Synthesis of different types of energy based controller for a Modular Multilevel Converter integrated in a HVDC link

Modular Multilevel Converters are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the 2 different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Moreover, for a given function, different ways of controlling this converter may be considered. This paper proposes an overview of the different solutions for controlling the MMC and proposes a methodology to synthesize the control architecture

The OURSE model: Simulating the World Refining Sector to 2030

The development of a model of the World Refining for the POLES model ( Contract n°151559-2009 A08 FR – with the Joint Research Centre Institute for Prospective Technological Studies of Commission of the European Communities) aims to represent the oil product's supply at a world-wide level in a global energy model. The World oil refining industry faces to several challenges such as the increasing oil derivatives demand in the transport sector, the improvement of the specifications of these products, the crude oil availability and the limitation of carbon emissions. An aggregated refining model linked to the POLES energy model has been developed to study these questions. The OURSE (Oil is Used in Refineries to Supply Energy) model is a world-wide aggregated refining model which is designed to simulate the world oil product supply for the POLES (Prospective Outlook for the Long-term Energy System) model. OURSE is able to simulate the impact on the world refining industry of changes in the crude oil supply (in costs and qualities) as well as in the oil product demand (in terms of level, structure and specifications). OURSE also enables to assess the consequences of a carbon emission regulation (caps and taxes) as the adoption of various kinds of alternative fuel policies. More precisely, these impacts are evaluated as regards the world refining structure (investments), but also its balance (production and trade of petroleum products), its pollutant emissions (CO2 and SO2) and its costs (of production, investments, etc.). Simulations for 2030 were performed. Thus, the paper presents the results of a prospective exercise for the oil refining industry which has been carried out with the worldwide refining model OURSE according to the oil product demand projections of European Commission for Europe with the PRIMES model (European Commission, 2010) and the IFP projections for the rest of the World.JRC.J.1-Economics of Climate Change, Energy and Transpor

MMC Stored Energy Participation to the DC Bus Voltage Control in an HVDC Link

The modular multilevel converter (MMC) is becoming a promising converter technology for HVDC transmission systems. Contrary to the conventional two- or three-level VSC-HVDC links, no capacitors are connected directly on the dc bus in an MMC-HVDC link. Therefore, in such an HVDC link, the dc bus voltage may be much more volatile than in a conventional VSC-HVDC link. In this paper, a connection between the dc bus voltage level and the stored energy inside the MMC is proposed in order to greatly improve the dynamic behavior in case of transients. EMT simulation results illustrate this interesting property on an HVDC link study case

Clinical, electroretinographic and histomorphometric evaluation of the retina in sheep with natural scrapie

Background: The retina is part of the diencephalon in a peripheral location and may be involved in prion diseases. Retinal function and structural changes were assessed in naturally scrapie-affected red face Manech ewes presenting the classical signs of the disease, and clinically healthy age-matched subjects for controls. Ophthalmic examination was done prior to electroretinography (ERG), which was carried out under conditions that allowed photopic and scotopic activities to be assessed. Histomorphometry of the inner and outer retinal layers was performed post-mortem, and retinas were also examined for evidence of abnormal prion protein (PrPSc) accumulation and glial fibrillary acidic protein (GFAP) upregulation as a marker of gliosis. Scrapie status was determined by examination of brain tissue Results: Ocular reflexes and ophthalmoscopy did not reveal any difference between scrapie affected and control animals. Although the light-and dark-adapted ERG responses of both rod-and cone-mediated functions had a similar waveform in scrapie-affected and control sheep, a significant reduction in the amplitude of the ERG a-and b-waves was observed in affected animals compared to controls. These functional alterations were correlated with a substantial loss of cells in the outer nuclear layer (ONL), lengthening and disorganization in photoreceptor segments, and substantial reduction in cellularity and thickness of the inner nuclear layer (INL). The degenerative changes in the INL and ONL were most marked in the central and paracentral areas of the scrapie retinas, and were accompanied in all scrapie retinas by PrPSc deposition in the ganglion cell and synaptic layers. GFAP immunoreactivity was mainly increased in the ganglion cell and inner plexiform layers. Conclusions: No appreciable fundoscopic changes were observed in the scrapie-affected ewes although reproducible changes in retinal function as measured by ERG were observed in these animals. The alterations in the receptoral and post-receptoral pathways corresponded to the degenerative lesions observed in the ONL and INL of the scrapie retinas. The retinal degeneration was associated with prion protein infectivity which presumably spread via the optic nerve

Control of DC bus voltage with a Modular Multilevel Converter

Modular Multilevel Converters (MMC) are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the two different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Most of the time, the DC-bus voltage is supposed to be constant. In an HVDC link, this corresponds to the substation which controls the power. This paper addresses the cases when the voltage is regulated by the converter and presents the different ways of voltage control

Synthesis of different types of energy based controller for a Modular Multilevel Converter integrated in a HVDC link

Modular Multilevel Converters are becoming increasingly popular with the development of HVDC connection and, in the future, Multi Terminal DC grid. A lot of publications have been published about this topology these last years since it was first proposed. Few of them are addressing explicitly the 2 different roles that are held by this converter in a HVDC link: controlling the power or controlling the DC voltage level. Moreover, for a given function, different ways of controlling this converter may be considered. This paper proposes an overview of the different solutions for controlling the MMC and proposes a methodology to synthesize the control architecture

Overvoltage Limitation Method of an Offshore Wind Farm with DC Series Parallel Collection Grid

This paper describes the characteristics of a series parallel wind farm (SPWF) topology and investigates the control strategy to ensure its safe operation. The SPWF was found to have advantages over other pure dc wind farm architectures in terms of lower construction cost and lower power losses in the collection system. However, unbalance power productions among the wind turbines cause the variations of their output voltages, which may endanger the safe operation of the entire wind farm. This paper proposes a global control strategy that prevents wind turbines from operating above their overvoltage capabilities.With an active participation of the onshore converter, the proposed strategy allows maximum power point tracking (MPPT) of the wind turbines. The practical limitations of this strategy are discussed and improvements are given. The feasibility of the proposed method is validated in a simulation of 300 MW wind farm developed in EMTP-RV

Losses estimation method by simulation for the Modular Multilevel Converter

The modular multilevel converter (MMC) is the most promising solution to connect HVDC grids to a HVAC one. The installation of new equipment in the HVDC transmission systems requires an economic study where the power losses play an important role. Since the MMC it is composed of a high number of semiconductors components, the losses estimation becomes complex. This paper proposes a simulation based method for the losses estimation that combines the MMC averaged and instantaneous model in a modular way. The method brings the possibility to perform comparisons in terms of losses for different modules technologies as well as different high and low level control techniques. Also the losses characteristics within the MMC are also discussed and the passive losses are firstly taken into accoun

Energy and director switches commutation controls for the alternate arm converter

The Alternate Arm Converter (AAC) is promising multilevel Voltage Source Converter (VSC) suitable for High Voltage Direct Current (HVDC) transmission systems. This converter exhibits interesting features such as a DC Fault Ride Through capability thanks to the use of Full-Bridge Sub-Modules (SM) and a smaller footprint than an equivalent Modular Multilevel Converter (MMC). After an analysis of the converter operating modes called Non-overlap and Overlap mode, a sequential representation of the AAC operation is proposed. The main originality of this paper is the use of the Petri Net to describe all the phases and to highlight their sequencing. According to the phases identified thanks to the sequential approach, models and control structures for the grid currents, the internal energy and the Zero Current Switching (ZCS) are detailed. Furthermore, the step-by-step approach proposed in this paper allows a clear and rigorous modelling of this complex converter