1,721,041 research outputs found
Wide Voltage Range Dual Active Bridge PV Retrofit Storage System
No full textThis paper presents a storage system integration on the photovoltaic module side of a traditional grid-connected PV plant. The proposed retrofit application is based on a wide voltage range Dual Active Bridge topology, used as bidirectional DC/DC converter. Wide voltage operation capability at PV side is required to allow the integration of the retrofit storage system on a broader range of existing PV plants, characterized by different PV string operating voltage and commercial grid-connected inverters. Dual Active Bridge topology was chosen as a galvanically-insulated bidirectional single stage conversion stage to interface storage batteries to the PV side of the existing photovoltaic plant. The storage battery is charged during the overproduction of the PV plant and the storage system sustains the end-user domestic loads when solar irradiation is insufficient. The proper operation of the commercial inverter, the design and control strategy of the whole system showed the effectiveness of the proposed solution. A full-size 3.2kW converter prototype was manufactured and experimental validation was carried out
A novel five-level single phase grid connected converter for renewable distributed systems
No full textIn low-power grid connected systems (renewable or traditional energy sources) a single phase converter is usually adopted. In order to reduce losses, costs and size the keyword is removing any kind of transformer. This paper deals with a novel five level converter topology that follows this trend. The proposed converter architecture is based on a full bridge topology with two more power switches and two diodes connected to the midpoint of the DC link. Since the two added levels are obtained by the discharge of two capacitors, the balancing of the midpoint voltage is taken into account.
Simulation and experimental results show the effectiveness of the proposed solution
Modular Multi-Three-Phase Electric Drives for Enhanced Reliability and Current Ripple Minimization
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Design and Optimization of a Magnetic Gear for a Conveyor System Application
No full textMagnetic gears have some advantages when compared to the traditional mechanical ones, especially in terms of maintenance and absence of lubrication. Many types of magnetic gears have been presented in the last years, with the aim of pushing the torque density to very high levels.This paper deals with the design and optimization of a magnetic gear (MG) for an industrial conveyor system. The design was carried out considering the geometrical constraints and the gear ratio imposed by the target application, with the aim of reducing the torque ripple and obtaining a balanced radial attraction force on the segmented ring. Two different internal permanent magnet inner rotor geometries were drafted and optimized by means of finite element simulations. The different designs were compared against each other by means of different figures of merit, including torque ripple, radial force on the segmented ring, power losses and mass of the permanent magnets
UNIPOLAR PWM FOR TRANSFORMERLESS GRID-CONNECTED CONVERTERS IN PHOTOVOLTAIC PLANTS
No full textIn domestic grid connected PV applications a single phase converter is usually used. In such a low power plants it is possible to adopt converter topology with no galvanic isolation between the photovoltaic panels and the grid. The absence of a high or low frequency transformer permits to reduce power losses, cost and size of the converter. On the other side in presence of a galvanic connection a large leakage ground current could arise due to parasitic PV panel capacitance. This leakage current causes electric safety problems, an increase of EMI and a reduction of the power quality. This paper presents a converter topology based on unipolar PWM modulation able to minimize the leakage ground current locking the common output voltage to VDC/2 as the converters topology based on bipolar modulation do. Simulation results show the effectiveness of the proposed topology. Eventually a comparison of the power losses of the proposed architecture with respect to some established topologies is presented
Hairpin-Wound Rim-Driven Propeller for Electric Boats on Inland Waterways
No full textElectric mobility on water is in the early stage of development but has a great potential, especially when considering inland waterway vessels. Inland waterway vessels are the best candidate to benefit from a battery electric propulsion system, since they typically operate in environments with restrictions on noise and emissions; they have short ranges and are relatively close to charging infrastructures. Rim-driven propellers actuated by large diameter hollow-shaft electrical machines are a promising technology. Rim-driven propellers present a number of advantages when compared to standard propellers, such as increased efficiency and a compact structure that is particularly suitable for small and lightweight boats. The present work details the design and numerical simulation of the electric machine for rim-driven propeller pod applied to a speedboat to be used on lakes and rivers. The electric machine main distinctive features are a high power density, a thin radial section and a hairpin winding construction
Assessment of a Multi-Functional Converter System for Traction Electric Drives
No full textThe introduction of strict regulations in terms of air pollution is pushing automotive industry and heavy equipments vehicles manufacturers to integrate electric drives into the powertrain. To overcome the limitations on maximum battery voltage, a DC-DC bidirectional boost converter stage between the battery and the inverter is widely adopted by manufacturers. However, these converters are bulky, expensive and impact on the system efficiency. For this reason, Multi-Functional Converter Systems (MFCS) have been introduced in order to avoid the voltage boost stage and take advantage of the electric motor and the inverter to integrate the boost converter within these two components. This paper carries out a comparison between a traditional architecture, with a DC-DC boost converter stage, and a MFCS, to determine the best solution in terms of efficiency, weight and encumbrance
Improved SVM Pattern for Single-Stage CSI With Discharge Path in Electric Drives Applications
No full textA recently proposed single-stage current source inverter (CSI) with discharge path exhibits the ability to control the drive from zero speed without the insertion of an additional pre-stage converter to control the input dc current. The size of the dc input inductor can be reduced to minimize the volume and weight of the power converter. With this choice, the output currents exhibit large distortion for the entire discontinuous conduction mode (DCM). The present work proposes a novel modulation pattern specific for the low-speed region in terms of reduction of the total harmonic distortion (THD). A fair comparison between the proposed pattern and the classical one is obtained, considering the same number of commutations per time unit. Simulations and experimental results confirm the validity and the considerable THD decrease of the proposed space vector modulation (SVM) pattern for the single-stage CSI with discharge path topology. In particular, the advantage is clear under DCM condition where the base pattern exhibits a large THD up to 15%, while the proposed one has an overall lower THD, with a maximum value of 8%
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