Junction Temperature Estimation Model of Power MOSFET Device Based on Photovoltaic Power Enhancer

In a photovoltaic power enhancer system, when it is operated in current-control mode, significant nonuniform temperature distribution occurs in the converter due to thermal coupling effects, dissipative boundary conditions, and differences in device losses within the in-phase bridge. Accurate on-site estimation of the power device’s junction temperature is critical in the system design. To address this problem, a novel thermal behavior estimation model based on electro-thermal analysis is proposed in this paper, which can be used for asymmetric power MOSFETs in a photovoltaic power enhancer system. Thermal coupling effects and dissipative boundary conditions are, firstly, analyzed in a three-dimensional finite element model. A coupling impedance matrix is constructed through step power response extraction to describe the significant thermal coupling effects among devices. The complete heat sink is decoupled into several sub-parts representing different dissipative boundary conditions. A compact RC network model for estimating junction temperature is established based on the combination of the coupling impedance and the sub-heat-sink impedance. The proposed model is verified by finite element simulation and experimental measurement.