This paper discusses the control strategy of DC-capacitor voltage in single-phase STATCOM with drastically reduced capacitance. Reduced capacitance results in a high amplitude of the capacitor voltage oscillation; therefore, the peak voltage control is important to keep the dimensional size of the capacitor compact. A good dynamic peak voltage estimation method has been proposed for the control. This paper discusses a dynamic performance improvement of the peak voltage control when the current set-point is quickly changed by applying an active power feed-forward control. The proposed control was demonstrated by laboratory experiments and achieved good results.