Coordinated control strategy based on network parameters for voltage sags compensating in Microgrid

Since Microgrid located downstream in distribution network, voltage sags caused by short circuit have become common power quality events that users of Microgrid have to face. According to where the short circuits occurred, voltage sags can be divided into two categories, interior voltage sag and exterior voltage sag. Exterior voltage sag caused by short circuit taking place in distribution network, and interior one caused by short circuit taking place in Microgrid itself. Therefore the compensation of voltage sag is also adjusted according to the category of sag, as well as choosing control strategy and capacity of compensator. In this paper the characteristics of two kinds of voltage sags are analyzed, according to the analysis results coordinated control strategy of voltage sags compensation have been proposed. Mitigating the exterior voltage sags needs relatively big capacity of compensator, so that power converters in electrical vehicle charging stations build main compensator. Interior voltage sags need only small power capacity on mitigation; therefore power converters of distributed generations within Microgrid build main compensators. In this paper the power control strategy is further studied. Microgrid is natural resistant network, which means the magnitude of voltage mainly depending on active power output of compensator. According to these features, the power control strategies of P-V droop is applied on voltage sag mitigation. The strategy proposed in this paper is approved to be effective by simulation test result.