Design for Reliability of Power Electronics Systems

Power density, efficiency, and reliability are the major concerns when designing a power electronic system. Latest advancements in power semiconductor devices (e.g., silicon-carbide and gallium-nitride devices) and converter-/system-level topological innovations have vital contributions to power density and efficiency. Nevertheless, dedicated heat sink and thermal management systems are required to dissipate the power losses in power electronic systems; otherwise, the power devices become heated up and eventually fail to operate. In addition, in many mission-critical applications (e.g., marine and aerospace systems), the operating condition (i.e., mission profiles) is usually harsh, where the input power or loading can change quickly and randomly, resulting in considerable temperature swings in the power electronics. This may induce failures in the power electronic systems (e.g., due to accumulative thermal fatigue). If untreated (i.e., ill-designed system without considering reliability), the cost of maintenance will increase, thus affecting the reputation and, more importantly, the cost of energy. Hence, it calls for highly reliable power electronic systems, where reliability together with various common design parameters should be considered in the design phase. Clearly, it is a prerequisite to know the main life-limiting factors so as to predict the lifetime. Then, the design for reliability (DfR) can be performed. In this chapter, the technological challenges in the DfR of power electronic systems are addressed and how the power electronics is loaded considering mission profiles is demonstrated. Further, the DfR approach is systematically exemplified in grid-connected photovoltaic power electronic systems.