A Fast-Decoupled Space Vector Modulation Scheme for Flying Capacitor-Based Multilevel Converters

Abstract

The space vector modulation (SVM) scheme is popularly implemented in multilevel converters. However, in flying capacitor-based (FC-based) multilevel converters, it becomes extremely challenging to implement due to the redundancy in phase voltage levels. The intrinsic property of line voltage redundancy of SVM in addition to the phase voltage redundancy of FC-based converters results in considerably increased computational complexity and storage requirements. In fact, one of the most important concerns about FC-based converters is the voltage control of the FCs. This article proposes a generalized decoupled SVM scheme for the FC-based multilevel converters, including the classic flying capacitor multicell (FCM) converters, which is less computationally complex. For balancing the FC voltages, an overall priority index is employed to determine the switching state with the best balancing characteristics. The proposed decoupled SVM scheme along with the capacitor voltage balancing scheme can be implemented intuitively and simply for all FC-based multilevel converters. The simulation results of a five-level FCM converter show the effectiveness of the proposed method in the regulation of FC voltages. Moreover, the proposed voltage balancing method is robust to static load and transient conditions. Also, experimental results demonstrate the effectiveness of the proposed method.