In a single-phase to three-phase inverter that does not have an inductor or electrolytic capacitor, the inverter must control not only the motor but also the input power factor because there is no power factor correction circuit or energy buffer. To improve the input power factor, several control methods are proposed. However, if the motor has large spatial harmonics caused by the rotor structure, the bandwidth limitations of the control system adversely affect the source current response and thereby cause source current harmonics. This paper proposes a harmonic current reduction controller that makes it possible to obtain a sinusoidal source current. The proposed controller focuses on the relationship between the source current and the average DC-link current and controls the source current using a feedforward control method. The effectiveness of the proposed method is experimentally verified.