Abstract: Based on the important role of automatic voltage control technology in reactive power support and safe and stable operation of the power grid, this paper introduces the mechanism of reactive power and voltage regulation in photovoltaic grid connection points. Taking inverters and static var generator（SVG） as research objects, the reactive power allocation strategy and SVG reactive power replacement method of photovoltaic power plants are studied and analyzed. The effectiveness of coordinated control and reactive power replacement of photovoltaic inverters and SVG is verified through on-site experiments in photovoltaic power plants, and it has reference significance for achieving automatic voltage control in regional power grids for new energy grid connected power stations.