This paper describes the experimental study on dynamic stability improvement of a single-machine (laboratory size 3kVA generator) connected to an infinite-bus power system using a phase shifter. A phase-shift injection is implemented by thyrister-associated fast tap-chenges based on a sliding mode control during transient conditions of generator. Digital simulation studies are also carried out to test the control scheme and the dynamic performances of system. As a result, the numerical studies show good agreement with the experimental results. The proposed controller utilizing the microcomputer is verified to damp the transient swing caused by a fault in power system.