Proportional-Integral and Proportional-Resonant Based Control Strategy for PUC Inverters

In this paper, a proportional-integral (PI) and proportional-resonant (PR) based control strategy is proposed for packed-U-cell (PUC) inverters. In the conventional PI-PI based control strategy, while the first PI regulates the DC capacitor voltage, the second PI regulates the AC load current. However, it is shown that the second PI cannot guarantee zero tracking error in the load current. The main reason of this comes from the fact that PI controllers are not able to achieve zero tracking error for the AC signals. Also, in an attempt to reduce the tracking error by tuning PI gains distorts the load current. In this study, a PI-PR based control strategy is obtained by replacing the second PI by a PR controller. The performances of both PI-PI and PI-PR control methods have been compared. It is shown that the load current to tracks its reference in all circumstances provided that the inverter current reference is generated accurately. Computer simulations are conducted to show the steady-state and dynamic performances of both control methods.