Modelling and control of multi-terminal HVDC networks for offshore wind power generation

Zhou, Shu 2011. Modelling and control of multi-terminal HVDC networks for offshore wind power generation. MPhil Thesis, Cardiff University. Item availability restricted.

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Abstract

Due to the recent developments in semiconductors and control equipment, Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) becomes a promising technology for grid connection of large offshore wind farms. The VSC-HVDC provides a number of potential advantages over the conventional HVDC, such as rapid and independent control of reactive and active power, black-start capability and no restriction on multiple infeeds. Therefore, VSC-HVDC will likely to be widely used in the future transmission networks and for offshore wind power connections. Multi-terminal VSC-HVDC (VSC-MTDC) system, which consists of more than two voltage source converter stations connecting together through a DC link, is able to increase the flexibility and reliability of transmission systems. It allows connection of multiple offshore wind farms to the AC grid. In this thesis, a three-terminal MTDC system was investigated using simulations and experiments. MTDC system with its control was implemented in PSCAD/EMTDC. The control strategy developed through simulation was verified using experiments. The results of PSCAD/EMTDC simulation and laboratory demonstration were then compared. Additionally, a scenario of four-terminal MTDC transmission system for Modelling and Control of Multi-Terminal HVDC Networks for Offshore Wind Power Generation IV offshore wind power generation was investigated. A control system was designed considering the operating characteristics of VSCs and wind farms. An open loop control method was used for the wind farm side VSCs to establish a constant AC voltage and frequency. Droop control was used for the grid side VSCs to generate DC voltage reference by measuring the DC current. When the system was under fault operation condition, the output power of wind farm was reduced by reducing the DC voltage reference. Simulation results show that good coordination was achieved among VSCs for voltage control and power sharing. The system is able to recover to the normal operation status automatically when subjected to AC balanced fault (three phase fault) and unbalanced fault (single phase fault) on the grid. Keywords: control system, modelling, MTDC, Multi-terminal, offshore, VSC-HVDC, wind power generation

Item Type:	Thesis (MPhil)
Status:	Unpublished
Schools:	Engineering
Subjects:	T Technology > TJ Mechanical engineering and machinery
Uncontrolled Keywords:	Control system; Modelling; MTDC; Multi-terminal; Offshore; VSC-HVDC; Wind power generation
Date of First Compliant Deposit:	30 March 2016
Last Modified:	19 Mar 2016 22:32
URI:	https://orca.cardiff.ac.uk/id/eprint/19615

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