High Number Of Output Levels Research Articles

A new cascaded asymmetrical multilevel inverter based on switched dc voltage sources

Multilevel inverters are now becoming an important element for medium-voltage high-power applications. A low switch count multilevel inverters are currently attracting more attention due to its high efficiency, low cost, and easy control. This paper proposes a new single-phase cascade asymmetrical multilevel inverter topology based on switched dc voltage sources which is capable of achieving a higher number of output levels using fewer number of switches, driver circuits, and dc voltage sources. Other advantages include the inherent generation of negative voltage levels and lower voltage stress across the switches. Three different approaches in selecting the magnitude of the sources for the cascade connection has been included to produce a higher number of voltage levels. Furthermore, the power loss and fault-tolerant analysis of the proposed basic module has also been discussed. To set the benchmark of the proposed multilevel inverter structure, a comparison with several recently proposed topologies is carried out. The comparison has been carried out for the basic module, generalized structure, and cascade connection. The proposed topology gave improved parameters for all three categories. Fundamental switching frequency modulation technique is used to achieve high-quality output voltage waveforms with lower harmonic contents and reduced switching losses. Finally, the operation and performance of the proposed basic module and its cascade connection for two modules are presented together with experimental results in several steady-state and dynamic operating conditions.

An asymmetrical multilevel inverter with optimum number of components based on new basic structure for photovoltaic renewable energy system

In this paper, a new basic structure of asymmetrical multilevel inverter with optimum number of components for photovoltaic (PV) renewable energy system is proposed. The aim is to reduce the number of components required to achieve a high number of output levels compared to older topologies. The inverter configuration comprises of two basic units connected to a packed H-Bridge. Cascaded operation of the inverter configuration is feasible for higher level generation. The magnitudes of the DC sources are selected in binary sequence to maximize the number of output levels. Solar panels with proportional-integral (PI) controlled DC-DC converters are used as the DC sources. The switch modulations are achieved by pre-defined switching angles which are calculated to minimize total harmonic distortion (THD) in the AC output waveforms. This method is used instead of the classic pulse width modulation (PWM) technique to reduce the total switching loss and the required processing power in generating the switching signals. Compared to the conventional multilevel inverter topologies, the proposed inverter is a better choice in terms of the number of components. It also achieves a good balance between the number of components and total blocking voltage. Hence, its installation will require smaller space and cost. Another merit of the proposed topology is that it produces AC output with low THD at high efficiency. The efficacy of the proposed asymmetrical 31-level inverter topology is simulated using MATLAB/Simulink and is further verified through experimental analysis.

Real-Time Implementation of a 31-Level Asymmetrical Cascaded Multilevel Inverter for Dynamic Loads

Among the renewable energy applications, the most popular inverters are cascaded multilevel inverters. Irrespective of numerous benefits these inverters face reliability issues due to the presence of more circuit components in the design. This has been a critical challenge for researchers in designing inverters with enhanced reliability by reducing the total harmonic distortion (THD). This paper proposes a 31-level asymmetric cascaded multilevel inverter for renewable energy applications. The proposed topology produces waveforms consisting of the staircase with a high number of output levels with lesser components with low THD. The investigations on the feasibility and performance of MLI under steady-state, transient, and dynamic load disturbances. The results are validated from a 1.6kW system which provides the proposed inverter.

Multi-Input Switched-Capacitor Multilevel Inverter for High-Frequency AC Power Distribution

This paper proposes a switched-capacitor multilevel inverter for high-frequency ac power distribution systems. The proposed topology produces a staircase waveform with higher number of output levels employing fewer components compared to several existing switched-capacitor multilevel inverters in the literature. This topology is beneficial where asymmetric dc voltage sources are available, e.g., in case of renewable energy farms based ac microgrids and modern electric vehicles. Utilizing the available dc sources as inputs for a single inverter solves the major problem of connecting several inverters in parallel. Additionally, the need to stack voltage sources, like batteries or supercapacitors, in series which demand charge equalization algorithms, are eliminated as the voltage sources employed share a common ground. The inverter inherently solves the problem of capacitor voltage balancing as each capacitor is charged to the value equal to one of the input voltage every cycle. State analysis, losses, and the selection of capacitance are examined. Simulation and experimental results at different distribution frequencies, power levels, and output harmonic content are provided to demonstrate the feasibility of the proposed multilevel inverter topology.

New Extendable 15-Level Basic Unit for Multilevel Inverters

In this paper, a new basic 15-level inverter is proposed. By developing the proposed basic unit, a 71-level inverter and generally an [Formula: see text]-level inverter are proposed. Then, the proposed multilevel inverter is compared with several conventional multilevel inverters in design of minimum 15 levels and 71 levels at the output. By comparing these inverters, it is obtained that the proposed inverter is able to generate higher number of output levels by using lower number of DC voltage sources and power electronic devices that lead to decreased complexity, installation space and total cost of the inverter. Finally, the correct performance of the proposed inverter is reconfirmed through the simulation and experimental results of a 15-level inverter.

Cascaded Multilevel Inverter using Single Voltage Source Topology

Multilevel inverter has become more popular and utilized in various applications like industries, home, and electric vehicles etc. This paper presents a cascaded H-bridge multilevel inverter with reduced DC source. Generally, each phase of the multilevel inverter requires n number of DC sources. In this paper we have proposed a multilevel topology which requires only one DC source for all the three phases and other sources are replaced by ultra capacitors. An adaptive PI controller is introduced for automatically maintains the voltage level of capacitor and we use higher number of output levels, so that the output produced by each inverter topology is equal to sinusoidal results which increase the quality of power. Simulation results shows that the proposed multilevel inverter with one DC source reduces the voltage sources from seven to one. Comparison between both the cascaded multilevel inverter using DC source and ultracapacitor source has been studied and it shows that the overall performance of ultracapacitor source is better than that of DC source.

Creative design of symmetric multilevel converter to enhance the circuit's performance

In this study, a new symmetric multilevel converter is introduced which is commonly suitable for medium-voltage applications and where higher number of output levels is required. The proposed inverter can generate all levels at the output associated with a lower number of circuit devices including switches and related gate driver circuits for each switch compared with the conventional symmetric cascaded converter, semi-cascaded converter and the recently introduced inverters. Owing to the lower number of circuit devices, the total cost and the installation area are reduced. Another advantage of the proposed inverter over the mentioned topologies is the lower number of on-state switches which causes a reduction on power losses. Simulation and experimental results are presented to validate the practicality of the proposed multilevel structure.

English

This paper presents a new control technique to regulate the capacitor voltage in cascaded multilevel inverters. Without requiring transformers, the scheme proposed here allows the use of a single dc power source with the remaining n − 1 dc sources being capacitors, which can achieve an effective role on harmonic elimination while generating the ideal output voltage. This paper focuses mainly to achieve an effective capacitor voltage regulation, and the effect of power factor on capacitor voltage regulation with the Phase shift modulation. The main advantages of this paper are to eliminate the harmonics, high-quality output power due to its high number of output levels. It shows hope to reduce the voltage ripple of the capacitors, which leads to higher power conversion efficiency with equal power distribution, reduces the initial cost, and complexity hence it is apt for industrial applications. Simulation work is done using the MATLAB software and experimental results have been presented to validate the theory.

IMPLEMENTATION OF MULTI TRANSFORMER CELL INVERTER WITH REDUCED SWITCHES IN LAST CELL

This paper proposes an isolated multi transformer cell inverter employing several transformer cells. Some of the cells contain two unidirectional switches that generate two voltage levels and only last cell has five switches that provide five voltage levels. The proposed inverter configuration reduces a number of switches compared with both traditional cascaded transformer multilevel inverter and other multi transformer inverters including six switches in last cell. Also, a prototype has been implemented using DSP-based processor provides a high number of output levels in symmetric and asymmetric states. The operation and performance of the suggested inverter has been proved by simulation result and experimental results.

A 7-Level Single DC Source Cascaded H-Bridge Multilevel Inverter with a Modified DTC Scheme for Induction Motor-Based Electric Vehicle Propulsion

This paper presents a new hybrid cascaded H-bridge multilevel inverter motor drive DTC scheme for electric vehicles where each phase of the inverter can be implemented using a single DC source. Traditionally, each phase of the inverter requires DC source for output voltage levels. In this paper, a scheme is proposed that allows the use of a single DC source as the first DC source which would be available from batteries or fuel cells, with the remaining () DC sources being capacitors. This scheme can simultaneously maintain the capacitors of DC voltage level and produce a nearly sinusoidal output voltage due to its high number of output levels. In this context, high performances and efficient torque and flux control are obtained, enabling a DTC solution for hybrid multilevel inverter powered induction motor drives intended for electric vehicle propulsion. Simulations and experiments show that the proposed multilevel inverter and control scheme are effective and very attractive for embedded systems such as automotive applications.

Performance Analysis of Seven Level Multilevel Inverter Using Renewable Energy Systems

With the increasing concerns on energy issues, the development of renewable energy sources is becoming more and more attractive. A new kind of wind-PV hybrid generated system that comprises of wind and photovoltaic generation subsystems as input to a cascaded H-bridge multilevel inverter is developed in this paper. In conventional methods the inverter with solar and wind energy sources are used. In this method a seven level multilevel inverter with wind–PV hybrid generation system as input are proposed for application to remote and isolated areas. The wind and the solar light are captured in greatest degree, as well as the multilevel inverter using pulse width modulation technique is adopted. The objectives of this hybrid system are, to satisfy the load power demand and, presence of high number of output levels in inverter to maintain the dc output voltage level of the inverter to produce a nearly sinusoidal output. This reduces harmonics in inverter output voltage. This paper discusses about the control of seven-level H-bridge cascaded multilevel inverter with Fast Fourier Transform analysis in inverter output voltage through simulation. The simulated wind-PV system consists of an AC-to-DC boost converter, aDC-to-AC nverter, a photovoltaic module, and wind module. Its shown by the simulations that a multilevel inverter utilizing renewable resource has lower Total Harmonics Distortion in output voltage. In this paper comparison of conventional inverter and proposed seven level cascaded H-bridge multilevel inverter using solar and wind energy sources are presented.

Hybrid Multicell Converter: Topology and Modulation

Multilevel converters have become an interesting alternative for medium- and high-voltage drives over the last decade. Among the existing alternatives, multicell structures offer advantages due to their modularity and scalability. This paper presents experimental results of a recently introduced multilevel topology. The converter is based on the mixture of the two most popular multicell topologies, namely, flying capacitor and cascaded multicell inverter. The new cell provides a high number of output levels, a low number of components, high modularity, and low losses. The results presented in this paper confirm that this new medium-voltage inverter topology is able to reach high-quality output voltages, allowing further advances in modulation techniques and other issues.

Fundamental Frequency Switching Strategies of a Seven-Level Hybrid Cascaded H-Bridge Multilevel Inverter

This paper presents a cascaded H-bridge multilevel inverter that can be implemented using only a single dc power source and capacitors. Standard cascaded multilevel inverters require <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> dc sources for 2 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> + 1 levels. Without requiring transformers, the scheme proposed here allows the use of a single dc power source (e.g., a battery or a fuel cell stack) with the remaining <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> -1 dc sources being capacitors, which is referred to as hybrid cascaded H-bridge multilevel inverter (HCMLI) in this paper. It is shown that the inverter can simultaneously maintain the dc voltage level of the capacitors and choose a fundamental frequency switching pattern to produce a nearly sinusoidal output. HCMLI using only a single dc source for each phase is promising for high-power motor drive applications as it significantly decreases the number of required dc power supplies, provides high-quality output power due to its high number of output levels, and results in high conversion efficiency and low thermal stress as it uses a fundamental frequency switching scheme. This paper mainly discusses control of seven-level HCMLI with fundamental frequency switching control and how its modulation index range can be extended using triplen harmonic compensation.

A Predictive Control With Flying Capacitor Balancing of a Multicell Active Power Filter

Unlike traditional inverters, multicell inverters have the following advantages: lower switching frequency, high number of output levels, and less voltage constraints on the insulated-gate bipolar transistors. Significant performances are provided with this structure which is constituted with flying capacitors. This paper deals with a predictive and direct control applied to the multicell inverter for an original application of this converter: a three-phase active filter. To take advantage of the capabilities of the multicell converter in terms of redundant control states, a voltage control method of flying capacitor is added, based on the use of a switching table. Flying capacitor voltages are kept on a fixed interval, and precise voltage sensors are not necessary. The association of predictive control and voltage balancing increases considerably the bandwidth of the active filter.