Model Railways Direct

[Otilia Mojarro]

GlasgowCity Council leaders have today formally approved plans to build a direct rail link between the airport, Paisley and Glasgow city centre after the final plans were unveiled in a November meeting.

Cllr Mark Macmillan, Renfrewshire Council leader and lead for enterprise on the Glasgow City Region cabinet, said yesterday: This project is simply vital to securing the long-term success of the local and regional economies.

Figures released by the ORR last week revealed how vital rail already is to the Scottish economy as Glasgow Central Station was found to be the busiest in the UK outside of the capital London, while Paisley Gilmour St is the fourth busiest in Scotland.

Cllr Frank McAveety, leader of Glasgow City Council and chair of the Glasgow City Region Cabinet, said of the project: A direct rail link to Glasgow Airport has been an ambition for a long time, but it's now going to be a reality.

The tram-train model was chosen after research found that the direct link, expected to reduce the time for all trips to the airport from Glasgow city centre, would most encourage people to use public transport to travel to and from the airport.

Glasgow Airport's head of planning and development, Ross Nimmo, fully supported the plans for the direct rail link, arguing: It has a very strong business case, with conservative estimates suggesting the airport is set to become one of the busiest train stations in Scotland.

Congress is debating the federal government's role in providing intercity passenger rail service.Many believe that Amtrak's future is now at a crossroads. Amtrak's worsening financial situationand its relatively small overall share of the intercity passenger market have led some policymakersto consider other models of passenger rail regulation. The experience of other countries is oftencited in debates about passenger rail regulatory regimes.The foreign experience can provide some perspective and some insight in the debate on U.S.intercity passenger rail. Many countries have dramatically reorganized the regulatory frameworkof their railroads. Market forces and political pressures were the underlying causes of railwayreform. The objectives of rail reform was to reverse declining market shares due to competitionfrom the automobile and airplane, to make the railroads more responsive to customers, and to reducethe railroads' dependence on government subsidies.In order to accomplish these objectives, governments have reorganized their railways alongseveral dimensions. Some national railroads were divided geographically into separate entities byregion. In some cases, national railroads were also divided by business sector, such as freightseparated from passenger services. Vertical integration, where one entity controlled both trainoperations and track infrastructure, versus vertical separation, where train operations and trackinfrastructure were controlled by separate entities, was another choice offered by rail policymakers.Rail policymakers also faced a choice between public versus private ownership. Levels ofprivatization can be distinguished among several foreign railroads. A final important element ofrailway regulation is the role of competition. Theoretically, competition in passenger rail service cantake the form of multiple train operating companies competing on the same track. However, inpractice, competition more readily takes the form of franchises bidding for government contracts toperform rail services and/or competition from other modes, such as automobile, bus, and airplane.The regulatory framework of passenger rail in seven countries is profiled: Argentina, Canada,France, Germany, Japan, Mexico, and the United Kingdom.The level of government support for passenger rail in Japan and European countries far exceedsthe level of government support in the United States. In many cases, at the initial stage ofrestructuring, foreign governments absorbed the large debt that the previous national railroad hadaccumulated. Even the most market-oriented governments have accepted some kind of publicsupport for new (high speed) track construction. Federal governments also provide direct operatingsubsidies to their railroads in most cases. In Japan, a few lines are able to cover their operatingexpenses without government operating subsidies. Although restructuring may provide opportunitiesfor increasing productivity and efficiency, many rail analysts contend that a more critical issue facingCongress is the high level of government spending a viable intercity passenger rail system requires.

The site is secure.

The ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

For complex shaped materials, computational efficiency and accuracy of DEM models are usually opposing requirements. In the literature, DEM models of railway ballast often use very complex and computationally demanding particle shapes in combination with very simple contact laws. In contrast, this study suggests efficient DEM models for railway ballast using simple particle shapes together with a contact law including more physical effects. In previous works of the authors, shape descriptors, calculated in a shape analysis of two types of ballast, were used to construct simple particle shapes (clumps of three spheres). Using such a shape in DEM simulations of compression and direct shear tests, accurate results were achieved only when the contact law included additional physical effects e.g. edge breakage. A parametrisation strategy was developed for this contact law comparing DEM simulations with the measurements. Now, all the constructed simple particle shapes are parametrised allowing to study their suitability and relating their shape descriptors to those of railway ballast. The most suitable particle shapes consist of non-overlapping spheres, thus have a high interlocking potential, and have lowest sphericity and highest convexity values. In a micromechanical analysis of the four best performing shapes, three shapes show similar behaviour on the bulk and the micro-scale, while one shape differs clearly on the micro-scale. This analysis shows, which shapes can be expected to produce similar results in DEM simulations of other tests/load cases. The presented approach is a step towards both efficient and accurate DEM modelling of railway ballast.

This paper applies a control method based on current control and sum-capacitor-voltage estimation to the direct ac/ac modular multilevel converter. As capacitor voltages are estimated, their measurements are not needed in the high-level control, which simplifies the communication between the main controller and the submodules of the converter. The stability of the internal dynamics of the converter, using the aforementioned control method, is studied using Lyapunov stability theory, proving that the system is globally asymptotically stable. The behavior of the converter is simulated focusing on three-phase 50 Hz to single-phase 16 (2)/(3) Hz conversion, which is typical for railway power supply systems of some European countries. Simulation results are in agreement with the expected behavior of the converter, both in steady-state and dynamic situations.

Modular multilevel converters (MMCs) have recently become the state-of-the-art solution for various grid-connected applications, such as high-voltage direct current (HVDC) systems and flexible alternating current transmission systems (FACTS). Modularity, scalability, low power losses, and low harmonic distortion are the outstanding properties that make MMCs a key technology for a sustainable future.

The main objective of this thesis is the modeling of grid-connected MMCs for stability analysis. The stability of the interconnected system, formed by the converter and the ac grid, can be assessed by analyzing the converter ac-side admittance in relation to the grid impedance. Therefore, a method for the calculation of the ac-side admittance of MMCs is developed. This method overcomes the nonlinearities of the converter dynamics and it can be easily adapted to different applications. Moreover, the effects of different control schemes on the MMC ac-side admittance are studied, showing how the converter admittance can be reshaped. This is a useful tool for system design, because it shows how control parameters can be selected to avoid undesired grid-converter interactions.

This thesis also studies ac/ac MMCs for railway power supplies, which are used in countries with a low-frequency railway grid, such as Germany (16.7 Hz) and Sweden (16 2/3 Hz). A hierarchical control scheme for these converters is devised and evaluated, considering the requirements and the operating conditions specific to this application. Furthermore, admittance models of the ac/ac MMC are developed, showing how the suggested hierarchical control scheme affects the three-phase and the single-phase side admittances of the converter. For computing the insertion indices, an open-loop scheme with sum capacitor voltage estimation is applied to the ac/ac MMC. Lyapunov stability theory is used to prove the asymptotic stability of the converter operated with the proposed control method. This specific open-loop scheme is also adapted to a modular multilevel matrix converter, which performs three-to-three phase direct conversion.

Finally, this thesis presents the design of a down-scaled MMC prototype for experimental verification, rated at 10 kW with 30 full-bridge submodules. The hardware and the software are designed to be easily reconfigurable, which makes the converter suitable for different research projects focused on MMCs. Experiments on this down-scaled MMC are used to support and validate the key results presented throughout the thesis.

Modulra multinivomvandlare (MMC) har under senare r utvecklats till den mest relevanta lsningen fr olika tillmpningar dr kraftelektroniska omriktare r anslutna till vxelstrmsnt, ssom system fr hgspnd likstrmsverfring (HVDC) och flexibla system fr verfring av vxelstrm (FACTS). Den modulra uppbyggnaden, skalbarhet, lga frluster och lga vertoner r egenskaperna som gr MMC omriktare till en central komponent fr framtida hllbara elenergisystem.

3a8082e126