Multilevel inverters have been widely used in medium and high voltage applications. Different modulation techniques have been proposed to control the multilevelinverter. This paper presents a switching strategy for cascaded multilevel inverters, based on space vector modulation. The SVPWM can be applied practically in hybrid multilevel inverters with different voltage steps; it can be applied to most multilevel topologies. This paper proposes a new algorithm for hybrid multilevel inverters with unequal voltage steps under the space vector pulse width modulation (SVPWM). The proposed algorithm offers an intuitive method for minimizing the totalharmonicdistortion (THD) of the output voltage of the inverter and uses simple arithmetic for determining the sector and does not require lookup tables. The proposed techniques lead to a significant reduction in THD. Finally, the algorithm was implemented on a Digital Signal Processor (DSP) and the scheme is explained for a seven level inverter, and experimental results are presented for a seven level inverter.
Abstract - This paper deals with reduction of totalharmonicdistortion in new Cascaded H-bridge multilevelinverter topology with artificial neural network technique. This topology consists of lower blocking voltage on switches and it requires less number of dc voltage sources, power switches which results in decrease the complexity and total cost of the inverter. Moreover, a new algorithm is used to determine the magnitude of dc voltage sources for generation of all voltage levels. Artificial Neural Network (ANN) is trained by the back-propagation algorithm of the Mean Square Error (MSE) between the output and the desired value. The performance and functional accuracy of the proposed topology using ANN technique in generating all voltage levels for 31-level inverter are simulated using MATLAB simulink.
According to the different types of major reference signals, PWM techniques can be divided into different categories Such as sine PWM, third harmonic injected PWM, sixty degree PWM, trapezoidal PWM etc. These techniques reduce the number of switching which reduces the switching loss . Based on the totalharmonicdistortion (THD) analysis, third harmonic injected PWM (THPWM) is better among them . THD is the measurement of harmonicdistortion present in the output signal of the inverter. THD should be kept as low as possible because higher THD has unfavorable effect on power supply
consisting of low cost, right performance and a few application which include PV panels and gas cells. Cascaded H-bridge MLI is one kind of these MLIs. Unlike the traditional inverter, the MLI's output voltage has a reduced THD with higher harmonic profile. Mathematical techniques for harmonic elimination are offered in some of the literatures however solving a non-linear transcendental equation set describing the SHE problem using these methods are not suitable for multi level inverters. A hybrid optimization set of rules to locate the most reliable switching angles in a MultilevelInverter (MLI) is proposed in this paper. The switching angles are optimized to reduce low frequency harmonics. TotalHarmonicDistortion (THD) method are implemented in order to lessen the switching losses. This paper summarizes different hybrid optimization techniques, which included the mechanisms of particle swarm optimization (PSO), genetic algorithm (GA), fuzzy logic controller and biography based algorithm which will optimize parameters. A comparative study of different algorithm has been studied.
Abstract: In this paper, a novel procedure to find the firing angles of the multilevel inverters of supply voltage and, consequently, to decline the totalharmonicdistortion (THD), has been presented. In order to eliminate more harmonics in the multilevel inverters, its number of levels can be lessened or pulse width modulation waveform, in which more than one switching occur in each level, be used. Both cases complicate the non-algebraic equations and their solution cannot be performed by the conventional methods for the numerical solution of nonlinear equations such as Newton- Raphson method. In this paper, Cuckoo algorithm is used to compute the optimal firing angle of the pulse width modulation voltage waveform in the multilevelinverter. These angles should be calculated in such a way that the voltage amplitude of the fundamental frequency be generated while the totalharmonicdistortion of the output voltage be small. The simulation and theoretical results for the 9-levels inverter offer the high applicability of the proposed algorithm to identify the suitable firing angles for declining the low order harmonics and generate a waveform whose totalharmonicdistortion is very small and it is almost a sinusoidal waveform.
Based on previous work that has been done, most researchers focus on the harmonic that occur on load and less concerned about the harmonics that occur at the power source. Power sources such as batteries, solar and other sources of DC supply which has a high TotalHarmonicDistortion (THD) in term of voltage. Thus, this study is to change the power source from DC supply to supercapacitor and monitor it performance for harmonic reduction in output of cascaded H-Bridge multilevelinverter by using MATLAB/SIMULINK.
This Section deals with the problem formulation of induction motor performance enhancement and the various challenges faced by the existing and proposed techniques. Evolutionary algorithms can be applied on various applications but it needs to be modified according to applications. Harmonic Elimination method provides an efficient method to remove lower order harmonics in various configurations of inverters. The selection of the type of inverter and the topology of the inverter plays an important role in the performance. This leads to a critical design requirement in terms of pulse wave design to be fed at the gate terminals of the various power electronics switches. The problem can also be visualized as an optimization problem with the pulse widths being the tuning parameters which needs to be optimized in terms of minimal TotalHarmonicDistortion of the output. As mentioned above the pulse gate design can be visualized as an optimization problem which can be solved using various optimization algorithms. The research problem which we are targeting here is the design of multilevel inverters and their optimal selection of pulse width in order to reduce the total harmonics distortion to a minimal value, thereby improving the performance of the induction machine. Many models have been proposed for representing harmonic sources as well as linear components. Various network harmonic solution algorithms have also been published. In the following sections, we briefly summarize the well-accepted methods for harmonic modelling and simulations. Other chapters in this tutorial will expand upon these ideas and illustrate how to set up studies in typical situations. The most commonly used index for measuring the harmonic content of a waveform is the totalharmonicdistortion (THD). It is a measure of the effective value of a waveform and may be applied to either voltage or current. Totalharmonicdistortion is the contribution of all the harmonic frequency currents to the fundamental. Just as waveforms can be added to produce distorted waves, distorted waves may be decomposed into fundamental and harmonic components.
As a result, continuous enhancements are desperately required on the potency front altogether industrial and client applications. Inverters play an important role in conversion of DC current obtained from these renewable sources of energy into AC current. once this process is done there'll be some loss in power due to the presence of harmonics and totalharmonicdistortion .So so as to achieve maximum power conversion and to prevent the device from getting damaged it is desirable to remove these harmonics and to attenuate the THD.
This project represent the research of harmonic minimization of a single phase cascaded H-bridge multilevelinverter (CHB-MLI). Multilevelinverter is used to combine a desired single or three-phase voltage waveform and also to minimize the harmonics in the electrical system. This project use cascaded H-bridge (CHB) topology due to least number of components use, output voltage level are doubled, and easy to controllled compared with diode clamp (DC) and flying capacitor (FC) topology. This research use three and five levels cascaded H-bridge multilevelinverter based on Newton-Raphson technique controller by using MATLAB/SIMULINK in order to reduce the harmonic in electrical system. The value of totalharmonicdistortion (THD) has been obtained based on the simulation design of three and five levels CHB-MLI.
(2.2) To minimize harmonicdistortion and to achieve adjustable amplitude of the fundamental component, up to m-1 harmonic contents can be removed from the voltage waveform. In general, the most significant low-frequency harmonics are chosen for elimination by properly selecting angles among different level inverters  , and high-frequency harmonic components can be readily removed by using additional filter circuits. According to equation (2.12), to keep the number of eliminated harmonics at a constant level, all switching angles must be less than π / 2. However, if the switching angles do not satisfy the condition, this scheme no longer exists. As a result, this modulation strategy basically provides a narrow range of modulation index, which is its main disadvantage. For example, in a seven-level equally stepped waveform, its modulation index is only available from 0.5 to 1.05. At modulation indexes lower than 0.5, if this scheme is still applied, the allowable harmonic components to be eliminated will reduce from 2 to 1. The totalharmonicdistortion (THD) increases correspondingly.
Genetic Algorithm (GA) has been proposed to solve the transcendental equations, -. Therefore in this proposed work by using an optimizing method like GA, an attempt is made to solve SHE equation whole range of modulation index and TotalHarmonicDistortion (THD). In this proposed work single phase cascaded H-bridge five level inverter is chosen for analysis.
Multilevel converters have drawn tremendous interest in recent years and have been studied for several high- voltage and high-power applications. Switching losses in these high-power high-voltage converters represent an issue and any switching transitions that can be eliminated without compromising the harmonic content of the final waveform is considered advantageous. The term multilevel starts with the introduction of the three-level converter. By increasing the number of levels in a given topology, the output voltages have more steps generation a staircase waveform, which approaches closely the desired sinusoidal waveform and also offers reduced harmonicdistortion. One promising technology to interface battery packs in electric and hybrid electric vehicles are multilevel converters because of the possibility of high VA rating and low harmonicdistortion without the use of a transformer. Harmonic Reduction-pulse-width modulation (HR-PWM) has been mainly developed for two- and three- level converters in order to achieve lower totalharmonicdistortion (THD) in the voltage output waveform. The main challenge associated with HR-PWM techniques is to obtain the analytical solution of the system for nonlinear transcendental equations that contain trigonometric terms which in turn provide multiple sets of solutions. Genetic algorithm has been recently introduced to optimize the sequence of the carrier waveform of the PWM as to minimize the THD and the distortion factor (DF) of output line voltage. An optimization technique assisted with a hybrid genetic algorithm was successfully applied to find the switching transitions (i.e. ., switching angles) of the HR- PWM ac/ac converter. More recently, a general genetic algorithm using Matlab GA optimization Toolbox was applied to solve the same problem of HR-PWM.
This paper presents a genetic algorithm (GA) optimization technique to find the optimum switching angles of 11-level inverter with minimum number of dc sources and switches in comparison with the cascade multilevelinverter in order to minimize the totalharmonicdistortion (THD) of their output voltage waveform. Theoretical and simulation results for an 11-level converter show the efficiency of the proposed algorithm to determine the optimum angles in order to decrease the undesired harmonics and produce very high quality output voltage waveform.
Abstract: In this paper, a novel procedure to find the firing angles of the multilevel inverters of supply voltage and, consequently, to decline the totalharmonicdistortion (THD), has been presented. In order to eliminate more harmonics in the multilevel inverters, its number of levels can be lessened or pulse width modulation waveform, in which more than one switching occur in each level, be used. Both cases complicate the non-algebraic equations and their solution cannot be performed by the conventional methods for the numerical solution of nonlinear equations such as Newton- Raphson method. In this paper, Cuckoo algorithm is used to compute the optimal firing angle of the pulse width modulation voltage waveform in the multilevelinverter. These angles should be calculated in such a way that the voltage amplitude of the fundamental frequency be generated while the totalharmonicdistortion of the output voltage be small. The simulation and theoretical results for the 7-levels inverter offer the high applicability of the proposed algorithm to identify the suitable firing angles for declining the low order harmonics and generate a waveform whose totalharmonicdistortion is very small and it is almost a sinusoidal waveform.
Abstract:-In present work, optimization techniques genetic algorithm (GA) and particle swarm optimization (PSO) are used to compute switching angles for the cascaded multilevelinverter for selective harmonic elimination and the results are compared. Switching angles obtained from PSO produced better output with less harmonic content. Due to better performance PSO results are used further to obtain training set for Artificial Neural Network (ANN). Hence implementation of ANN for the elimination of low order harmonics is presented. Output voltage for nine level inverter is obtained for both single phase and three phase Cascaded MultilevelInverter (CMLI). Switching angles are calculated through GA and PSO for various modulation indices and for minimum TotalHarmonicDistortion (THD). Simulation results are presented using MATLAB and m file program. Through ANN real time implementation is possible with significantly reduced lower harmonics and improved performance.
Abstract- This paper proposes a comparison between cascaded seven level inverter and nine level inverter using Phase opposition and disposition Pulse Width Modulation control scheme. The number of switches used in the cascaded seven and nine level inverter is identified and the TotalHarmonicDistortion (THD) between them is compared. As the level gets increased the number of switches gets increased so the reduced switch topology is used with Pulse Width Modulation control scheme. The number of switches used in the reduced switch seven level and nine level inverter topology will be less when compared to the cascaded seven level and nine level inverter. The TotalHarmonicDistortion (THD) between cascaded multilevelinverter and the reduced switch multilevelinverter is compared. The results are observed by MATLAB/SIMULINK software.
Multilevelinverter have been attracting increasing interest recently due to the increased Quality Power to bring into being good quality results and for accurate evaluation, improving harmonic performance, In this project, an attempt has been made to improve the quality of power. A three level cascaded multi level inverter with identical dc supply is designed . Multilevel inverters continue to receive more and more attention because it avoid the use of extra clamping diodes and voltage balancing capacitors and thus it requires least number of components with compare to diode- clamped and flying capacitors type multilevel inverters topologies and thus it has modular structure with simple switching strategy and occupies less space and thus switching devices losses and stress is reduced, the output voltage amplitude is increased and improved overall harmonic profile can be achieved. high voltage operation capability, low switching losses, high efficiency. With its modularity and flexibility, the cascaded multilevelinverter shows superiority in high-power applications, because by connecting the H-bridge in series one can get required output voltage as well as power. In cascaded H-bridge multilevelinverter separate DC sources configuration is used to avoid short circuit of DC source. Here in this proposed project consists of three series H-bridge inverter units, each bridge module comprises of four Gate turn-offs Thyristor (GTO).
Abstract- In general the Induction Motor is known to be a constant speed motor. In most of the industries the induction motor is mainly used for Drive Systems. But due to the advances in computer technology the speed of the induction motor can be controlled under certain conditions. There are many ways to control the speed of the Induction Motor for variable speed applications. The basic method is 2-level inverter controlled by microcontroller using space vector modulation. In this method the output of the inverter may not be exactly sinusoidal and hence at the star point of the Induction Motor winding, causing a Voltage HarmonicDistortion in the output of the inverter. To minimize the voltage harmonicdistortion a multilevelinverter can be used. In addition, the harmonic frequencies will not produce usable torque but causes heating the Induction motor windings, which are harmful to the insulation. In this paper two level and three level inverter fed induction motor driven at various frequencies are reported. Simulation, experimentation and the measurement of voltage totalharmonicdistortion have also been reported. In the experiment the Arduino microcontroller, Line Impedance Stabilization Network, opto- isolator, Hall Effect sensor, H-bridge inverter and other necessary electronic circuits are used. The measurements are recorded using Agilent make Mixed signal Oscilloscope. The Fast Fourier transform has been carried out for the experimental result, using signal analysis software. Simulation has been implemented using the MATLAB/Simulink. The results of simulation and experimentation are compared and tabulated.
This paper concentrates on enhancing the productivity of the multilevel in- verter and nature of yield voltage waveform. Seven level lessened switches to- pology has been actualized with just seven switches. Essential Switching plan and Selective Harmonics Elimination were executed to diminish the Total Harmonics Distortion (THD) esteem. Selective Harmonics Elimination Stepped Waveform (SHESW) strategy is executed to dispense with the lower order harmonics. Fundamental switching plan is utilized to control the switches in the inverter. The proposed topology is reasonable for any number of levels. The harmonic lessening is accomplished by selecting fitting switching angles. It indicates would like to decrease starting expense and unpredictability con- sequently it is able for modern applications. In this paper, third and fifth level harmonics have been disposed of. Simulation work is done utilizing the MATLAB/Simulink programming results have been displayed to accept the hypothesis.