Hierarchical voltage control strategy based on typical scenes in AC/DC Hybrid distribution network with operation of multiport Flexible DC looped network

For distribution network with a large number of distributed generation, the output fluctuation of distributed power sources and load variation will cause voltage over-limit. Aiming at AC voltage control of AC/DC hybrid distribution network, this paper proposes the hierarchical voltage control framework. Based on bus voltage level, we construct typical scenes while the voltage is normal, mild over-limit and severe over-limit. Under normal scene, the paper proposes to improve the dynamic reactive power reserve capacity of distribution network through global optimization. Under voltage mild over-limit scene, the coordinated strategy of centralized/local control is implemented to correct bus voltage which is slightly deviated. Under voltage severe over-limit scene, the paper proposed to reduce voltage over-limit level into normal state by rapid emergency support of reactive power of VSC (Voltage Source Converter). Finally, based on practical network the simulation is performed to validate the rationality and efficiency of the proposed strategy.