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This paper presents a dual modular multilevel converter (MMC) topology that utilizes energy exchange between adjacent-arm submodules (SMs), operating with out-of-phase modulation. The proposed configuration is applicable to medium-voltage high-power variable-speed drives incorporating open-end stator winding machines. A novel concept of power decoupling between adjacent-arm SMs in the dual MMC topology is realized through high-frequency transformer-based dc–dc converter modules. This concept offers a significant reduction in the sizing requirement of the SM capacitance and the stored energy in the MMC system, while avoiding the problem of wide voltage fluctuations of SM capacitors, especially at low operating frequencies. The proposed configuration can produce dc voltage; therefore, a machine speed range from zero speed to the rated speed is possible under the rated torque operating condition. The operating principles of the proposed dual MMC configuration are elaborated and necessary mathematical analysis is derived. Simulation and experimental results verify the concept of the proposed drive configuration. [ABSTRACT FROM AUTHOR]

Bipolar repetitive high-voltage pulse generators are commonly used in modern pulsed power applications. Conventionally, bipolar high-voltage pulses can be generated by adding a high-voltage H-bridge at the output stage of a unipolar high-voltage pulse generator which increases complexity and cost of the bipolar high-voltage pulse generator. In this paper, a boost-inverter-based bipolar high-voltage pulse generator with high-voltage gain is proposed. The proposed generator can provide high-voltage bipolar output pulses with the desired specifications from a low input dc voltage. The proposed generator is based on employing two bidirectional boost dc–dc converters, where the load is connected differentially between the boost converters’ output terminals. In the proposed approach, four controlled switches are required. Only two out of these four switches are rated at the high-voltage output level which affects positively the system cost. A detailed illustration of the proposed approach along with the design of its passive components is presented in this study. Simulation and experimental results are used to validate the proposed approach. [ABSTRACT FROM AUTHOR]

Conventional dual-active bridge topologies provide galvanic isolation and soft-switching over a reasonable operating range without dedicated resonant circuits. However, scaling the two-level dual-active bridge to higher dc voltage levels is impeded by several challenges among which the high dv/dt stress on the coupling transformer insulation. Gating and thermal characteristics of series switch arrays add to the limitations. To avoid the use of standard bulky modular multilevel bridges, this paper analyzes an alternative modulation technique, where staircase approximated trapezoidal voltage waveforms are produced; thus, alleviating developed dv/dt stresses. Modular design is realized by the utilization of half-bridge chopper cells. This way the analyzed dc-dc transformer employs modular multilevel converters operated in a new mode with minimal common-mode arm currents, as well as reduced capacitor size, hence reduced cell footprint. Suitable switching patterns are developed and various design and operation aspects are studied. Soft-switching characteristics will be shown to be comparable to those of the two-level dual-active bridge. Experimental results from a scaled test rig validate the presented concept. [ABSTRACT FROM AUTHOR]