Centralized control strategies for HVDC connection of offshore wind farms based on diode rectifier units.

Nami, Ashkan

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Centralized control strategies for HVDC connection of offshore wind farms based on diode rectifier units.

Author(s): Nami, Ashkan

Advisor(s): Rodríguez Amenedo, José Luis
Arnaltes Gómez, Santiago

Tutor: Rodríguez Amenedo, José Luis

Department/Institute: UC3M. Departamento de Ingeniería Eléctrica

Degree: Programa de Doctorado en Ingeniería Eléctrica, Electrónica y Automática por la Universidad Carlos III de Madrid

Issued date: 2020-07

Defense date: 2020-10-23

Committee: Presidente: Massimo Bongiorno.- Secretario: Jaime Manuel Alonso-Martínez de las Morenas.- Vocal: Ana María Llor Carrasco

Sponsor: This Thesis work has been financed by: • Pre-doctoral research training contract (PIPF) supported by Univerisdad Carlos III de Madrid, from 01/04/2016 to 31/03/2020. • Mobility Scholarship for researchers in foreign research centers (Industry or Academia) supported by ABB AB. Destination: ABB Corporate Research Center, Västerås, Sweden. From 14/08/2017 to 12/02/2018. • Autonomous Community of Madrid under the PRICAM research project (S2013-ICE-2933). • ABB Corporate Research Center, Västerås, Sweden (10.13039/501100013902).

Has part: https://doi.org/10.3390/en11102718
https://doi.org/10.1109/TEC.2019.2949892
https://doi.org/10.23919/EPE.2019.8914820
https://doi.org/10.23919/EPE.2019.8914734
https://doi.org/10.1109/IECON.2019.8927598

Project: Comunidad de Madrid. S2013-ICE-2933

Keywords: Wind farms , Wind energy , Offshore wind power plant , Wind turbine generator system , High voltage alternating current , HVAC , High voltage direct current , HVDC , OWF interconnection technology , LCC-rectifier-based HVDC , Diode-based HVDC

URI: http://hdl.handle.net/10016/31887

Rights: Atribución-NoComercial-SinDerivadas 3.0 España

Abstract:

The possibility of using diode rectifier in the offshore substation for high voltage direct current (HVDC) connection of offshore wind farms (OWFs) has recently received an increasing interest due to its lower cost and losses together with its higher reliabi The possibility of using diode rectifier in the offshore substation for high voltage direct current (HVDC) connection of offshore wind farms (OWFs) has recently received an increasing interest due to its lower cost and losses together with its higher reliability compared with the voltage source converter (VSC) based HVDC link. However, the main drawback of the diode rectifier solution is that the system frequency has to be controlled to guarantee the diode rectifier commutation, given that the isolated offshore AC-grid can not generate the required frequency with the wind turbine generator systems (WTGSs) conventional control systems. This Thesis presents a direct frequency control for such an application whose principles are derived from the AC-side dynamics of a diode rectifier (DR) based HVDC system indicating that the frequency control can be achieved by reactive power balance at the rectifier station without a capacitor bank placed at the diode rectifier station. The proposed control system is implemented by a VSC connected to the rectifier station that is always needed for the centralized frequency control where the WTGSs conventional control systems are not changed. A hybrid HVDC system consisting of the DC-parallel connection of a low-power VSC with the rectifier station is also proposed in this Thesis, which is compared with the traditional VSC-HVDC connected OWFs. Besides the frequency control and diode rectifier harmonic currents compensation, the OWFs start-up is addressed in the centralized hybrid topology, overcoming all the DR-HVDC link drawbacks. Finally, a centralized control strategy of the parallel operation of the DR-HVDC and VSC-HVDC links for OWFs connection is presented. The VSC-HVDC controls the voltage and frequency of the offshore AC-grid needed for the OWFs start-up. The proposed centralized grid forming control is based on controlling the OWFs voltage by controlling the active power balance at the VSC-HVDC AC-bus. This leads to an onpitimized system where the VSC-HVDC can be sized just to support the system energization; while once the OWFs are in operation, the DR-HVDC will be loaded automatically. Stability analysis and simulation results provided throughout this Thesis verify the performance of the proposed control systems. [+]

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