Droop setting design for multi-terminal HVDC grids considering voltage deviation impacts

In multi-terminal high voltage direct current (HVDC) grids, the widely deployed droop control strategies will cause a non-uniform voltage deviation on the power flow, which is determined by the network topology and droop settings. This voltage deviation results in an inconsistent power flow pattern when the dispatch references are changed, which could be detrimental to the operation and seamless integration of HVDC grids. In this paper, a novel droop setting design method is proposed to address this problem for a more precise power dispatch. The effects of voltage deviations on the power sharing accuracy and transmission loss are analysed. This paper shows that there is a trade-off between minimizing the voltage deviation, ensuring a proper power delivery and reducing the total transmission loss in the droop setting design. The efficacy of the proposed method is confirmed by simulation studies.

Catalyst Deactivation on a Two-Stroke Engine

With the legislative demands increasing on recreational vehicles and utility engined applications, the two-stroke engine is facing increasing pressure to meet these requirements. One method of achieving the required reduction is via the introduction of a catalytic converter. The catalytic converter not only has to deal with the characteristically higher CO and HC concentration, but also any oil which is added to lubricate the engine. In a conventional two-stroke engine with a total loss lubrication system, the oil is either scavenged straight out the exhaust port or is entrained, involved in combustion and is later exhausted. This oil can have a significant effect on the performance of the catalyst.
To investigate the oiling effect, three catalytic converters were aged using a 400cm₃ DI two-stroke engine. A finite level of oil was added to the inlet air of the engine to lubricate the internal workings. The oil flow rate is independent of the engine speed and load.

Three catalysts were aged for 50 hours, experiencing a constant space velocity and set engine conditions. The engine was fueled on petrol and later on propane to eliminate the effects, if any, of petrol additives on catalyst deactivation. The oiling rate was varied to investigated deactivation from oil contamination. Post-mortem analysis was performed on the three catalysts. This consisted of a controlled light-off test performed on a catalyst rig, during which period, temperatures were measured and recorded towere aged for 50 hours, experiencing a constant space velocity and set engine conditions. The engine was fueled on petrol and later on propane to eliminate the effects, if any, of petrol additives on catalyst deactivation. The oiling rate was varied to investigated deactivation from oil contamination. Post-mortem analysis was performed on the three catalysts. This consisted of a controlled light-off test performed on a catalyst rig, during which period, temperatures were measured and recorded to find out where deactivation of each catalyst was occurring. The recorded results were all analyzed and these showed that from the measured light-off temperatures the aged catalysts behaved similarly. However the pattern in the light-off was significantly different when the engine was fueled by propane as opposed to gasoline.

Temporal Narrowing of Neutrons Produced by High-Intensity Short-Pulse Lasers

The production of neutron beams having short temporal duration is studied using ultraintense laser pulses. Laser-accelerated protons are spectrally filtered using a laser-triggered microlens to produce a short duration neutron pulse via nuclear reactions induced in a converter material (LiF). This produces a similar to 3 ns duration neutron pulse with 10(4) n/MeV/sr/shot at 0.56 m from the laser-irradiated proton source. The large spatial separation between the neutron production and the proton source allows for shielding from the copious and undesirable radiation resulting from the laser-plasma interaction. This neutron pulse compares favorably to the duration of conventional accelerator sources and should scale up with, present and future, higher energy laser facilities to produce brighter and shorter neutron beams for ultrafast probing of dense materials.

An Adaptive Predictive Control Strategy for RMPPT under Partially Shaded Conditions

As one of key technologies in photovoltaic converter control, Maximum Power Point Tracking (MPPT) methods can keep the power conversion efficiency as high as nearly 99% under the uniform solar irradiance condition. However, these methods may fail when shading conditions occur and the power loss can over as much as 70% due to the multiple maxima in curve in shading conditions v.s. single maximum point in uniformly solar irradiance. In this paper, a Real Maximum Power Point Tracking (RMPPT) strategy under Partially Shaded Conditions (PSCs) is introduced to deal with this kind of problems. An optimization problem, based on a predictive model which will change adaptively with environment, is developed to tracking the global maxima and corresponding adaptive control strategy is presented. No additional circuits are required to obtain the environment uncertainties. Finally, simulations show the effectiveness of proposed method.

The Value of Full Scale Prototype Data - Testing Oyster 800 at EMEC, Orkney

This paper demonstrates the unparalleled value of full scale data which has been acquired from ocean trials of Aquamarine Power’s Oyster 800 Wave Energy Converter (WEC) at the European Marine Energy Centre (EMEC), Orkney, Scotland.
High quality prototype and wave data were simultaneously recorded in over 750 distinct sea states (comprising different wave height, wave period and tidal height combinations) and include periods of operation where the hydraulic Power Take-Off (PTO) system was both pressurised (damped operation) and de-pressurised (undamped operation).
A detailed model-prototype correlation procedure is presented where the full scale prototype behaviour is compared to predictions from both experimental and numerical modelling techniques via a high temporal resolution wave-by-wave reconstruction. This unquestionably provides the definitive verification of the capabilities of such research techniques and facilitates a robust and meaningful uncertainty analysis to be performed on their outputs.
The importance of a good data capture methodology, both in terms of handling and accuracy is also presented. The techniques and procedures implemented by Aquamarine Power for real-time data management are discussed, including lessons learned on the instrumentation and infrastructure required to collect high-value data.

Investigating Tools used to Analyse the Impact of a Wave Farm on the surrounding Wave Field

For wave energy to become commercially viable, it is predicted that wave energy converters (WECs) will need to be installed in large wave farms. This will required an extensive environmental impact study. Assessments of impacts of these sites requires prior numerical modelling however the available tools have not been fully validated.
This project investigates the area surrounding an array of five scaled WEC models using experimental techniques. It then assesses the suitability of numerical tools to be validated with this experimental data. Validated numerical tools could then be used to predict parameters relating to the models such as reflection and transmission coefficients.
The physical aspect of this project was conducted in the Portaferry wave basin owned by Queen’s University Belfast. The device studied was a bottom hinged oscillating wave surge converter (OWSC) which penetrates the surface (similar to the Oyster device). The models were tested at 40th scale.