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The wireless control of modular multilevel converter (MMC) submodules might offer advantages for MMCs with a high number of submodules. However, the control system should tolerate the stochastic nature of the wireless communication, continue the operation flawlessly or, at least, avoid overcurrents, overvoltages, and component failures. The previously proposed control methods enabled to control the submodules wirelessly with consecutive communication errors up to hundreds of control cycles. The submodule control method in this paper facilitates the MMC to safely overcome communication errors that last longer and when the MMC experiences significant electrical disturbances during the errors. The submodules are proposed to operate autonomously by implementing a replica of the central controller in the submodules and drive the replicas based on the local variables and the previously received data. The simulation and experimental results verify the proposed control method. Part of proceedings: ISBN 978-9-0758-1537-5, QC 20230118

Recent developments in high-voltage (HV) silicon and silicon carbide (SiC) power semiconductor devices are challenging state-of-the-art converter and auxiliary power supply (APS) designs. There has been comparably little research on how the APS of converter submodules can be realized. The APS is, however, 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. The wide range of possible solutions for APSs motivates an overview of state-ofthe- art and alternative concepts. Such a review is presented in this article, along with a qualitative evaluation regarding APS requirements for high-power converter applications. Moreover, future prospects of internal and external APS designs are discussed. Internal solutions may build on state-of-the-art topologies in the near future, but utilize HV SiC technology in the APS circuit itself to enable improved efficiency, reliability, simplicity, and compactness. The active voltage-divider-based APS is a promising concept if the required power is relatively low. Series-connected bootstrap circuits or snubber-based power tapping could provide a reduction of complexity and cost. It is recognized that several advantages are achievable by employing external APS concepts. Light-based power supply systems, comparably expensive today but under rapid development and with optimistic cost predictions, are considered most useful in this respect. Their extreme voltage isolation capability and immunity to electromagnetic interference, combined with various benefits on converter and system level, enable them to be a competitive solution for future APS concepts QC 20200831

The breakdown voltages of the currently available 1.2 and 1.7-kV classes Silicon Carbide (SiC) transistors are not sufficient to operate under medium blocking voltages. On the other hand, the fabrication yields of the available high-voltage SiC transistors are still low, resulting in low current capabilities. Series-connection of several individual transistors is the solution to meet medium blocking voltages and high current ratings. This paper identifies the most crucial design challenges of gate and base drive circuits suitable for driving fast-switching series-connected SiC transistors. These challenges are presented and analyzed using Finite Element Method simulations and experimental investigations.

The modular multilevel converter is one of the most preferred converters for high-power conversion applications. Wireless control of the submodules can contribute to its evolution by lowering the material and labor costs of cabling and by increasing the availability of the converter. However, wireless control leads to many challenges for the control and modulation of the converter as well as for proper low-latency high-reliability communication. This paper investigates the tolerable asynchronism between phase-shifted carriers used in modulation from a wireless control point of view and proposes a control method along with communication protocol for wireless control. The functionality of the proposed method is validated by computer simulations in steady state. QC 20181203

In future HVDC systems, many DC circuit breakers (DCCBs) will be required. In this paper, an advanced test circuit for DCCBs is described. A DC source is combined with a capacitor bank. In contrast to other test circuits, the proposed test circuit allows to replicate constant DC and temporary faults. In addition to conventional faults, this enables testing of auto-reclosing, proactive commutation, and complex test sequences combining all of these modes. The test circuit is easy to setup and also suitable for smaller research facilities. Experimental results from a down-scaled mock-up are included to demonstrate the capabilities of the test circuit. QC 20210525

As regards modular multilevel converter submodules, a different number of switches may be involved in the transitions between voltage levels depending on the submodule type and choice of switching states. In this paper, an investigation of the average switching frequency associated with different choices of bypass states is performed for the semi-full-bridge submodule. Theoretical considerations and simulation results show that the average switching frequency per device can be halved by using the proposed alternative bypass state. Moreover, the switching losses can be reduced by up to 60%. Finally, a comparative study with the full-bridge submodule has been conducted. QC 20181210

A considerable part of the fuel energy in vehicles never reaches the wheels and entirely converts to waste heat. In a heavy duty vehicle (HDV) the heat power that escapes from the exhaust system may reach 170 kW. The waste heat can be converted into useful electrical power using thermoelectric generator (TEG). During the last decades, many studies on the electrical power conditioning system of TEGs have been conducted. However, there is a lack of studies evaluating the electrical instrumentation, the impact of the converter-efficiency, and the TEG arrangement on a real large-scale TEG on-boarda drivable vehicle. In this study, the most important parameters for designing electrical power conditioning systems for two TEGs, developed for a real-scale HDV as well as experimental results demonstrating the recovered electrical power, are presented. Eight synchronous inter-leaved step-down converters with 98 % efficiency with perturb and observe maximum power point tracker was developed and tested for this purpose. The power conditioning system was communicating with the on-board computers through the controller area network and reported the status of the TEGs and the recovered electrical power. The maximum recovered electrical power from the TEGs reached 1 kW which was transmitted to the electrical system of the vehicle, relieving the internal combustion engine. QC 20180206

Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs) have the potential to increase the power density in power electronics converters compared to the currently used silicon (Si). Their benefits are higher efficiency, higher switching speeds, and higher operating temperatures. Moreover, SiC MOSFETs, which are normally-off, offer the possibility to directly replace Si Isolated-Gate-BipolarTransistors (IGBTs) in already existing converter designs with minimal circuit changes. Nevertheless, as an emerging technology, the reliability performance remains to be investigated. A reliability analysis has been performed based on a full-bridge resonant converter rated at 60 kW for modern Electrostatic Precipitator (ESP) power supplies. This analysis shows that introducing SiC devices will increase the lifetime of the converter while reducing the losses. The investment costs of replacing the Si IGBTs with SiC MOSFETs can thus be covered with the reduction of the losses over the economical operational lifetime. Furthermore, a theoretical analysis on how introducing SiC MOSFETs could increase the power density of the converter while maintaining the efficiency and the reliability. Finally, an analysis on introducing redundancy as a way to improve the reliability of the system has been performed. QC 20170530