A Back-to-Back 2L-3L Grid Integration of a Marine Current Energy Converter

Apelfröjd, Senad; Ekström, Rickard; Thomas, Karin; Leijon, Mats

doi:10.3390/en8020808

Cited by 5 publications

(4 citation statements)

References 18 publications

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“…An overview of the electrical system at the S öderfors test site is shown in Figure 3. The system is extensively described in [18] and a comprehensive simulation study of the system can be found in [20]. An overview of the system will be given in this section.…”

Section: Electrical Systemmentioning

confidence: 99%

“…The generator is mounted on the same axis as the turbine without a gearbox. The electrical energy is transmitted to an onshore cabin via an approximately 150 m long cable [18]. In the onshore cabin, the electrical grid connection system is located.…”

mentioning

confidence: 99%

“…In the onshore cabin, the electrical grid connection system is located. The grid connection system is based on a B2B converter technology [18], [19]. A simulation model of the system has been presented in [20].…”

mentioning

confidence: 99%

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A comparison of AC and DC collection grids for marine current energy

Fjellstedt,

Forslund,

Thomas

2023

Proc. EWTEC

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Important questions to enable the use of marine current energy are how the electrical system is designed, how multiple energy converters are interconnected offshore and how the power is transmitted to the shore. The Division of Electricity at Uppsala University have constructed and deployed a marine current energy converter in the river Daläven in Söderfors, Sweden. In the study presented in this article, a model of a near-shore low-voltage AC collection grid and a near-shore low-voltage DC collection grid is presented for the technology at the Söderfors test site. The models are implemented in MATLAB/Simulink. For collection grids of five turbines, it is shown that the proposed control schemes are able to deliver power to the distribution grid. The controllers are able to achieve this even when one turbine is suddenly disconnected from the grid. Furthermore, it is shown that the conduction losses of the DC system are higher than the losses of the AC system for nominal and high water speeds. However, in a qualitative comparison between the systems it is concluded that despite the higher losses, the DC system can be an interesting option. This is because fewer components need to be placed in the turbine, which is beneficial in offshore systems where space is a limiting factor. Furthermore, a DC system can be less expensive since fewer cables are needed.

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Section: Electrical Systemmentioning

confidence: 99%

mentioning

confidence: 99%

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A comparison of AC and DC collection grids for marine current energy

Fjellstedt,

Forslund,

Thomas

2023

Proc. EWTEC

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“…This setup is used as a reference for the work regarding components of the grid connection in this paper. The electrical system at the test site consists of a back-to-back converter with a two-level voltage source converter on the generator side and a three-level voltage source converter on the grid side [5,6]. The grid-side converter is connected to the grid through an LCL-filter constructed by an LC-filter and the inductance of a power transformer.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of the Frequency Response of an LC-Filter and Power Transformer for Grid Connection

2023

Self Cite

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The power delivered by a voltage source inverter needs to be filtered to fulfill grid code requirements. A commonly used filter technology is the LCL-filter. An issue with the LCL-filter is the occurrence of a resonance peak, which can be mitigated with active or passive damping methods. The transfer function of the filter is often used to investigate the frequency response of the system and propose damping methods. The use of an LC-filter combined with a power transformer to form an LCL-filter has not been extensively investigated. Therefore, the study in this article introduces a model for an LC-filter and power transformer for the grid connection and a derived transfer function for the model. The transfer function for the system is validated with simulations and experimental investigations. The results from simulations and the results from a direct solution of the derived analytical function overlap almost perfectly. The magnitudes of the experimental results are approximately 1 dB lower than the simulation and analytical results before the resonance frequency. At the resonance frequency, the experimental results are approximately 13.4 dB lower. The resonance frequency, however, occurs at approximately the same frequency. It is also concluded that the system is significantly damped.

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