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Terahertz (THz) imaging and tomography are modern imaging techniques permitting 2D and 3D inspection of objects over a broadband frequency range. The enormous quantity of information is then obtained. To be analyzed efficiently, an automated 3D data and image processing tool is needed. We present a complete data and image processing sequence to perform non-destructive inspection obtained from time...
There is increasing interest in interconnecting individual wind turbines in offshore wind farms using DC networks rather than AC networks. As the output from each turbine/generator is normally low (less than 6 kV), DC-DC converters may be required to step-up the voltage to an intermediate level to interconnect the turbine outputs, and another DC-DC converter to step-up this intermediate voltage to...
In this paper, a combinational AC/DC power flow approach is proposed for the solution of the combined AC/DC network. The unified power flow approach is extended to include DC voltage droop control. In the VSC based MTDC grids, DC droop control is regarded as more advantageous in terms of operational flexibility, as more than one VSC station controls the DC link voltage of the MTDC system. This model...
Offshore wind power is attracting increasing levels of research and investment. The use of HVDC transmission and development of DC grids are topics with similar levels of interest that go hand in hand with the development of large scale, far from shore wind farms. In this paper, technical challenges resulting from the interaction between power electronic DC-DC converters and the cables in a DC transmission...
This paper compares six DC/DC converter topologies for offshore wind HVDC applications. The topologies include five conventional transformer based topologies and one novel transformerless topology. Detailed models of the DC/DC converters are simulated using PLECS, and the component stress, component count and losses are presented. The overall performance of each topology is evaluated based on the...
This paper proposes control strategies for arrays of direct drive wave energy converters. Two control strategies taken from the theoretical study of the hydrodynamic properties of oscillating bodies are applied to a wave energy converter (WEC) system including a linear generator (LG) and voltage source converter system. The purpose of this study is to investigate the feasibility of the control strategies...
Marine energy devices such as wave energy converters and tidal current turbines are set to play a significant role in contributing to electricity generating by renewable means. The offshore location where these devices operate demands high reliability and robust fault tolerance. Bearing failure is a key issue for renewable energy devices and is a cause of significant downtime in wind turbines. Bearing...
This paper describes causal sub-optimal control of a direct drive linear generator to extract the maximum power from real sea conditions without wave prediction. The reaction force required to control the buoy to move in phase with the ocean waves is provided by the linear generator. After determining the power take-off force based on the model of a machine, the required currents from the generator...
Terahertz pulsed imaging is able to show differences between normal and diseased regions in biological tissues. Fluctuations in the generation and detection of the terahertz source as well as the optical alignment in the imaging system are key factors affecting the imaging results. In this paper, we assess the variation in our imaging system and propose a new data processing approach to improve the...
Burn wounds are common in daily life. Existing medical imaging modalities are limited in detecting the depth and extent of the wound. Terahertz images of burns have shown contrast between burn-damaged tissue and healthy tissue. In this study we use terahertz pulsed imaging to measure the thickness of the stratum corneum on the palm of the hand beneath a plaster and discuss the feasibility of using...
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