Multi-physics Coupling Simulation Analysis of DC-link Capacitors under DC Superimposed Multi-harmonic Voltage

The DC-link capacitor exhibits abnormal temperature rise and bulging deformation when subjected to the concurrent influences of DC superimposed multi-harmonic voltage and high-temperature environments, significantly diminishing its operational lifespan. This study develops a multi-physics coupling analysis model for metallized film capacitors (MFC), taking the impact of the current density distribution along the copper busbars on the overall temperature rise within the capacitors into account, which is calculated to be 16.23% of the total loss. Simulation analyses were conducted to explore the internal multi-physics field distributions of MFC under the conditions of superimposed multi-harmonic voltages. The findings reveal that stresses induced by multi-harmonic superpositions intensify the losses in the capacitor electrode and dielectric, resulting in an increase in both the capacitor hot spot temperature and thermal stress values. Additionally, thermal expansions caused by uneven thermal stresses in the capacitor units lead to increased spacing between the capacitor plates, with the capacitance of individual units experiencing a maximum decay of up to 1.71%.