Reactive power/voltage regulation problems include continuous variables（for example， Mvar powers of generators and condensers） and discrete variables（i.e.， capacitors， reactors， OLTCs， and so on）. In Automatic Voltage Control（AVC）， coordination of continuous and discrete variables must be considered inside one substation or among power plants and substations. A coordination strategy—“discrete variables are firstly adjusted， continuous variable is followed by secondary refined adjustment” is presented. A centralized control mode， which uses local VQC devices as backup controllers， is designed to solve voltage coordination problems inside one substation. For each substation， the regulating direction of reactive sources is determined by expert rules firstly， then total Mvar output required is allocated between continuous variables and discrete variables according to sensitivity analysis. The proposed approach has been implemented in several regional and provincial power grids in China. The application results have validated the efficiency and practicability of the proposed method.