New control approach for four-wire active power filter based on the use of synchronous reference frame

Abstract Since the development of the first theories for the active power filters (APF) control, many efforts have been concentrated to improve their performances because the number of non-linear loads did not stop to increase. Moreover, the appearance of non-linear load of different types, three-phase or single-phase, provokes unbalanced system, which requires more elaborated controls especially in term of robustness. For the unbalanced non-linear loads, the reduction of neutral current is one of the two aims of different APF's controls studied in this paper. This will be highly appreciated by the distribution networks. The second aim is naturally to obtain an acceptable THD for each line current. In this paper, three control methods, all based on the instantaneous powers theory introduced by H. Akagi [H. Akagi, Y. Kanazawa, A. Nabae, Generalized theory of the instantaneous reactive power in three-phase circuits, in: Proceedings of International Power Electronics Conference, Tokyo, Japan (1983) 1375–1386.] are compared and advantages and drawbacks of each approach are discussed. Then, the improvements will be presented for these controls so as to obtain better results in case of unbalanced system. The simulation results will show the effectiveness of these improvements. Finally, in order to improve again the performances of APF, a new control is proposed. This approach is based on the use of synchronous reference frame and its effectiveness will be validated through numerical simulations.