Abstract
To protect HVdc grids from dc faults, the concept of a hybrid dc circuit breaker is widely accepted due to its low conduction losses and fast interruption speed. For a well-built dc grid, a massive number of hybrid dc circuit breakers have to be installed. This will lead to high capital costs. An interlink dc circuit breaker based on an idea of sharing a main breaker branch between two circuit breakers is proposed to reduce the overall costs of circuit breakers in a dc grid. Compared to existing hybrid dc circuit breakers, the interlink hybrid dc circuit breaker can achieve the same dc fault interruption capability with fewer components. Novel structures of main breaker branches are designed and their parameters are determined to make the interlink hybrid dc circuit breakers be capable for both unidirectional and bidirectional interruption on demand. For a unidirectional interlink hybrid dc circuit breaker, the size of metal-oxide varistors (MOVs) is reduced by 50%. For a bidirectional interlink hybrid HVdc circuit breaker, the number of IGBTs and MOVs are reduced by 25%. The interlink hybrid dc breakers are verified and compared to the hybrid dc circuit breaker via a three-terminal HVdc grid in PSCAD/EMTDC.
Highlights
T HE dc grid based on voltage-source-converter (VSC) technology is a preferable choice for transmitting power from remote energy sources to multiple load centers
Compared to using bidirectional hybrid dc circuit breaker (HCB), the number of IGBTs and metal-oxide varistors (MOVs) are reduced by 25% by using the Y-connected branch
For a unidirectional interlink hybrid dc circuit breaker (IHCB), an interlink main breaker branch is shared by two low-loss branches to achieve the same function as that of two unidirectional HCBs
Summary
T HE dc grid based on voltage-source-converter (VSC) technology is a preferable choice for transmitting power from remote energy sources to multiple load centers. The dc grid protection via unidirectional HCBs is proposed in [8] to reduce the overall cost of hybrid dc circuit breakers. Sharing main breaker branch is still a cost-effective solution as the presence of multiple faults occurring on different transmission lines at the same time is extremely rare. An interlink hybrid dc circuit breaker (IHCB) based on the concept of sharing the main breaker branch is proposed to reduce the size of the main breaker branches without increasing the number of low loss branches. The operation between a main breaker branch and two low-loss branches are designed to ensure correct protection against faults on two transmission lines and the dc bus.
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