According to the coordinated control principle—“firstly adjusting discrete variable， then refining continuous variable”， an efficient real-time coordinated control scheme， which chooses bus voltage limits in the substation as coordinated constraints and updates these constraints simultaneously， is presented to coordinate the voltage control variables among power plants and substations. Firstly， a dummy condenser is added in the side of substation， then the expected Mvar outputs of the dummy condenser and control strategies of the discrete devices in the substation are obtained by expert rules. The expected Mvar output is then converted into the updated real-time constraints on coordinated variables， which are included in the regional coordinated secondary voltage control（CSVC） model. This CSVC model doesn't include discrete variables， so avoids to solve a mixed-integer programming problem. The proposed approach has already been implemented in several regional /provincial power grids in China， and shows higher control reliability.