Introduction  Researches already done on AC/DC interactions in power grid mainly focuses on certain aspects by means of theoretical analysis or digital simulation. With systematic analysis absent, it is not conducive to get a comprehensive understanding of interactions between AC and DC systems.

  Method  Based on a large number of studies, this paper established a analysis framework for load center power grids with multiple HVDC infeeds. Firstly, occurrence, development, recovery of HVDC commutation failures and blocking were analyzed, and typical parameters were given. Then meanings and mechanisms of AC/DC interactions were studied,commonly used analysis methods and criteria used in practice were summarized.

  Result  The essence of AC/DC interactions are defined. AC/DC interaction analysis framework for load center grids with multiple HVDC infeeds is proposed schematically for the first time.

  Conclusion  This paper provides useful reference for further study on AC/DC interaction related problems.