An online technique for condition monitoring of capacitor in PV system

Abstract

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.

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

“…In [70]- [75], [80], high-frequency sampling devices are required. The schemes in [76]- [77] and [81]- [84] do not need high-frequency sampling devices, and the calculation model is simple. However, additional hardware circuits are required.…”

“…23(c), the difference between the capacitor voltages sampled at points c and e are due to RESR. And, the voltage difference at points d and f is only due to C. Using (9), RESR and C are calculated as (28), where Vdc is the average capacitor voltage [81].…”

Modified hybrid model of boost converters for parameter identification of passive components

“…However, apart from the capacitors, the degradation of inductor may also create undesired circuit performance, such as cycle oscillation and increased power loss [12]. Moreover, in some cases, the identification results of capacitor parameters are dependent on the values of inductor parameters [13][14][15]. Similarly, the inductance and equivalent resistance are important health indicators for an inductor.…”

“…In [17], voltage and current ripples are measured and processed through a band-pass filter to calculate ESR at a certain frequency where the capacitance impedance can be neglected. In some special circumstances, capacitor parameters can be calculated only by measuring the voltage ripple at particular instants within a switching cycle and the current sensor is not needed any more [13][14][15]. In [13], a current-sensorless online identification method of capacitor's ESR and C for continuousconduction-mode (CCM) Buck converter is proposed.…”

“…The ESR is estimated by sampling output voltage ripple at two instants within a switching cycle through an external trigger circuit. In [14], similar method is implemented in Boost converter by sampling the voltage at four instants. However, the parameter estimation results of capacitor through these current-senseless methods are dependent on the parameter values of the inductor in the circuit.…”