Online capacitance estimation of DC-link electrolytic capacitors for three-phase AC∕DC∕AC PWM converters using recursive least squares method

Abstract

A novel online capacitance estimation method for a DC-link capacitor in a three-phase AC/DC/AC PWM converter is prepared. At no load, a controlled AC current with a lower frequency than the line frequency is injected into the input side, which then causes AC voltage ripples at the DC output side. By extracting the AC voltage and current components on the DC output side using digital filters, the capacitance can then be calculated using the recursive least squares method. The proposed method can be simply implemented with only software and no additional hardware. Experimental results confirm that the estimation error is less than 0.26%.

Design & Analysis of Grid Feeding PV System with Using Improved H6 Topology

“…In this, the RMS of capacitor current is calculated using digital controllers with high sampling rate. Both the techniques [14], [15] require measurement of capacitor current for which a current sensor is placed deteriorate the capacitor voltage waveform as discussed in [13].To avoid high sampling rate and additional dc-link current sensor, techniques are suggested in [16]- [19]. These techniques estimate capacitance and/or ESR based on the low frequency measurements.…”

“…Capacitor current is reconstructed by using line currents and switch states of the inverter. Thereafter, the recursive leastsquares method is used for the estimation of ESRor capacitance [16] ,a method based on the precharging of the electrolytic capacitor via a charging resistor is discussed. The charging current and the voltage across the capacitor is used to determine the delay time of this RC circuit.…”

Capacitance Online Estimation Based on Adaptive Model Observer

“…Also, the capacitors will be used in different application scenarios based on different capabilities such as filtering and energy storage. Because of its manufacturing drawbacks, long-time running and outer damages such as mechanical and electrical stresses, capacitors are easy to degrade and fatigue, which will cause the rated capacitance vary and probably cause failure for overall system [1], [2]. For example, many computers cannot be restarted because the capacitors in the mainboard are damaged in a form of capacitor plague.…”

Method for DC-link capacitance identification in voltage-source converters

“…Another online approach is to inject a low-frequency sinusoidal signal into the power-producing component of the converter current reference [7]. The injection signal causes low-frequency oscillations in the converter power and further in the DC-voltage.…”

“…The injection signal causes low-frequency oscillations in the converter power and further in the DC-voltage. In order to estimate the capacitance, the oscillatory component of the DC-voltage has been used together with the capacitor current as inputs for a recursiveleast-squares algorithm [7]. Alternatively, a low-frequency sinusoidal signal has been injected into the reference of the DC-link voltage controller [8] or the torque-producing current component in the case of motor drives [10] for capacitance estimation.…”