Online Monitoring Technique for Aluminum Electrolytic Capacitor in Solar PV-Based DC System

To interconnect low-voltage solar photovoltaics (PV) with dc system, a dc-dc boost converter is required. To minimize the switching frequency oscillations in solar PV voltage, aluminum electrolytic capacitors (AECs) are connected between solar PV and the converter. Operational life of AECs depends on electrical and environmental parameters and is less than that of solar PV panels. Equivalent series resistance (ESR) of AEC increases with life, thereby increasing the voltage ripple across PV terminals. This results in less power extraction from solar PV. This paper proposes a method for health monitoring of AEC using the parameters measured for maximum power point tracking (MPPT) (PV voltage and current). The proposed technique is applicable for both continuous conduction mode and discontinuous conduction mode of operation of the converter. Effect of temperature on ESR is incorporated for accurate determination of the health of capacitor. Key advantage is that no additional current or voltage sensor is required to implement this technique, thereby offering a low-cost solution. Further, the proposed technique does not require significant processing capabilities and is implemented in the same digital controller used for MPPT. Detailed simulation studies are carried out and results are included in this paper. A laboratory prototype of dc-dc boost converter is developed for experimentation. Results are in agreement with that obtained from simulation studies.