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This article presents a new three-phase five-level converter topology with a single dc source. The proposed topology combines the features of the conventional flying capacitor multicell and diode-clamped multilevel topologies. An important advantage of the proposed topology is the reduced volt-ampere, and hence, the volume, of the flying capacitors in its structure while keeping the same voltage blocking capability for semiconductor switches. The appropriate modulation strategy along with the flying capacitor voltage balancing technique is presented. To show the advantages of the proposed converter, different performance criteria such as switch count and rating, volt-ampere of flying capacitors, component cost, losses, and switching frequency are compared with some existing five-level topologies with a single dc source and the same voltage rating of switches. The results indicate that the proposed structure is superior to other five-level converters from different standpoints of the performance criteria. Simulation results are shown to verify the converter operation and its performance. The validity of the theoretical analysis is verified by experimentation on a scaled-down prototype system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This article proposes a four-level single flying capacitor converter (4L-SFCC) topology along with a new modulation technique. The proposed four-level single flying capacitor converter (4L-SFCC) topology has only one flying capacitor in each phase. This results in no redundant switching states associated with each voltage levels, and thus conventional modulation techniques cannot fulfill the capacitor voltage balancing requirement. Therefore, a new modulation technique is also proposed in this article in which the average capacitor current is set to zero during each sampling time, resulting in no net capacitor voltage change and hence voltage balancing during each sampling period. The proposed modulation scheme does not significantly increase the switching frequency and has equal switching frequency for all semiconductor switches, which is an advantage in terms of equalized switching losses. Simulation results are used to further evaluate the performance of the proposed converter. A laboratory-type experimental setup is used to validate the theoretical results. [ABSTRACT FROM AUTHOR]

This article presents a simple yet effective capacitor voltage balancing method for a five-level nested neutral point clamped (NNPC) converter. The NNPC has been recently developed for medium-voltage high-power applications and has interesting features. This hybrid topology has three flying capacitors in each leg. Like other flying capacitor-based topologies, it is necessary to regulate and balance the voltage of the flying capacitors in an NNPC converter to certain values. In this article, a new approach is proposed to accomplish this task. The proposed regulation technique employs line current direction and voltage deviation of flying capacitors to achieve regulation. The charging/discharging status of flying capacitors with respect to different switching states is used to define a priority index. This index is eventually used to select the proper switching state. A detailed investigation is presented to determine the best switching state for each level of the output voltage. The proposed method does not need any cost function and is very intuitive and simple to implement. Using simulations, the amplitude of the flying capacitor voltage ripple is measured, which shows reduction under all operating conditions. The feasibility and performance of the proposed method are confirmed by using a laboratory-type experimental setup. [ABSTRACT FROM AUTHOR]

This paper presents a new six-level flying capacitor based (FC-based) multilevel converter with one dc source and the capability of operating in all power factors and modulation indexes. Multilevel converters with one dc voltage source are attractive in many applications as they do not need rather expensive and bulky multiwinding input transformer connection at the dc side. On the other hand, not all classic multilevel converters with one dc source can produce any desirable number of output voltage levels at all power factors and/or modulation indexes. In this paper, a hybrid structure is proposed in which six voltage levels can be realized at the ac terminals. The modulation technique and the control strategy for the FC voltage balancing are presented. To show the advantages of the proposed converter, different performance criteria, such as switch count and rating, the size of capacitors, switching frequency, and power losses, are compared with other existing six-level topologies. The results indicate that the proposed structure is superior to other six-level converters from different standpoints. Simulation results are used to further evaluate the performance of the proposed converter. A laboratory-type experimental setup is used to validate the theoretical results. [ABSTRACT FROM AUTHOR]