Reliability Comparison of DC Link Capacitor Bank for Different Configurations

A single phase grid connected solar Photovoltaic (PV) inverter requires capacitor banks as an energy buffer at a dc-link. The capacitor bank consists of Aluminum Electrolytic Capacitors (AECs), which are prone to early failure due to various electrical and environmental stresses. Most of the existing literature focuses on reliability evaluation of single capacitor at the dc-link of PV inverter rather than a capacitor bank. The current paper uses a Physics-of-Failure (PoF) based approach to evaluate the lifetime of capacitor banks with different series/parallel combination of capacitors. The terminal capacitance of these banks is kept close to the desired capacitance. From the analytical and simulation studies, it is identified that the reliability of the bank increases with increase in the number of capacitors in a capacitor bank. These findings are validated on an experimental prototype of a single phase grid connected solar PV inverter.