Mission Profile Based System-Level Reliability Analysis of DC/DC Converters for a Backup Power Application

Abstract

Abstract-Reliability analysis is an important tool for assisting the design phase of a power electronic converter to fulfill its life-cycle specifications. Existing converter-level reliability analysis methods have two major limitations: 1) based on constant failure rate models and 2) lack of considerations of long-term operation conditions (i.e., mission profile). Although various studies have been presented on power electronic component-level lifetime prediction based on wear-out failure mechanisms and mission profile, it is still a challenge to apply the same method to the reliability analysis of converters with multiple components. Component lifetime prediction based on associated models provides only a Bx lifetime information (i.e., the time when X% items fail), but the time-dependent reliability curve is still not available. In this paper, a converter-level reliability analysis approach is proposed based on time-dependent failure rate models and longterm mission profiles. Two different methods to obtain the component-level time-to-failure are illustrated by a case study of dc/dc converters for a 5 kW fuel cell based backup power system. The reliability analysis of the converters with and without redundancy is also performed to assist the decision making in the design phase of the fuel cell power conditioning stage.Index Terms-Fuel cell system, system-level reliability, Weibull distribution, power semiconductor, capacitor, reliability block diagram.

The Impact of Topology and Mission Profile on the Reliability of Boost-type Converters in PV Applications

“…In order to find the failure probability function, the measured test data for a radial lead electrolytic capacitors with the rated lifetime of 5000 hours at the rated ripple current and upper category temperature of 105 o C is used, where 9 × (56 μF/ 35 V) electrolytic capacitors were tested [6]. The selected output capacitors for dc/dc converters belong to these type of capacitors.…”

“…The selected output capacitors for dc/dc converters belong to these type of capacitors. Hence, the B 1 , B 10 damage and consequently B 1 , B 10 lifetime of capacitors can be calculated based on the real test data [6]. The obtained lifetime data for B 1 , B 10 can be used to find out the Weibullbased unreliability functions [6].…”

“…Hence, the B 1 , B 10 damage and consequently B 1 , B 10 lifetime of capacitors can be calculated based on the real test data [6]. The obtained lifetime data for B 1 , B 10 can be used to find out the Weibullbased unreliability functions [6]. Finally, the total reliability of the output capacitor bank (i.e., series and parallel connection of the capacitors for enough current rating) can be found by using a series reliability network model.…”

“…Design for Reliability (DfR) is becoming more appealing especially for renewable applications [5], [6]. In this approach, power converter components are designed based on the target mission profile to approach a desired lifetime with an acceptable probability.…”

“…In this approach, power converter components are designed based on the target mission profile to approach a desired lifetime with an acceptable probability. The reliability of an isolated dc/dc converter is analyzed for fuel-cell applications in [6]. The impact of mission profile on the reliability of IGBTs in a three-phase PV inverter is studied in [7], [8].…”