scholarly journals Novel Control Approach for a Hybrid Grid-Forming HVDC Offshore Transmission System

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1681 ◽  
Author(s):  
Shangen Tian ◽  
David Campos-Gaona ◽  
Vinícius A. Lacerda ◽  
Raymundo E. Torres-Olguin ◽  
Olimpo Anaya-Lara

This article describes a hybrid topology of high-voltage direct current (HVDC) for offshore wind farms using a series connection of a voltage source converter (VSC) and six-pulse diode rectifier (6P-DR). In this topology, the offshore side VSC (OF-VSC) acts as a grid-forming converter to maintain the PCC (point of common coupling) voltage of offshore wind farms (WF) and frequency. In addition, the OF-VSC functions as an active power filter to suppress the 5th, 7th, 11th, and 13th order harmonic current components produced by the 6P-DR, making it almost sinusoidal. Due to the 6P-DR being used in the hybrid converter, this new configuration reduces the total cost of the converters and losses, while preserving the power flow to the onshore gird. Compared to the fully-rated converter and hybrid converter based on a 12-pulse diode rectifier, the power loss and cost are reduced, and in addition, the proposed hybrid converter does not require a phase shift transformer nor a high number of diodes. A 200 MW in an HVDC transmission system using the hybrid configuration was simulated in PSCAD. The results show that the system operated correctly and the harmonic components were filtered.

Author(s):  
M. Mohan ◽  
K. Panduranga Vittal

In recent years, offshore wind energy has increased significantly. The continuous increase in the offshore wind power generation level brings the requirement of the offshore wind farms (OWFs) integration with an AC grid. The multi-terminal (MT) voltage source converters (VSC)-based high voltage direct current (HVDC) transmission system is an emerging technology and also the best option to interconnect the large-scale OWFs to the AC grid. This paper presents the design, modeling, and control of MT VSC-HVDC transmission system linked offshore wind farms. Different cases of MT VSC-HVDC transmission systems are developed, and its simulation studies are carried out using PSCAD/EMTDC. The test results show the transient performance of the MT VSC-HVDC transmission systems under various AC and DC fault conditions. The studies also include the influence of wind variabilities as in the form of gust and ramp pattern during steady state and fault conditions.


Theoretical review of various topologies of high voltage DC links in application to off shore wind forms has been studied and analysed. In addition to that, various types of high voltage DC links such as back to back, two terminal, multi-terminal systems has been covered under this study. The Line-Commutated Converters, Voltage Source Converter, Modular Multi-Level Converter as well as some of advanced hybrid high voltage DC topologies in application to off shore wind forms has been reviewed. This study covers complication arising from large-scale wind power generation. The review paper also points out the scope of future research in high voltage DC converters.


2020 ◽  
Vol 10 (5) ◽  
pp. 1833
Author(s):  
Ali Raza ◽  
Muhammad Younis ◽  
Yuchao Liu ◽  
Ali Altalbe ◽  
Kumars Rouzbehi ◽  
...  

Although various topologies of multi-terminal high voltage direct current (MT-HVdc) transmission systems are available in the literature, most of them are prone to loss of flexibility, reliability, stability, and redundancy in the events of grid contingencies. In this research, two new wind farms and substation ring topology (2WF-SSRT) are designed and proposed to address the aforementioned shortcomings. The objective of this paper is to investigate MT-HVdc grid topologies for integrating large offshore wind farms with an emphasis on power loss in the event of a dc grid fault or mainland alternating current (ac)grid abnormality. Standards and control of voltage source converter (VSC) based MT-HVdc grids are defined and discussed. High voltage dc switch-gear and dc circuit topologies are appraised based on the necessity of dc cables, HVdc circuit breakers, and extra offshore platforms. In this paper, the proposed topology is analyzed and compared with the formers for number and ratings of offshore substations, dc breakers, ultra-fast mechanical actuators, dc circuits, cost, flexibility, utilization, and redundancy of HVdc links. Coordinated operation of various topologies is assessed and compared with respect to the designed control scheme via a developed EMTDC/PSCAD simulation platform considering three fault scenarios: dc fault on transmission link connecting the wind farm to mainland power converters, dc fault within substation ring of VSC-HVdc stations, and ultimate disconnection of grid side VSC station. Results show that 2WF-SSRT is a promising topology for future MT-HVdc grids.


2002 ◽  
Vol 26 (6) ◽  
pp. 383-395 ◽  
Author(s):  
Vassilios G. Agelidis ◽  
Christos Mademlis

The technology associated with offshore wind farms is discussed in detail. First, the various offshore wind turbines are reviewed and the factors influencing their characteristics are outlined in comparison with their onshore counterparts. This overview serves as a basis for the discussion that follows regarding the possible electrical connection within the farm, and between the farm and the grid. Voltage-source converter-based HV DC connection is compared with HVAC connection. Finally, a novel multilevel converter-based HVDC system, based on flying capacitor multilevel converters is proposed, as a possible interface between the farm and the grid.


2020 ◽  
Vol 165 ◽  
pp. 06012
Author(s):  
Jinke Li ◽  
Jingyuan Yin ◽  
Yonggao Guan ◽  
Zhenquan Wang ◽  
Tao Niu ◽  
...  

High-voltage direct current (HVDC) transmission systems are a promising solution for long distances power transmission offshore wind farms. In order to satisfy the reliability requirements of receiving-end grid and system, the topology, operation and control of HVDC transmission systems for offshore wind farms should be paid more attention. Thus, the aim of this manuscript is to offer a comprehensive summary of existing topology, operation and control methods applied to HVDC transmission system for offshore wind farms. Special attention is provided to the ac grid fault through control methods, droop control methods, power sharing rules and specific requirements of HVDC system planning, model, design and investment. The results are important for understanding the operation of VSC-HVDC in offshore wind farms.


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