A new DC-DC converter concept allowing line commutated converters and voltage source converters based HVDC systems connectivity

Elgenedy, Mohamed A. and Ahmed, Khaled Hani and Aboushady, Ahmed A. and Abdelsalam, Ibrahim (2020) A new DC-DC converter concept allowing line commutated converters and voltage source converters based HVDC systems connectivity. IET Power Electronics. ISSN 1755-4535

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    Abstract

    The common two challenges in high voltage dc (HVDC) multi-terminal transmission are the dc fault isolation and the dc voltage stepping up/down. Additionally, interconnecting voltage source converter (VSC) and line commutated converters (LCC) based HVDC network topologies has been challenging. This paper, introduces a new dc-dc converter topology concept connecting both LCC and VSC based HVDC networks with bidirectional power flow without operation stoppage. The proposed topology is formed of two front-to-front connected bridges with an ac-link formed of a capacitor and an inductor (which can be replaced by a transformer for voltage step up/down). The LCC-HVDC network bridge is formed of insulated gate commutated thyristors while the VSC-HVDC network bridge is formed of insulated gate bipolar transistors. Therefore, ON/OFF switching of both bridges and bi-directional power flow are possible. Moreover, the reactive power transfer is nullified at rated active power exchange between the proposed converter bridges. The proposed concept detailed analysis and control equations are introduced. Different operation scenarios are simulated. In addition to a scaled-down experimentation to test the applicability of power transfer scenarios without operation stoppage in normal operation.