287 research outputs found
Mitigation Technique for Cascaded H-Bridge Multilevel Inverters Based on Pulse Active Width Modulation
No full textThis article considers l-level cascaded H-bridge (CHB) inverters and proposes a new modulation method based on pulse active width modulation (PAWM), capable to minimize all harmonics with order n < 2l +1 and to satisfy the European harmonic standards for medium-voltage-level applications EN 50 160 and CIGRE WG 36-05. A mathematical theorem and its proof are presented, stating the features of the procedure, which
is an improvement of the selective harmonic elimination (SHE) PAWM proposed by Buccella et al. After a detailed description of the method, simulation and experimental results have been included, showing its capability to reduce low-order harmonics
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
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
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
INTERMEDIATE SYMMETRIES IN THE SPONTANEOUS BREAKING OF SUPERSYMMETRIC SO(10)
No full text We study the supersymmetric spontaneous symmetry breaking of SO(10) into SU (3) ⊗ SU (2) ⊗ U (1) for the most physically interesting cases of SU(5) or flipped SU (5) ⊗ U (1) intermediate symmetries. The first case is more easily realized while the second one requires a fine-tuning condition on the parameters of the superpotential. This is because in the case of SU(5) symmetry there is at most one singlet of the residual symmetry in each SO(10) irreducible representation. We also point out on more general grounds in supersymmetric GUTs that some intermediate symmetries can be exactly realized and others can only be approximated by fine-tuning. In the first category, there could occur some tunneling between the vacua with exact and approximate intermediate symmetry. The flipped SU (5) ⊗ U (1) symmetry improves the unification of gauge couplings if (B-L) is broken by ‖(B-L)‖ =1 scalars yielding right-handed neutrino masses below 1014 GeV . </jats:p
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
Mathematical proof of a harmonic elimination procedure for multilevel inverters
No full textIn this paper, a single phase cascaded H-bridge inverter with s variable dc sources (s≥2), l=2s+1 levels has been considered. A mathematical proof is presented to demonstrate that, under a particular choice of the switching angles, which number corresponds to the number of dc sources i.e. s, and of the dc voltages, all harmonics are eliminated from the output voltage waveform, except those of order n=4p⋅s±1, p=1,2,.... With this method, the dc voltage sources vary linearly according to the modulation index m, while the switching angles do not depend on m. The resulting output voltage has low total harmonic distortion, that remains independent on m. Compared to a conventional selective harmonic elimination procedure and to a pulse amplitude method, the proposed procedure reduces distortion in a wide range of modulation index
General Formula for SHE Problem Solution
No full textThis paper considers cascaded H-bridges multilevel inverters with 2 n dc sources, n integer, n > 0 and proposes a new general formula to compute those 2 n switching angles capable of eliminating n + 1 harmonics and their respective multiples from the output voltage waveform. The proposed procedure uses only scalar products and avoids linear systems, therefore it has a low computational cost. Computed angles do not depend on modulation index, moreover, voltage sources vary linearly. A mathematical proof is given to validate the formula. Three-phase implementations eliminate or mitigate a significant amount of low order harmonics, thus resulting in very low total harmonic distortion. The proposed formula has been experimentally validated using a single-phase nine-level cascaded H-bridge inverter prototype, resulting in a Total Harmonic Distortion (THD) of 5.59%; the first not-mitigated harmonic is the 17th
Analysis and Implementation of Multilevel Inverter for Full Electric Aircraft Drives
No full textIn modern aircrafts, hydraulic or pneumatic actuators have been already replaced with electric counterparts, but the advancement of the inverter and motor technology has made possible that the propulsion system can be powered by electrical sources. These high power requirements can not be efficiently fulfilled by using a typical two level converter; the multi-level converter represents a suitable solution for this application. This paper presents a cascaded H-bridge, a 9-level permanent magnet synchronous motor drive for full electric aircrafts. Harmonic analysis is presented considering different levels of a multi-level inverter. Simulation results and experimental validation with a test-rig confirms the accuracy of the proposed system
A comparison between real-time harmonic elimination procedures for single phase CHB 5-level inverter
No full textIn this paper, single phase cascaded H-bridge (CHB) 5-level inverters are considered and a pulse amplitude modulation (PAM) procedure operating at fundamental frequency, ables to remove the third and fifth harmonics and their respective multiple, is proposed. Each H-bridge is fed by equal voltage sources linearly dependent on modulation index. This procedure is compared with another PAM procedure that uses disequal dc voltage sources and with the classical selective harmonic elimination (SHE) technique working at fundamental frequency. The presented procedure eliminates more harmonics, therefore it returns lower Total Harmonic Distortion (THD) in comparison to the other considered strategies. Experimental results are shown, confirming the validity of the proposed procedure
- …
