To solve the problem of reactive power non-coordination among strongly coupled plants

a coordinating method for strongly coupled plants for automatic voltage control (AVC) is proposed. The coupling coefficient among plants is introduced

and the plant coordinating group is generated as the coordinating unit. The reactive power unbalanced index among strongly coupled plants is defined. And the current operation state of power grid is determined. In the event the pilot bus voltage is not controlled in place

the control strategy of voltage regulation and reactive power tracking control is adopted so that the pilot bus voltage will be enabled to guarantee that the reactive power unbalanced index between strongly coupled plants will meet the control requirement while tracking optimal settings. If the pilot bus voltage is already in place

reactive correction control based on the objective of plant-to-plant coordination will be carried out to reduce the deviation in reactive load while ensuring that the pilot bus voltage is maintained within the range of control dead zone. Reactive regulating commands will be added to the traditional voltage regulating commands to suppress possible irrational reactive power distribution or reactive fluctuation between strongly coupled plants. Application of the proposed method in a number of regional and provincial grids in China shows that the proposed method is able to reduce irrational reactive power distribution between strongly coupled plants. This work is supported by National Key Technologies R&D Program (No. 2013BAA02B01)

National Science Fund for Distinguished Young Scholars (No. 51025725) and National Natural Science Foundation of China (No. 51277105).