195 research outputs found
DC Current Elimination for MPC for CHB-STATCOM Employing Current Transformer Sensors
No full textCurrent transformers are widely used as sensors in high-power converters. However, they are incapable of handling DC components, resulting in potential malfunctions. This paper shows that, in a cascaded H-bridge static synchronous compensator with finite control set model predictive control, they can be easily suppressed by adding a cluster balancing optimization algorithm. Experimental evidence is provided by implementing the proposed cluster balancing optimization algorithm on a three-phase, 5-level STATCOM
Spontaneously broken SU(5) symmetries and 1-loop effects in the early universe
No full text?his paper studies the 1-loop eEective potential and spontaneous-spmetrybreaking
pattern for SU(5) gauge theory in de Sitter spacetime. Curvature effects
modify the flat-space effective potential by means of a very complicated special function
previously derived in the literature. An algebraic technique already developed by Buccella
ef al to study spontaneous symmelry breaking of SU(n) for renormalikable polynomial
potentials is here generalized, for SU(5), to the much more difficult case of a de Sitler
background. A detailed algebraic and numerical analysis provides a better derivation of
the stabilily of the exlrema in the maximal subgroups SU(4) x U(l), SU(3) x S U ( 2 ) x
U( l ) , S U ( 3) X U ( 1 ) X U ( 1 ) XR311, SU( 2) x S U (2 ) x U ( l ) x U ( 1 ) x R2211 , w h e r e
R311 and R2211 discrete symmetries select particular directions in the corresponding
two-dimensional strata. One thus obtains a deeper understanding of the result, previously
found wilh a different numerical analysis, predicting the slide of the inflationary universe
into either the SU(3) x SU(2) x U(I) or SU(4) x U(1) extremum. Interestingly,
using this approach, one can easily generalize all previous results to a more complete
SU(5) tree-level potential also containing cubic terms
Analytical formula for harmonic elimination problem in multilevel inverter
No full textThis paper presents a solution of the selective harmonic elimination problem in multilevel converters based on an analytical formula. Three phase l-level cascaded H-bridges (CHB) inverters with l = 2s + 1, s = 2n number of both dc sources and switching angles are considered to delete n harmonics, arbitrarily chosen, and their multiple from output voltage waveform, imposing the amplitude of the fundamental harmonic. The procedure calculates the unknown switching angles depending on modulation index
Enhancing Voltage Gain and Assessing Current THD in Transformer of Photovoltaic Applications through a New Triple Active Bridge Converter
No full textA novel Triple Active Bridge converter is proposed delivering a considerably higher voltage gain and lowering transformer's Total Harmonic Distortion compared to the conventional Dual Active Bridge. The design of the converter, circuit operation modes, and its steady-state behavior are all thoroughly examined in this work. The converter optimizes the control system adding an extra degree of freedom, useful to control the voltage gain by combining the fundamental PWM method with the proposed architecture, which also increases efficiency and reduces THD.The efficacy of the proposed approach is validated by simulations
An Algorithm for Harmonic Elimination in Three-Phase Multilevel Inverters
No full textThis paper considers three phase, l -level, cascaded H-bridges inverters with l = 2s + 1, where s = 2 n is number of dc sources, and proposes a procedure that imposes the amplitude of the fundamental harmonic and eliminates n arbitrarily chosen harmonics and their multiples from the output voltage wave-form. It works at fundamental switching frequency and returns the unknown switching angles through a simple mathematical expression that is function of the modulation index. A theorem proves the expression, then, both simulation and experimental results successfully validate the method
Efficiency Optimization of Induction Motor by Automatic Voltage Regulator of Synchronous Generator Based on Search-based Method
No full textThis article proposes a new method to optimize the efficiency of a 7.5 kW induction motor connected to a synchronous generator. The Synchronous generator is a part of an emergency power system supposed to provide power for the induction motor. In this proposed method, the efficiency of induction motor is optimized by the automatic voltage regulator of synchronous generator under different loads. The centerpiece of automatic voltage regulator is a DC/DC buck converter which feeds excitation winding. Due to improvement of induction motor efficiency, the cost of generation is significantly reduced. In the proposed method, a search-based method is utilized to adjust the output voltage of synchronous generator in order to find the maximum efficiency of induction motor. Furthermore, losses equations are presented which are applied in efficiency calculation. As a result of not using speed sensor, the motor equations arc used to estimate the motor slip in each step of search method. Results of the proposed method is presented to verify the method performance using MATLAB/Simulink
Low Q 2 boundary conditions for DGLAP equations dictated by quantum statistical mechanics
No full textWe discuss the role of quantum statistical mechanics in the description of the parton distribution functions in the proton. It provides the low Q 2 boundary conditions for DGLAP equations in terms of Fermi–Dirac and Bose–Einstein functions of the fractional momentum variable x. The successful comparison with experimental data on both the unpolarised and polarised deep inelastic structure functions is reviewed. We argue that the statistical approach for the nucleon parton distributions functions has the nice feature that the free model parameters are fixed from data with high statistics and small systematic uncertainties, providing a strong constraint on the information not supplied by the experiments
Shielding Performances of Reinforced Walls to the Field Radiated by Lightning
No full textA method is given for evaluating the electromagnetic field within a building affected by an indirect lightning strike. Models are introduced for the lightning channel and for the reinforcement in each wall of the building. The shielding action exerted by the reinforced concrete walls of the building is analysed and the influence is ascertained of various parameters, such as distance between walls and ground resistivity. In order to acquire a complete model of a real building account is taken of door and window opening
EMI in a reinforced concrete control building during breaker and disconnector operations in HV substations
No full textPane di festa. Le cuddure a Roccafiorita e Limina
No full textIl capitolo analizza gli usi rituali delle cuddure, dolce tipico della Valle d'Agrò, e ne indaga le valenze simboliche legate al ciclo di morte-rinascita proprio delle festività pasquali
- …
