Condition Monitoring of Electrolytic Capacitors in Boost Converters by Magnetic Sensors

The aluminum electrolytic capacitors (AEC) are important in filtering and energy storage applications since they are of high energy density and low cost. However, the AECs suffer from low reliability and limited lifetime due to the electrolyte vaporization. The degradation of AECs challenges the reliability and efficiency of the power electronic systems. Therefore, it is essential to monitor the condition of AECs for system reliability and efficiency. In this paper, a real-time condition monitoring technique for input and output AECs based on the estimation of equivalent series resistance (ESR) was developed for the boost converter. The ESRs were estimated by using the capacitor and inductor current obtained through the magnetic-field sensing by magnetic sensors. The influences of the load, duty cycle, inductance, ESR, and capacitance on the ESR estimation were investigated to develop the proposed methodology. The proposed methodology can largely improve the accuracy of the estimated ESR of output AEC in the boost converter. The higher accuracy enables predictive maintenance of AECs and contributes to the reliability and efficiency of power electronic systems. The simulation and experimental results from -25 degrees C to 100 degrees C verified that the proposed methodology could be used to estimate the ESR of input and output AECs accurately. The experimental results showed that the compact tunnel magnetoresistance (TMR) sensors were capable of measuring the capacitor and inductor current for the estimation of ESR. This technique is cost-effective and non-invasive since it can be implemented with TMR magnetic sensors and does not require the Hall-effect current transducers with magnetic concentrators of larger volume, higher cost, and limited bandwidth or invasive shunt resistors.