Reliability of Capacitors for DC-Link Applications in Power Electronic Converters—An Overview

Abstract

DC-link capacitors are an important part in the majority of power electronic converters which contribute to cost, size and failure rate on a considerable scale. From capacitor users' viewpoint, this paper presents a review on the improvement of reliability of dc link in power electronic converters from two aspects: 1) reliability-oriented dc-link design solutions; 2) conditioning monitoring of dc-link capacitors during operation. Failure mechanisms, failure modes and lifetime models of capacitors suitable for the applications are also discussed as a basis to understand the physics-of-failure. This review serves to provide a clear picture of the state-of-the-art research in this area and to identify the corresponding challenges and future research directions for capacitors and their dc-link applications.

Evaluation of functional reliability indices for DC-link capacitors in pulse-width modulation converters

“…The lifetime for both electrolytic and film capacitors can be derived from the "lifetime doubles in every 10 °С" rule as follows [9,11,14]:…”

“…Methods for predicting the effect of ripple current stress on the power losses, temperature rise, and expected lifetime of the dc-link capacitors used in the variable-frequency drives, power converters, rectifiers, electric vehicle drive systems, photovoltaic inverters, wind turbine and fuel cell power converters have been presented in [8][9][10][11][12][13][14][15][16][17]. But so far none of the recognized approaches has been applied for evaluating the functional reliability indices of the dc-link capacitors, such as the probability to aging failure (a conditional probability that capacitor will fail in a subsequent period t after having survived for T operating hours) and the unavailability of aging failure (average probability that capacitor is found not available due to aging failure).…”

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

“…However, among the semiconductor devices the capacitors are the most fragile components in the converters [1]. A typical reason for the capacitor failure is the long-term wear out, which can be seen as a change of electrical parameters of the capacitor [2], [3]. Monitoring electrical parameters of the capacitor provides information of the capacitor condition.…”

“…Condition of the capacitor can be monitored by estimating or measuring the capacitance, which is typically reduced at the end of the lifetime [3]. In the case of aluminium electrolytic capacitors, also increased equivalent series resistance (ESR) has been used as an end-of-life indicator [2].…”

Mission profile translation to capacitor stresses in grid-connected photovoltaic systems

“…Therefore, the power difference has to be balanced using energy storage elements in those PV systems. Conventionally, capacitors are widely used at the DC-link and serve as the energy storage elements to perform functions like power balancing, ripplevoltage limiting, and sufficient energy provision during the hold-up time of the system [9]- [11].…”