An efficient active ripple filter for use in single-phase DC-AC conversion system

The objective of this paper is to propose an active ripple filter (ARF) for eliminating the double-line-frequency (DLF) current ripple of a single-phase DC/AC conversion system. The proposed ARF and its control strategies can not only prolong the usage life of battery energy device but also improve the DC/AC system performance. At first, the phenomena of DLF current ripple and the operation principle of the ARF are illustrated. Then, steady-state analysis, small-signal model and control loop design of the ARF circuit architecture are derived. The proposed control system structure includes: (1) a current control loop to provide the excellent ripple cancelling performance on the output of the battery energy device; (2) a voltage control loop for the high-side capacitor voltage of ARF circuit to achieve good steady-state and transient-state responses; (3) a voltage feed-forward control loop for the low-side voltage of ARF circuit to cancel the voltage fluctuation caused by the instability of the battery energy device. Finally, the feasibility of proposed concept can be verified by the system simulation, and the results show that the low DLF current ripple can be achieved.