A Novel Sensor-less On-line Estimation Method of IGBT Junction Temperature

Thermal management and condition monitoring of power converters demand the accurate estimation of the junction temperature of insulated-gate bipolar transistor (IGBT). With existing iteration methods, the junction temperature is fed forward to calculate the power loss and derive the junction temperature of the next cycle, causing the problem of accumulated calculation error. This letter proposes a novel iterative algorithm to improve the calculation accuracy. Unlike the conventional solutions, utilizing the junction temperature of the previous moment to calculate the power losses, the proposed iteration method uses junction temperature and power losses of the same moment to tackle the accumulated error problem. Since the iterative equation has unique solution, the convergence value is the actual junction temperature and power losses. The initial power losses has no influence on the result, so it is not necessary to obtain the accurate power loss for the estimation of junction temperature. Power cycling experiment is performed to verify the advantages of the novel iterative algorithm. The novel method solves the accumulated error compared to the traditional method. The accuracy of the novel method is also verified by the result of 100mA current test during power cycling.