Research on microgrid protection based on transient polarity comparison

Due to the characteristic of flexible operation mode of distributed power, the fault current between grid connected and islanding way is very different, conventional three-section over-current protection isn't suitable for microgrid power system. A big challenge is brought forward for microgrid protection, to satisfy quick acting and selective requirement. A microgrid protection principle based on transient polarity comparison is proposed in this paper, and it can adapt to the different operation mode. The one-dimensional discrete wavelet transform by Mallat algorithm is researched to extract the fault transient high frequency information, which is used as the basis of fault judgement. It can realize fault location by comparing the polarity of the transient high frequency signal. Furthermore, this realizing scheme of equipment is designed. Finally, the simulation work is carried out by Matlab to verify the correctness of the protection principle.