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

Abstract

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 depend 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 (CCM) and Discontinuous Conduction Mode (DCM) 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 to that obtained from simulation studies.

An Overview of Condition Monitoring Techniques for Capacitors in DC-Link Applications

“…Based on this, [82] further proposed an improved estimation scheme to monitor the capacitors for a converter operated in discontinuous conduction mode (DCM). In [83], a similar scheme is proposed for a CCM flyback converter, as shown in Fig.…”

“…Using capacitor voltages of particular instants to calculate RESR and C. RESR: <6.2% [82] Real-online estimation, low-frequency sampling, no capacitor current sensor. RESR: <5.83% [83] C: <9.5% [83] Real-online estimation, low-frequency sampling, no capacitor current sensor.…”

Review of Health Monitoring Techniques for Capacitors Used in Power Electronics Converters

“…Hence, replacing all the capacitors in a bank when one or more capacitors fail is an effective measure to maintain the reliable operation of the system [21]. The use of ESR as an indicator for the health monitoring of capacitors has been reported by several studies [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. However, these studies are only applicable for the condition monitoring of The use of ESR as an indicator for the health monitoring of capacitors has been reported by several studies [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39].…”

A Low-Cost, High-Precision Method for Ripple Voltage Measurement Using a DAC and Comparators

“…According to differences in data acquisition, the current research achievement of using ripple to evaluate the health state of AECs can be summarized as the indirect calculation of ripple through simulation software [9][10][11], the offline computing from sampled data [12], AEC parameter calculation based on the mathematical model of a particular topology and some specific measurement value (voltage or current) [13][14][15][16][17][18][19], and direct measurement of ripple through high-cost oscilloscopes, data acquisition cards, or high-speed analog-to-digital converters (ADCs) [20][21][22][23]. Nevertheless, the developed methods are rarely adopted in practical industry applications due to the increased cost, complexity, and other relevant issues [8,24].…”