A new AC-AC chopper based var compensator is proposed.It does not require the DC-link energy storage and can effectively enhance the system reliability.The basic principles and compensation characteristics of the Buck AC/AC chopper based var compensator are described，the relationship between duty ratio and compensation current is derived，and the system analysis model is developed.A new direct current control method based on the second order generalized integral is proposed for the var compensator with detailed design criteria as well.The experimental and simulation results demonstrate that the real- time compensation of reactive power in grid side can be realized by this var compensator based on a direct current controlled Buck AC/AC chopper.