Abstract
The aluminum electrolytic capacitor (AEC) is one of the most vulnerable parts in power electronic converters and its reliability is crucial to the whole system. With the growth of service time, the equivalent series resistance (ESR) increases and the capacitance (C) decreases due to the loss of electrolytes, which will result in extra power loss and even damage to transistors. To prevent significant damages, the AEC must be replaced at an optimal period and online health monitoring is indispensable. Through the analysis of degradation parameters (ESR and C), ESR is proved to be a better health indicator and therefore is determined as the monitoring parameter for AEC. From the capacitor perspective, ESR estimation schemes of output capacitors for a Buck converter are studied. Based on the voltage–current characteristics, two ESR calculation models are proposed, which are applicable for both continuous conduction mode (CCM) and discontinuous conduction mode (DCM). From the point of implementation view, the advantages and disadvantages of the two estimation schemes are pointed out, respectively. A Buck prototype is built and tested, and simulation and experimental results are provided to validate the proposed ESR estimation schemes.
Highlights
For the advantages of high power, density and efficiency, power electronic converters (PECs) have been widely used in many different fields such as new energy, industry and aviation [1,2,3,4].PECs have synthetic complexities such as high stress and strong nonlinearity, which causes challenges to their operational reliability
To address the aforementioned issues, equivalent series resistance (ESR) is chosen as the monitoring parameter for aluminum electrolytic capacitor (AEC) and two ESR calculation models are derived for Buck converters from a capacitor perspective in this paper
From capacitor perspective, the output structure of power electronic converter can be illustrated as shown in Figure 3, where ils is the total current of the capacitor branch and load branch, iC is the current of the capacitor branch, the electrolytic capacitor Cf is equivalent to a capacitance C in series with a resistance ESR, and Ro is the output load
Summary
For the advantages of high power, density and efficiency, power electronic converters (PECs) have been widely used in many different fields such as new energy, industry and aviation [1,2,3,4]. The evaporation of the electrolyte is the main degradation pattern of AECs, which will increase the equivalent series resistance (ESR) and decrease the capacitance (C) gradually These degradations will increase voltage and current ripples, producing more power loss and even device damage. In [15], capacitor voltage and current ripples are extracted by a band-pass filter and ESR is calculated at the centre frequency. Similar methods are applied to a CCM boost converter in [21] and realized for DCM in [22] These current-sensorless methods are affected by other parameters such as the duty cycle and filter inductance. To address the aforementioned issues, ESR is chosen as the monitoring parameter for AEC and two ESR calculation models are derived for Buck converters from a capacitor perspective in this paper.
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