André Schön

A new HVDC-DC converter with inherent fault clearing capability

For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses, and high investment costs. With the newly presented HVDC-DC auto transformer it is possible to directly link two DC lines with different voltage levels. In this paper the ability of this HVDC-DC converter to interrupt DC faults is investigated and compared to the state of the art topology of linking two DC lines via an AC connection.

High power HVDC-DC converters for the interconnection of HVDC lines with different line topologies

The structural change in energy generation and distribution will demand that large amounts of power are transported over long onshore distances. High Voltage Direct Current (HVDC) power transmission is most suitable for that task since, compared to High Voltage Alternating Current (HVAC) power transmission, there are no stability issues and the transmission losses are much lower. However the junction points of a segmented HVDC transmission corridor still have to be realized as AC nodes, since missing components, like DC breakers and or efficient HVDC-DC converters prevent the direct interconnection of transmission segments to a radial or even meshed DC grid. With the new HVDC auto transformer topology the direct interconnection of HVDC lines with different voltage levels becomes feasible. In this paper the ability of this new HVDC-DC converter topology to connect different DC line topologies and to preserve the transmission redundancy in case of a DC pole malfunction is investigated.

Average loss calculation and efficiency of the new HVDC auto transformer

For the upcoming need to transfer bulk power over long onshore distances, HVDC power transmission is the preferred choice. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, that still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses, and high investment costs. In this paper the conversion efficiency of the new HVDC auto transformer is compared to the conventional two stage topology with a full AC link.

A modular and scalable HVDC current flow controller

Due to technical and economic benefits there is an increasing interest in establishing an overlaying HVDC grid. Therefore, a current flow control is essential. In this paper a modular and scalable HVDC current flow controller is presented, which allows a direct exchange of power between two or more cables. In the first section the functional principle of the HVDC Balancing MMC is presented and a fundamental analysis of the steady state operation is done. In the second section an average loss calculation is described. In both sections the general results are discussed for a chosen point of operation.

Comparison of modular multilevel converter based HV DC-DC-converters

Efficient HV DC-DC converters are one key component of a future HVDC backbone grid. In this paper three promising MMC based HV DC-DC converter topologies, namely the front-to-front converter, the HVDC auto transformer and the modular multilevel DC converter are compared in terms of functionality, conversion efficiency and topology effort.

Analysis and semiconductor based comparison of energy diverting converter topologies for HVDC transmission systems

Energy diverting converter topologies are important power electronic components for HVDC connected offshore wind parks to meet grid code requirements. In this paper, three different types of energy diverting converter topologies are investigated. In the first section, the topologies are introduced and compared under general aspects. Afterwards, an approach for a sinusoidal voltage modulation of a MMC based braker is presented. Within its operation range it allows the use of half bridge submodules and also the use of full bridge submodules. Finally the topologies are compared to each other under aspects of braking performance, including a detailed loss calculation for the MMC braker topology.

Enhancement of the new HVDC auto transformer for inherent DC fault clearing capability

Abstract The structural change in energy generation and distribution, especially with renewable power sources and their volatile and demand independent generation behavior in areas with low load or at the periphery of the AC grid brings various challenges. Amongst others the need to transport high amounts of power over long distances between generation and load centers brings an AC grid to its limits. Therefore High Voltage Direct Current (HVDC) power transmission is the preferable choice for that task, since compared to High Voltage AC transmission, there are no stability issues and the transmission losses are much lower. However, components like HVDC-DC converters and a protection concept for DC line faults present challenges, which still have to be solved. As up today, the sections of a segmented DC transmission corridor would still be linked via an AC connection, leading to high transformation losses and high investment costs. With the newly presented HVDC-DC auto transformer [1–5]* it is possible to directly link two DC lines with different voltage levels. In this paper it is shown, that this topology is also able to securely prevent high DC fault currents and to isolate a faulty DC line at the interconnection point of different HVDC voltage levels. This ability and the resulting topological efforts are compared to the state of the art topology of linking two DC lines with different voltage levels via an AC connection.