The Existed Problems and Possible Solutions of Distributed Generation Microgrid Operation

Many distribution systems nowadays have significant penetration of distributed generation (DG) and thus, islanding operation of these distribution systems is becoming a viable option for economical and technical reasons. The DG should operate optimally during both grid-connected and islanding mode, which can be achieved with change in operating strategy. This paper summarizes the excited methods already put forward, and discusses some possible solutions that may well settle the following issues, such as maintain voltage and frequency within acceptable limit etc. Moreover, the concept of Virtual Grid is introduced as a possible solution for the technical challenges presented. Based on Central Control Unit (CCU), a protection scheme is presented that is coordinated to avoid nuisance tripping of the DGs and non-critical loads in grid-connected state and islanding mode. Lastly, combined with the status of protection and control of distributed network nowadays, this paper presents a feasible solution for forming of islanding, operation during islanding and resynchronization.