Reduction of Switches and DC Sources in Cascaded Multilevel Inverter

Harmonics and increasing number of switches and DC sources for increasing level is the major issue in the cascaded multilevel inverter for the application of medium and high voltage power system applications. In this paper several new techniques are used to reduce the switches and DC sources, which overcome the disadvantages of cascaded multilevel inverter. The THD values for various levels (seven & nine) are compared with and without PWM technique

Simulation and Implementation of a High Performance Torque Control Scheme of IM Utilizing FPGA

Thi paper presents a novel approach to design and implementation of a high perfromane torque control scheme i.e. direct torque control with space vector modulation(DTC-SVM) of three phase induction motor using Field Programmable gate array (FPGA). The conventional direct torque control (DTC) is one of control scheme that is used commonly in induction motor control system. This method supports a very quick and precise torque response. However, the conventional DTC is not perfect and has some disadvantages. To minimize the ripples of the electromagnetic torque and flux linkage and to fix the variable switching frequency produced in the conventional DTC, this paper proposes improved DTC-SVM concept. Both simulation and experimental results show that the proposed scheme can dramatically improve the steady state performance while preserving the dynamic performance of the conventional DTC.DOI:http://dx.doi.org/10.11591/ijece.v2i3.20

Dynamically Reconfigurable Control Struture for Three Phase Induction Motor Drives

Field Programmable Gate Arrays (FPGAs) are a suitable hardware platform for the industrial control systems. These dynamically reconfigurable FPGAs can be used as an alternative digital solution to conventional microcontrollers and DSPs to ensure fast operation. This paper presents the feasibility of embedding the Direct Torque Control with Space Vector Modulation (DTC-SVM) of an induction motor into FPGA.The DTC-SVM of induction motor drives is simulated in a Matlab/Simulink environment using a Xilinx System Generator.DOI: http://dx.doi.org/10.11591/ijpeds.v2i1.18

Energy Efficient Approach for Collision Avoidance in Wireless Sensor Networks

One of the main challenges in the wireless sensor network is to improve the performance of the network by extending the lifetime of the sensor nodes. Excessive packet collisions lead to packet losses and retransmissions, resulting in significant overhead costs and latency which in turn makes a need to design a distributed and scalable time slot allocation. A new proposal is proposed which avoids collisions between packets and also provides increased energy efficiency and further prolong network lifetime, in wireless sensor network

High-Risk Cervical Human Papillomavirus Infections among Human Immunodeficiency Virus-Positive Women in the Bahamas

Background\ud \ud High-risk (HR) HPV genotypes other than 16 and 18 have been detected in a significant proportion of immunocompromised females. We aim to evaluate the frequency of HR HPV genotypes in a population of HIV-positive Caribbean women.\ud Methods\ud \ud One hundred sixty-seven consecutive, non-pregnant, HIV-positive females ≥18 years were recruited in this study. Each participant received a vaginal examination, PAP smear, and completed a questionnaire. DNA was extracted for HPV testing in 86 patients.\ud Results\ud \ud Mean age was 39.1 years for women positive for HR HPV and 43.1 years for women negative for HR HPV (P value = 0.040). 78% (130/167) of the women had HR HPV infections; the prevalence of abnormal cervical cytology was 38% among women who were HR HPV-positive compared to women who were HR HPV-negative (22%). Fifty-one percent of the 86 women with available genotype carried infections with HPV 16 and/or HPV 18; genotypes of unknown risk were also frequently observed. Women who had a CD4+ count of ≤200 had 7 times increased odds of carrying HR HPV infection in comparison to women with CD4+>200.\ud Conclusions\ud \ud HR HPV infections in HIV infected females may consist of more than just HPV 16 and 18, but also HPV 52 and 58. Further studies are needed to determine whether HPV 52 and 58 play a significant role in the development of cervical cytological abnormalities in HIV+ women

An early developmental vertebrate model for nanomaterial safety:Bridging cell-based and mammalian toxicity assessment

Background. With the rise in production of nanoparticles for an ever-increasing number of applications, there is an urgent need to efficiently assess their potential toxicity. We propose a nanoparticle hazard assessment protocol that combines mammalian cytotoxicity data with embryonic vertebrate abnormality scoring to determine an overall toxicity index. Results. We observed that, after exposure to a range of nanoparticles, Xenopus phenotypic scoring showed a strong correlation with cell based in vitro assays. Magnetite-cored nanoparticles, negative for toxicity in vitro and Xenopus, were further confirmed as non-toxic in mice. Conclusion. The results highlight the potential of Xenopus embryo analysis as a fast screening approach for toxicity assessment of nanoparticles, which could be introduced for the routine testing of nanomaterials

Investigation on D-STATCOM Operation for Power Quality Improvement in a Three Phase Three Wire Distribution System with a New Control Strategy

This paper deals with the issue of modeling and analysis of power controllers, power electronic-based equipment aimed at improving the reliability, stability and quality of power flows in low voltage distribution networks. A new control scheme is proposed to generate the PWM signal based on the measurements of voltage, and no reactive power measurements are required. The operation of the proposed control method is presented for D-STATCOM. Simulations and analysis are carried out in MATLAB/PLECS with this control method for the proposed systems. The reliability of the control scheme in the system response to the voltage instabilities due to system faults or load variations is proved obviously in the simulation results. Keywords: D-STATCOM, PWM, VSC, MATLAB/PLECS

Climate and southern Africa's water-energy-food nexus

In southern Africa, the connections between climate and the water-energy-food nexus are strong. Physical and socioeconomic exposure to climate is high in many areas and in crucial economic sectors. Spatial interdependence is also high, driven for example, by the regional extent of many climate anomalies and river basins and aquifers that span national boundaries. There is now strong evidence of the effects of individual climate anomalies, but associations between national rainfall and Gross Domestic Product and crop production remain relatively weak. The majority of climate models project decreases in annual precipitation for southern Africa, typically by as much as 20% by the 2080s. Impact models suggest these changes would propagate into reduced water availability and crop yields. Recognition of spatial and sectoral interdependencies should inform policies, institutions and investments for enhancing water, energy and food security. Three key political and economic instruments could be strengthened for this purpose; the Southern African Development Community, the Southern African Power Pool, and trade of agricultural products amounting to significant transfers of embedded water