In this paper, power-over-fiber technology is used for combined power and data transfer applying amplitudemodulated light representing a pulse-width modulated signal that could be used for control of, for instance, power semiconductor devices in high-power converters. Even though the concept is generally applicable, an experimental verification aiming for a gatedriver of a switch in a modular multilevel converter is presented. In order to achieve a good resilience against electromagnetic noise, a concept where the modulated light is demodulated as a comparably powerful current signal is employed. A 5 MHz boost converter steps up the voltage to 15-20 V, such that silicon or silicon-carbide based power devices could be controlled. From the results, it can be concluded that it is possible to achieve transmission of a control signal with a latency of less than 500 ns for a gate drive unit of a high-power converter. The concept can easily be scaled up to powers of several watt.

An investigation of the voltage imbalance of the two capacitors of the semi-full-bridge submodule is performed. Since the capacitances are not exactly the same, there may be a difference between the capacitor voltages. The resulting current-spike when they are connected in parallel has been analyzed in a full-scale laboratory experiment.

No abstract

In this paper, a comparison of the energy storage requirements is performed for the modular multilevel converter (MMC) with half-bridge and full-bridge submodules as well as for the alternate arm converter (AAC). Concerning the AAC, the operational mode with overlap period is taken into account and an analytical relation between the overlap angle and the modulation index is presented. This ensures that the net energy exchange for the converter arms is zero over each half cycle.

Recent advancements in silicon carbide (SiC) power semiconductor technology enable developments in the high-power sector, e.g., high-voltage direct current (HVdc) converters for transmission, where today silicon (Si) devices are state-of-theart. New submodule (SM) topologies for modular multilevel converters (MMCs) offer benefits in combination with these new SiC semiconductors. This paper reviews developments in both fields, SiC power semiconductor devices and SM topologies, and evaluates their combined performance in relation to core requirements for HVdc converters: grid code compliance, reliability, and cost.A detailed comparison of SM topologies regarding their structural properties, design and control complexity, voltage capability, losses, and fault handling is given. Alternatives to state-of-the-art SMs with Si insulated-gate bipolar transistors (IGBTs) are proposed, and several promising design approaches are discussed. Most advantages can be gained from three technology features. Firstly, SM bipolar capability enables dc fault handling and reduced energy storage requirements. Secondly, SM topologies with parallel conduction paths in combination with SiC metal-oxide-semiconductor field effect transistors (MOSFETs) offer reduced losses. Thirdly, a higher SM voltage enabled by higher blocking voltage of SiC devices results in reduced converter complexity. For the latter, ultra-high-voltage (UHV) bipolar devices, such as SiC IGBTs and SiC gate turn-off thyristors (GTOs), are envisioned. Index Terms-HVdc transmission, modular multilevel converter, power semiconductor devices, silicon carbide, submodules. I. INTRODUCTIONH VDC transmission technology requires integration into the existing alternating current (ac) grid. The conversion is performed via high-power converters. The modular multilevel converter (MMC) is a versatile and flexible topology with several options for optimization. MMCs have been intensively investigated since the early 2000's. It was identified, that modularity, scalability, built-in redundancy, and harmonic performance are advantageous for meeting widely varying requirements in grid applications. Compared to previous voltage source converters (VSC), the need for bulky harmonic filters is Keijo Jacobs

In this paper, a novel submodule cluster topology for modular multilevel converters is proposed. The cluster is composed of an arbitrary amount of submodule segments. Depending on the amount of capacitors in the cluster, the converter conduction losses can be reduced significantly. The topology enables electronic protection against explosion, thus, reducing the requirements for submodule bypass equipment. Implications for the converter operation and functionality are investigated and a wireless control scheme is proposed.

Parts of the paper have been presented at EPE'17 ECCE Europe (see end of introduction).

Recent developments in medium-voltage (MV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. The APS is an important converter component, which energizes the gate-drive units and, therefore, has an influence on the overall reliability and efficiency of the converter system. There has, however, been comparably little research on how the APS of high-power converter submodules can be realized, in particular for high-voltage (HV) applications. New, or improved, solutions may build on state-of-the-art topologies in the near future, but utilize MV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. Externally-fed APS concepts could provide several further advantages. Their various benefits on converter and system level may enable them to be a competitive solution for future APS concepts. Especially light-based power supply systems are considered most useful since they offer extreme voltage isolation capability and immunity to electromagnetic interference.This article presents a review of the wide range of solutions for APSs, possible implementation options, and the most important design considerations. The different solutions are evaluated in a qualitative fashion, providing an overview of available APS concepts with regard to the requirements for high-power converter applications.