Mission Profile-Based System-Level Reliability Prediction Method for Modular Multilevel Converters

Abstract

This paper proposes a mission profile-based reliability prediction method for Modular Multilevel Converters (MMCs). It includes key modeling steps, such as long-term mission profile, analytical power loss models, system-level and component-level thermal modeling, lifetime modeling, Monte-Carlo analysis, and redundancy analysis. Thermal couplings and uneven thermal stresses among sub-modules are considered. A case study of a 15-kVA down-scale MMC has been used to demonstrate the proposed method and validate the theoretical analysis. The outcomes serve as a first step for developing realistic reliability analysis and model-based design methods for full-scale MMCs in practical applications.

Power Electronics Reliability: State of the Art and Outlook

“…mission profile). The methods and modeling procedures demonstrated in [86,87] represent the state of the art for case studies on PV inverter and MMC, respectively.…”

“…For dynamic thermal profiles, Rainflow counting [89] is widely used to extract the periodic temperature swings for the packaging-related wearout of power semiconductor switches. The use of Rainflow counting is discussed in detail in [86,87]. Depending on the available mission profile information, the tool runs part or all of the six steps.…”

“…The details of mission-profile-based reliability prediction methods and the corresponding software tools can be found in [86][87][88]. A few additional aspects are discussed below:…”

“…While the mission profile enables more realistic reliability prediction, it increases the complexity and computational burden, especially considering the dynamic thermal profile modeling [86,87]. Consequently, it could be more feasible to simplify mission profiles by identifying the representative profiles.…”

“…This implies that the accuracy of the enclosure temperature modeling is even more critical than that of the temperature rise due to self-heating in this example. In another case study of MMC in [87], there is a maximum of 17°C difference in local ambient temperatures among the 24 sub-modules. The setup and measurements are shown in Fig.…”