Multilevel Current Source Inverter Research Articles

Single-Rating Multilevel Current Source Inverter with Fault Tolerance

Single-Rating Multilevel Current Source Inverter with Fault Tolerance

MATLAB Simulation of Sinusoidal Pulse Width Modulation based Three and Seven Level Current-Source Inverters

Here, a multilevel current-source inverter (MCSI) topology is analyzed. Here, the issue of constructing a novelmodular single-rating inductor MCSI has been explored. The proposed topology isbuilt with identical modules where all inductors carry the sameamount of current, simplifying the construction and operationof industrial applications with higher efficiency. A new state machine approach with a proper implementation of the phase-shifted carrier-sinusoidal pulse width modulation (PSC-SPWM) allows both current balancein all modules and effective switching-frequency minimization. The performance of the MSCI proposed is simulated with MATLAB. As a result of this topology and PSC-SPWM utilization, current balance was achieved in both main and sharing inductors, even under load and operating point changes. The switching frequency was drastically reduced with a new state machine approach, taking the advantage of the three different zero-states of the topology. The topology adopted allows operation with high efficiency by reducing the current through the inductors and the losses in the switches.

Three-phase boost-stage coupled current source inverter concept and its space vector modulation

The current source inverter (CSI) is essentially a converter with inherent boost capability and has been preliminarily applied in the field of renewable energy generation systems. However, conventional CSIs are mostly operated independently. Several existing multilevel CSI topologies entirely rely on parallel combinations, which seems to be not very suitable for capacity expansion. To solve this issue, this paper proposes a concept of three-phase boost-stage coupled current source inverter (BSC-CSI) through the duality principle, which can output multi-level currents with a reduced number of switches as well as hardware costs. Compared with the state-of-the-art CSIs, the proposed BSC-CSI can notably simplify the implementation of the multi-level modulation scheme and meanwhile ensure the power devices switch under lower current stress. To further take full advantage of the modularity and scalability, the BSC-CSI can be constructed by hybrid using silicon-carbide (SiC) and silicon (Si) based semiconductor switches for improving efficiency. The experimental results have verified the theoretical findings.

Performance Evaluation of Symmetrical Current Source Multilevel Inverter

In this paper proposes a Current Source Multilevel Inverter (CSMLI) with a single rating inductor topology. The multilevel inverters are generally acquainted with power converter's applications because of decreased dv/dt, di/dt stress, and extremely efficient for minimising harmonic distortion in the both output voltage and current. The proposed nine-level current source inverter has analyses under symmetrical operation, and their operation are compared using PI and Fuzzy PI controllers with multicarrier PWM topology. PV utilized as a DC source, photovoltaic energy is an environmentally friendly energy with high potential, simple construction, maintenance, dependability and long life. MATLAB/Simulink simulation has been made for the proposed converter to get its exhibition measures. Some test results are given to confirm the presented Current Source Multilevel Inverter.

Current Balancing Algorithm for Three-Phase Multilevel Current Source Inverters

In high power, medium voltage applications, Current Source Inverters CSIs are connected in parallel to accommodate high DC currents. Using a proper multilevel modulation technique, parallel-connected CSIs can operate as a Multilevel CSI (MCSI). The most common modulation technique for MCSIs is the Phase-Shifted Carrier SPWM (PSC-SPWM). The proper operation of the MCSI requires each CSI modules to have the same average current flowing through its sharing inductors. In practice, the average currents of the CSI modules deviate from their nominal values. Therefore, current balancing mechanisms must be implemented. In the literature, several solutions have been proposed to tackle the current imbalance problem. Most of these solutions are based on altering the phase-shift or magnitude of the carrier waveforms of the PSC-SPWM. They require dedicated PI controllers and they are applicable to MCSIs with specific numbers of levels. This paper proposes a Current Balancing Algorithm (CBA) that can be implemented in any MCSI with any number of levels. The proposed CBA does not require any PI controllers, nor does it require any alteration to the PWM carrier waveforms. The CBA is implemented using a modified Level-Shifted SPWM (LS-PWM). The modified LS-SPWM is shown to produce lower THD and lower di/dt when compared to the PSC-SPWM. The CBA and modified LS-SPWM where implemented in a proof-of-concept lab prototype. The experimental results are presented for the five-level and seven-level cases.

Pure Sinusoidal Output Single-Phase Current-Source Inverter with Minimized Switching Losses and Reduced Output Filter Size

This paper proposes a novel single-phase current-source inverter that generates a pure sinusoidal waveform with minimized switching losses and using a small-size output filter capacitor. The proposed method is investigated by incorporating a conventional multilevel current-source inverter with a linear amplifier. The conventional multilevel technique uses fundamental switching frequency instead of using high-switching frequency modulation for the H-bridge circuit. The linear amplifier such as class-A or class-D types has a function to reform the staircase waveform generated by the multilevel inverter into a pure sinusoidal by using superimposition technique. As a result, pure sinusoidal output current is generated with a small ripple and the system only requires a small output filter capacitor for smoothing the waveform. Based on the simulation and experimental results, the proposed system presents not only the optimal configuration, but also an option as to whether to obtain excellent power efficiency or very low output harmonic. Implications of the results and future research directions are also presented.

High-level number multilevel single-phase current-source inverter with reduced switching device count

This paper proposes an advanced technique in generating a pure sinusoidal output current waveform for the high number multilevel lsingle-phase current-source inverter (CSI) with reduced switching device count. Previous multilevel CSI development proposed a new technique in generating pure sinusoidal output by compensating the staircase current with a linear current. This linear current compensation intends to reduce the output filter capacitor size without sacrificing inverter efficiency. However, this hybrid multilevel CSI would give higher efficiency and performance if applie in high number of levels. Consequently, the system needs high switching device count. Too many switching devices utilization will decrease the performance and the power density of the CSI as well. Therefore, this technique is introduced and only possible to be realized if the number of levels is higher than 5-level. By applying multilayer stagemethod while managing the DC current module activation sequences, the high number of levels CSI can be constructed with only using few DC current modules. As a result, according to the computer comparison simulation, the implementation of the proposed technique delivers relatively equal results compared to the conventional one just by utilizing fewers witching devices.

A comparative study of cascade H-bridge multilevel voltage source inverter and parallel inductor multilevel current source inverter

This paper presents the analysis study between multilevel inverters that are often classified into multilevel voltage source and multilevel current source inverters. For multilevel voltage source inverter (MVSI), the specific topology studied for this work is the Cascaded H-Bridge MVSI. Whereas, the multilevel current source inverter (MCSI) is based on Paralleled Inductor Configuration MCSI. For this study, the analysis between these converters are done with respect to the number of components, the advantages and disadvantages of each converters during performing inverter operation. In term of output voltage and current quality, the percentage of the Total Harmonic Distortion (THD) are measured and compared for both topologies. MATLAB/Simulink software has been used in this research to design and simulate in order to study the performances of both inverters.

A New Predictive Control Strategy for Multilevel Current-Source Inverter Grid-Connected

The DC/AC converters—commonly called inverters—transform the DC into AC and are classified as Voltage-Source Inverters (VSIs) or Current-Source Inverters (CSIs). A variant of the CSIs are the Multilevel Current-Source Inverters (MCSIs). In this paper, a new predictive control strategy for an MCSI with multiple inputs and grid-connected is proposed. The control technique uses the advantages of the Sliding Mode Control (SMC) for the balance of current in the input and Predictive Control (PC) to obtain a suitable grid current, since it separates both functions. The calculations are based on conventional Kirchhoff’s Voltage Law (KVL) and knowledge of the mathematical model of the system is not required. Generally, traditional MCSIs use large input inductors (100–1000 mH). In this paper, it is achieved a reduction in size of the input inductors. Simulation results are shown to validate the proposed control.

A Load Commutated Multilevel Current Source Inverter Fed Open-End Winding Induction Motor Drive With Regeneration Capability

This paper presents a load commutated silicon controlled rectifier (SCR) based multilevel current source inverter (CSI) fed open-end winding induction motor (IM) drive with regeneration capability. Multilevel current waveform is realized using two isolated load commutated SCR-based CSIs connected in shunt configuration, but operated with a phase shift of 30 $^\circ$ thereby attaining significant reduction in harmonic distortion of the motor current. The multilevel CSI connected to one side of the stator windings supplies real power to the motor. The other end of the stator winding is directly interfaced with a capacitor-fed voltage source inverter (VSI). The control scheme of the VSI facilitates load commutation of the multilevel CSI under all conditions of operation, including regenerative braking. The proposed scheme is experimentally verified on an IM with open-end stator winding, with the help of a digital signal processor TMS320F28335.

Power loss analysis of current-modules based multilevel current-source power inverters

A power loss analysis of multilevel current-source inverter (MCSI) circuits developed from two basic configurations of three-level current-source inverters, i.e. H-bridge and common-emitter inverter configurations is presented and discussed. The first circuit topology of the MCSI is developed by using DC current modules connected to the primary three-level H-bridge inverter. The second MCSI circuit is created by connecting the current-modules to a three-level common-emitter inverter. The DC current modules work generating the intermediate level waveform of the inverter circuits. Power loss analysis of the both topologies was carried out to explore the efficiency performance of the inverter circuits. The results showed that for the H-bridge and common-emitter MCSI using DC current modules, the amount of conduction losses in the inverter circuits could be diminished when the level number of AC output current increase. The measurement test results have also proved that using these MCSI topologies, the power conversion efficiency will also increase.

A Programmable Single-Phase Multilevel Current Source Inverter

The conventional single-phase multilevel current source inverters suffer from the high count of switches for increasing the levels. Therefore, how to generate more levels with reduced-count of switches is attractive. In this paper, a programmable single-phase current source inverter is presented. It can achieve the programmable level output with only five switches. Different from the existing single-phase reduced-count multilevel inverters, it has the advantages of a simple structure and programmable level output. Finally, the simulation and experimental tests are carried out. And, the experimental results verify the effectiveness of the proposed programmable multilevel inverter.

Simultaneous DC Current Balance and Common-Mode Voltage Control With Multilevel Current Source Inverters

The current source converter (CSC) has been popular in high-power medium-voltage applications. To increase the system power capacity and reduce the output harmonics, parallel connection of CSCs with multilevel current output is a practical approach. There are mainly two types of parallel based configurations. The structure with an independent dc link for each paralleled CSC can be regarded as the first configuration, where the dc current flowing into each CSC can be controlled from the rectifier side independently. The second type is constructed with only one current source rectifier (CSR) on the grid side and paralleled current source inverters (CSIs) on the load side, which could potentially reduce the cost and size of the system. However, with a common dc source, the dc current for each CSC should be carefully controlled with proper modulation design. At the same time, the common-mode voltage (CMV), which increases the motor line-to-ground voltage and causes additional stress to the insulation system, should also be suppressed. In this paper, with a focus on the shared dc-link structure, we thoroughly analyze the dc-link current flow and common-mode loop circuit. We propose a multilevel modulation strategy of the parallel CSI system considering the requirement of dc current balancing and CMV reduction to improve the overall system performance. The effectiveness of the proposed method is verified by both simulation and experiment in a transformerless parallel CSC system.

Parallel Inductor Multilevel Current Source Inverter for Input Ripple Current Reduction in PEM Fuel Cell Applications

ABSTRACT In a power conditioning fuel cell system, the application of a single phase voltage source inverter (VSI) generates a second harmonic (100/120 Hz) ripple current. The harmonic current reduces life, efficiency and performance of the fuel cells due to hysteresis loss effects. This paper proposes current source inverter (CSI) with multilevel features to reduce the second harmonic (100/120 Hz) current ripple drawn from the Proton Exchange Membrane (PEM) fuel cell. The employment of energy recovery scheme in the proposed five-level multilevel current source inverter (MCSI) introduces a single switching state for each output current level. The proposed energy recovery scheme is able to balance the sharing inductor currents effectively. In addition, the proposed MCSI is also integrated with a boost DC current source in order to reduce the size of input DC link inductor and minimize the circuit structure for a reliable power conditioning PEM fuel cell system application.

Control System to Balance Internal Currents of a Multilevel Current-Source Inverter

Multilevel current-source inverters have proved to be a high-performance option for industrial applications due to reliability, fault-tolerant capabilities, quasi soft switching, and the use of lower filter capacitor values. One of its major challenges is to balance the internal currents that feed each module. Imbalances could be caused by manufacturing deviations of the reactive components, temperature drift or aging, nonlinear loads, and modulation errors, among others. Using the well-known phase-shift carrier sinusoidal pulse width modulation, a slight change in the amplitude of the carrier signals produces a variation in the average value of the internal currents. In this paper, we introduce a control strategy to balance the current of the inductors and its implementation in a prototype. Simulation and experimental results at different operating conditions show a robust behavior of the control system along with a low distortion in the output voltages and currents of the converter.

A Comparative Study of Phase Offset Disposition Sinusoidal Pulse Width Modulation (POD-SPWM) and Symmetrical Pulse Width Modulation Switching Techiques for Generalized Current Source Multilevel Inverter(MCSI)

<p>This paper presents a comparison between two switching techniques namely Phase Offset Disposition Sinusoidal PWM (POD-SPWM) and Symmetrical PWM switching for a generalized current source multilevel inverter (MCSI) topology. One of the advantages of MCSI is it can reduce the total harmonic distortion (THD) at the output load current with a sinusoidal current waveform. In this paper, the generalized MCSI with the different levels has been developed with Matlab@simulation software in order to study the performance of the two switching schemes for the operation of the MCSI. From the simulation results, POD-SPWM switching technique can give better THD results compare to symmetrical switching technique.</p>

Fuzzy PI Control of Symmetrical and Asymmetrical Multilevel Current Source Inverter

Multilevel inverters are most popular in power converter applications due to reduced dv/dt, di/dt stress upon the switches and reduced harmonics. This paper suggests a circuit configuration of multilevel current source inverter with single-rating inductor topology. The proposed nine-level current source inverter has been tested under symmetrical and asymmetrical modes of operation for different loads, and their operations are compared using PI and fuzzy PI controllers with multicarrier PWM strategy. MATLAB/Simulink simulation has been carried out for the proposed inverter to obtain its performance measures.

Novel 1-? Multilevel Current Source Inverter for Balanced /Unbalanced PV Sources

Novel 1-? Multilevel Current Source Inverter for Balanced /Unbalanced PV Sources

Modified Synchronous Pulsewidth Modulation of Current-Fed Five-Level Inverter for Solar Integration

Large-scale photovoltaic (LSPV) energy conversion systems have been installed at many places across the world. The essential component of the LSPV system is the dc-ac conversion stage. The usage of multilevel converters is one of the recent advances in the dc-ac conversion stage of the LSPV system to enable transformer-less inversion. Current-fed multilevel inverter has been chosen in this paper as it provides high power inversion with inherent voltage boosting, and thus, avoids the usage of transformer. High power conversion necessitates low device switching frequency operation in order to satisfy thermal constraint of semiconductor devices and also to improve efficiency. However, low device switching frequency operation leads to higher harmonic distortion of inverter output currents. Synchronous optimal pulsewidth modulation (SOP) technique is an emerging low device switching frequency modulation technique that has been successfully implemented for voltage-source multilevel inverters. However, the state-of-the-art SOP technique cannot be directly applied to modulate current-source multilevel inverter topologies due to additional constraints on the switching commutations. Therefore, the purpose of our study was to propose a modified SOP technique to achieve: low device switching frequency and minimal harmonic distortion of inverter output currents. The topology of current-fed five-level inverter was used for demonstrating the performance of proposed technique. A generalized conversion method was introduced in the modified SOP technique for including switching constraints of the current-fed inverter. In addition, a state-sequencing machine was developed by utilizing redundant inverter states to produce equal switching commutation among all semiconductor devices at minimal switching frequency of 350 Hz. The experimental results obtained from the five-level current-source inverter of 1.2 kW demonstrated the effectiveness of the proposed SOP technique.

A novel symmetric/asymmetric multilevel current source inverter topology with lower number of components and lowest power rating of switches

ABSTRACTA novel multilevel current source inverter (MCSI) configuration is introduced in this paper. The ability of handling with asymmetrical DC sources is one of the substantial advantages of the proposed inverter. In asymmetric mode, by appropriate selection of DC sources magnitude, a considerable increase can be obtained in the number of output levels without any manipulation on inverters’ hardware. In MCSIs, the number of required circuit devices is very important because the overall costs, circuit size, reliability and control complexity are dependent on them directly. The proposed inverter can generate all desired current levels using a lower number of elements. Besides, it is known that reduction of number of switches from conventional inverters imposes an undesired increase in total semiconductor device power (SDP). But, the total SDP of the proposed inverter is kept equal to conventional inverter. To validate the superiority of the proposed inverter, a full comparison is provided. Also, the computer simulation and experimental results are presented.