A Capacitance Estimation of Film Capacitors in an LCL-Filter of Grid-Connected PWM Converters

Abstract

A capacitor deterioration of LCL-filter grid-connected PWM converters is progressed by the self-healing mechanism. It leads to the degradation of the filter performance and drop of power factor. Thus, it is required to diagnose fault-point of capacitors and determine the replacement time. Typically, the fault of capacitors is determined when the capacitance is reduced up to 80% from initial value. This paper proposes algorithm to the determine capacitor replacement time of an LCL filter. The algorithm takes the advantage of change of the response on the injected resonant frequency corresponding to 80% value from the initial capacitance. The results of the algorithm are demonstrated through simulations and experiments.

Analysis and Design of Grid-Connected Photovoltaic Systems With Multiple-Integrated Converters and a Pseudo-DC-Link Inverter

“…In recent years, an important research effort has been devoted to find the simple and efficient methods of MPPT [17][18][19][20][21][22][23][24]. For a low-cost implementation along with strong tracking performances, a dynamically rapid method, known as the ripple-correlation control [25][26][27][28][29][30] is applied to the MPPT controller of the MIP in analog manner. Most of grid-connected inverters cause a double-line-frequency ripple on the input side, the ripple-correlation MPPT has a benefit of utilizing the doubled-line-frequency ripple inherently existing in the MIP.…”

Research on Discretization PI Control Technology of Single-Phase Grid-Connected Inverter with LCL Filter

“…From formula (18), the output voltage of inverter is positive and the inner inductance current increases when sin(2 res ) is greater than zero. When sin(2 res ) is less than zero, the output voltage of inverter is positive, but the inner inductance current decreases.…”

“…An active damping strategy with harmonics compensation which can alleviate the harmonics around the resonance frequency caused by the LCL filters is proposed in [18]. However, whether LCL filter can effectively suppress the harmonic current with different switching frequencies is not deeply analyzed [19].…”