1,720,968 research outputs found
Comparative study of variant topologies for MMC
No full textOn the base of the MMC principle, this work considers different topologies of sub module (or elementary converter) which make the High Voltage AC/DC converter more flexible and easy suitable respect to different voltage and current levels. A topological study is consolidated and extended on three different topologies proposed as elementary converter and their employment for the MMC structure is treated. For each cell, topology advantages and limits are discussed in terms of current and voltage. Under SPWM modulation conditions, an analytical approach for the power losses evaluation is proposed for the three topologies used in the MMC structure. A comparison on the efficiency is proposed by fixing the DC voltage and the operating power. By considering the basic topology of the MMC (composed by elementary cells) also an evaluation of the power losses is performed by considering the staircase modulation which is becoming more and more diffused especially for a high number of levels. © 2014 IEEE
LLC resonant converters in PV applications comparison of topologies considering the transformer design
No full textIn this paper the use of an LLC resonant converter used as MPPT-tracker in the photovoltaic field has been studied. Two different utilization schemes has been considered: direct connection of the PV module to the grid and the string connection scheme. Each solution is limited from the efficiency of the power converter, due mainly to the transformer. In this work the impact of the transformer design on size and losses have been considered in both cases and compared each other to obtain indications that permits to choose the best topology. Both transformers are been constructed using an hard interleaved coil scheme and the same ferrite material. Comparing the designs can be observed that the transformer for the direct connection to the grid has the volume and the weight that is tens times greater than the string solution, so the final converter is bigger. In conclusion the weight and the volume can be reduced with the string derived solutio
Comparison of ultrafast chargers for plug in electrical vehicles in terms of grid integration
No full textThe ultrafast DC charging for Plug In Electrical Vehicles, is very attractive solution for end users, thanks to the opportunity to reduce charging time. The drawback of this solution is the grid impact of this system, due to the high peak power, that impose the use of local energy storages. Another opportunity to help the power grid is to provide ancillary services and use the energy stored into Electrical Vehicles. These functions are called Vehicle to Grid (V2G) and are considered the most promising techniques for the future. In this paper different fast dc charging architectures have been studied and compared each other to select the best solution grid integration, efficiency and costs
Comparison of high voltage modular AC/DC converters
No full textIn this paper, AC/DC converters for high voltage and high power applications are compared. Particularly Flying Capacitor Multicell and Modular Multilevel topologies are under consideration. The study is achieved in terms of power losses and total energy stored in the capacitors. A brief description of the topologies is given, and the main sizing criteria such as DC voltage, AC current and capacitor voltage ripple are presented. The Methodology for the analytical calculation of the losses in the devices is described for each topology. By considering a typical high power case study, simulation results are used to validate the analytical calculation. Finally, the calculation of the energy stored in the capacitors completes the comparative study
Chopper Controlled Steinmetz Circuit for Voltage Balancing in Railway Substations
No full textAbstract—this paper presents a new technique in voltage
balancing for single-phase railway substations. Using the concept
of Chopper Controlled Impedance, the authors study the
feasibility of an active Steinmetz circuit based on AC choppers.
The low power losses in semiconductor devices make the
proposed topology an interesting alternative to classical solutions
such as those based on Voltage Source Inverters (VSI). Design
criteria are presented using information obtained from
measurements carried out on a substation of the French National
Railways. Finally, the study is validated by means of simulati
LLC resonant converters in PV applications comparison of topologies considering the transformer design
No full textIn this paper the use of an LLC resonant converter as Maximum Power Point Tracker (MPPT) in a photovoltaic application is presented. Two different implementations are considered: direct connection of the photovoltaic (PV) module to the grid and the string connection circuit. In Each solution the power converter efficiency is mainly limited by the step-up transformer. The impact of the transformer design on size and losses is considered in both cases with the view to choose the best topology. Both transformers are constructed using a hard interleaved coil structure and the same ferrite material. Finally, it is shown that the direct connection to the grid has a volume and a weight that is ten times greater than the string solution. © 2013 IEEE
Reactive power compensation in railways based on AC boost choppers
No full textIn this study, a new topology, using AC choppers is proposed for reactive power compensation in 25 kV/50 Hz railway
networks. The low losses of these converters compared to other solutions such as voltage-sourced inverters-based STATCOMs,
makes this approach attractive for high-power, single-phase systems such as railway networks. A possible solution based on the
controlled impedance concept working in boost mode is proposed and applied to a substation in the French rail network. Design
method presented end simulation results which confirm the performance of this low-cost and low-loss solution. Finally, the
experimental results achieved on a 1.2 MVAR prototype are presented
Chopper-Controlled Steinmetz Circuit Based on Direct Power Control for Electric Railway Substations
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