PWM Harmonic Signature Based Islanding Detection for a Single-Phase Inverter with PWM Frequency Hopping

Distributed generation (DG) has gained popularity in recent years due to the increasing requirement for renewable power sources. A problem that exists with DG systems is the islanding of DG units that creates safety issues for personnel as well as the potential for damage to utility infrastructure. Therefore, islanding detection methods are utilized to mitigate the risk of islanded operation of DG units. A new passive method of islanding detection based on the signature of the PWM voltage harmonics is proposed. The viability of the algorithm is investigated with the use of an analytical and time domain model of the inverter and further validated with experimental results. Furthermore, an extension of the detection scheme is proposed for use in multiinverter scenarios composed of adaptive frequency hopping to eliminate unwanted tripping

Real-time Measurement of Temperature Sensitive Electrical Parameters in SiC Power MOSFETs

This paper examines a number of techniques for junction temperature estimation of SiC MOSFETs devices based on the measurement of Temperature Sensitive Electrical Parameters (TSEPs) for use in online condition monitoring. Linearity, sensitivity to temperature and circuit design for practical implementation are discussed in detail. A demonstrator based on the measurement of the quasi-threshold voltage, the turn-on transient characteristic (di/dt), the on-state voltage and the gate current peak is designed and validated. It is shown that the threshold voltage, the estimation of the gate current peak and the on-state voltage have potentially good sensitivity to temperature variation and linearity over a wide operating range. Very low sensitivity to temperature is shown for (di/dt). The proposed method can provide a valuable tool for continuous health monitoring in emerging applications of SiC devices to high reliability applications

Design and Control of On-board Bidirectional Battery Chargers with Islanding Detection for Electric Vehicle Applications

Electric vehicles have gained popularity over the last decade due to concerns regarding climate change as well as depleting fossil fuel reserves. One of the important components of electric vehicles is the battery charging system that has been the focus of recent research interest in terms of vehicle to grid (V2G) power transfer with the aim of providing peak load levelling for the grid as well as a buffer for excess renewable energy. The research addressed in this thesis is focused on single-phase on- board bidirectional chargers for electric vehicle applications where emphasis is given to the design, control and islanding detection aspects. A comparative study between a low frequency transformer based and high frequency DAB based bidirectional charging system is carried out and the weight, cost and efficiency between the two topologies compared. An optimised LCL filter design method for the two converters is presented which characterises the high frequency current ripple as well as the losses in the damping resistor. Controller design, simulation and experimental validation of the two converters are also presented. The impact of 3rd harmonics on the performance of second order generalised integrator (SOGI) phase locked loops (PLLs) is investigated through an analytical method to predict the resulting output harmonic magnitudes. Two modified SOGI PLLs are presented where the harmonic rejection performance has been improved. A new PLL structure based on the novel IIR filter proposed by Ed Daw et al. is investigated for application in grid converters. The new PLL is evaluated with hardware-in-the-loop (HIL) simulations for transient and abnormal grid conditions and compared with the SOGI PLL for performance evaluation as well as computational requirements. The new PLL is validated in bidirectional charger hardware. A new islanding detection algorithm based on the detection of high frequency switching harmonic signature with frequency hopping is presented which has the advantage of multi-inverter compatibility. The difficulty in detection for PWM harmonic based methods when capacitive loads are present is analysed. Furthermore, the algorithm is validated in hardware

DNA Vaccines against Dengue Virus Type 2 Based on Truncate Envelope Protein or Its Domain III

Two DNA vaccines were constructed encoding the ectodomain (domains I, II and III) of the DENV2 envelope protein (pE1D2) or only its domain III (pE2D2), fused to the human tissue plasminogen activator signal peptide (t-PA). The expression and secretion of recombinant proteins was confirmed in vitro in BHK cells transfected with the two plasmids, detected by immunofluorescence or immunoprecipitation of metabolically labeled gene products, using polyclonal and monoclonal antibodies against DENV2. Besides, results reveal that the ectodomain of the E protein can be efficiently expressed in vivo, in a mammalian system, without the prM protein that is hypothesized to act as a chaperonin during dengue infection. Balb/c mice were immunized with the DNA vaccines and challenged with a lethal dose of DENV2. All pE1D2-vaccinated mice survived challenge, while 45% of animals immunized with the pE2D2 died after infection. Furthermore, only 10% of pE1D2-immunized mice presented some clinical signs of infection after challenge, whereas most of animals inoculated with the pE2D2 showed effects of the disease with high morbidity degrees. Levels of neutralizing antibodies were significantly higher in pE1D2-vaccinated mice than in pE2D2-immunized animals, also suggesting that the pE1D2 vaccine was more protective than the pE2D2

A Dynamic Landscape for Antibody Binding Modulates Antibody-Mediated Neutralization of West Nile Virus

Neutralizing antibodies are a significant component of the host's protective response against flavivirus infection. Neutralization of flaviviruses occurs when individual virions are engaged by antibodies with a stoichiometry that exceeds a required threshold. From this “multiple-hit” perspective, the neutralizing activity of antibodies is governed by the affinity with which it binds its epitope and the number of times this determinant is displayed on the surface of the virion. In this study, we investigated time-dependent changes in the fate of West Nile virus (WNV) decorated with antibody in solution. Experiments with the well-characterized neutralizing monoclonal antibody (MAb) E16 revealed a significant increase in neutralization activity over time that could not be explained by the kinetics of antibody binding, virion aggregation, or the action of complement. Additional kinetic experiments using the fusion-loop specific MAb E53, which has limited neutralizing activity because it recognizes a relatively inaccessible epitope on mature virions, identified a role of virus “breathing” in regulating neutralization activity. Remarkably, MAb E53 neutralized mature WNV in a time- and temperature-dependent manner. This phenomenon was confirmed in studies with a large panel of MAbs specific for epitopes in each domain of the WNV envelope protein, with sera from recipients of a live attenuated WNV vaccine, and in experiments with dengue virus. Given enough time, significant inhibition of infection was observed even for antibodies with very limited, or no neutralizing activity in standard neutralization assays. Together, our data suggests that the structural dynamics of flaviviruses impacts antibody-mediated neutralization via exposure of otherwise inaccessible epitopes, allowing for antibodies to dock on the virion with a stoichiometry sufficient for neutralization

Impact of fashion involvement and hedonic consumption on impulse buying tendency of Sri Lankan apparel consumers : the moderating effect of age and gender

Fashion and clothing are the foremost aspects of human life. Previous studies have identified many variables as antecedents of fashion-related impulse purchases. The role of fashion involvement and hedonic consumption as predictors of fashion related impulse buying are less examined. Extant literature suggests that there can be a moderating effect of age and gender on the relationship between fashion involvement, hedonic consumption, and impulse purchases of apparels. This research aims to examine the impact of fashion involvement and hedonic consumption on the impulse buying tendency of Sri Lankan apparel consumers with the moderating effect of age and gender. The study was guided by the positivistic paradigm. The researcher employed a single cross-sectional design for the study, and the population was Sri Lankan apparel consumers who were above twenty years old. The sample of the study was drawn from the Colombo district, where 324 responses were obtained using a structured questionnaire. According to statistical analysis, there was a positive impact of fashion involvement and hedonic consumption on the impulse buying tendency of Sri Lankan apparel consumers. Further, the researcher examined the moderating effect of age and gender on relationships between fashion involvement, impulse buying and hedonic consumption. However, it was revealed that there is no significant moderating effect from age and gender on the aforesaid relationship. Based on the findings of the study, it is suggested to practitioners of fashion retailing to stimulate and fulfil hedonic needs and desires of fashion consumers to persuade consumers for more fashion-oriented impulse purchases. Future studies under the same topic could be conducted with cultural influences on the impulse purchase of fashions and situational factors such as time and money availability

DNA vaccine coding for the full-length infectious Kunjin virus RNA protects mice against the New York strain of West Nile virus

A plasmid DNA directing transcription of the infectious full-length RNA genome of Kunjin (KUN) virus in vivo from a mammalian expression promoter was used to vaccinate mice intramuscularly. The KUN viral cDNA encoded in the plasmid contained the mutation in the NS1 protein (Pro-250 to Leu) previously shown to attenuate KUN virus in weanling mice. KUN virus was isolated from the blood of immunized mice 3-4 days after DNA inoculation, demonstrating that infectious RNA was being transcribed in vivo; however, no symptoms of virus-induced disease were observed. By 19 days postimmunization, neutralizing antibody was detected in the serum of immunized animals. On challenge with lethal doses of the virulent New York strain of West Nile (WN) or wild-type KUN virus intracerebrally or intraperitoneally, mice immunized with as little as 0.1-1 μg of KUN plasmid DNA were solidly protected against disease. This finding correlated with neutralization data in vitro showing that serum from KUN DNA-immunized mice neutralized KUN and WN viruses with similar efficiencies. The results demonstrate that delivery of an attenuated but replicating KUN virus via a plasmid DNA vector may provide an effective vaccination strategy against virulent strains of WN virus