Abstract
Offshore wind farms (OWFs) integration are attractive extensively for furnishing more robust power than land wind farms. This paper introduces a modular combined DC-DC autotransformer (MCAT), which contributes to the offshore wind power integration of DC grids with different voltage levels. Traditional DC transformers contains medium- or high-frequency converter transformers, which have the disadvantages of high manufacturing difficulty and cost. These shortcomings seriously affect the progress of commercial application of DC transformers. To solve these problems, in the proposed MCAT, converter transformers are replaced with a DC-isolation capacitor and a compensation inductor in series to reduce the footprint of offshore platforms and improve economy. Theoretical analysis is carried out for the MCAT operation principle. Selection methods of main circuit parameters for the MCAT are discussed in detail. Then, corresponding control strategies of the MCAT are proposed. Finally, the effectiveness of the proposed MCAT and its control strategies are validated by time domain simulations in PSCAD/EMTDC. The time-domain simulation results show the correctness of the main circuit parameters and the rationality of the MCAT control strategies.
Highlights
Power Integration with DCOffshore wind energy has drawn wide interest due to its distinctive advantages, such as rich wind resources, high utilization hours, and no need to occupy land resources [1].Recently, China has proposed to build new power systems dominated by renewable energy, which facilitates the rapid development of offshore wind farms (OWFs).The high voltage direct current (HVDC) transmission system is preferred to the traditional AC transmission system for the grid integration of large-scale OWFs
In the modular combined DC-DC autotransformer (MCAT), the expensive converter transformers are substituted with the DC-isolation capacitor and compensation inductor in series to reduce the footprint of the offshore platforms
The selection methods of main circuit parameters for the MCAT are discussed in detail
Summary
Offshore wind energy has drawn wide interest due to its distinctive advantages, such as rich wind resources, high utilization hours, and no need to occupy land resources [1]. Topologies have need forconverter a transformer or the transformer which does notnon-isolated have to be rated for the fulla smaller footprint and less operation losses and reduce the footprint of an offshore platform power of the DC-DC converter [11]. The main topologies disadvantage these topologies is that where large power transmission is required, such as OWFs. A step-up unidirectional it is difficult to balance the sharing of currents or voltages in semiconductor devices and DC-DC large autotransformer is brieflyObviously, introducedresonant in [14], but the footprint ofsuitable this topology achieve power transmission. Aiming at imDC-isolated capacitor and a compensation inductor in series, which are much smaller in size proving operation efficiency and reducing the cost, this paper proposes a modularand cost than transformers, and do not incur additional power losses in series resonance.
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