Reliability aspects in microgrid design and planning: Status and power electronics-induced challenges

Microgrids are highlighted as the technology which can help in providing sustainable and efficient electrical energy solutions. They employ distributed energy resources to efficiently supply local load and increase the reliability of the local network. Design and planning are of a pivotal importance in yielding all of the advantages this concept can provide. Reliability-oriented design is of a special interest for microgrids utilizing a large share of the renewable energy-based, power electronics-interfaced distributed energy resources. A state-of-the-art overview included in this paper has shown that the main reliability-oriented microgrid design improvements are done in the field of distributed energy resources sizing and scheduling combined with the relevant forecasting and optimization methods. It is, further on, concluded that the standard power system reliability assessment within the design often excludes the wear-out failure of power electronics. However, previous field experience has shown that the power electronics is prone to wear-out failure and can have adverse impact on the reliability of the power electronics-dominated system. Therefore, it is necessary to adjust the current reliability methods to enable accurate investigation of power electronics reliability and its impact on system design. To do so, the main characteristics of the wear-out modelling concepts together with the recent publications bridging the power electronics and power system reliability are discussed in detail. Finally, the main findings included in this overview paper can serve as basis for development of the new procedures for reliability-oriented design and planning of future, power electronics-dominated microgrids.