An on-line harmonics elimination PWM scheme for three-phase voltage source inverters

An on-line harmonic elimination PWM (HEPWM) scheme for three-phase voltage source inverters is proposed. It is based on curve fitting method derived from the trajectories of the exact (off-line) HEPWM angles. The main advantage of the technique is its fast and efficient realization using a microprocessor. An outline to obtain the switching angles is presented. The method is proven by experimental result

AC voltage regulation of a bidirectional high-frequency link converter using a deadbeat controller

This paper presents a digital controller for AC voltage regulation of a bidirectional high-frequency link (BHFL) inverter using Deadbeat control. The proposed controller consists of inner current loop, outer voltage loop and a feed-forward controller, which imposes a gain scheduling effect according to the reference signal to compensate the steady-state error of the system. The main property of the proposed controller is that the current- and the voltage-loop controllers have the same structure, and use the same sampling period. This simplifies the design and implementation processes. To improve the overall performance of the system, additional disturbance decoupling networks are employed. This takes into account the model discretization effect. Therefore, accurate disturbance decoupling can be achieved, and the system robustness towards load variations is increased. To avoid transformer saturation due to low frequency voltage envelopes, an equalized pulse width modulation (PWM) technique has been introduced. The proposed controller has been realized using the DS1104 digital signal processor (DSP) from dSPACE. Its performances have been tested on a one kVA prototype inverter. Experimental results showed that the proposed controller has very fast dynamic and good steady-state responses even under highly nonlinear loads

Effect of equivalent salt deposit density on flashover voltage of contaminated insulator energized by HVDC

In Malaysia, the demand for electric power is increasing day by day due to more consumption of power in the industrial sector. Recently, the high voltage DC transmission lines are under construction near the coastal environments for transmitting the power to the all states of Malaysia. Therefore, there is a concern about the reliability of these systems especially under adverse environmental conditions due to sea salt spray contamination. This reliability of this contaminated insulator can be improved through its performance studies. For this performance study, an analytical expression between flashover voltage and ESDD of the contaminated insulator has been proposed using Dimensional Analysis technique. The results obtained from the analytical expression are compared with the experimental results and in close agreement are foun

Deteksi Kandungan Air Relatif pada Daun sebagai Acuan Induksi Pembungaan Jeruk Siam Jember

Penelitian bertujuan untuk : (1) Menentukan nilai optimal RWC untuk induksi pembungaan Jeruk Siam Jember berdasarkan gejala kelayuan visual sebagai respons tanaman terhadap pengeringan; (2) Menentukan nilai optimal Kadar Lengas Tanah pada saat pengeringan untuk induksi pembungaan; (3) Menganalisis dampak pengeringan terhadap pembungaan dan pembuahan Jeruk Siam Jember. Penelitian ini merupakan penelitian lapangan (action research) yang dilaksanakan di salah satu kebun jeruk siam milik petani di daerah sentra produksi. Pengambilan sampel dilakukan secara purposive sampling dengan kreteria umur tanaman sama, vigor tanaman identik, dan sudah berproduksi. Untuk mendapatkan nilai RWC dan Kadar Lengas Tanah yang optimal dilakukan dengan cara membagi lahan pertanaman menjadi lima petak percobaan. Masing-masing petak minimal terdapat 16 tanaman dan dipisahkan dengan batas parit sedalam 60 cm dan lebar 50 cm. Petak-petak percobaan tersebut selanjutnya diberi perlakuan pengeringan sebagai berikut: (1) Pengeringan selama dua minggu (P1); (2) Pengeringan selama tiga minggu (P2); (3) Pengeringan selama empat minggu (P3); (4) Pengeringan selama lima minggu (P4). Pengairan dilakukan dengan cara memompa air irigasi ke permukaan lahan sampai mencapai kapasitas lapang. Dengan cara demikian petak lain yang masih dalam perlakuan pengeringan tetap kering.. Data yang terkumpul dianalisis secara deskriptif statistik Hasil Penelitian menunjukkan bahwa perlakuan Pengeringan selama 3 minggu (P2 menunjukkan hasil yang terbaik dengan jumlah bunga jeruk paling banyak secara signifikan dibanding perlakuan lainnya

Underground Phased Arrays and Beamforming Applications

This chapter presents a framework for adaptive beamforming in underground communication. The wireless propagation is thoroughly analyzed to develop a model using the soil moisture as an input parameter to provide feedback mechanism while enhancing the system performance. The working of array element in the soil is analyzed. Moreover, the effect of soil texture and soil moisture on the resonant frequency and return loss is studied in detail. The wave refraction from the soil–air interface highly degrades the performance of the system. Furthermore, to beam steering is done to achieve high gain for lateral component improving the UG communication. The angle enhancing the lateral wave depends upon dielectric properties and usually ranges from 0∘ to 16∘. These dielectric properties change with the change in soil moisture and soil texture. It is shown from the experiments that optimal UG lateral angle is high at lower soil moisture readings and decreases with decrease in soil moisture. A planar structure of antenna array and different techniques for optimization are proposed for enhanced soil moisture adaptive beamforming. UG channel impulse response is studied from the beamforming aspect to identify the components of EM waves propagating through the soil. An optimum steering method for beamforming is presented which adapts to the changing values of soil moisture. Finally, the limitations of UG beamforming are presented along with the motivation to use it

Asymmetrical Nine-Level Inverter Topology with Reduce Power Semicondutor Devices

In this paper a new single-phase multilevel inverter topology is presented. Proposed topology is capable of producing nine-level output voltage with reduce device counts. It can be achieved by arranging available switches and dc sources in a fashion such that the maximum combination of addition and subtraction of the input dc sources can be obtained. To verify the viability of the proposed topology, the circuit model is developed and simulated in Matlab-Simulink software. Experimental testing results of the proposed nine-level inverter topology, developed in the laboratory, are presented. A low frequency switching strategy is employed in this work. The results show that the proposed topology is capable to produce a nine-level output voltage, capable in handling inductive load and yields acceptable harmonic distortion conten

Updated Values of Running Quark and Lepton Masses

Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale M_Z \approx 91.2 GeV and the would-be GUT scale \Lambda_GUT \sim 2 \times 10^16 GeV. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above M_Z. In particular, we take into account the possible new physics scale (\mu \sim 1 TeV) to be explored by the LHC and the typical seesaw scales (\mu \sim 10^9 GeV and \mu \sim 10^12 GeV) which might be relevant to the generation of neutrino masses. For illustration, the running masses of three light Majorana neutrinos are also calculated. Our up-to-date table of running fermion masses are expected to be very useful for the study of flavor dynamics at various energy scales.Comment: 23 pages, 6 tables, 2 figures; version published in PR

Extremal Black Attractors in 8D Maximal Supergravity

Motivated by the new higher D-supergravity solutions on intersecting attractors obtained by Ferrara et al. in [Phys.Rev.D79:065031-2009], we focus in this paper on 8D maximal supergravity with moduli space [SL(3,R)/SO(3)]x[SL(2,R)/SO(2)] and study explicitly the attractor mechanism for various configurations of extremal black p- branes (anti-branes) with the typical near horizon geometries AdS_{p+2}xS^{m}xT^{6-p-m} and p=0,1,2,3,4; 2<=m<=6. Interpretations in terms of wrapped M2 and M5 branes of the 11D M-theory on 3-torus are also given. Keywords: 8D supergravity, black p-branes, attractor mechanism, M-theory.Comment: 37 page

Statistical analysis for the impact of smoking on the behavior and health of Qatari adolescents

The links between the use of tobacco and health risks are well known. Most of the younger smokers reside in Asia which includes Qatar, the focus country of this study. Cigarette smoking among children is rising at an alarming rate worldwide including Qatar. As youth make up a significant percentage of the population and to achieve the health objectives of the Qatar Vision 2030, it is essential to ensure the health and well-being of adolescents, as they are the future of Qatar. This study focuses on exploring the patterns of tobacco use and its impacts on the adolescents by conducting a survey in different schools across Qatar. The questionnaire was administered in five schools, selected by proportional random sampling. The responses were recorded from the sample for general questions regarding interest in physical activities, relationship with family and friends, mental satisfaction, health, academics and access to cigarettes. 2018 Walter de Gruyter GmbH, Berlin/Boston 2018.Scopu

Underground Wireless Channel Bandwidth and Capacity

The UG channel bandwidth and capacity are vital parameters in wireless underground communication system design. In this chapter, a comprehensive analysis of the wireless underground channel capacity is presented. The impact of soil on return loss, bandwidth, and path loss is discussed. The results of underground multi-carrier modulation capacity are also outlined. Moreover, the single user capacity and multi-carrier capacity are also introduced with an in-depth treatment of soil texture, soil moisture, and distance effects on channel capacity. Finally, the chapter is concluded with a discussion of challenges and open research issues