Modified passivity-based control method for three-phase cascaded unidirectional multilevel converters.

In this paper, taking into account the unidirectional conduction property of diodes, with an emphasis on the enhancement of system tolerance and robustness, a modified passivity-based control (PBC) method is introduced to three-phase cascaded unidirectional multilevel converters. This is the first time the PBC method has been utilized in cascaded unidirectional multilevel converters. This paper applies the PBC method to the current control loop and the overall DC bus voltage control loop. Meanwhile, considering that the classical PBC method regulates DC voltage with a steady-state error, the overall DC bus voltage is regulated via a combination of the PBC method and a PI controller to ensure zero-voltage tracking error. Moreover, the tolerance and robustness of the modified PBC method are verified by a theoretical analysis. Simulation results are furnished for assessing the correctness of the theoretical analysis, and the performance of the modified PBC method for three-phase cascaded unidirectional multilevel converters. [ABSTRACT FROM AUTHOR]