In this study, the three-level inverter structure has beenwas used in STATCOM, which has advantages such as loss and harmonics less than the two-level structure. For the first time, an improved one-cycle control method has beenwas used in the STATCOM compensator to control switching. With the presence of the proposed controller, STATCOM successfully corrected the disturbances of power quality such as voltage shortages, voltage overvoltage, voltage fluctuations, voltage harmonics, and so on. Advantages of single-cycle control over other controllers, such as PWM, include having a lower-error response in steady-state mode and a better response in dynamic mode. For the first time, in order to increase the response speed of single-cycle control, a change in its structure was created for use in the STATCOM compensator. Also, for one-cycle control, more robust paths have beenwere created that have dynamic performance inon all of the different disturbances in the network.