Application of Valley-Fill Circuit to Inverter Air Conditioners

This paper presents an input current harmonics suppression method using a valley-fill circuit in single phase to three phase motor drive system for small-capacity air conditioners. The basic principle of the valley-fill circuit and its advantages are briefly explained. Then, a new motor control method suitable for valley-fill inverters to achieve input current harmonics suppression is proposed. A 1kW experimental prototype is built to evaluate the proposed method. Results show that the proposed method could suppress input current harmonics below the IEC 61000-3-2 limit values. In addition, it is confirmed that the AC to AC power conversion efficiency of the proposed method is maximum 2.0 points higher than general boost choppers. Moreover, the total system efficiency is maximum 0.5 points higher in the light load range, which contribute to actual operating efficiency of air conditioners.