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Paralleling of power semiconductor devices is inevitable considering their widespread application and exploitation in the extended horizon of these applications. However, paralleling of power semiconductor devices is prone to severe unbalancing corresponding to the non-idealities of device parameters, which leads to non-identical dynamic and static characteristics of the power devices, as well as the operating conditions and aging. Therefore, the currents are generally non-uniform and cause the derating of the system. This paper discusses and analyzes issues associated with the paralleling of IGBT power devices, which can evoke serious reliability issues. Furthermore, the paper examines the techniques and methodologies that have been proposed to reduce the issue of current unbalancing of parallel-connected power devices. [ABSTRACT FROM AUTHOR]

The causes of many bridge failures have been reported to be local scour around abutments. This study examines roughening elements as devices with which to intercept the downflow responsible for the formation of the principal vortex, which is what triggers local scour around abutments. Two vertical wall abutments with different widths were examined under four different hydraulic conditions in a clear-water regime. Elements with different thicknesses (t) and protrusions (P) with the same dimensions, (P = t = 0.05 L, 0.1 L, 0.2 L, and 0.3 L, where L is the length of the abutment) and with varying depths of installation (Z) were considered. Elements were installed in two positions: between the sediment surface and water elevation and buried within the sediment. To determine the optimum depth of installation, one element was first installed on the sediment surface, and the number of elements was increased in each subsequent test. The results show that installing elements between water surface elevation and the sediment's initial level did not show any defined trend on scour depth reduction. However, the optimum installation depth of the elements is 0.6–0.8 L below the initial bed level. Moreover, the roughening elements with thickness and protrusion of P = t = 0.2 L resulted in the most effective protection of the foundation. The best arrangement, (P = t = 0.2 L and Z = >0.6–0.8 L) reduced the maximum scour depth by up to 30.4% and 32.8% for the abutment with smaller and larger widths, respectively. [ABSTRACT FROM AUTHOR]

This article presents a new cascaded control strategy to control the power flow in a renewable-energy-based microgrid operating in grid-connected mode. The microgrid model is composed of an AC utility grid interfaced with a multi-functional grid interactive converter (MF-GIC) acting as a grid-forming converter, a photovoltaic (PV) power-generation system acting as grid-feeding distributed generation unit, and various sensitive/non-sensitive customer loads. The proposed control strategy consists of a fractional order PI (FO-PI) controller to smoothly regulate the power flow between the utility grid, distributed generation unit, and the customers. The proposed controller exploits the advantages of FO (Fractional Order) calculus in improving the steady-state and dynamic performance of the renewable-energy-based microgrid under various operating conditions and during system uncertainties. To tune the control parameters of the proposed controller, a recently developed evaporation-rate-based water-cycle algorithm (ERWCA) is utilized. The performance of the proposed control strategy is tested under various operating conditions to show its efficacy over the conventional controller. The result shows that the proposed controller is effective and robust in maintaining all the system parameters within limits under all operating conditions, including system uncertainties. [ABSTRACT FROM AUTHOR]

Power electronic converters are used for an efficient and controlled conversion of power generated from renewable energy sources and can interface generated power to the grid. Among available power converters, voltage source inverters (VSIs) have been widely employed for grid-connected applications due to better controllability with higher efficiency. Although various conventional, as well as modern control techniques, have been developed for grid connected VSI system, there is a need to select suitable control technique based on application and control requirements. Hardware-in-the-loop (HIL) is considered as a realistic approach for the development of system and control due to the inclusion of an actual hardware system. In this paper, a HIL approach is adopted for the comprehensive analysis and development of a grid connected VSI system using a field programmable gate array (FPGA). The control techniques must deal with trade-off, based on the features and limitations. Therefore, a grid-connected VSI system is developed considering employment of two different conventional control techniques: hysteresis current control (HCC) and PI-based space vector modulation (PI-SVM), as well as finite state model predictive control (FS-MPC) as a modern control technique for investigation considering different parameters. All three control systems are developed through a digital simulator of Xilinx that is integrated with MATLAB-Simulink, while considering an FPGA based system development and testing through FPGA HIL co-simulation methodology. [ABSTRACT FROM AUTHOR]

Time of concentration (TC) is a parameter in runoff estimation, used to study and design different types of projects in watersheds. Any error in TC calculation leads to an inaccurate estimation of the design flow, which can lead to over-sizing or under-sizing of designed facilities that can have great economic and environmental consequences. Therefore, choosing the correct method to estimate TC is of great importance. Due to the diversity of estimation methods in the literature, the obtained TC values are different. This study aims to present a new method to calculate TC, based on its main concept, i.e., the time required for a water parcel to reach its outlet from the farthest hydrological point of a watershed. A two-dimensional hydraulic simulation was used to model the water parcel travel. A watershed was selected as a case study, and its time of concentration was determined by salt solution tracing. The field measurement results were used for calibration of the numerical simulation model. Meanwhile, 31 empirical relations in the literature were reviewed to determine the most accurate ones. Estimated TC values were compared with the measured ones, and the relative error percentage was used to evaluate the accuracy of the result. In the empirical TC methods, the maximum error was above 300%, and the minimum error was 6.7% for the field studied area. The relative errors of hydraulic simulation outputs were between 3 and 27%. The results showed that only three empirical methods, namely Simas and Hawkins, SCSlag, and Yen and Chow, had the least errors respectively equal to 6.7%, 8.660%, and 13.5%, which can be recommended for the studied area and those with similar hydrological characteristics. On the other hand, hydraulic simulation is also introduced as an efficient method to determine TC which can be used in any desired watershed. [ABSTRACT FROM AUTHOR]

A systematic and simple approach to develop a 20 W audio frequency range switch mode amplifier is presented in this paper. A non-linear sliding mode (SM) technique-based low cost analog controller enables the realized amplifier to deliver highly linear and efficient operation throughout the audio frequency spectrum. The theoretical aspects and practical limitations in the design and realization of subsystems, such as the signal conditioning stage, power stage and sliding mode controller, are considered, while the viable solution is also stated and justified. The hardware realization scheme is also elaborated, based on which the laboratory prototype is fabricated. Hardware results with a 4 Ω resistive load are given on which the performance of the amplifier is evaluated. The total harmonic distortion (THD) below 1% and 73% efficiency at peak load make the amplifier well suited for high quality audio application. [ABSTRACT FROM AUTHOR]

In this paper, an advanced electrothermal simulation strategy is applied to a 3.3 kV silicon carbide MOSFET power module. The approach is based on a full circuital representation of the module, where use is made of the thermal equivalent of the Ohm's law. The individual transistors are described with subcircuits, while the dynamic power-temperature feedback is accounted for through an equivalent thermal network enriched with controlled sources enabling nonlinear thermal effects. A synchronous step-up DC-DC converter and a single-phase inverter, both incorporating the aforementioned power module, are simulated. Good accuracy was ensured by considering electromagnetic effects due to parasitics, which were experimentally extracted in a preliminary stage. Low CPU times are needed, and no convergence issues are encountered in spite of the high switching frequencies. The impact of some key parameters is effortlessly quantified. The analysis witnesses the efficiency and versatility of the approach, and suggests its adoption for design, analysis, and synthesis of high-frequency power converters in wide-band-gap semiconductor technology. [ABSTRACT FROM AUTHOR]

The enzyme mimetic activity of nanomaterials has been applied in colorimetric assays and point-of-care diagnostics. Several nanomaterials have been exploited for their peroxidase mimetic activity toward 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide. However, an efficient nanomaterial for the rapid and strong oxidation of TMB remains a strategic challenge. Therefore, in this study, we developed copper-loaded tin oxide (SnO2-Cu) nanocomposites that rapidly oxidize TMB. These nanocomposites have strong absorption at 650 nm and can be used for highly sensitive colorimetric detection. An environmentally friendly (green), rapid, easy, and cost-effective method was developed for the synthesis of these nanocomposites, which were characterized using ultraviolet-visible, energy-dispersive X-ray, and Fourier-transform infrared spectroscopy, as well as scanning electron microscopy. This is the first green synthesis of SnO2-Cu nanocomposites. Their enzyme mimetic activity, which was first studied here, was found to be strongly dependent on the temperature and pH value of the solution. The synthesized nanocomposites have the advantages of low cost, high stability, and ease of preparation for enzyme mimetic applications. Hence, SnO2-Cu nanocomposites are a promising alternative to peroxidase enzymes in colorimetric point-of-care diagnostics. [ABSTRACT FROM AUTHOR]

In this paper, finite-set model-predictive control (FS-MPC) is inducted for a motor drive system. The dynamic response and multiple constraint handling nature of FS-MPC are the major factors that stand out among the controller family. However, for real-time implementation, the computational burden of FS-MPC is a primary concern. Due to the parallel processing nature and discrete nature of the hardware platform, the field-programmable gate array (FPGA) can be an alternative solution for the real-time implementation of the controller algorithm. The FPGA is capable of handling the computational requirements for FS-MPC implementation; however, the system development involves multiple steps that lead to a time-consuming debugging process. Moreover, specific hardware coding skill makes it more complex, corresponding to an increase in system complexity, which leads to a tedious task for the system development. This paper presents a FPGA-based implementation of the predictive current control of a permanent magnet synchronous motor (PMSM). FS-MPC of the PMSM drive system is designed and implemented using the digital model integration approach provided by the Xilinx system generator (XSG) and VIVADO platform. The step change in the load disturbance as well as the reference speed is considered for the analysis of the controller for the motor drive system. Moreover, the steady state error and harmonic distortion in the motor current is considered for an in-depth analysis of the system performance corresponding to different sampling frequencies. [ABSTRACT FROM AUTHOR]

The proportional-integral (PI)-based control for the motor drive system is commonly used in industrial applications. However, motor drive system development and prototyping are tedious tasks especially considering a field programmable gate array (FPGA)-based real-time system implementation. In addition, the time-synchronization of the feedback control loop is another vital aspect concerning sampling time for the discrete-time controller. This paper presents an FPGA-based design and development of a permanent magnet synchronous motor (PMSM) drive system considering the impact of time-synchronization corresponding to the sampling time criteria for a feedback control loop. Furthermore, the repercussion of time-synchronization is examined for the transient conditions due to a step change in load as well as motor speed. The field-oriented control (FOC) of the PMSM drive system is designed and implemented for the system authentication using a digital model integration approach provided by the Xilinx system generator (XSG) and VIVADO platform. Moreover, harmonic distortion in the motor current is considered for an in-depth analysis of the system performance corresponding to sampling time as well as switching frequencies. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide is a low-reactivity reactive oxygen species (ROS); however, it can easily penetrate cell membranes and produce highly reactive hydroxyl radical species through Fenton's reaction. Its presence in abnormal amounts can lead to serious diseases in humans. Although the development of a simple, ultrasensitive, and selective method for H2O2 detection is crucial, this remains a strategic challenge. The peroxidase mimetic activity of palladium nanoclusters (PdNCs) has not previously been evaluated. In this study, we developed an ultrasensitive and selective colorimetric detection method for H2O2 using PdNCs. An unprecedented eco-friendly, cost-effective, and facile biological method was developed for the synthesis of PdNCs. This is the first report of the biosynthesis of PdNCs. The synthesized nanoclusters had a significantly narrow size distribution profile and high stability. The nanoclusters were demonstrated to possess a peroxidase mimetic activity that could oxidize peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB). Various interfering substances in serum (100 μM phenylalanine, cysteine, tryptophan, arginine, glucose, urea, Na+, Fe2+, PO43−, Mn+2, Ca2+, Mg2+, Zn2+, NH4+, and K+) were included to evaluate the selectivity of the assay, and oxidation of TMB occurred only in the presence of H2O2. Therefore, PdNCs show an efficient nanozyme for the peroxidase mimetic activity. The assay produced a sufficient signal at the ultralow concentration of 0.0625 µM H2O2. This colorimetric assay provides a real-time, rapid, and easy-to-use platform for the detection of H2O2 for clinical purposes. [ABSTRACT FROM AUTHOR]

Recent developments in the area of nanotechnology have focused on the development of nanomaterials with catalytic activities. The enzyme mimics, nanozymes, work efficiently in extreme pH and temperature conditions, and exhibit resistance to protease digestion, in contrast to enzymes. We developed an environment-friendly, cost-effective, and facile biological method for the synthesis of ZnO-Pd nanosheets. This is the first biosynthesis of ZnO-Pd nanosheets. The synthesized nanosheets were characterized by UV–visible spectroscopy, X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray. The d-spacing (inter-atomic spacing) of the palladium nanoparticles in the ZnO sheets was found to be 0.22 nm, which corresponds to the (111) plane. The XRD pattern revealed that the 2θ values of 21.8°, 33.3°, 47.7°, and 56.2° corresponded with the crystal planes of (100), (002), (112), and (201), respectively. The nanosheets were validated to possess peroxidase mimetic activity, which oxidized the 3,3′,5,5′-tetramethylbenzidine (TMB) substrate in the presence of H2O2. After 20 min of incubation time, the colorless TMB substrate oxidized into a dark-blue-colored one and a strong peak was observed at 650 nm. The initial velocities of Pd-ZnO-catalyzed TMB oxidation by H2O2 were analyzed by Michaelis–Menten and Lineweaver–Burk plots, resulting in 64 × 10−6 M, 8.72 × 10−9 Msec−1, and 8.72 × 10−4 sec−1 of KM, Vmax, and kcat, respectively. [ABSTRACT FROM AUTHOR]

Finite set-model predictive control (FS-MPC) is used for power converters and drives having unique advantages as compared to the conventional control strategies. However, the computational burden of the FS-MPC is a primary concern for real-time implementation. Field programmable gate array (FPGA) is an alternative and exciting solution for real-time implementation because of the parallel processing capability, as well as, discrete nature of the hardware platform. Nevertheless, FPGA is capable of handling the computational requirements for the FS-MPC implementation, however, the system development involves multiple steps that lead to the time-consuming debugging process. Moreover, specific hardware coding skill makes it more complex corresponding to an increase in system complexity that leads to a tedious task for system development. This paper presents an FPGA-based experimental implementation of FS-MPC using the system modeling approach. Furthermore, a comparative analysis of FS-MPC in stationary αβ and rotating dq frame is considered for simulation as well as experimental result. The FS-MPC for a three-phase voltage source inverter (VSI) system is developed in a realistic digital simulator integrated with MATLAB-Simulink. The simulated controller model is further used for experimental system implementation and validation using Xilinx FPGA: Zedboard Zynq Evaluation and Development Kit. The digital simulator termed as Xilinx system generator (XSG) provided by Xilinx is used for modeling-based FPGA design. [ABSTRACT FROM AUTHOR]

The conversion and control for the utilization of power generated from energy sources can be performed using a power electronic converter system. The voltage source inverter (VSI) is one of the commonly used converter topologies, being controlled by a switching control algorithm for power conversion. Finite set-model predictive control (FS-MPC) is a modern switching control algorithm and has received significant attention due to its predictive nature. In this paper, the implementation of FS-MPC is presented for the load-side current control of a three-phase VSI system using an integrated platform of MATLAB/Simulink and Xilinx system generator (XSG). The XSG provides the functionality of digital design and intuitive implementation of field-programmable gate array (FPGA) controlled systems. The additional functionality of hardware-in-the-loop (HIL) co-simulation using FPGA is used for the testing and validation of controller performance. The controller performance is validated through three platforms: MATLAB/Simulink, XSG and HIL co-simulation using ZedBoard Zynq evaluation and development FPGA kit. [ABSTRACT FROM AUTHOR]