Nonintrusive Capacitor Monitoring in Photovoltaic Inverters Based on MPPT-Induced Voltage Transients

Capacitors are essential components in power electronic systems, as their condition directly impacts the system's performance and efficiency. This paper introduces a non-intrusive method for monitoring capacitor health by utilizing the transient conditions created by variations in the maximum power point tracking (MPPT) reference voltage. These transient conditions generate low-frequency signals within the system. By capturing the low-frequency content from the PV voltage and the estimated capacitor current (derived from the inverter output current), the method can estimate the capacitance without the need for additional sensors. Importantly, this approach uses the same signals employed for converter control, eliminating the requirement for additional sensors, and does not need injection of any signal, ensuring that the method does not disrupt the normal operation of the converter. The effectiveness of this method was confirmed through simulations conducted using MATLAB/SIMULINK, as well as practical testing on a laboratory prototype of a three-phase inverter.