A Thermal Modeling Method for Power Capacitors under Long Timescale Dynamic Operation Profiles

This paper proposes a thermal modeling method for film capacitors, which is applicable for high power converters with long timescale dynamic operation profiles, such as traction and wind power systems. The proposed frequency domain modeling analyzes the effects of power loss and ambient temperature comprehensively in realistic mission profiles. Furthermore, the transfer function is discretized to concurrently obtain the iterative model with temperature rise by the influence of power loss and ambient temperature. This method has two advantages, as follows: Firstly, discrete realistic operating profiles including power loss and ambient temperature at different sampling times can be conveniently introduced into the thermal model simultaneously. Secondly, the effect of temperature-dependent equivalent series resistance and thermal resistance can be further considered in discrete frequency domain modeling. The full power experiments for capacitor stress testing demonstrate the reasonableness and accuracy of the proposed method in hot spot temperature and lifetime expectancy calculations.