Multilevel Voltage Source Inverter Research Articles

A new multilevel voltage source inverter configuration with minimum number of circuit elements

An advanced configuration for multilevel voltage source converters is proposed. The proposed converter is able to apply asymmetrical DC sources. The configuration of the proposed inverter is well designed in order to provide the maximum number of voltage levels in output terminals using lower number of circuit devices. The authority of the proposed inverter versus the conventional H-bridge cascaded inverter and the most recently introduced ones, is verified with a provided comparison study. The proposed inverter is able to generate the desired voltage levels using a lower number of circuit devices including power semi-conductor switches, IGBTs, diodes, related gate driver circuits of switches and DC voltage sources. As a result, the total cost and installation area are considerably reduced and the control scheme gets simpler. To confirm the feasibility of the proposed multilevel structure, both the simulation and experimental results are provided and compared which shows good agreements.

Mathematical Derivation of Switching Angles of Multilevel Voltage Source Inverter based on Alternative Phase Opposition Disposition (APOD)

Modular structured multilevel inverter is very useful for electrical application especially in high voltage and high power applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a newmathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Alternative Phase opposition disposition (APOD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result.

Optimal configuration for cascaded voltage source multilevel inverter based on series connection sub-multilevel inverter

AbstractIn this study, a new configuration for cascaded voltage source multilevel inverter based on series connection of improved sub multilevel inverter module is presented. An algorithm is proposed to determine the magnitude of dc voltage source to generate a large number of output voltage levels with reduced device count. It is especially suitable for of renewable energy applications. To demonstrate the advantages of proposed configuration, the comparative analysis provided with other multilevel configurations in term of a number of switches, gate driver circuits and blocking voltage on switches. The comparison results confirm that the proposed configuration offers less number of components. Moreover, the magnitude of blocking voltage on switches and losses are lower in the proposed configuration. Multicarrier based sinusoidal pulse width modulation scheme is adopted for generating switching signals using dSPACE real-time controller. To validate the performance of proposed topology under steady state a...

High-performance multicell series inverter-fed induction motor drive

The multilevel voltage-source inverter (VSI) topology of the series multicell converter developed in recent years has led to improved converter performance in terms of power density and efficiency. This converter reduces the voltage constraints between all cells, which results in a lower transmission losses, high switching frequencies and the improvement of the output voltage waveforms. This paper proposes an improved topology of the series multicell inverter which minimizes harmonics, reduces torque ripples and losses in a variable-speed induction motor drive. The flying capacitor multilevel inverter topology based on the classical and modified phase shift pulse width modulation (PSPWM, MPSPWM) techniques are applied in this paper to minimize harmonic distortion at the inverter output. Simulation results are presented for a 2-kW induction motor drive and the results obtained demonstrate reduced harmonics, improved transient responses and reference tracking performance of the voltage in the induction motor and consequently reduced torque ripples.

A 17-Level Switched Voltage Source Multi-Level Inverter Topology with Low-Switching Frequency Control

Higher number of output voltage level has always been preferred in multi-level inverter configurations due to its associated advantages: low output waves’ distortion, low-value filter components, etc. Series expansion to desired number of output voltage level is possible in conventional multi-level inverter topologies, but at increased power circuit component count and complexity. This article proposes a 17-level switched voltage source multi-level inverter topology that reduces the component count in 3-Φ multi-level inverter configurations. The switching sequences ensure minimum number of switching transitions among the constituted power switches. A comparison between the proposed inverter configuration, classical cascade H-bridge inverter, and some of the recent developed multi-level inverter topologies shows reduction in the power circuit devices in the proposed inverter. Appropriate modulation scheme is employed for low switching frequency operation of the proposed inverter topology. Implementation of optimum switching angles on the proposed inverter topology results in low total harmonic distortion values in the phase and line voltage waveforms. Simulation and experimental verifications are carried out on the proposed inverter topology for a resistive-inductive load; corresponding results are presented.

Quasi-Z-Source Inverter With a T-Type Converter in Normal and Failure Mode

This paper presents a three-phase multilevel quasi-Z-source inverter (qZSI) topology operating in normal and fault-tolerant operation mode. This structure is composed by two symmetrical quasi-Z-source networks and a three-phase T-type inverter. Besides the intrinsic advantages of multilevel voltage source inverters, the proposed structure is also characterized by their semiconductor fault tolerance capability. This feature is only obtained through changes on the modulation scheme after the semiconductor fault and does not require additional extra-phase legs or collective switching states. In certain fault types, the reduction of the output power capacity will be compensated by the boost characteristic of the qZSI. The fault-tolerant behavior of the proposed topology is demonstrated by several simulation results of the converter in normal and fault condition. To validate the characteristics of this multilevel qZSI, an experimental prototype was also built to experimentally confirm the results.

Reduction of Circuit Devices in Developed Symmetrical/Asymmetrical Multilevel Converters

In this paper, a developed configuration for multilevel voltage source inverters (MVSIs) is proposed. The proposed topology can be used as symmetric and asymmetric inverters. In asymmetric mode, DC source magnitudes are defined in a way that the number of output levels gets more than the case when the symmetrical DC sources are applied. In this regard, to calculate the required magnitudes of DC voltage sources several different solutions are proposed. In multilevel inverters, the overall costs, circuit size and installation area, complexity of control scheme and reliability are directly dependent on the number of circuit devices needed. The provided comparison study among suggested inverter in all defined solutions, cascaded H-bridge (CHB) and recently proposed converters, validates that the proposed inverter uses reduced number of circuit devices. The given simulation results confirm the feasibility of the proposed modular structure. Also, to approve the practicability of the proposed inverter, a prototype of the proposed topology has been implemented. Finally, simulation and experimental results are compared with each other and the provided comparison shows that the obtained results are in good agreements.

A New Topology for a Single Phase Multilevel Voltage Source Inverter with Reduced Number of Components

Multilevel inverters have gained much attention for its operation involving applications ranging values of high power rating. This paper proposes a switching topology for asymmetric multilevel inverter utilizing less number of power electronics components. When the number of the output level increases, it requires more switching states and eventually the number of switching components. The increased number of switches results in higher switching losses which may lead to power loss, and reduction of efficiency of the overall conversion system. The salient feature of this proposed topology is that the module can be used as a sub multiple level structure and can be extended for any number of level with minimal increase in the switching components.

Influence of crossover methods used by genetic algorithm-based heuristic to solve the selective harmonic equations (SHE) in multi-level voltage source inverter

Genetic Algorithms (GA) has always done justice to the art of optimization. One such endeavor has been made in employing the roots of GA in a most proficient way to determine the switching moments of a cascaded H-bridge seven level inverter with equal DC sources. Evolutionary techniques have proved themselves efficient to solve such an obscurity. GA is one of the methods to achieve the objective through biological mimicking. The extraordinary property of crossover is extracted using Random 3-Point Neighbourhood Crossover (RPNC) and Multi Midpoint Selective Bit Neighbourhood crossover (MMSBNC). This paper deals with solving of the selective harmonic equations (SHE) using binary coded GA specific to knowledge based neighbourhood multipoint crossover technique. This is directly related to the switching moments of the multilevel inverter under consideration. Although the previous root-finding techniques such as N-R or resultant like methods endeavor the same, the latter offers faster convergence, better program reliability and wide range of solutions. With an acute algorithm developed in Turbo C, the switching moments are calculated offline. The simulation results closely agree with the hardware results.

An Innovative Scheme of Symmetric Multilevel Voltage Source Inverter With Lower Number of Circuit Devices

In this paper, an advanced configuration for a symmetric multilevel voltage source inverter is proposed. The authority of the proposed inverter versus the conventional cascaded H-bridge inverter and those most recently introduced is verified with provided comparisons. The proposed inverter is able to generate the desired voltage levels using a lower number of circuit devices, including power semiconductor switches and related gate driver circuits of switches. As a result, the total cost is considerably reduced, and the control scheme gets simpler. Moreover, the reduced amount of on-state switches in the suggested configuration decreases voltage drops. Furthermore, power losses are diminished. The given simulation results confirm the feasibility of the proposed configuration. To approve the practicability of the proposed inverter, a prototype of the proposed topology has been implemented. Finally, simulation and experimental results are compared, and the provided comparison shows that the obtained results are in good agreement.

Design and implementation of 15‐level cascaded multi‐level voltage source inverter with harmonics elimination pulse‐width modulation using differential evolution method

This study describes the application of a soft computing method - known as differential evolution (DE) to implement the harmonics elimination pulse-width modulation (HEPWM) for a 15-level, multi-level voltage source inverter (MVSI). The main feature of this technique is the wide range of fundamental output voltage that can be achieved, while maintaining a very low total harmonics distortion (below 6%). The fundamental voltage can be controlled very precisely (very small step size) and the trajectories of the HEPWM angles are continuous over the whole range of modulation index - making it very suitable for utility and variable speed drives application. The study details the procedures to obtain the HEPWM angles trajectories, which include the formulation of objective functions, appropriate selection of the DE evolutionary parameters and stopping criterions. The viability of the proposed method is simulated using MATLAB/Simulink and verified by a three-phase, cascaded-type MVSI test rig. Experimentally, The HEPWM waveforms are implemented using the Altera field programmable gate array, whereas the 15-level MVSI is built using metal-oxide semiconductor field effect transistor H-bridge. Selected results are presented; the simulation and hardware results are found to be in very close agreement with the theoretical predictions.

Mathematical Formulation of Multilevel Voltage Source Inverter Switching Instants

Modular structured multilevel inverter is very useful for electrical application especially in high power and high voltage applications. The main function of this multilevel inverter is to produce multilevel AC output voltage from several separate DC sources. This project is to derive a new mathematical formulation of multilevel voltage source inverter switching instants. The proposed method for this project is based on the sinusoidal natural sampling PWM (SPWM) by comparing several modified modulation signal with a triangular carrier signal. This resulting intersection points between this modulation and carrier signal become the switching instants of the PWM pulses. Derivation also based on Phase opposition disposition (POD). A cascaded multilevel inverter is selected as a topology for this project due to major advantages compare with other topology. The derived formula is analyzed by using MATLAB simulation software. It is found that the results that use the derived formula are almost identical to simulation result.

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.

Switching Voltage Modeling and PWM Control in Multilevel Neutral-Point-Clamped Inverter under DC Voltage Imbalance

This paper presents a novel switching voltage model and an offset-based pulse width modulation (PWM) scheme for multilevel inverters with unbalanced DC sources. The switching voltage model under a DC voltage imbalance will be formulated in general form for multilevel neutral-point-clamped topologies. Analysis of the reference switching voltages from active and non-active switching voltage components in abc coordinates can enable voltage implementation for an unbalanced DC-source condition. Offset voltage is introduced as an indispensable variable in the switching voltage model for multilevel voltage-source inverters. The PWM performance is controlled through the design of two offset components in a subsequence. One main offset may refer to the common mode voltage, and the other offset restricts its effect on the quality of PWM control in related DC levels. The PWM quality can be improved as the switching loss is reduced in a discontinuous PWM mode by setting the local offset, which is related to the load currents. The validity of the proposed algorithm is verified by experimental results.

Multilevel voltage source inverter with optimised usage of bidirectional switches

This study presents a multilevel voltage source inverter that has been designed to reduce circuit complexity by optimising the use of bidirectional switches. The proposed inverter is built by adding an auxiliary circuit comprising an arrangement of bidirectional switches to the three-phase, six-switch, full-bridge configuration. Several bidirectional switches are made to function in the optimised mode in which their operations are divided among the three phases. The presence of the optimised mode considerably reduces the number of power switches as the number of levels in the line-to-line voltage waveform increases. A novel modulation scheme based on space vector concept with virtual vectors utilisation has also been developed. A detailed study of the proposed inverter is described through the example of a five-level structure. The performance of the proposed inverter is analysed through MATLAB/SIMULINK simulation and verified via the practical tests conducted on a laboratory prototype with a DSP-based controller. A comparison is also made against classical multilevel inverters to complete the analysis.

Performance evaluation of photovoltaic grid connected shunt active power filter

This paper describes the performance of photovoltaic (PV) Generator connected to a grid with shunt active power filter (APF). The PV system utilises perturb and observe maximum power point tracking algorithm to extract maximum power from the sun and injecting the same to the grid. Shunt active power filter (SAPF) is used to reduce the harmonics present in the photovoltaic generation based on PQ modified theory. The control algorithm and regulation of voltage source multilevel inverter (MLI) functioning as a harmonic filter uses the pulse width modulation (PWM) technique. PQ theory identifies the currents of references, which provides possibility for controlling the currents injected at the point of common coupling (PCC). Regulator is used to determine DC link voltage of PWM control inverter. Two switching schemes namely; Sinusoidal PWM and pseudo random carrier PWM have been applied and the performance results of both techniques have been studied. The simulations have been completed using MATLAB/Simulink software and the result shows that improvement in power quality and power factor for the pseudo random PWM technique is quite large than sinusoidal PWM.

Space‐vector pulse‐width modulation algorithm for multilevel voltage source inverters based on matrix transformation and including operation in the over‐modulation region

Multilevel voltage source inverters are most promising when employed in high-power and high-voltage applications. As the number of inverter levels increases, the algorithm of space-vector pulse-width modulation (SVPWM) becomes increasingly complex. Based on the intrinsic relationship between SVPWM algorithms for 2-level inverters and those for arbitrary-level inverters, here a novel SVPWM algorithm is proposed for an arbitrary-level inverter. Considering that the nearest three vectors are used to synthesise the reference vector, the on-time of the voltage vector for an arbitrary-level inverter can be acquired from that for a 2-level inverter via the use of a linear transformation. This algorithm is verified through simulation and experiments, with the latter proving that the proposed algorithm can meet the real-time requirements of multilevel inverters.

Application of differential evolution for cascaded multilevel VSI with harmonics elimination PWM switching

Harmonic elimination pulse width modulation (HEPWM) method has been widely applied to multilevel voltage source inverter (MVSI) to remove low frequency harmonics from its output voltage. However, the computation of the HEPWM switching angles for MVSI is very challenging due to several constraints, namely angle sequencing, very tight angular spacing and the numerous possibilities of angles distribution ratio. Realizing the potential of Differential Evolution (DE) to handle complex problems, this work proposes its application to solve the HEPWM problem for cascaded MVSI. Its emphasis is on improving the availability of HEPWM for higher output voltage by extending the maximum range of modulation index (M). It also removes the discontinuities in the switching angles and reduces the number of distribution ratio required to obtain the required solution. Compared to the most advanced (similar) work, i.e., 7-level MVSI with seventeen switching angles, DE covers a wider range of M; the maximum achievable M is 2.80. Furthermore, it exhibits very low second order distortion factor (DF2): for the worst case, the value of DF2 is 0.0014%. To verify the viability of the proposed algorithm, simulation is carried out and hardware prototype is constructed. Both results show very good agreement with the theoretical prediction.

Design of New Single-phase Multilevel Voltage Source Inverter

Multilevel inverters with more number of levels can produce high quality voltage waveforms. In this paper, a new single-phase structure for multilevel voltage source inverter is proposed which can generate a large number of levels with reduced number of IGBTs, gate driver circuits and diodes. Three algorithms for determination of dc voltage sources’ magnitudes are presented which provide odd and even levels at the output voltage waveform. A comparison is presented between proposed multilevel inverter and conventional cascade topology. The proposed topology is analyzed by the experimental and simulation results. DOI: http://dx.doi.org/10.11591/ijpeds.v5i1.6218

FUZZY BASED CASCADED MULTILEVEL SHUNT ACTIVE POWER FILTER FOR POWER LINE CONDITIONERS

In this paper shunt active power filter is used to improve the power quality at distribution system. Due to nonlinear loads, current harmonics, unbalanced voltages and current and reactive power problems will be created in the network. The Instantaneous real power theory (IRPT) provides the real power calculation with PI controller will not provide accurate result and good performance under both steady state and transient state. Compensating above problems by using fuzzy based on Cascaded multi-level voltage source inverter. The inverter switching signals are generated based on the triangular sampling current controller provides power line conditioning. The Paper deals with three phase, five level cascaded multi level voltage source inverter based shunt active filter with PI and Fuzzy controller by using MATLAB/Simulink.