Reactive power control method and reactive power control system for wind farm clusters

The invention discloses a reactive power control method and a reactive power control system for wind farm clusters. The method comprises the following steps: a wind farm cluster control device extracts the target grid-connection point voltage of each wind farm in a wind farm cluster from a voltage instruction issued by a dispatching center; the wind farm cluster control device detects a preset range to which the current grid-connection point voltage uploaded by each wind farm belongs; if the current grid-connection point voltage uploaded by any wind farm is within a normal operation range, the AVC substation of the wind farm enters a local control mode under control; if the current grid-connection point voltage uploaded by any wind farm is within an abnormal operation range, the AVC substation of the wind farm enters a coordinated control mode under control, a coordinated AVC substation is chosen from the wind farm cluster according to the sensitivity of reactive voltage and the reactive power adjustable capa