays after a grid fault and support voltage recovery following fault clearance, over-current capability of a power module sustained for several seconds may be required. Over-current capability of existing power modules, however, is only dozens of microseconds, which is far from meeting the demand. This study proposes a solution to increase the transient thermal capacity, and hence increase the over-current capability as well as the safe operation area (SOA) of power semiconductor modules, by integrating phase change material (PCM) inside the module. Liquid metal enclosed in a copper framework is employed to constrain the junction-temperature from rising rapidly and to extend the over-current enduring time without significantly losing the thermal conductivity. The power module is optimized using finite element analyses (FEA) based on the case study of a grid-connected inverter; the appropriate material type, quantity of the PCM are determined. Simulation and experimental results demonstrate that the junction temperatures of the IGBT and diode chips are somewhat clamped during phase change period. With appropriate quantity of PCM, the customized power module can handle current three times of its nominal value for approximately 3 seconds, thus the SOA is extended.