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In previous researches, a signal-based model of power network and STATCOM accompanied by its controller is presented. Using such a model, considering shunt filters is so complicated. Implementing filters is the most popular method of harmonic elimination in networks which contain FACTS & power electronic devices. Also, there is a need to simulate the real model of power network and STATCOM switching...
Photovoltaic and fuel-cell dc voltage, most of the time converts to ac voltage in a two-stage process. In the first stage, a dc-dc convertor boosts the dc voltage and then, the increased dc voltage turn into ac voltage using an inverter. This topology has two major problems. First and foremost, the overall reliability of system declines. More importantly, multiple problem of using large electrolyte...
Because of nonlinear nature of corresponding equations in SHEPWM switching strategy, applied to stepped waveform of multilevel inverter's output voltage, using genetic algorithm Toolbox of MATLAB software is a normal solution. Two approaches for solving the equations have been selected in literature. In the first, the equations are solved by constructing nonlinear equally constraints, while in the...
In the standard selective harmonic elimination (SHE)-pulse-width modulation (PWM) technique for multilevel converters, in order to eliminate N 2 1 non-triplen odd harmonics of the ac-side voltage and to regulate the output voltage amplitude, N switching angles need to be determined. Therefore a set of N non-linear transcendental equations must be solved to find the desired switching angles for any...
Multilevel Inverters inject lesser harmonics in comparison with common 3-level inverters. However, this amount is notable. THD is a proper index to evaluate the amount of harmonics. Line voltage THD of a 5-level inverter's stepped waveform has been formulated in literature. In this paper, the method of calculating the formulas is developed. So, the formulas of line voltage THD for a 7-level inverter...
In this paper, two standalone PV systems are compared. One of them has two series PVs that are connected to DC/DC and then DC/AC converters for feeding the AC load. The other configuration uses two separate PV and DC/DC converters, with series DC/AC converters on the AC load side. It is shown that the series inverter has advantages like improved harmonic condition, keeping both PVs in maximum power...
Selective Harmonic Elimination PWM switching strategy has shown tremendous advantages in comparison with well-known SPWM strategy. But, its implementation on Distribution Static Var Compensator (DSTATCOM) is hard because of nonlinear nature of DSTATCOM and severe variation of DC capacitor voltage. In this paper, a controller based on PI controller is designed to overcome such problems. Thus, Modulation...
Minimum THD is achieved, when THD Minimization (THDM) switching Strategy is employed. In this strategy, desired fundamental component is satisfied. Since the corresponding equations are nonlinear, a fitness function is constructed and evolutionary based algorithms are the best choice. In this paper, a new method based on Imperialist Competitive Algorithm (ICA) is employed to apply THDM strategy on...
Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) is a well-known Switching Strategy which is applied in multilevel Inverters. The aim of this strategy is eliminating low order harmonics. Basically, harmonic equations are nonlinear and solving them is a major problem for researchers. Evolutionary Algorithms have shown an effective ability for this aim, because they find solution for all...
Cascade Multilevel Inverter (CMI) is widely used in family of Multilevel inverters. THD Minimization (THDM) switching strategy is a well-known strategy which is applied to reduce amount of whole voltage harmonics. Two methods based on Approximate and Integrating methods have been proposed in literature to calculate line voltage THD of multilevel inverter with stepped waveform. In this paper, THDM...
Cascade Multilevel Inverter (CMI) is widely used in family of Multilevel inverters. THD Minimization (THDM) switching strategy is a well-known strategy which is applied to reduce amount of whole voltage harmonics. Two methods based on Approximate and Integrating methods have been proposed in literature to calculate line voltage THD of multilevel inverter with stepped waveform. In this paper, THDM...
Several switching strategies have been developed to overcome the unbalanced working period and power sharing in cascaded multilevel inverters, but the power sharing problem is remained unsolved yet. In this paper, a novel switching method which equalizes the modules' power sharing is presented.
Multilevel inverters, the next generation of DC-AC inverters, are widely used in industrial applications especially in high voltage and power. Multilevel inverters include several DC sources which are not equal in practice. Output voltage waveform of these inverters contains harmonic contents. Total Harmonic Distortion (THD) is the most used index to evaluate harmonic content of any waveform. Calculation...
In this paper, the Optimal Minimization of the Total Harmonic Distortion (OMTHD) technique is improved to calculate minimum phase THD and approximate line to line THD versus variable Modulation Indices (M). In Developed single-phase OMTHD technique, the Fitness function is proposed to minimize phase THD, and fundamental component as a constraint is separately added to Fitness function to adjust the...
Distributed Generation source are widely used because of their remarkable advantages. Photovoltaic (PV) cells which produce DC voltage in their output belong to these sources and should be connected to the network through a power electronic interface. At the other hand, considering PV characteristics show that maximum power can be extracted at the optimal operating point which depends on the solar...
Multilevel inverters introduce harmonic to the network, beside their enormous advantages. THD is one of the most important indexes to evaluate harmonic contents of waveforms. Conventional method of line voltage THD calculation gives approximate answers but its accurate value is important. In this paper, a series of analytical formula is found to calculate line voltage THD of 5-level inverter with...
A new generation of DC to AC inverters which is called Multilevel Inverter, has many industrial applications, especially in high-voltage and high-power. In spite of nearly sinusoidal waveform, multilevel inverters produce noticeable harmonic content. THD is normally used as a benchmark to evaluate harmonic contents. THD is one of important factors to produce losses in devices such as induction motors,...
Multilevel inverters have found wide applications in industry, especially in high-voltage and high power. Many researchers have attended to decrease the produced harmonic content of output voltage waveform. One of the criteria to determine the harmonic content, which is very popular, is Total Harmonic Distortion (THD). Therefore, determination of its actual amount is important. The voltage of three-phase...
Unified Power Quality Conditioner (UPQC) is a series-parallel element in the Flexible AC Transmission System (FACTS) family. In this paper, a UPQC with cascaded multilevel inverter is proposed. Voltage sag, unbalance and load power factor in distribution system is mitigated using proposed multilevel UPQC. There is no need of using transformer and filter when multilevel UPQC is applied and it is one...
So far, several methods have been presented to eliminate and minimize the low order voltage harmonics at multi-level inverter's output. Harmonics optimization aims to eliminate the low order harmonics, if it is possible, or at least to minimize them. Thus, harmonics optimization can be considered as a generalized form of harmonics elimination. In this way, this paper applies an advanced variation...
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