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Grid tied single-phase solar inverters offer less operational life when compared with the Photovoltaic (PV) panels due to the use of aluminium electrolytic capacitor (AEC). With time, AEC degrades, resulting in an increase in ripple voltage on PV panel. This would reduce the power extraction efficiency of the system, thereby a loss of revenue. This study proposes a simple and cost-efficient online technique for monitoring the health of AECs. The proposed technique suggests evaluating the AEC impedance at twice the grid frequency. Sampling of PV voltage, PV current and inductor current is required to determine the second harmonic impedance of AEC. These voltage and current sensors are present in commercially available solar PV inverters for their control operation. The proposed technique could be extended to other single-phase inverter applications provided that voltage and current sensors are available. Suitable mathematical model of the technique is derived to determine the effect of sampling instant on the accuracy of the results. Criteria for the replacement of capacitor based on impedance monitoring is defined. For validation of the proposed technique, detailed simulation studies are carried out for a single-phase PV system. The technique is verified experimentally on a scaled down solar PV inverter prototype.

DC-DC converters are used to interconnect solar photovoltaic (PV) to a dc microgrid or to a battery. Capacitors are connected at the output of a PV terminal to minimize power pulsation. Operational life of capacitor decreases due to various electrical and environmental parameters. In this paper, a method for condition monitoring of the capacitors used in PV system is proposed. The technique combines the estimation of equivalent series resistance (ESR) and capacitance in one tool. This technique allows reliable prediction of capacitor life as compared to existing techniques. The proposed method can be implanted in the same microcontroller that is used for implementing the maximum power point tracking. To validate the efficacy of the method detailed simulation studies are performed in MATLABSimulink.

DC-link electrolytic capacitors are used in single phase solar PV inverters to suppress second harmonic and switching voltage ripples. Electrolytic capacitors are less reliable than other components of PV system. Degradation of these capacitors affects the performance of the system. Reduction in capacitance and increase in equivalent series resistance (ESR) due to ageing increases ripples in dc voltage. Among the ripples present, second harmonic voltage ripple dominates. DC-link voltage ripple causes oscillations in PV operating point thereby reducing PV power extraction efficiency. Technique for online monitoring of PV power extraction efficiency is proposed in this paper. Electrolytic capacitor is selected for power extraction efficiency greater than 99%. Replacement of capacitor is suggested based on deterioration in extraction efficiency. However, frequent replacement of capacitor increases cost of maintenance. Therefore, optimal value of extraction efficiency is determined in this paper, at which total payback period including maintenance cost is minimized. Detailed simulation studies are carried out using Simulink and results are included. Analysis on the payback period for the proposed scheme is presented in this paper. Keywords-diagnostics; electrolytic capacitor; online monitoring; payback period; PV power extraction efficiency; second harmonic ripples; solar PV inverter 978-1-4799-7800-7/15/$31.00 ©2015 IEEE