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Due to the successive switching actions in a power electronic system, considerable conducted electromagnetic interference (EMI) is generated. This has been a major concern in designing power converters, which requires additional EMI filtering efforts. Passive EMI filters are the most common solutions to EMI reduction but usually consume a large portion of the volume as well as weight in power converters. Active EMI filters (AEFs) or hybrid EMI filters (HEFs) are considered best candidates over traditional passive EMI filters to achieve higher power density in power converters. The utilization of current transformer to sense or to compensate the EMI noise can increase the volume of an AEF. In this article, a transformer-less AEF, sprung from the concept of virtual impedance enhancement, is proposed. The proposed design features feedforward control with current-sensing-voltage-compensating. The operation principle of the proposed AEF is thoroughly introduced, and its performance is evaluated through simulations and experiments. Experimental results with an ac–dc power converter and a dc–ac inverter show that the proposed AEF can be generally applied to reduce conducted EMI on either ac or dc power lines. [ABSTRACT FROM AUTHOR]

Fusarium infections in solid-organ transplant recipients are rare and carry high mortality. We report a case of a kidney transplant recipient who developed infection with Fusarium species. The patient received treatment with oral voriconazole for five months with good response. [ABSTRACT FROM AUTHOR]

Objective To compare two influenza polymerase chain reaction (PCR) methods. Methods A total of 749 suspected MERS-CoV patients presenting at Johns Hopkins Aramco Healthcare, Saudi Arabia, each submitted a clinical sample for influenza A reflex testing using the on-site Cepheid® Xpert Flu assay and at the Ministry of Health laboratory by the Roche PCR assay. Results There was 92.12% overall agreement between the two methods. Specificity of the Cepheid® Xpert Flu was 95.8% for H1N1 and 94.4% for total influenza A. Cepheid® Xpert Flu sensitivity for influenza A was 100% for younger patients (0–19-year age group) but significantly lower both for older patients (68.2% for 60–79-year and 50% for ≥80-year age groups) and overall for males compared to females (72.6% and 94.0%, respectively). Conclusions Specificity of the Cepheid® Xpert Flu test was high; however, sensitivity for total influenza A was lower particularly in males and older patients. [ABSTRACT FROM AUTHOR]

An analytical three-phase induction machine model is proposed, derived, and validated in this paper. This model is capable for arbitrary qd0-frame analysis and core loss estimation at both line-fed and inverter-fed situations. Detailed model-based machine copper and core loss estimations are presented. A simulation verification of the model consistency is given under a changing load profile in MATLAB/Simulink. Then, the model is verified comprehensively using three induction machines (1.5 HP, 3 HP, and 10 HP), where the model is proved to be scalable, and to provide excellent machine loss estimation in line-fed situation and inverter-fed situation with machine input line filters, as well as in the flux-weakening region. Finally, a series of sensitivity tests of the model parameters are performed and the effects of the parameters on the machine losses are discussed. It is believed that the proposed model will be beneficial for various qd0-frame model-based research works of three-phase induction machines. [ABSTRACT FROM AUTHOR]

This paper presents generalized logic-based methods for intelligent fault diagnosis in power electronic converters based on correlation between faults and basic measurements. Fault recovery is then applied based on this correlation by using necessary signals and quantities from existing measurements. The main purpose of the proposed fault diagnosis methods is for power electronic systems to survive from fault conditions that could occur in various components, to cope with the notion of a smart grid and extend their lifetime. The proposed methods are online, i.e., real-time or near-real-time, and can be applied to any power electronic system. Existing intelligent control of power electronic systems along with various short- and open-circuit faults in major power electronic components are reviewed. Two methods are established to diagnose faults and engage redundancy for fault recovery with one method using combinational logic and another using fuzzy logic. In both methods, two quantities are observed for each of the measured signals: 1) the signal's average value and 2) the signal's RMS value. Total harmonic distortion is also used in some simulations but is not required in experimental implementation. A systematic methodology to reduce the number of measured quantities while maintaining effective diagnosis is introduced. A solar PV microinverter in standalone mode is used as an example testing platform for the proposed methods. A simulation model is experimentally validated and the effect of each fault on different voltage and current measurements are observed, then both methods are tested in simulation and hardware. Results show the ability of both methods to diagnose several faults in the inverter's power stage along with their ability to engage redundancy for fault recovery. [ABSTRACT FROM AUTHOR]

This paper presents a combinational-logic-based approach for identifying faults that could occur in the drivetrain of an electric vehicle (EV). A real-time simulation model of an EV is used to study the behavior of available sensor signals and control commands, with specific measured quantities, during vehicle operation. Those quantities could be, but are not limited to, mean values of the phase currents, DC bus current, traction motor speed (if available), in addition to control command quantities. Focus is given to these quantities which are abundant in vehicle inverters and controllers for no added sensing costs. Those quantities carry information of offsets and disturbances that could occur under faulty operating conditions compared to nominal operation, and are thus observed and studied under these conditions. Using such information, a method is developed using simple combinational logic and thresholds to diagnose a fault occurring at any time during a vehicle drive cycle. By combining features of measured quantities that behave similarly irrespective of when the fault occurs during a driving cycle, the proposed method is fault-time-insensitive. The proposed method is presented and validated by real-time simulations to capture over 20 different faults injected at different drive cycle times and in different drivetrain components—electric machine, inverter, transmission, and sensors. Results show that the proposed method is able to robustly and successfully diagnose different faults irrespective of when would they occur. [ABSTRACT FROM AUTHOR]

This paper links the theory of ripple correlation control (RCC) and extremum seeking control (ESC) with emphasis on application in a solar photovoltaic (PV) system. ESC has been well-established in the automatic control literature to find the extremum of an objective function. The RCC theory and applications have been developed in the power electronics literature for real-time optimization. Both ESC and RCC are reviewed and discussed. RCC is formulated in a similar approach to ESC, but distinct based on the source of perturbations—mainly external perturbations with ESC and inherent ripple with RCC. While some recent ESC implementations utilize inherent perturbations, RCC uses high-frequency perturbations in power electronics systems not currently utilized by ESC. The formulation and equivalencies presented here are intended for future research in both methods which can benefit from existing research for further development in theory and applications. Shared aspects that include stability and convergence characteristics are discussed. RCC formulation from an ESC perspective is then applied for maximum power point tracking of a solar PV panel, using high-frequency inherent ripple in power electronics. This RCC formulation is confirmed to have high tracking effectiveness and fast convergence. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of induction machines (IMs) and interior permanent-magnet synchronous machines (IPMSMs) in traction applications. Machines are chosen to have similar ratings to operate in the same vector-controlled drive system and to achieve a fair comparison. Due to the dynamic nature of traction applications, static efficiency maps are not used. Instead, energy consumption is evaluated for both IMs and IPMSMs during typical drive cycles. Machine efficiency is also evaluated during the drive cycle to account for steady-state and transient conditions. The results of these comparisons show that the IPMSM can have higher efficiencies for most conditions. After comparing IMs and IPMSMs, loss minimization is integrated into the IM drive. Optimal flux commands are dynamically set, and then, energy and efficiency are compared with those of the IPMSM. Results show that IMs can achieve efficiencies comparable to the IPMSMs when loss minimization is applied. The efficiency gap between the IM and IPMSM is thus reduced, and these results are verified in both a hybrid electric vehicle simulator and a hardware-in-the-loop experimental setup. [ABSTRACT FROM AUTHOR]

Vector-controlled induction motor drives include several design and control variables that affect power losses. Flux may be weakened to reduce machine losses; switching and conduction losses in the inverter are affected by the flux ripple and current hysteresis bands. This paper combines the machine and inverter to investigate the effects of various control variables on the total system power loss. Both indirect field-oriented control and direct torque control are evaluated. Power losses considered include semiconductor switching and conduction losses and machine core and copper losses. Magnetic saturation is taken into account. A 1.5-hp system is simulated and experimentally tested to find minimum-loss operating points for various control variable combinations. Experimental results show that the operating point for minimum system-level power loss is slightly different from that for minimum machine power loss, but both can yield significant energy savings. The results presented here suggest that, for efficient system operation, control aspects should be utilized and integrated into motor drive designs. [ABSTRACT FROM PUBLISHER]

This paper presents an efficient, low-cost, and versatile LED-based solar simulator intended to produce a well-characterized spectrum for tests of solar cells and other photosensitive devices. Three major design aspects are addressed: LED spectra, power converters for LED drive, and control. The visible light of a standard solar spectrum is simulated using six LED colors. The number of LEDs and their placement for uniformity are addressed. Boost converters under current-mode control are used to achieve reproducible LED brightness through adjustable currents, or equivalent radiant-flux commands. The independent control of the six colors can simulate a range of different light sources and solar spectra. Uniformity tests verify that the system achieves standard spectral uniformity requirements over an area of 100 mm \times 100 mm in simulations and 100 mm \times 50 mm in experiments. LEDs in the proposed simulator consume less power and reduce the simulator size compared to the available state of the art. The user-friendly interface also allows active control of the simulated spectrum. [ABSTRACT FROM AUTHOR]

This paper reviews and compares available techniques for minimizing power loss of induction motors. It identifies a separate category of loss minimization techniques (LMTs)—hybrid LMTs. Techniques have different convergence rates, parameter dependence, and convergence errors. Offline techniques are introduced and real-time techniques are detailed. Real-time LMTs are divided into model-based, physics-based, and hybrid categories. Application of a real-time LMT to a hybrid electric vehicle (HEV) is examined. Simulation and experimental results verify the characteristics of each category of real-time LMTs. Sensitivity of real-time LMTs to motor parameters is discussed. It is shown that techniques can be chosen based on application-specific requirements and that hybrid LMTs balance partial parameter independence and fast convergence to achieve the best overall performance. [ABSTRACT FROM PUBLISHER]

A smooth fault-tolerant control (FTC) of induction motor drives with sensor failures is presented in this paper. The drive uses concurrently active direct torque control (DTC), indirect field-oriented control (IFOC), and volts-per-hertz (V/f) controllers as replacements of each other in the case of sensor failure or recovery. Speed encoder, current, and voltage sensors are considered. The DTC and IFOC controllers are properly modified and integrated with the V/f controller in synchronous frame, which allows switching between dc-type voltage commands of different controllers. Therefore, difficult synchronization of different controllers is avoided, and a simple rate limiter is able to achieve smooth handoff transition of different controllers. Details of the DTC, IFOC, and V/f controllers, as well as their integration are presented. Simulation and experimental verification of the proposed FTC are given, where normal abc-frame switching and the proposed synchronous-frame switching of controllers are compared with different switching schemes and at different machine operation conditions. Simulation and experimental results show significantly smoother handoff transients. [ABSTRACT FROM AUTHOR]

This paper highlights key contributions in extremum seeking (ES) control and ripple correlation control (RCC). Maximum power point tracking (MPPT) utilizing the 120-Hz inherent inverter ripple is shown to be developed in the early 1980s. Even though that specific MPPT development did not explicitly mention ES control, the analysis presented there shows otherwise. RCC stability and operating properties are also addressed where the fundamental difference between RCC and popular ES control methods is the perturbation source. Since RCC utilizes inherent switching ripple in power electronics, the high ripple frequency leads to fast RCC convergence. [ABSTRACT FROM AUTHOR]

This paper presents a time-efficient modeling and simulation strategy for aggregated microinverters in large-scale photovoltaic systems. As photovoltaic microinverter systems are typically comprised of multiple power electronic converters, a suitable modeling and simulation strategy that can be used for rapid prototyping is required. Dynamic models incorporating switching action may induce significant computational burdens and long simulation durations. This paper introduces a single-matrix-form approach using the average model of a basic microinverter with two power stages consisting of a dc-dc and dc-ac converter. The proposed methodology using a common or intermediate source between two average models of cascaded converters to find the overall average model is introduced and is applicable to many other converter topologies and combinations. It provides better flexibility and simplicity when investigating various power topologies in system-level studies of microinverter and other power electronic systems. A 200 W prototype microinverter is tested to verify the proposed average and dynamic models. Furthermore, MATLAB/Simulink (2010a, Mathworks, Natick, MA, USA) is used to show the improved simulation speed and maintained accuracy of the multiple microinverter configurations when the derived average model is compared to a dynamic switching simulation model. [ABSTRACT FROM AUTHOR]

In this paper, power loss and cost models of power electronic converters based on converter ratings and datasheet information are presented. These models aid in creating rapid prototypes which facilitate the component selection process. Through rapid prototyping, users can estimate power loss and cost which are essential in design decisions. The proposed approach treats main power electronic components of a converter as building blocks that can be arranged to obtain multiple topologies to facilitate rapid prototyping. In order to get system-level power loss and cost models, two processes are implemented. The first process automatically provides minimum power loss or cost estimates and identifies components for specific applications and ratings; the second process estimates power losses and costs of each component of interest as well as the whole system. Two examples are used to illustrate the proposed approaches—boost and buck converters in continuous conduction mode. Achieved cost and loss estimates are over 93% accurate when compared to measured losses and real cost data. This research presents derivations of the proposed models, experimental validation of the models and demonstration of a user friendly interface that integrates all the models. Tools presented in this paper are expected to be very useful for practicing engineers, designers, and researchers, and are flexible and adaptable with changing or new technologies and varying component prices. [ABSTRACT FROM AUTHOR]

Power electronics (PE) and high-frequency switching circuits are key to superior performance of electric vehicles. It is vital to monitor the condition of the PE components in real-time for safety and reliability. In this article, we propose two anomaly detection methods based on a combination of data preprocessing to suppress noise and outliers, multivariate regression models to predict signals of interest under nominal operation, and sequential analysis of residuals. In particular, the methods utilize median filtering to extract on-state medians in each switching cycle in nonlinear autoregressive exogenous neural network models or filtered on-state data in partial least squares-based models to represent the nominal circuit behavior. Optimal and approximate dynamic programming-based feature selection methods are developed to select the most informative signals or their transformations. Predictions from the learned models are used to generate the residuals for anomaly detection by Page’s cumulative sum test. The proposed models and anomaly detection methods are validated on three accelerated aging experimental datasets, comprised of 60 power mosfet devices with low-frequency and high-frequency switching under disparate operating conditions. Due to the simplicity and efficiency of the data-driven anomaly detection schemes, the proposed methods can potentially be embedded in real-time digital platforms. [ABSTRACT FROM AUTHOR]

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

One of the major issues with pulsewidth modulation (PWM) is that considerable conducted emissions will be generated from power electronics converters. Random modulations are considered one of the viable solutions to reduce conducted electromagnetic interference (EMI) without adding bulky passive filtering components. Literature that investigates the application of such techniques in active front end (AFE) drives is limited. In this article, a novel random switching frequency PWM (RSF-PWM) is proposed for a grid-tied AFE drive to suppress conducted emissions. The statistical behavior of switching frequency is based on uniform distribution. Simulation and experiments are carried out on a 10-hp AFE drive. Results demonstrate that the proposed RSF-PWM can effectively reduce conducted EMI by approximately 20 dB within low-frequency range, compared with conventional constant switching frequency PWM. [ABSTRACT FROM AUTHOR]

This article proposes an unsupervised learning approach for fault prognosis of silicon carbide (SiC) mosfets. The proposed approach utilizes the changing trend of a device's voltage, current, temperature, and other device characteristics with its degradation. The failure modes of semiconductors are reviewed along with existing methods for fault prognosis. The proposed approach is the first to address prognostics of SiC devices, and it can avoid the effects from system noise and data errors. It is not limited to offline analysis and is targeted at online implementation. It is easy to implement on standard digital platforms, and has fast computational speed. Offline data analysis is performed to verify the effectiveness of the proposed method, and a processor-in-the-loop system is used to verify its ability to perform online fault prognosis. [ABSTRACT FROM AUTHOR]

This paper proposes an optimal efficiency control scheme for a wind system with doubly fed induction generator (DFIG). The suggested control scheme combines loss minimization (LM) in the DFIG and maximum power point tracking (MPPT) in the wind turbine and therefore maximum electrical energy generation, by the same wind energy potential, is achieved. Moreover, since the cut-in wind speed is reduced, extension of the exploitable wind speed range toward the lower speed region is attained. The LM is achieved by properly controlling the flux-linkage of the DFIG with respect to the stator current and the MPPT is accomplished by regulating the rotor speed through the rotor current. The parameters of the LM and MPPT controllers can be determined experimentally, and thus, the knowledge of the wind energy conversion system (WECS) model is not required. For the implementation of the proposed control strategy, a new structure of the WECS has been adopted. However, the hardware requirements of the WECS and considerably the cost have not been considerably affected compared to the conventional configuration. Selective simulation and experimental results are presented to validate the effectiveness of the proposed control strategy and demonstrate the operational improvements. [ABSTRACT FROM AUTHOR]