An Electro-Thermal-Degradation Coupled Model of Converter Damping Capacitors for Health-Aware Control in Power Distribution Systems

The reliable operation of multi-microgrids and active power distribution systems relies heavily on power electronic converters, yet current optimal control strategies often overlook the unperceived degradation of passive components like damping capacitors. This paper proposes a multi-physics electro-thermal-degradation coupled model for damping capacitors that incorporates frequency-dependent damage effects to support parameter-adaptive control. We introduce a frequency-weighted damage function, W(f), and a Thermal Damage Equivalent Power (PTDE) to quantify the accelerated destructive impact of high-frequency harmonics in pulsed currents, which conventional average power loss methods fail to capture. This PTDE is integrated into a transient thermal model to determine hotspot temperatures, which, combined with electrical stresses, drive a dynamic feedback loop that reveals the self-accelerating failure mechanism of the capacitors. Experimental validation confirms that pulsed currents induce significantly faster degradation than sinusoidal currents of equivalent average power, verifying the accuracy of our frequency-weighted theory. Ultimately, this coupled model provides a robust foundation for parameter estimation, enabling health-aware control strategies, resilient energy routing, and predictive maintenance in modern power distribution systems.