Comparative Study of IGBT Lifetime Damage in Photovoltaic Inverters Under Different MPPT Control Methods

Abstract

To address thermal-fatigue damage in power devices of photovoltaic inverters, this paper investigates a three-phase photovoltaic inverter and establishes a fourth-order Foster thermal-network model based on IGBT power-device parameters. Five MPPT control methods, namely fixed duty cycle, fixed-step perturb and observe (P&O), adaptive-step P&O, incremental conductance (INC), and constant voltage (CV), are simulated and compared. Junction-temperature time-series data are collected, and rainflow counting is used to extract the junction-temperature swing, mean junction temperature, and cycle count. A relative Miner damage index is then adopted to compare thermal-fatigue differences under different MPPT control methods. The simulation results show that, compared with the fixed-duty-cycle case, the lifetime damage ratio under different MPPT control methods ranges from 1.136 to 1.147. Among the MPPT cases, the CV method produces the lowest lifetime damage, whereas the fixed-step P&O method produces the highest lifetime damage. The results provide a theoretical basis and an analysis method for IGBT lifetime-oriented optimization of photovoltaic inverters.