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The protection and interconnection of HVDC grids

Li, Chuanyue ORCID: 2017. The protection and interconnection of HVDC grids. PhD Thesis, Cardiff University.
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It is cost-effective to construct a High Voltage Direct Current (HVDC) grid via interconnecting existing HVDCs. The grid protection and the interconnection between HVDCs are studied in the thesis. The future HVDC grid will be protected via the hybrid HVDC circuit breakers due to their high interrupting speed and low conduction losses. The hybrid DC circuit breakers have to be installed at each line end to fulfil the requirement of the grid protection. The overall cost of the breakers used in a HVDC grid will be extremely high as each breaker contains a large number of semiconductor switches. The research question in this part is how to reduce the cost of the hybrid DC circuit breakers. The novel interlink hybrid HVDC circuit breakers based on the concept of sharing main breaker branch will be proposed to reduce the size of the main breaker branch. An alternative method through coordination of converters and hybrid HVDC circuits breakers will be proposed to reduce the current rating of the breaker. Most of the commissioned HVDC projects are point-to-point Line Commutated Converter (LCC) HVDCs. The interconnection of LCC-HVDCs will achieve the benefits of the grid operation, such as highly efficient and flexible power transportation, and high security of power transportation. However, benefits of the interconnection are hindered by the disadvantages of the LCC-HVDC. The first one is that a LCC-HVDC has to reverse its voltage polarity in order to reverse its power. The second one is that a LCC-HVDC is at risk of the commutation failure, which will cause a DC fault when a commutation failure occurs. The research question in this part is how to achieve the interconnection of LCC-HVDCs with the benefits of the grid operation. Interconnection of LCC-HVDCs with the capability of power reversal and commutation failure mitigation will be studied, and the corresponding controls for the interconnection system will be proposes.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: HVDC; Hybrid DC circuit breaker; HVDC grid protection; Interconnection of HVDC grids.
Date of First Compliant Deposit: 13 December 2017
Last Modified: 22 May 2023 01:18

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