In recent years, the debasement of the power quality of a distribution system such as deterioration of voltage imbalance and current imbalance or the increase of harmonics has been apprehended with diversification of the load by progress of power electronics technology and with increase of the amount of connection of a distributed generators for home use with the reduction of the effect on the environment. In this paper, the authors propose the restraint method of harmonics and improvement of voltage imbalance in distribution system utilizing the power conditioner systems of photovoltaic systems and verify the validity of the proposal method by the numerical calculation using an analytical model of distribution system.