Type Multilevel Inverter Research Articles

CASCADE TOPOLOGIES FOR THE ASYMMETRIC MULTILEVEL INVERTER BY NEW MODULE TO ACHIEVE MAXIMUM NUMBER OF LEVELS

ABSTRACT:Â Multilevel inverters have been introduced as useful devices to connect between DC-AC systems. They are high quality output and cost benefit systems with a wide range of applications. Asymmetric multilevel inverters are a type of multilevel inverters with unequal DC link to create more voltage levels through fewer components. This paper presents new topologies of cascade multilevel inverter by a new module with a reduced component. Base module produces 13 levels by two types of unequal DC sources and 10 switches. Modular can be used to produce more and higher voltages levels. The designing of proposed multilevel inverter makes some preferable index with better quality than similar modular multilevel inverters, such as less semiconductors and DC sources, low switching frequency, creating of negative levels without any additional circuit, and module in cascade connections. Also, two cascade topologies are presented in the modular connections of the proposed module to achieve high and significant number of levels. Nearest level control (NLC) method as a switching technique is used in step changing levels for topologies to get more quality and lower harmonics. The presented module and cascade topologies are simulated by MATLAB/Simulink and are implemented by the experimental prototype in laboratory to validate the performance of proposed topologies in which simulated and experimental results show a good performance with the high quality output.

Investigation on cascade multilevel inverter with symmetric, asymmetric, hybrid and multi-cell configurations

In recent past, numerous multilevel architectures came into existence. In this background, cascaded multilevel inverter (CMLI) is the promising structure. This type of multilevel inverters synthesizes a medium voltage output based on a series connection of power cells which use standard low-voltage component configurations. This characteristic allows one to achieve high-quality output voltage and current waveforms. However, when the number of levels increases switching components and the count of dc sources are also increased. This issue became a key motivation for the present paper. The present paper is devoted to investigate different types of CMLI which use less number of switching components and dc sources and finally proposed a new version of Multi-cell based CMLI. In order to verify the proposed topology, MATLAB – simulations and hardware verifications are carried out and results are presented.

An Improved Phase-Shifted Carrier Pulse Width Modulation Based on the Artificial Bee Colony Algorithm for Cascaded H-Bridge Multilevel Inverters

Cascaded H-bridge multilevel (CHBML) inverters usually include a large number of isolated dc-voltage sources. Some faults in the dc-voltage sources result in unequal cell dc voltages. Unfortunately, the conventional phase-shifted carrier (PSC) PWM method that is widely used for CHBML inverters cannot eliminate low frequency sideband harmonics when the cell dc voltages are not equal. This paper analyzes the principle of sideband harmonic elimination, and proposes an improved PSCPWM that can eliminate low frequency sideband harmonics under the condition of unequal dc voltages. In order to calculate the carrier phases, it is necessary to solve transcendental equations for low frequency sideband harmonic elimination. Therefore, an approach based on the artificial bee colony (ABC) algorithm is presented in this paper. The proposed PSCPWM method enhances the reliability of CHBML inverters. The proposed PSCPWM is not limited to CHBML inverters. It can also be applied to other types of multilevel inverters. Simulation and experimental result obtained from a prototype CHBML inverter verify the theoretical analysis and the achievements made in this paper.

Formulation of phase voltage and calculation of its total harmonic distortion in multilevel Z‐source inverter

Multilevel inverters have recently been received more attention in the power industry. Two traditional types of multilevel inverters are multilevel voltage-source inverter and multilevel current-source inverter. Despite this widespread use, multilevel Z-source inverter (ML-ZSI) has not been regarded enough, because a unique approach to voltage control of ML-ZSI has not yet been presented. Besides, the phase voltage and its total harmonic distortion (THD) have not been calculated for ML-ZSI so far. This study proposes two new methods for the formulation of phase voltage in ML-ZSI. The first method is based on Fourier series analysis of the phase-voltage waveform, and the second utilises the staircase waveform of the phase voltage. In addition, two new methods are introduced for computing the phase-voltage THD in ML-ZSI: approximate method and waveform-integration method. Although the waveform-integration method leads to the accurate answer, using this method is more difficult than an approximate method. The detailed description of suggested methods and comparison with each other are presented in this study. Simulation and experimental results are also given to demonstrate the new features of the proposed methods.

Enhanced Performance of a DVR using Mixed Cascaded Multilevel Inverter

This proposed paper studies the design and performance of a new 'Dynamic voltage restorer' (DVR) using a new hybrid 7 level PWM inverter. The new multilevel inverter is a combination of the capacitor clamped and the cascaded H-bridge type multilevel inverters. This new topology provides different levels of output voltages and high modularity. In the paper, the sag or swell are detected in a transmission line and the voltage is injected from the multilevel inverter through a boost transformer. Simulation results in matlab show that the performance of the new mixed multicell inverter is better than the traditional MLIs and normal inverters with the advantages like absence of the filter.

Space Vector Modulation Controlled Single Phase Five Level Inverter for Fuel Cell Applications

In low power system a single phase converter is usually adopted. This paper deals with five-level Converter topology with SPWM technique. A review of the state of the art of five-level topologies and theoretical power loss comparison with proposed solution is realized. The main characteristics of these modulations are reduced, switching losses, balanced power loss dissipation among the devices with in a cell and among the series connected cells. A Neutral point Clamped type of Multilevel Inverter is more efficient .The proposed converter architecture is based on Single-Phase five-level system for Fuel cell with Polymer Exchange type. In this system, Space Vector Modulation (SVM) technique is used. Simulation and Experimental results show the effectiveness of the proposed solution.

Multi Level Inverter with Dc Link Switches

This paper presents a single phase 5 level inverter with dc link Switches using POD technique .The proposed multi level inverter is capable of generating 5 level output with less component count .This technique uses single carrier wave and two sine waves for pulse generation .The entire system is designed and implemented using MATLAB/Simulink .The inverter is connected to a R-load and performance are analysed. I. INTRODUCTION Now a days Multi level inverter are extensively used due to their increased power rating, reduced EMI , improving harmonic performance. Multi level inverters are switched at low switching frequency when compared to two level inverters, hence the switching losses are almost negligible .The multi level converter topology has drawn tremendous interest in the power industry since it can provide the high power required for high power applications.. To cope up with the problems associated with the two-level inverter, multi-level inverters (MLIs) are introduced Multi level inverters are classified into 3 types  Diode clamped multi level inverter  Cascaded H bridge multi level inverter  Flying capacitor type multi level inverter The applications of multilevel inverter are reactive power compensation, variable speed drives etc. The topological structure of Multi level inverters should be capable of withstanding high input voltage for high power applications. A new multi level inverter is proposed which is capable of reducing problems faced by usage of conventional multi level inverters. The advantages of proposed multi level inverter when compared with conventional Multi level inverter are : 1. Number of devices of the proposed multi-level inverter is fewer than that of the conventional multi-level inverters. Therefore, the proposed system is more reliable and cost competitive than the conventional two-level and multilevel inverters.2. Only one carrier signal is required to generate switching pulses to 8 switches used in proposed Multi level inverter (1).

Accurate THD Formulas for Multilevel Inverters with MILP Optimization

This study aims to derive simple formulas for calculating the accurate Total Harmonic Distortion (THD) of Multilevel Inverter (MLIs), that considers all low and high order harmonics, for single phase and three phase MLIs., since the THD is a main criterion when judging the performance of a MLI. In addition, a formula for the percentage route mean square value of high order harmonics %V HOrms is derived. These formulas could be applied for all types of MLIs that use different switching techniques for harmonics elimination or reduction, so long as the switching angles of the phase voltage are known and it is specially suitable to be applied with the Mixed Integer Linear Programming (MILP) optimization model, which is constructed for determining the switching angles of the MLI that minimize the absolute values of any undesired harmonics. This study aims also to show that this MILP model can produce solutions that have low values of the accurate THD, by giving the detailed solutions of two cases taken from the references.

Simplified space vector modulation technique for seven‐level cascaded H‐bridge inverter

A simplified space vector modulation (SVM) technique is proposed for the seven-level cascaded H-bridge (CHB) inverter. It is based on decomposing the seven-level space vector hexagon into a number of two-level space vector hexagons. The presented technique significantly reduces the calculation time and efforts involved in the SVM of a seven-level inverter; without any loss in the output voltage magnitude or increase in the total harmonic distortion content. A further simplified technique is also presented in this study, which significantly reduces the complexity and effort involved in the seven-level SVM. Simulation results for the seven-level CHB inverter using the proposed techniques are presented. The results are compared with results using sinusoidal pulse-width modulation (PWM) and third harmonic injection PWM to prove the validity of the proposed techniques. The proposed technique is perfectly general and can be applied to all types of multilevel inverters and extended to higher level inverters.

COMPARATIVE ANALYSIS OF MULTILEVEL INVERTER TOPOLOGIES FOR INDUCTION MOTOR DRIVE APPLICATIONS

Induction motors are widely used in industries, bec ause they are rugged, reliable and economical and h ence they are called as work horse power of industry. Induction motor drive requ ires suitable converters to get the required speed and torque without or negligible ripples. Multilevel inverters can do this job. But the conventional MLIs such as Diode Clamped MLIs r equires extra diodes in conjunction with the active switches, Flying capaci tor MLIs requires extra Capacitors and control also difficult if the levels increases and the Cascaded H-bridge MLIs requires separate dc sources which limits its use. This paper proposes a new type of multi level Inverter which converts the dc into ac using less n umber of switches when compared to conventional mul tilevel Inverters. The proposed Inverter uses only seven switches to get 1 3-level output voltage compared conventional cascad ed H-bridge uses twelve switches. The comparison between the conventional M LIs and proposed inverter is presented in this pape r. Finally the induction motor using proposed inverter with thirteen level i s simulated using Matlab/Simulink environment and t he corresponding results are presented in this paper.

Hysteresis Current Controller based Transformerless Split Inductor-NPC - MLI for Grid Connected PV- System

Non-conventional energy sources are breeding more and more widespread, mainly due to the fact of that they generate energy by keeping the spotless environment .The Multilevel inverters are highly being used in high-power medium voltage applications due to their better performance compared to two-level inverters. Among various types of multilevel inverters, neutral point clamped multi-level inverter (NPC-MLI) is suitable for a transformerless photovoltaic (PV) grid-connected system. Eliminating the leakage current is one of the most key issues for transformerless inverters Split Inductor MLI (SI-MLI) in grid-connected PV system applications, where the technical challenge is how to keep the system common-mode voltage constant to eradicate the leakage current & shoot-through possibility. The proposed elite Hysteresis Current Control (HCC) offers an admirable current control performance to SI-NPC-MLI. It is performed based on the error current value (Δi) and hysteresis Band value (h) produced between SI-MLI and grid. The proposed SI-NPC-MLI-HCC topology is guarantees for no shoot-through possibility and also maintains lower Voltage and current total harmonics distortion (THD). Test results verify the theoretical analysis and the validity of the system is verified through MATLAB/Simulink and the results are compared with conventional topologies

Design of Control System Used for Cells Cascaded Multilevel Converter Based on TMS320F2407

Because of its advantages, such as low input and output harmonics, high input power factor and efficiency, cells cascaded multi-level converter is widely used in the field of variable voltage and variable frequency control. Through the analysis of the multi-level converter’s structure and its PWM (Pulse Wavelength Modulation) control theory, a new structure of control system based on TMS320F2407 DSP was proposed. The control system structure and components of the central system and subsystem are given in this paper. SPWM control was achieved and multi-level PWM inverter output waveforms were produced. The results show that this type of multi-level inverter has superior performance.

Charge Balance Control Methods for a Class of Fundamental Frequency Modulated Asymmetric Cascaded Multilevel Inverters

Modulation strategies for multilevel inverters have typically focused on synthesizing a desired set of sinusoidal voltage waveforms using a fixed number of dc voltage sources. This makes the average power drawn from different dc voltage sources unequal and time varying. Therefore, the dc voltage sources are unregulated and require that corrective control action be incorporated. In this paper, first two new selections are proposed for determining the dc voltage sources values for asymmetric cascaded multilevel inverters. Then two modulation strategies are proposed for the dc power balancing of these types of multilevel inverters. Using the charge balance control methods, the power drawn from all of the dc sources are balanced except for the dc source used in the first H-bridge. The proposed control methods are validated by simulation and experimental results on a single-phase 21-level inverter.

DC링크 스위치를 갖는 단상 5레벨 인버터

본 논문에서는 기존의 멀티레벨 인버터와는 달리 DC링크단에 스위치를 설치함으로써 성능을 향상시킨 새로운 형태의 H-브리지 멀티레벨 인버터를 제안한다. 제안된 방식은 계통 연계형 단상 멀티레벨 인버터로서 기존의 단상인버터에 비하여 출력 전압 파형이 정현파에 가깝고, 고압 대용량 시스템용 멀티레벨 인버터로의 확장도 용이할 뿐만 아니라 직렬연결을 통하여 간단히 전압레벨을 확장할 수 있다는 장점을 갖는다. 동일한 5레벨의 경우 기존의 H-브리지 직렬형이나 NPC형 멀티레벨 인버터는 가제어 스위치가 8개 사용되는 반면에 제안한 멀티레벨 인버터는 가제어 스위치가 6개 사용되기 때문에 회로 구성이 간단하여 신뢰도가 높고 경제적인 구현이 가능하고 스위칭 손실이 줄어서 효율이 향상되는 특징이 있다. POD 변조기법을 기반으로 하여 반송파 신호 하나만을 사용하는 새로운 PWM 방법을 제시하였으며 DC링크 커패시터 전압의 균형을 위한 스위칭 시퀀스에 대해서도 검토하였다. 제안된 토폴로지의 타당성을 시뮬레이션과 실험을 통하여 확인하였다. This paper proposed a new multi-level inverter topology based on a H-bridge with two switches and two diodes connected to the DC-link. The output voltage of the proposed topology is quite closer to a sinusoidal waveform compared with a typical single phase inverter. The proposed multi-level inverter is applicable to a power conditioning system for renewable energy sources, and it can be also used as a building block of a cascaded multi-level inverter for a high voltage application. In case of conventional H-bridge type or NPC type multi-level inverter, 8 controllable switches are used to obtain a 5 level output voltage, but the proposed multi-level inverter requires only 6 controllable switches. Thus the circuit configuration is quite simple, reliable and cost-effective implementation is possible. The efficiency can be improved owing to the reduction of the switching loss. A new PWM method based on POD modulation is suggested which requires only one carrier signal. The switching sequence to make the capacitor voltage balanced is also considered. The feasibility is studied through simulation and experiment.

Improving the Power Quality by MLCI type DSTATCOM

paper proposes multilevel inverter type DSTATCOM for mitigating voltage sag at the load side. Cascaded H-bridge configuration for multilevel inverter with advanced phase shifted pulse width modulation technique is presented. Voltage sags are generated by faults the distribution feeder. First addresses with the three-phase 5-level cascaded multi level inverter and second addresses with the three-phase 7-level cascaded multi level inverter based on the shunt active power filter for mitigating the voltage disturbances. The proposed multilevel topology is simulated using MATLAB. The simulation results of the Five- level and Seven-level cascaded multilevel inverters are compared in different aspects.

Based Flying Capacitor Converter Wind Power Generator System

Direct drive wind power system need full-scale high power converter, such as flying capacitor multilevel converter. On the realization of high power electronic equipment, an important problem is that the working frequency of high power devices is too low to apply excellent modulated technique such as PWM. In large-power equipment, the switching frequency of power electronics devices is such low that good control performance can't be obtained with a single converter. In order to overcome this problem, Carrier phase-shifted SPWM technique (CPS-SPWM) has been researched. Reactive power compensation and harmonic reduction are two relevant research problems that exist in wind power system. With the advancement of modern power electronics technology in both circuits and devices, new and better solutions are being proposed and applied to solve these two problems. To compensate reactive power, a flying capacitor type multilevel inverters with a Carrier Phase-Shifted SPWM(CPS-SPWM) switching scheme is proposed. All this verified by simulation and experiment.

A general method used to conduct a harmonic analysis on carrier-based pulse width modulation inverters

A method used to determine the harmonic components of the output waveform of a pulse width modulation (PWM) inverter is presented. The method calculates the Fourier coefficients of individual positive and negative pulses of the output PWM waveform and adds them together using the principle of superposition to calculate the Fourier coefficients of the entire PWM output signal. This method allows direct calculation of harmonic magnitudes and angles without having to use linear approximations, look-up tables, or Bessel functions. The method presented is a general method that can easily be extended to various types of multilevel inverters and PWM schemes.

05/02513 A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system

05/02513 A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system

A new control scheme of a cascaded transformer type multilevel PWM inverter for a residential photovoltaic power conditioning system

From the viewpoint of high quality output voltage generation in a residential photovoltaic system, a multilevel inverter employing cascaded transformers can become a good substitute for the conventional pulse width modulated inverters and other multilevel counterparts. However, to obtain more sinusoidal output voltage waves, it should increase the number of switching devices and transformers resulting in a cost increase. To alleviate this problem, an efficient switching pattern is proposed and applied to a multilevel inverter equipped with two cascaded transformers, which have a series-connected secondary. Operational principle and analysis are illustrated focusing on a change of the switching pattern. High-performance of the proposed multilevel scheme embedded in a photovoltaic power conditioning system is verified by computer-aided simulations and experimental results.

A Unique Fault-Tolerant Design for Flying Capacitor Multilevel Inverter

This paper presents a unique design for flying capacitor type multilevel inverters with fault-tolerant features. When a single-switch fault per phase occurs, the new design can still provide the same number of converting levels by shorting the fault power semiconductors and reconfiguring the gate controls. The most attractive point of the proposed design is that it can undertake the single-switch fault per phase without sacrificing power converting quality. Future more, if multiple faults occur in different phases and each phase have only one fault switch, the proposed design can still conditionally provide consistent voltage converting levels. This paper will also discuss the capacitor balancing approach under fault-conditions, which is an essential part of controlling flying capacitor type multilevel inverters. Suggested fault diagnosing methods are also discussed in this paper. Computer simulation and lab results validate the proposed controls.