부산대학교 도서관

In order to improve the performance of a 3−level neutral point clamped (3L−NPC) grid−connected inverter with fnite control set model predictive control (FCS−MPC), this paper proposes a modifed FCS−MPC algorithm based on the rearranged control set (MFCS−MPC). By adding synthetic virtual voltage vectors to rearrange the fnite control set (FCS) of the 3L−NPC inverter, the frequency spectrum of output leg voltage becomes concentrated, which is benefted for decreasing total harmonic distortion (THD) of grid currents and makes it easier to design output flters for the grid−connected inverter. Moreover, based on switching state sequences of virtual voltage vectors, the modifed predictive model of the proposed method is established considering capacitor voltage diference. Besides, according to the location of the reference output voltage vector, a preselection step is incorporated into MFCS−MPC to narrow the control set for predictions, which avoids evaluating all candidate voltage vectors in the control set, and hence, the online computational burden is signifcantly reduced. A prototype of 3L−NPC grid−connected inverter is established to validate the proposed MFCS−MPC method and the experimental results show that this method has excellent static and dynamic performance, with a low THD for a wide range of modulation indexes.