Recently the wide growth of nonlinear load has issued the problem of power quality. The requirement of power quality for precise equipment, which is often used in the industrial process, is very strict. The poor power quality may result in the misoperation or destruction of the precise equipment and leads to suspend or even damage the production process. In this project, a shunt active power conditioner (APC) is proposed for electric power quality improvement in the load side to advance the reliability of precise equipment. In the proposed active power conditioner, only a power converter is used to supply a high quality voltage to the load. A link inductor is inserted between the mains and the power converter to block the power disturbance from the mains, and a battery set is placed at the dc side of power converter to supply the back-up power. Hence, the proposed active power conditioner can solve the problems of power quality. Moreover, the proposed active power conditioner can be operated as a power conversion interface between the battery set, solar cell, fuel cell and the utility.