1,720,999 research outputs found
Performance evaluation of a hybrid-excited flux-switching PM motor for traction applications
No full textThe need for high energy density and high efficiency electrical machines and drives for road traction applications is growing rapidly, due to their environmental benefits compared to traditional internal combustion propulsion systems. The demanding specifications defined by the US Drive 2020 program make the design of high-performance traction motors a challenging task. In particular, providing high torque and achieving a wide constant power speed range often represent a compromise in the design phase. Hybrid-excited flux-switching permanent magnet machines have been proposed as good candidates for road traction applications due to their desirable characteristics of design flexibility and control simplicity. This paper aims to investigate the design and performance of hybrid-excited flux-switching permanent magnet machines with particular interest in flux-regulation capability
DSCC Converter as Energy Router for Rural Energy Communities: a Case Study Under Vertical Imbalance
No full textThe sustainable electrification of rural communities relies on the effective utilization and integration of renewable energy sources, which are generally connected to the grid using multiple independent converters. In contrast, the adoption of a single centralized multiport converter acting as energy router can help to reduce operation costs, to increase power density, and to simplify energy management and maintenance, offering a more efficient solution compared to multiple converters. This paper investigates the use of modular multilevel converters acting as a multiport energy router to connect various energy sources to the grid. In this scenario, a vertical imbalance in the arm voltages of the converter, due to the different operation patterns of the connected sources, can harm the stability of the converter. The system's internal dynamics can be leveraged as a control mechanism to ensure system functionality and to prevent unequal stress on semiconductor devices within the individual cells. A case study involving vertical imbalance is analyzed in this paper to assess the converter's potential to improve the reliability and efficiency of renewable energy integration in rural electrification projects
Improving Rural Microgrid Performance with SiC MOSFET-Based Three-Phase Inverters
No full textMicrogrids represent a fundamental solution for the electrification of rural communities, providing clean energy through renewable resources. This article explores the importance of integrating SiC MOSFET based three-phase inverters. These new generation transistors are known for their good electrical and thermal characteristics, guaranteeing significant advantages in terms of energy efficiency, thermal management, and operational reliability, making them ideal for high-power and high-frequency applications. The research focuses on the design, analysis, and future modeling of a three-phase inverter, whose results demonstrate an improvement in its performance with a significant reduction in losses compared to those that would occur with the use of a traditional silicon transistor. Furthermore, a suggestion is made on the possible construction of a thermal model, which would allow the simulation of the inverter for the optimization of the entire microgrid. The results highlight how the use of SiC MOSFETs can improve the performance of microgrids, supporting the electrification of rural areas with sustainable energy solutions
A Single-Cell-Based Injection Method for Circulating Current Control in MMC
No full textModular multilevel converters are becoming more and more attractive for many high-voltage high-power applications. However, due to their topology and operation they present technical challenges in the implementation of the control system, such as balancing of the submodule capacitor voltages and suppressing the circulating currents. The circulating current introduces additional power losses, increases the current stress on power devices and reduces their lifetime. The aim of this paper is to propose an innovative control technique for the elimination of the circulating current by injecting a low-frequency alternating signal into a single submodule of each converter arm, to also achieve a reduction of the voltage ripple across capacitor, beneficial to extend their lifetime. Experimental results performed on a seven-levels converter are presented to validate the proposed technique and assess its performance in comparison with state-of-the-art approaches
An Innovative Single-Cell-Based Injection Method to Improve Efficiency and Reliability of MMC with Low Implementation Burden
No full textModular multilevel converters are increasingly gaining popularity in various high-voltage and high-power applications. However, their operation poses some technical challenges in implementing the control system, including issues, such as balancing submodule capacitor voltages and mitigating circulating currents. The presence of circulating currents leads to additional power losses, increases thermal stress on the power devices, and shortens their lifetime. This article introduces an innovative control technique to eliminate circulating currents by injecting a low-frequency alternating signal into a single submodule of each converter arm. The proposed method not only addresses circulating current mitigation but is also able to reduce capacitor voltage ripple and peak arm current, thereby enhancing the overall converter's lifespan and efficiency. Results of experimental tests on a seven-level converter are presented to prove the effectiveness of the proposed technique and compare its performance with existing state-of-the-art approaches
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Performance assessment of ferrite- and neodymium-assisted synchronous reluctance machines
No full textGrowing attention towards environmental sustainability of energy conversion and stricter efficiency standards are encouraging the market penetration of high-efficiency electrical motors. Current regulations define international efficiency classes and the testing procedures for direct-on-line machines only, commonly induction motors. Synchronous reluctance machines are a valid alternative to the widely employed induction motors for variable-speed applications, due to their low manufacturing cost and higher efficiency. With proper design, torque ripple can be mitigated as much as to make rotor skewing unnecessary for most of applications. The low power factor downside can be fixed by inserting low-cost ferrite magnet into the rotor barriers, with benefits also on the torque capability and constant power speed range. The aim of this pajer is to assess the performance and efficiency potential of one synchronous reluctance and two permanent magnet-assisted synchronous reluctance machine prototypes, obtained by replacing the rotor of a general-purpose induction motor with the said synchronous reluctance ones. The rotor barriers have been designed by means of a genetic optimization algorithm has and then adapted to insert commercially available magnets, compliant with minimum extra-cost requirements. The two prototypes were comprehensively characterized, to validate the design phase and to investigate the performance of the machines. The provided experimental results are critically examined and commented
Operation Analysis and Comparison of T-type NPC Si IGBT and SiC MOSFET Inverter-Based Highspeed Drives
No full textWideband-gap (WBG) power devices such as silicon carbide (SiC) switches have become increasingly popular, due to their ability to increase efficiency and reduce size of power electronic converters. They can viably supply high-speed electrical drives, with profitable application in aeronautical or electric vehicles. High frequency operation of the SiC devices, emphasizes the effect of parasitics, which generates reflected wave transient overvoltage on motor terminals, significant in the case of long-shielded cable which connects the inverter and the induction motor. In this paper SiC MOSFET-based inverter is systematically studied and compared to the performance of Si-based inverter for low-voltage induction motor loads, in terms of efficiency and switching performance. In particular, Si-based inverter configuration is the T-type Neutral Point Clamped (T-NPC) 3-level (3L) inverter, and SiC-based inverter is standard 2-level (2L) configuration, which can eventually replace the 3L topologies. The fair comparison of the two inverters has been introduced and switching performance, overvoltages, and power losses have been analyzed. Simulations are carried out by realistic models of power switch modules
Automated HF modelling of induction machines considering the effects of aging
No full textThe use of wide bandgap semiconductor devices, such as SiC and GaN MOSFETs, in high-frequency converters introduces new challenges for the design of electric drives. The very fast switching transient of which these devices are capable, in fact, can become a serious threat for the reliability of the entire system. Electromagnetic interferences due to the high dv/dt and di/dt, voltage reflections along the cable that cause overvoltage and ringing at the motor terminals, and large common-mode voltages that produce current circulation in the motor bearings are recognized as the major phenomena leading to premature failure of the drive. It is therefore important for designers to approach the problem from a system point of view, having the possibility to accurately model the system in the high-frequency domain to take appropriate measures to increase reliability. In this paper, an automated fitting procedure is proposed to identify the high-frequency model of an induction machine, which is based on using a genetic optimization algorithm to find the best rational approximation for the motor characteristics. A series of accelerated electrical aging tests have also been performed on the motors. The results are used iteratively in the proposed fitting procedure to obtain a time-varying model taking into account the aging progression. © 2019 IEEE
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