Provided is an electric power converter. A First and second series circuits of switching devices and a series circuit of capacitors are connected in parallel. Between the connection point in the first series circuit of switching devices and the connection point in the series circuit of capacitors, a first bidirectional switch is connected and, between the connection point in the second series circuit of switching devices and the connection point in the series circuit of capacitors, a second bidirectional switch is connected. The connection point in the first series circuit of switching devices is connected through a reactor to an input-output common connection line connected to one end of an AC power supply and the other end of the AC power supply is connected to the connection point in the series circuit of capacitors.

Electric power converter

Multilevel inverters (MLIs) are a great development for industrial and renewable energy applications due to their dominance over conventional two-level inverter with respect to size, rating of switches, filter requirement, and efficiency. A new single-phase cascaded MLI topology is suggested in this paper. The proposed MLI topology is designed with the aim of reducing the number of switches and the number of dc voltage sources with modularity while having a higher number of levels at the output. For the determination of the magnitude of dc voltage sources and a number of levels in the cascade connection, three different algorithms are proposed. The optimization of the proposed topology is aimed at achieving a higher number of levels while minimizing other parameters. A detailed comparison is made with other comparable MLI topologies to prove the superiority of the proposed structure. A selective harmonic elimination pulse width modulation technique is used to produce the pulses for the switches to achieve high-quality voltage at the output. Finally, the experimental results are provided for the basic unit with 11 levels and for cascading of two such units to achieve 71 levels at the output.

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Optimal Design of a New Cascaded Multilevel Inverter Topology With Reduced Switch Count

This letter presents a compact switched capacitor multilevel inverter (CSCMLI) topology with reduced switch count and with self-voltage balancing and boosting ability. The operational mode of the proposed CSCMLI is discussed. A comparative analysis in terms of number of switches and blocking voltages is presented against recent switched capacitor multilevel inverter topologies. Further to enhance the quality of the output voltage, a new level shifted multicarrier pulsewidth modulation (PWM) technique is recommended. This modulation technique produces low THD and high rms voltage. The proposed modulation technique is implemented in the nine-level CSCMLI with single dc source and two capacitors. The simulated and experimental results are verified for a switching frequency of 50 Hz and 2.5 kHz using the proposed PWM control.

Compact Switched Capacitor Multilevel Inverter (CSCMLI) With Self-Voltage Balancing and Boosting Ability

Multilevel inverters are a new family of converters for dc-ac conversion for the medium and high voltage and power applications. In this paper, two new topologies for the staircase output voltage generations have been proposed with a lesser number of switch requirement. The first topology requires three dc voltage sources and ten switches to synthesize 15 levels across the load. The extension of the first topology has been proposed as the second topology, which consists of four dc voltage sources and 12 switches to achieve 25 levels at the output. Both topologies, apart from having lesser switch count, exhibit the merits in terms of reduced voltage stresses across the switches. In addition, a detailed comparative study of both topologies has been presented in this paper to demonstrate the features of the proposed topologies. Several experimental results have been included in this paper to validate the performances of the proposed topologies with different loading condition and dynamic changes in load and modulation indexes.

/pdf/a-new-multilevel-inverter-topology-with-reduce-switch-count-mwmm7jrvr4.pdf

A New Multilevel Inverter Topology With Reduce Switch Count

Multilevel inverters (MLIs) have gained increasing interest for advanced energy-conversion systems due to their features of high-quality produced waveforms, modularity, transformerless operation, voltage, and current scalability, and fault-tolerant operation. However, these merits usually come with the cost of a high number of components. Over the past few years, proposing new MLIs with a lower component count has been one of the most active topics in power electronics. The first aim of this article is to update and summarize the recently developed multilevel topologies with a reduced component count, based on their advantages, disadvantages, construction, and specific applications. Within the framework, both single-phase and three-phase topologies with symmetrical and asymmetrical operations are taken into consideration via a detailed comparison in terms of the used component count and type. The second objective is to propose a comparative method with novel factors to take component ratings into account. The effectiveness of the proposed method is verified by a comparative study.

Voltage Source Multilevel Inverters With Reduced Device Count: Topological Review and Novel Comparative Factors

This paper presents a novel step-up dc to ac converter with only one power supply. These types of converters are suitable for renewable and sustainable energy applications with low input dc sources. The proposed topology has the ability of self-voltage balancing and does not apply end side H-bridge to produce a bipolar staircase waveform. Consequently, switching losses and voltage stress of semiconductor components are reduced to a great extent. A small dc voltage source can be used to achieve a high voltage high quality ac waveform through switching the precharged capacitors in series and in parallel. Circuit configuration and its operation principle, capacitors’ charging process, thermal model, capacitances, and losses calculations are discussed in details. Moreover, the comparison of the proposed circuit with the other single source multilevel converters shows that the proposed topology reduces the number of circuit elements. Finally, a laboratory nine-level prototype is built to verify the theoretical analyses and feasibility of the proposed topology. The experimental results show that the converter efficiency at 1 KW output power is 92.75%.

/pdf/a-novel-step-up-single-source-multilevel-inverter-topology-3dqh10j0cn.pdf

A Novel Step-Up Single Source Multilevel Inverter: Topology, Operating Principle, and Modulation

This paper proposes a new single-phase five-level converter based on the switched-capacitor technique. The capacitor charging in the proposed converter is carried out in a self-balancing form which does not need closed-loop modulations or additional balancing circuits. The proposed topology is a voltage booster without using end-side H-bridge for changing load voltage polarity. So, switching losses and total voltage stress of semiconductor components reduce in the proposed converter. The performing modes of the proposed topology, its modulation scheme, capacitors’ balancing analysis, capacitance and loss calculations, and also the development of the proposed converter for enhancing the quality of output voltage waveform are discussed in depth. Moreover, the comparison of the proposed structure with the other multilevel topologies shows that the proposed converter can reduce the number of semiconductor elements and the required isolated dc sources. Finally, the simulation and experimental results validate the appropriate performance of the proposed converter.

A Five-Level Step-Up Module for Multilevel Inverters: Topology, Modulation Strategy, and Implementation

This study presents a new module for multilevel inverters with reduced components Each module produces 25 levels using four asymmetrical DC voltage sources (two 1V DC and two 5V DC sources) and 10 semiconductor switches A significant advantage of the suggested module is its potentiality in producing voltage levels with negative polarity without any end side H-bridge inverter Therefore, switches with lower voltage ratings are used in its structure Series connection of the proposed structure leads to a modular topology which produces more voltage levels using reasonable number of switches, gate driver circuits, power diodes and less DC voltage sources These advantages are analysed by comparing this structure with other state-of-the-art topologies Selective harmonic elimination pulse width modulation (SHE-PWM) scheme is used to achieve output voltage with high quality To produce all voltage levels, two algorithms are proposed to determine DC voltage sources magnitude The accuracy of the suggested module performance in producing all voltage levels is verified by simulation and experimental results

Cascaded multilevel inverter based on symmetric–asymmetric DC sources with reduced number of components

This study presents a new module for cascaded multilevel inverters (MLIs) based on switched-capacitor technique. Charging of the capacitors in the proposed switched-capacitor cell is performed in a self-balancing form. Voltage boosting capability and generating bipolar voltage levels without requiring an end-side H-bridge inverter are remarkable benefits of the proposed topology. Thereby, semiconductors with lower-voltage ratings are applied in its circuit. Comparison of the proposed inverter with traditional topologies and other recently introduced MLIs shows that the proposed topology reduces the number of circuit elements and also total blocking voltage by switches. Moreover, the proposed inverter configuration and its operating principle, capacitance, and power loss calculations, and also topology extension to achieve higher levels are investigated in depth. Finally, an experimental prototype is built to verify the theoretical analysis and feasibility of the proposed topology.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-pel.2017.0478

Step-up switched-capacitor module for cascaded MLI topologies

Distributed virtual inertia is an approach of providing synthetic inertia in small-scale modern grids dominated by converter-based generators. In this method, the inertial response of synchronous machines is emulated by the energy stored in the dc-link capacitors of grid-tied converters. Nonetheless, it results in instability of the interfaced converter in weak grids. To overcome this problem and get the most benefit out of the acceptable dc-link capacitor voltage deviations, a new compensation technique is proposed in this article. The grid-interactive converter in the presented framework is controlled in the current control mode, compositing of two conventional inner and outer control loops, distributed virtual inertia controller, and a novel compensator. The detailed small-signal representation of the whole control scheme in state-space form is derived. Then, it is revealed that the coupling between d- and q- axis controllers introduced by the distributed virtual inertia gain and its differential operator gives rise to the system instability in weak grids, which can be eliminated through the ancillary compensator. The time-domain simulation model is built to confirm the efficacy of the proposed control technique. The results depict that the ancillary active power provided by the proposed approach during frequency disturbance is 14% of the converter power rating of 20 kW, which yields the improvement of frequency rate of change by 18.82%.

/pdf/a-control-technique-based-on-distributed-virtual-inertia-for-1yls31utj1.pdf

Meysam Saeedian

Papers

A Novel Step-Up Single Source Multilevel Inverter: Topology, Operating Principle, and Modulation

A Five-Level Step-Up Module for Multilevel Inverters: Topology, Modulation Strategy, and Implementation

Cascaded multilevel inverter based on symmetric–asymmetric DC sources with reduced number of components

Step-up switched-capacitor module for cascaded MLI topologies

A Control Technique Based on Distributed Virtual Inertia for High Penetration of Renewable Energies Under Weak Grid Conditions