A Modified Seven Level Cascaded H Bridge Inverter

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Presently Multilevel inverters are extensively used for high-voltage applications and their execution is exceptionally better to that of regular two-level inverters due to minimized harmonic distortion, lower electromagnetic interference and larger DC link voltages. Nevertheless certain shortcomings are faced such as adding in number of components and voltage balancing problem. In order to overcome these, a seven-level hybrid inverter has been proposed. This topology requires a lesser number of power switches which results in the decrease of multifaceted nature, add up to cost and weight of the inverter. Finally this can be able to generate near sinusoidal voltages and approximately fundamental frequency switching. The simulation and the experimental results of a modified cascaded seven level H bridge inverter with and without LC filter are presented for validation.

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A Modified Seven Level Cascaded H Bridge
Inverter
ABSTRACT:
Presently Multilevel inverters are extensively used for high-voltage applications and their
execution is exceptionally better to that of regular two-level inverters due to minimized harmonic
distortion, lower electromagnetic interference and larger DC link voltages. Nevertheless certain
shortcomings are faced such as adding in number of components and voltage balancing problem.
In order to overcome these, a seven-level hybrid inverter has been proposed. This topology
requires a lesser number of power switches which results in the decrease of multifaceted nature,
add up to cost and weight of the inverter. Finally this can be able to generate near sinusoidal
voltages and approximately fundamental frequency switching. The simulation and the
experimental results of a modified cascaded seven level H bridge inverter with and without LC
filter are presented for validation.
KEYWORDS:
1. Cascaded H-bridge inverter (CHBI)
2. Seven level hybrid inverter
3. Asymmetrical DC sources
4. Total harmonic distortion (THD)
5. Pulse Width modulation (PWM)
6. Multi-level Inverter
SOFTWARE: MATLAB/SIMULINK
CONCLUSION:
A modified cascaded seven level H-bridge inverter was fabricated which has the benefit of
reduced THD, portability, and cost has compared to normal cascaded H-bridge inverter. Since

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In this paper, the disturbances in power system due to low quality of power are discussed and a current injection method to maintain the sinusoidal input current which will reduce the total current harmonic distortion (THD) as well as improve the power factor nearer to unity is proposed. The proposed method makes use of a novel controlled diode rectifier which involves the use of bidirectional switches across the front-end rectifier and the operation of the converter is fully analyzed. The main feature of the topology is low cost, small size, high efficiency and simplicity, and is excellent for retrofitting front-end rectifier of existing ac drives, UPS etc. A novel strategy implementing reference compensation current depending on the load harmonics and a control algorithm for three-phase three-level unity PF rectifier which draws high quality sinusoidal supply currents and maintains good dc link- voltage regulation under wide load variation. The proposed technique can be applied as a retrofit to a variety of existing thyristor converters which uses three bidirectional switches operating at low frequency and a half-bridge inverter operating at high frequency .The total power delivered to the load is processed by the injection network, the proposed converter offers high efficiency and not only high power factor but also the Total Harmonic Distortion is reduced. Theoretical analysis is verified by digital simulation and a hardware proto type module is implemented in order to confirm the feasibility of the proposed system. This scheme in general is suitable for the common variable medium-to high-power level DC load applications.

Performance Analysis of H-bridge and T-Bridge Multilevel Inverters for Harmon...

International Journal of Power Electronics and Drive Systems

This paper deals with the design of cascaded 11 level H- bridge inverter. It includes a comparison between the 11 level H-bridge and T-bridge multilevel inverter. The cascaded inverter of higher level is a very effective and practical solution for reduction of total harmonic distortion (THD).These cascaded multilevel inverter can be used for higher voltage applications with more stability. As the level is increased the output waveform becomes more sinusoidal in nature. The inverter is designed using multicarrier sinusoidal pulse width modulation technique for generating triggering pulses for the semiconductor switches used in the device. Through this paper it will be proved that a cascaded multilevel H-bridge topology has higher efficiency than a T-bridge inverter, as whichever source input voltage is provided since input is equal to the output voltage. In T-bridge inverter, the output obtained is half of the applied input, so efficiency is just half as compared to H-bridge. The output waveform is distorted and has higher THD. The simulation is performed using MATLAB /Simulink 2013 software.

High frequency ac-link pv inverter

Asoka Technologies

In this paper, a high-frequency ac-link photovoltaic (PV) inverter is proposed. The proposed inverter overcomes most of the problems associated with currently available PV inverters. In this inverter, a single-stage power-conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the input voltage, maximum power point tracking, generating low-harmonic ac at the output, and input/output isolation. This inverter is, in fact, a partial resonant ac-link converter in which the link is formed by a parallel inductor/capacitor (LC) pair having alternating current and voltage. Among the significant merits of the proposed inverter are the zero-voltage turn-on and soft turn-off of the switches which result in negligible switching losses and minimum voltage stress on the switches. Hence, the frequency of the link can be as high as permitted by the switches and the processor. The high frequency of operation makes the proposed inverter very compact. The other significant advantage of the proposed inverter is that no bulky electrolytic capacitor exists at the link. Electrolytic capacitors are cited as the most unreliable component in PV inverters, and they are responsible for most of the inverters’ failures, particularly at high temperature. Therefore, substituting dc electrolytic capacitors with ac LC pairs will significantly increase the reliability of PV inverters. A 30-kW prototype was fabricated and tested. The principle of operation and detailed design procedure of the proposed inverter along with the simulation and experimental results are included in this paper. To evaluate the long-term performance of the proposed inverter, three of these inverters were installed at three different commercial facilities in Texas, USA, to support the PV systems. These inverters have been working for several months now.

Improved 25-level inverter topology with reduced part count for PV grid-tie a...

International Journal of Power Electronics and Drive Systems

A new bidirectional multilevel inverter topology with a high number of voltage levels with a very reduced number of power components is proposed in this paper. Only TEN power switches and four asymmetric DC voltage sources are used to generate 25 voltage levels in this new topology. The proposed multilevel converter is more suitable for e-mobility and photovoltaic applications where the overall energy source can be composed of a few units/associations of several basic source modules. Several benefits are provided by this new topology: Highly sinusoidal current and voltage waveforms, low Total Harmonic Distortion, very low switching losses, and minimum cost and size of the device. For optimum control of this 25-level voltage inverter, a special Modified Hybrid Modulation technique is performed. The proposed 25-level inverter is compared to various topologies published recently in terms of cost, the number of active power switches, clamped diodes, flying capacitors, DC floating capacitors, and the number of DC voltage sources. This comparison clearly shows that the proposed topology is cost-effective, compact, and very efficient. The effectiveness and the good performance of the proposed multilevel power converter (with and without PWM control) are verified and checked by computational simulations.

PERFORMANCE EXPLORATION OF SINGLE PHASE DAB DC-DC CONVERTER UNDER LOAD VARIATION

IRJET Journal

The document analyzes the performance of a single phase Dual Active Bridge (DAB) DC-DC converter under varying load conditions. It aims to achieve high efficiency and quick dynamic response. The converter uses phase shift pulse width modulation control of switches. Simulation results in Matlab/Simulink show the load voltage and power performance with and without a proportional-integral voltage controller. The controller helps regulate the voltage and improve the dynamic response during load changes.

U26130135

IJERA Editor

Design and simulation of single phase five-level symmetrical cascaded h-bridg...

Asoka Technologies

Multilevel inverter is an effective and practical solution for increasing power demand and reducing harmonics of ac waveforms. Such inverters synthesize a desired output voltage from several levels of dc voltages as inputs. This paper analyzes the performance of five level cascaded H-bridge multilevel inverter with reduce number of power switches. Further by reducing switches and increasing level will reduce filter cost & harmonic content. 5- Level cascaded H-bridge asymmetrical multilevel inverter topology requires 8 switches but in this new multilevel inverter it requires 6 switches in which same multilevel is obtained. Invariably switching losses and cost also reduced. In this .paper only multilevel inverter circuitry will be studied. The performance has been analyzed by the MATLAB/Simulink.

A Novel Three Phase Multi-string Multilevel Inverter with High DC-DC Closed o...

rnvsubbarao koppineni

This document proposes and analyzes a novel three-phase multi-string multilevel inverter for photovoltaic systems. The inverter uses a high step-up DC-DC converter to boost and stabilize the output DC voltage from multiple renewable energy sources. It then uses a simplified multilevel inverter topology with only six switches instead of the eight switches used in conventional cascaded H-bridge multilevel inverters, reducing losses. Simulation and experimental results show the inverter provides improved output waveforms, lower harmonics, reduced size and cost compared to other topologies.

High step up quasi-z source dc-dc converter

Asoka Technologies

In this paper, a high step-up Quasi-Z Source (QZS) DC-DC converter is proposed. This converter uses a hybrid switched-capacitors switched-inductor method in order to achieve high voltage gains. The proposed converter have resolved the voltage gain limitation of the basic QZS DC-DC converter while keeping its main advantages such as continuous input current and low voltage stress on capacitors. Compared to the basic converter, the duty cycle is not limited, and the voltage stress on the diodes and switch isn’t increased. In addition to these features, the proposed converter has a flexible structure, and extra stages could be added to it in order to achieve even higher voltage gains without increasing the voltage stress on devices or limiting the duty cycle. The operation principle of the converter and related relationships and waveforms are presented in the paper. Also, a comprehensive comparison between the proposed and other QZS based DC-DC converters is provided which confirms the superiority of the proposed converter. Simulations are done in PSCAD/EMTDC in order to investigate the MPPT capability of the converter. In addition, the valid performance and practicality of the converter are studied through the results obtained from the laboratory built prototype.

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