37 research outputs found
Hybrid genetic algorithm approach for selective harmonic control
The paper presents an optimal solution for a selective harmonic elimination pulse width modulated (SHE-PWM) technique suitable for a high power inverter used in constant frequency utility applications. The main challenge of solving the associated non-linear equations, which are transcendental in nature and, therefore, have multiple solutions, is the convergence, and therefore, an initial point selected considerably close to the exact solution is required. The paper discusses an efficient hybrid real coded genetic algorithm (HRCGA) that reduces significantly the computational burden, resulting in fast convergence. An objective function describing a measure of the effectiveness of eliminating selected orders of harmonies while controlling the fundamental, namely a weighted total harmonic distortion (WTHD) is derived, and a comparison of different operating points is reported. It is observed that the method was able to find the optimal solution for a modulation index that is higher than unity. The theoretical considerations reported in this paper are verified through simulation and experimentally on a low power laboratory prototype. (C) 2007 Elsevier Ltd. All rights reserved
Optimal SHE-PWM Technique for Three-Level Voltage Source Converter Control
Selective harmonic elimination pulse-width modulation (SHE-PWM) technique for three-level voltage source converter is presented in this paper. It is mathematically defined using Fourier-based equations to describe the output voltage waveform. An efficient minimization technique assisted with hybrid genetic algorithm is then applied to obtain the optimal switching angles. Different operating points including single- and three-phase systems are presented to demonstrate the effectiveness of the proposed method Selected simulation and experimentally validated results are reported to show the effectiveness of the proposed method Copyright (C) 2008 Praise Worthy Prize S.r.l. - All rights reserved
A novel voltage balancing control method for flying capacitor
The voltage unbalancing issue remains a challenge for the multilevel flying capacitor (FC) converter. It becomes more prominent when the number of levels of the converter is higher than three which needs to be addressed. The phase-shifted sinusoidal PWM (PS-SPWM) method has a certain degree of self-balancing characteristic in the ideal symmetrical circuit. However, the use of only the said method is not sufficient to deal with the problem and a closed-loop control is required to realize the voltage balancing control task. The paper proposes a closed-loop control method based on the PS-SPWM strategy and a novel algorithm for the stated problem. The algorithm takes advantage of switching redundancies in order to adjust the switching time of selected switching states to maintain the capacitor voltages balanced without adversely affecting the system's performance. Description and analysis of the method along with simulation results are presented to confirm its feasibility
Multimodular systems based on multilevel flying capacitor converters
Multimodular systems based on the multilevel flying capacitor (FC) converter topology are discussed in this paper. Three control techniques are studied and their performance is compared against specific criteria. Different types of multicarrier sinusoidal PWM (MSPWM) techniques used for each module along with the phase-shifting (PS) concept among the different modules are considered. Techniques with high frequency modulation ratio and the fundamental frequency PWM (FFPWM) are studied. The total harmonic distortion (THD) of the output quantities, the system's bandwidth, and the potential switching losses are discussed. Simulation results are given to support the findings