Asymmetrical Multilevel Inverter Research Articles

Cascaded Envelope Type Asymmetric Multilevel Inverter with Binary configuration

Cascaded Envelope Type Asymmetric Multilevel Inverter with Binary configuration

An improved asymmetrical multilevel inverter topology with reduced semiconductor device count

An improved asymmetrical multilevel inverter topology with reduced semiconductor device count

Design and analysis of a novel quasi Z source based asymmetric multilevel inverter for PV applications

A novel Quasi Z source (QZS) based Asymmetric Multilevel Inverter for Photovoltaic application is proposed in this paper. It consists of an Impedance source-based dc-dc converter and Asymmetric Multilevel Inverter (AMLI). QZS network can buck/boost the input DC voltage eliminating separate DC-DC boost converter. MLI topology with reduced switches and DC input provide high quality output with large levels. DC input magnitude of the inverter is based on an algorithm. The system ensures high voltage gain, low switching stress, lessened gate circuitry, high reliability and better harmonic profile. Low THD values ensures reduced filter size and hence cost. The theoretical concepts and parameter design of the proposed topology is illustrated in detail. The performance analysis is verified using Matlab/Simulink environment.

Power Quality Enhancement Employing Evolutionary Algorithm based 17 Level Asymmetrical Multilevel Inverter

Power Quality Enhancement Employing Evolutionary Algorithm based 17 Level Asymmetrical Multilevel Inverter

Performance Analysis of a Half Bridge Cell Based Asymmetrical Multilevel Inverter Topology with Minimum Components

Background: In Multilevel Inverters (MLI) as the number of level increases, there is a proportionate increase in the count of the semiconductor devices that are employed. Methods: This paper deals with an asymmetrical cascaded H-bridge inverter topology with half bridge cells to produce seven level output voltage waveform. Nearest Level Control (NLM) technique is used to produce the switching pulses. The operating principle of the proposed MLI and its performance abilities is verified through MATLAB/Simulink and a prototype is developed to provide the experimental results. Results: Total Harmonic Distortion (THD) is computed for proposed MLI for different types of loads in simulation environment as well as in the developed hardware prototype. Comparison between the proposed MLI and recent topologies demonstrates the advantageous features. Conclusion: The simulation and hardware results confirm the suitability of the proposed seven level MLI as the total component count, and the requirement of DC sources reduces considerably.

A Novel Higher Level Symmetrical and Asymmetrical Multilevel Inverter for Solar Energy Environment

ABSTRACT In this paper, a higher level symmetrical and asymmetrical multilevel inverter (MLI) with reduced device count is proposed for renewable energy systems. Multilevel inverters are recently gaining importance in renewable energy systems and other DC to AC conversion applications due to reducing voltage stress, low total harmonic distortion (THD) and high-quality output as compared to classical inverters. This paper present a basic cell unit of reduced device count (RDC) MLI with six switching devices is proposed. The topology has advantages of reduced device count over existing topologies for the same number of output levels, thus improving operating efficiency and reliability. Upon cascading two such basic cells with 12 devices synthesizes a 49 level output with an estimated THD of 1.63%. The other advantages accrued due to reduced device count are a reduction in switch driver circuits, less number of required dc voltage sources, less installation space and reduction in cost. The major benefit of the proposed topology is that it can deliver power from an asymmetrical source to load even under sudden variation in environmental conditions. The proposed MLI topology is simulated in MATLAB/Simulink environment and a laboratory prototype is developed and tested in the lab. The control paradigm is developed as the Simulink model, which is interfaced with dSPACE DS-1104 for generating control pulses to drive switches of proposed MLI topology. The experimental results validate the concept and paradigm of the proposed MLI topology.

Asymmetrical Multilevel Inverter with Low THD

Asymmetrical Multilevel Inverter with Low THD

A New Asymmetrical MLI with Reduced Switch Count for a Three Phase Induction Motor

This work explores a novel multilevel inverter (MLI) topology to minimize the number of power switches in the passage of current to accomplish each level of the output voltage. The unequal magnitudes of the dc voltage sources in attempt to realize higher levels of the output voltage bring in the asymmetrical nature of operation. It involves a series parallel switched configuration with bidirectional switches to avert the flow of circulating current in between the two H - bridges in each phase of the MLI. The effort incites to use the theory of a new Pulse Width Modulation (PWM) strategy for mitigating the higher frequency components of the voltage applied to the stator. It imbibes the Phase Disposition (PD) principles in the modulating strategy for arriving at the sinusoidal shape for the output voltage . Total Harmonic Distortion (THD) indexed by lower values for the output voltage over the traditional firing scheme serves to be the highlight for the MLI in acclaiming its place in the inverter world. The results obtained through MATLAB based simulation over a range of modulation indices. The performance measured in terms of the THD claims its suitability for use in Induction Motor (IM) drives.

Asymmetric diode-clamped multi-level inverter based renewable power generation system

ABSTRACT In this paper, a grid-connected power conversion topology is developed to convert a DC power from the renewable energy into a high-quality AC power. This grid-connected power conversion topology consists of an asymmetric diode-clamped multi-level inverter (DCT-MLI) and a dual-output DC-DC power converter. The asymmetric DCT-MLI includes two diode-clamped arms, two DC capacitors, and a filter inductor. The novelty of proposed asymmetric DCT-MLI is that the voltages of the two DC capacitors are in a multiple relationship. As a result, the asymmetric DCT-MLI will generate an AC voltage with more voltage levels by the power circuit similar to the symmetric DCT-MLI, and the capacity of filter inductor is further reduced. The dual-output DC-DC power converter combines a boost converter and a charge pump circuit to generate two DC voltages in a multiple relationship to supply the asymmetric DCT-MLI. The salient feature is that only a power electronic switch is used in the dual-output DC-DC power converter such that the control circuit is simplified. A hardware prototype is set up to verify the performances of the proposed grid-connected power conversion topology.

Compact symmetrical and asymmetrical multilevel inverter with reduced switches

The need for a multilevel inverter for medium voltage high power applications has attracted researchers and industrialists to focus on the design of hybrid multilevel inverter topology that uses a considerably lesser number of switches and sources. This paper proposes a symmetrical and asymmetrical multilevel inverter with reduced switches. The novelty of the proposed arrangement is lesser ON state switches and reduced total blocking voltages across switches. The optional series connection of the basic unit increases output voltage levels with high-quality output voltage. There are multiple algorithms proposed by varying the DC sources to generate different voltage levels using the same configuration. A suitable comparison is presented with conventional topologies and inverters of the same structure. The proposed topology is simulated and validated on hardware setup for both 7 levels, symmetrical and 15 levels, asymmetrical is performed using dSPACE 1104 controller. The impact of change in modulation index on the power and efficiency of the proposed 15-level inverter is validated under laboratory setup. The feasibility of this topology favors renewable energy integration applications.

A Novel Multilevel Inverter with Reduced Number of Switches Using Simplified PWM Technique

Multilevel inverter (MLI) topologies greatly sustained the emergence of modish power-electronic device as an expressive substitute of traditional two-level inverters in the area of medium-voltage high-power energy conversion schemes. It recommends the most outstanding solutions for high-power applications particularly in distributed generation schemes and plays a key role for establishment of novel MLI structures with fewer switching components. This paper proposes the novel 7-level asymmetric MLI topology and administered by both fundamental frequency-based pulse-width modulation (PWM) scheme and advanced multi-carrier PWM scheme. The proposed asymmetric 7-level smart MLI topology offers low switching elements, low gate drive circuits, low cost, minimum space requirement, low-voltage dv/dt switch stress, low switching loss and high efficiency over the traditional topologies. The critical evaluation of proposed 7-level asymmetric MLI performance is verified by MATLAB/Simulink platform and validated through experimental prototype; results are illustrated with proper comparisons.

Operation and Control of a Grid-Connected Asymmetrical Cascaded Multilevel Inverter

This article presented a new structure for the grid-connected multilevel inverters (MLIs) circuit with the ability of the cascaded connection. The proposed inverter is capable of transformerless connection of distributed generation resources to the network. The control system manages the power injection to the grid by minimizing the output current harmonics as well as exchanging reactive power with the grid. The self-balancing state of the capacitors' voltage is occurred only with the switching technique without any measurement sensors. An enhanced phase-locked loop (EPLL) and a proportional resonant (PR) controller are employed for the proposed asymmetric MLI. An important feature of the proposed inverter is the ability of stable performance and fast dynamics of the control system to the changes of the reference values. Simulation and experimental results are presented in order to validate the performance accuracy of the proposed MLI.

27-Level asymmetric multilevel inverter for photovoltaic energy conversion

This paper presents a novel structure to inject the electric energy from photovoltaic modules to the grid based on a 27-level asymmetric multilevel inverter. This work proposes mixing existing approaches based on string and central inverters to implement a hybrid structure that generates highly sinusoidal waveforms. Indeed, the presented structure allows for a staircase AC voltage waveform with a low level of harmonic distortion, which is a key feature for photovoltaic energy conversion. The proposal is supported with theoretical analyses that include system modeling and a suitable control strategy to track both the active and reactive power. A low power proof-of-concept prototype was built to validate the properness of the proposal. Several dynamic tests were performed, such as severe load impacts, partial shading and fault ride-through capability.

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.

Performance evaluation of a reduced components count single‐phase asymmetric multilevel inverter with low standing voltage

Performance evaluation of a reduced components count single‐phase asymmetric multilevel inverter with low standing voltage

FPA Optimized Selective Harmonic Elimination in Symmetric–Asymmetric Reduced Switch Cascaded Multilevel Inverter

Symmetrical and asymmetrical multilevel inverters (MLIs) have demonstrated its usefulness in a wide range of applications. This is accomplished due to the ongoing improvement by reducing the converter size and enhancement in the voltage quality. In this article, a generalized cascaded MLI structure is developed, which can operate in both symmetric and asymmetric modes. Comparative assessment in terms of the number of components and voltage stress warrants the design superiority. A new selective harmonic elimination (SHE) control using flower pollination algorithm (FPA) is investigated for the developed asymmetrical MLI. The salient features of the FPA such as less burdensome compilation and ability tos single-stage local and global search ascertain the elimination of the targeted harmonics through optimum angles computation. Moreover, the competence of the FPA is verified by comparing it with well-known SHE algorithms. Simulation analysis is carried out in MATLAB/Simulink environment, which validates the workability of the developed system. Experimental tests using fundamental and high switching frequency control techniques are further conducted under a dynamic environment to demonstrate the efficacy of the proposed methodology.

Novel harmonic elimination strategy based on Multi-Objective Grey Wolf Optimizer to ameliorate voltage quality of odd-nary multi-level structure

In this paper, a novel Asymmetrical Multi-Level Inverter (AMLI) is suggested to solve the voltage quality problem. The suggested AMLI has been constructed based on series connection of sub-AMLIs to create a high-step quasi-sinusoidal voltage with considering few semiconductor switches. The ladder capacitors of sub-AMLI have been clamped to the H-bridge structure via several bi-directional switches. Based on an innovative geometric progression for DC power supplies of AMLI, it can operate as so-called odd-nary AMLI. It has effectually created a quasi-sinusoidal with high steps i.e., low Total Harmonic Distortion (THD) with respect to low number of switches. The performance of suggested AMLI has been thoroughly compared with other inventive asymmetrical and symmetrical multilevel inverters. Following that, scission-style harmonic elimination based on Pulse Width Modulation (PWM) is introduced to enhance voltage quality of AMLI. Three prominent criterions related to voltage quality i.e., desired fundamental component, elimination of third harmonic and reduction of THD have been assigned as objective functions of optimization problem. Considering the multi-objective nature of the optimization problem, non-dominated sorting Multi-Objective Grey Wolf Optimizer (MOGWO) has been implemented to solve the optimization problem, and then compared with Non-dominated Sorting Genetic Algorithm II (NSGA-II). To sum up, the relevant analytical studies along with both the simulation and experimental results have transparently validated the performance of suggested AMLI. Also, the voltage quality problem using MOGWO-based scission-style harmonic elimination strategy has been well approved.

Modelling and Simulation of an Asymmetrical Modular Multilevel Inverter with Less Number of Components

ABSTRACT This paper presents a modified topology for asymmetric modular multilevel inverter as a fundamental block. It consists of eight switches (including six bidirectional-conducting unidirectional-blocking switches and two bidirectional-conducting bidirectional-blocking switches) and four DC sources with unequal magnitudes, which generates 13-level output voltage. The proposed topology offers special features such as reduced number of switches, isolated DC sources, economical and less complexity with modular structure as compared to other contemporary topologies. Moreover, significant reduction in switch voltage can be achieved. The comparative study of proposed topologies with the conventional and recent topologies have been presented in terms of power switches, gate drivers, isolated DC voltage sources and total standing voltage on the switches. A multicarrier-based sinusoidal pulse width modulation scheme is adopted for generating the gate pulses using real-time simulation with dSPACE DS 1104. The proposed topology offers a fewer number of ON-state switches which lead to the reduction in power loss. The feasibility of proposed multilevel inverter, the simulation and experimental results are analysed under steady state and dynamic states.

Research on Modified Hybrid Frequency Modulation Technology of Type-III Asymmetric CHB Multilevel Inverters

Asymmetric Cascaded H-bridge (ACHB) level inverters can output more voltage waveforms with fewer cascaded units while ensuring the quality of output voltage waveforms, so they have attracted more and more attention. Taking the topology of Type-III asymmetric CHB multilevel inverters as the research object, a Modified Hybrid Frequency Pulse Width Modulation (MHF-PWM) strategy is proposed in this paper. This modulation strategy overcomes the local overshoot of low-voltage unit in the presence of traditional Hybrid Frequency Pulse Width Modulation (HF-PWM), thus completely eliminating the low frequency harmonics in the output voltage waveform of Type-III ACHB nine-level inverters, and the Total Harmonic Distortion (THD) of output line voltage of the modulation strategy is lower than that of PS-PWM strategy in the whole modulation degree, which effectively improves the quality waveform of the output line voltage. At the same time, the strategy can also improve the problems of current backflow and energy feedback caused by the high-voltage unit pouring current to the low-voltage unit, thereby reducing the imbalance of the output power of the high-voltage and low-voltage units. Finally, the Matlab/Simulink simulation model and experimental platform are established to verify the validity and practicality of the modulation strategy.

A novel PV fed asymmetric multilevel inverter with reduced THD for a grid‐connected system

A novel PV fed asymmetric multilevel inverter with reduced THD for a grid‐connected system