Special Issue "Control and Protection of HVDC-Connected Offshore Wind Power Plants"

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: closed (30 April 2020).

Special Issue Editors

Dr. Ömer Göksu
Website
Guest Editor
Department of Wind Energy, Technical University of Denmark, Copenhagen, Denmark
Interests: Control and modelling of wind turbines/wind power plants; wind turbine converter control; grid integration; grid services; grid codes; HVDC connections; fault analysis
Dr. Jayachandra N. Sakamuri
Website
Guest Editor
Department of Wind Energy, Technical University of Denmark, Copenhagen, Denmark
Interests: HVDC control and modelling; HVDC converter control; multi-terminal DC grids; HVDC grid protection; integration of wind and solar; high voltage switchgear
Prof. Dr. Nicolaos Antonio Cutululis
Website
Guest Editor
Department of Wind Energy, Technical University of Denmark, 4000 Roskilde, Denmark
Interests: wind power; offshore wind; offshore grids; control of wind power; electrical design

Special Issue Information

Dear colleagues,

As offshore wind power plant (OWPP) sites are getting very far from onshore connection points, HVDC connection is becoming the preferred solution over long AC connection today. The ambitious targets for offshore wind installations in the EU 2030 and 2050 plans will also require more DC connections. DC-interconnected HVDC networks (multiterminal/meshed HVDC) within the North Sea are also being considered as a future solution. The control and protection schemes in the 100% converter-based offshore network require special considerations due to the characteristics of the converters (wind turbine and HVDC converters). There are additional challenges in terms of harmonic interactions and instabilities in the HVDC-based offshore networks. Moreover, considering the high share of offshore wind in the power systems, certain system services need to be provided from HVDC-connected OWPPs. Overall, novel control and design for the offshore HVDC network (e.g. OWPP design, HVDC converter technologies) would be adopted for the efficient deployment of offshore wind. The focus of this Special Issue includes (but is not limited to):

Control of HVDC-connected OWPPs:

  • Parallel HVDC converters
  • Cluster control of several OWPPs
  • Grid forming OWPPs
  • Stability and harmonic interactions

Protection of HVDC-based offshore networks:

  • Symmetrical/asymmetrical offshore AC faults
  • DC faults
  • Protection schemes
  • Field experiences

Long HVAC vs. HVDC transmission

Interconnection of HVDC offshore:

  • Multiterminal/meshed HVDC grids
  • AC interconnections offshore

Novel HVDC connection technologies:

  • Hybrid HVDC; e.g. VSC–LCC–DR (diode rectifier),
  • MMCs (half bridge/full bridge/mixed arm/novel MMC)
  • DC wind turbines/wind power plants

Grid services by HVDC-Connected OWPPs:

  • Synthetic inertia and frequency support
  • Black start
  • Voltage/reactive power support

Grid code analysis and recommendations

Dr. Ömer Göksu
Dr. Jayachandra N. Sakamuri
Dr. Nicolaos A. Cutululis
Guest Editors

Manuscript Submission Information

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Keywords

  • wind power
  • offshore wind
  • HVAC
  • HVDC
  • control
  • protection
  • grid integration
  • grid codes
  • ancillary services
  • clusters
  • meshed offshore grids
  • multi-terminal DC grids
  • wind turbines

Published Papers (5 papers)

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Research

Open AccessArticle
Analysis of Local Measurement-Based Algorithms for Fault Detection in a Multi-Terminal HVDC Grid
Energies 2019, 12(24), 4808; https://doi.org/10.3390/en12244808 - 17 Dec 2019
Cited by 1
Abstract
One of the most important challenges of developing multi-terminal (MT) high voltage direct current (HVDC) grids is the system performance under fault conditions. It must be highlighted that the operating time of the protection system needs to be shorter than a few milliseconds. [...] Read more.
One of the most important challenges of developing multi-terminal (MT) high voltage direct current (HVDC) grids is the system performance under fault conditions. It must be highlighted that the operating time of the protection system needs to be shorter than a few milliseconds. Due to this restrictive requirement of speed, local measurement based algorithms are mostly used as primary protection since they present an appropriate operation speed. This paper focuses on the analysis of local measurement based algorithms, specifically overcurrent, undervoltage, rate-of-change-of-current, and rate-of-change-of-voltage algorithms. A review of these fault detection algorithms is presented. Furthermore, these algorithms are applied to a multi-terminal grid, where the influence of fault location and fault resistance is assessed. Then, their performances are compared in terms of detection speed and maximum current interrupted by the HVDC circuit breakers. This analysis aims to enhance the protection systems by facilitating the selection of the most suitable algorithm for primary or backup protection systems. In addition, two new fault type identification algorithms based on the rate-of-change-of-voltage and rate-of-change-of-current are proposed and analyzed. The paper finally includes a comparison between the previously reviewed local measurement based algorithms found in the literature and the simulation results of the present work. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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Open AccessArticle
Impact of Primary Frequency Control of Offshore HVDC Grids on Interarea Modes of Power Systems
Energies 2019, 12(20), 3879; https://doi.org/10.3390/en12203879 - 14 Oct 2019
Abstract
Offshore high-voltage DC (HVDC) grids are developing as a technically reliable and economical solution to transfer more offshore wind power to onshore power systems. It is also foreseen that the offshore HVDC grids pave the way for offshore wind participation in power systems’ [...] Read more.
Offshore high-voltage DC (HVDC) grids are developing as a technically reliable and economical solution to transfer more offshore wind power to onshore power systems. It is also foreseen that the offshore HVDC grids pave the way for offshore wind participation in power systems’ balancing process through frequency support. The primary frequency control mechanism in an HVDC grid can be either centralized using communication links between HVDC terminals or decentralized by the simultaneous use of DC voltage and frequency droop controls. This paper investigates the impact of both types of primary frequency control of offshore HVDC grids on onshore power system dynamics. Parametric presentation of power systems’ electro-mechanical dynamics and HVDC controls is developed to analytically prove that the primary frequency control can improve the damping of interarea modes of onshore power systems. The key findings of the paper include showing that the simultaneous use of frequency and DC voltage droop controls on onshore converters results in an autonomous share of damping torque between onshore power systems even without any participation of offshore wind farms in the frequency control. It is also found that the resulting damping from the frequency control of offshore HVDC is not always reliable as it can be nullified by the power limits of HVDC converters or wind farms. Therefore, using power oscillation damping control in parallel with frequency control is suggested. The analytical findings are verified by simulations on a three-terminal offshore HVDC grid. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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Open AccessArticle
Coordinated Control of HVDC and HVAC Power Transmission Systems Integrating a Large Offshore Wind Farm
Energies 2019, 12(18), 3435; https://doi.org/10.3390/en12183435 - 06 Sep 2019
Abstract
The development of efficient and reliable offshore electrical transmission infrastructure is a key factor in the proliferation of offshore wind farms (OWFs). Traditionally, high-voltage AC (HVAC) transmission has been used for OWFs. Recently, voltage-source-converter-based (VSC-based) high-voltage DC (VSC-HVDC) transmission technologies have also been [...] Read more.
The development of efficient and reliable offshore electrical transmission infrastructure is a key factor in the proliferation of offshore wind farms (OWFs). Traditionally, high-voltage AC (HVAC) transmission has been used for OWFs. Recently, voltage-source-converter-based (VSC-based) high-voltage DC (VSC-HVDC) transmission technologies have also been considered due to their grid-forming capabilities. Diode-rectifier-based (DR-based) HVDC (DR-HVDC) transmission is also getting attention due to its increased reliability and reduced offshore platform footprint. Parallel operation of transmission systems using such technologies can be expected in the near future as new OWFs are planned in the vicinity of existing ones, with connections to more than one onshore AC system. This work addresses the control and parallel operation of three transmission links: VSC-HVDC, DR-HVDC, and HVAC, connecting a large OWF (cluster) to three different onshore AC systems. The HVAC link forms the offshore AC grid, while the diode rectifier and the wind farm are synchronized to this grid voltage. The offshore HVDC converter can operate in grid-following or grid-forming mode, depending on the requirement. The contributions of this paper are threefold. (1) Novel DR- and VSC-HVDC control methods are proposed for the parallel operation of the three transmission systems. (2) An effective control method for the offshore converter of VSC-HVDC is proposed such that it can effectively operate as either a grid-following or a grid-forming converter. (3) A novel phase-locked loop (PLL) control for VSC-HVDC is proposed for the easy transition from the grid-following to the grid-forming converter in case the HVAC link trips. Dynamic simulations in PSCAD validate the ability of the proposed controllers to ride through faults and transition between grid-following and grid-forming operation. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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Open AccessFeature PaperArticle
Power Oscillation Damping from Offshore Wind Farms Connected to HVDC via Diode Rectifiers
Energies 2019, 12(17), 3387; https://doi.org/10.3390/en12173387 - 02 Sep 2019
Cited by 2
Abstract
Diode rectifiers (DRs) have elicited increasing interest from both industry and academia as a feasible alternative for connecting offshore wind farms (OWFs) to HVDC networks. However, before such technology is deployed, more studies are needed to assess the actual capabilities of DR-connected OWFs [...] Read more.
Diode rectifiers (DRs) have elicited increasing interest from both industry and academia as a feasible alternative for connecting offshore wind farms (OWFs) to HVDC networks. However, before such technology is deployed, more studies are needed to assess the actual capabilities of DR-connected OWFs to contribute to the secure operation of the networks linked to them. This study assessed the capability of such an OWF to provide support to an onshore AC network by means of (active) power oscillation damping (POD). A semi-aggregated OWF representation was considered in order to examine the dynamics of each grid-forming wind turbine (WT) within a string when providing POD, while achieving reasonable simulation times. Simulation results corroborate that such an OWF can provide POD by means of OWF active power controls similar to those developed for OWFs connected to HVDC via voltage source converters, while its grid-forming WTs share the reactive power consumption/production and keep the offshore voltage frequency and magnitude within their normal operating ranges. Open-loop test results show that such capability can, however, be restricted at operating points corresponding to the lowest and highest values of active power output. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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Open AccessArticle
Control Strategies of Full-Voltage to Half-Voltage Operation for LCC and Hybrid LCC/MMC based UHVDC Systems
Energies 2019, 12(4), 742; https://doi.org/10.3390/en12040742 - 23 Feb 2019
Cited by 2
Abstract
With the increasing demand of transmitting bulk-power over long-distance, the ultra high-voltage direct-current (UHVDC) transmission systems become an attractive option. Nowadays, not only the line commutated converter (LCC) based systems, but also the modular multilevel converter (MMC) based systems have reached UHVDC levels. [...] Read more.
With the increasing demand of transmitting bulk-power over long-distance, the ultra high-voltage direct-current (UHVDC) transmission systems become an attractive option. Nowadays, not only the line commutated converter (LCC) based systems, but also the modular multilevel converter (MMC) based systems have reached UHVDC levels. The converter stations of UHVDC systems normally utilize two series-connected valve-groups to reduce the difficulties of device manufacturing and transportation. This high-voltage and low-voltage valve-group configuration allows the UHVDC systems to achieve a full-voltage to half-voltage operation which increases the flexibility of the systems. However, the existing research only focuses on the full-voltage to half-voltage control of LCC-UHVDC systems. The control strategies for hybrid LCC/MMC UHVDC systems are underresearched. Moreover, the approaches to reduce the load-shedding caused by the full-voltage to half-voltage control for both LCC and hybrid LCC/MMC based UHVDC systems have not been investigated. In this paper, full-voltage to half-voltage control strategies for both LCC and hybrid LCC/MMC based UHVDC systems have been proposed. Moreover, to avoid load-shedding caused by the half-voltage operation, a power rescheduling method that re-sets the power references of the half-voltage operating and full-voltage operating poles has been proposed. The proposed full-voltage to half-voltage control strategies and power rescheduling method can achieve a stable and fast control process with a minimum power loss. The proposed methods have been verified through the time-domain simulations conducted in PSCAD/EMTDC. Full article
(This article belongs to the Special Issue Control and Protection of HVDC-Connected Offshore Wind Power Plants)
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