Switched Capacitor Multilevel Inverter Research Articles

A Switched Z-Source and Switched Capacitor Multi-Level Inverter Integrated Low Voltage Renewable Source for Grid Connected Application

Most of the renewable sources generate power at lower voltage levels in the range of 20-50V which cannot be utilized by the loads. Therefore, stacking multiple modules in series increases the voltage level or using conventional boost converter or QZSis helpful. However, due to series stacking and boost converter or QZS there is a great power loss and also have reliability issues.The QZS inverter has very less boosting gain in the range of 2times. Theconventional boost converter or QZSis replaced with SZSC for voltage boosting and inverter operation. The SZSC boosts the voltage 4-5 times to the input voltage level. For further mitigation of harmonics, the conventional 6-switch inverter is replaced with switched capacitor MLI. Multiple renewable sources are at the input which include PV array, battery unit and PMSG wind module. The battery unit is a support to the renewable sources PV array and wind module. The DC link voltage stability is achieved by the battery unit placed in parallel to the renewable sources. The renewable sources share power to the grid through the SZSC and switched capacitor MLI. For DC voltage stability a CV control is integrated to SZSC. And for synchronized power sharing to the grid, a grid voltage feedback synchronization control is included for the control of MLI. A low rating renewable system is modelled and integrated to grid using Simulink MATLAB software. A comparative analysis is carried out operating the system with QZS and SZSC. The performances of the SZSC and MLI are evaluated by the graphs generated by the simulation of the modelled system.

A Switched-Capacitor Multilevel Inverter With Modified Pulsewidth Modulation and Active DC-Link Capacitor Voltage Balancing

Although switched-capacitor (SC) multilevel inverters (MLIs) offer self-voltage balancing of flying capacitors and voltage gain higher than unity, the advantages come at the cost of high current stress and power loss in the SC circuit and DC source. Moreover, the voltage balancing is often restricted to a limited range of modulation index. Another problem of MLIs with neutral-point clamped (NPC) front end is with DC-link capacitor voltage balancing under unbalanced load conditions, imploring sensor-based closed-loop control. This paper proposes a unity gain five-level active-NPC SC-MLI with inrush charging current attenuation and actively balanced DC-link capacitor voltages under all load conditions and over the entire range of modulation index and power factor. The modified pulse-width modulation results in most switches operating at a low switching frequency, minimizing switching losses in the SC circuit. The proposed MLI attains a maximum efficiency of 98.04% at an output power of 510 W. Experiments on a 2 kVA laboratory prototype validate the theoretical analysis. Results from transformerless grid-connected solar PV system show that the proposed MLI can inject power into the grid with a unity power factor under conditions of varying irradiance and provide the grid with reactive power as well.

A 17-level quadruple boost switched-capacitor inverter with reduced devices and limited charge current

In this paper, a quadruple boost switched-capacitor multi-level inverter is proposed. The proposed structure utilizes a DC source, 11 switches, and a diode to achieve 17-level output voltage levels. This structure consists of three capacitors with the ability for self-balancing voltages. The capacitors achieve automatic voltage balancing through a series/parallel connection with the input voltage source. To control the switching pulses of the switches, level-shifted pulse width modulation (LS-PWM) strategy has been employed. A comparative evaluation has been performed between the proposed structure and structures presented in recent articles, considering various parameters such as voltage gain, number of DC sources, number of semiconductor devices, maximum blocking voltage (MBV), and total standing voltage (TSV). Considering this comparison, the lower number of semiconductor devices for generating a 17-level output with suitable voltage gain, and especially the cost-effectiveness of the structure, are the main advantages of the proposed configuration. In addition, a soft charging method has been employed to limit the inrush current of capacitors. Moreover, the power losses of the proposed structure have been investigated, indicating its acceptable efficiency. Finally, for the analysis and validation of the proposed structure's performance, an experimental prototype has been implemented and evaluated under various conditions. The results indicate satisfactory performance of the proposed structure under various stable and dynamic operating conditions.

A single‐source nine‐level solar‐PV inverter with quadruple voltage boosting and high reliability

SummaryAn increase in generation from distributed energy sources like solar PV has motivated researchers to explore better electrical energy conversion solutions. Multilevel inverters with fewer component count and boosting capabilities contribute to a reliable and efficient single‐stage solution. This work proposes a reliable single‐source switched capacitor multilevel inverter capable of producing nine‐level boosted AC voltage with its stand‐alone and grid‐connected operation. It employs 11 switches, three diodes, and three switched capacitors. The main feature of the proposed topology is its ability to produce quadruple boosting with respect to the DC input voltage. Another advantage is the exhibition of low capacitor currents due to frequent charging durations in one operational cycle. The selection criterion for the switched capacitors is also presented. The topology's performance is evaluated in MATLAB/Simulink under various conditions and in PLECS environments for its efficiency. It was then realized on an experimental prototype in stand‐alone mode. The topology is then modified in terms of topology and modulation to mitigate the leakage current, thus making it suitable for grid‐connected operation. This operation is validated on the hardware‐in‐the‐loop platform. Further, the reliability analysis explores a high total mean time to failure (MTTFT) of nearly 253,164 hours/failures compared to recent switched capacitor topologies and an efficiency of above 95%. The low inrush currents, high MTTFT value, and better efficiency make it a suitable topology for renewable microgrids' stand‐alone and grid‐integrated operation.

A Voltage-Boosting Seven-Level Switched Capacitor Multilevel Inverter With Reduced Device Count

A Voltage-Boosting Seven-Level Switched Capacitor Multilevel Inverter With Reduced Device Count

Seven‐level single‐source switched capacitor inverter with triple boosting capability and high reliability

SummaryA single‐source switched capacitor multilevel inverter (SCMLI) topology utilizing only 10 switches and 1 diode with the capability of generating seven output voltage levels and a triple voltage boosting factor is proposed in this paper. The converter has capacitors that are self‐balanced and do not require any additional circuitry. The multicarrier sinusoidal pulse width modulation (PWM) technique is used to generate various switching signals for the 10 switches. Moreover, the reliability analysis using the Markov model has been carried out to assess the lifespan of power electronic components used in the proposed converter. The converter's performance is analyzed when an open circuit fault occurs in one or multiple switches. Power loss and efficiency in the converter are calculated by PLECS software using thermal modeling. The efficiency of SCMLI was found to be 97.6% for a 300 W load. The inverter working is verified by building a 500 W prototype in the lab. The experimental results in steady‐state and dynamic conditions agree with the theoretical and simulation analysis.

Nine level asymmetrical switched capacitor multilevel inverter fed induction heated autoclave system for medical applications

Nine level asymmetrical switched capacitor multilevel inverter fed induction heated autoclave system for medical applications

A dual source fed eleven level switched capacitor multilevel inverter with voltage boosting capability

This work introduces an 11-level switched-capacitor multilevel inverter (SCMLI) designed for solar photo-voltaic (PV) applications, capitalizing on the growing popularity of multilevel inverters due to their superior power quality. With a 1.67-times boosting capability, the proposed SCMLI employs 10 switches, 2 DC supplies, and 2 capacitors to achieve an 11-level output voltage waveform. The topology requires only seven driver circuits, incorporating 2 bidirectional switches and 3 complementary pairs of switches. The proposed inverter has intrinsic capacitor self-balancing features since the capacitors are connected across the DC voltage source at different times throughout a basic cycle to charge the capacitors at a level of input voltage. A thorough comparison between the topology and recently developed SCMLI’s has been presented. The comparison demonstrates the effectiveness in terms of switches, capacitors, sources, efficiency, total standing voltage (TSV), and boosting capacity. To experimentally validate its performance, the suggested SCMLI undergoes testing using a frequency-based switching method. The topology exhibits low total harmonic distortion (THD) of 7.65% in its output voltage waveform and 0.89% in the output current waveform.

Switched-Capacitor Multilevel Inverter With Input Source-Load Common Ground for Applications Supplied by Green Energy

Switched-Capacitor Multilevel Inverter With Input Source-Load Common Ground for Applications Supplied by Green Energy

Design of Switched Capacitor Multilevel Inverter with Selective Harmonic Elimination

In this paper, Selective Harmonic Elimination (SHE) technique is applied to control multilevel inverters that can be used to eliminate the low order dominant harmonics. This is considered a low frequency technique, in which the switching angles are predetermined based on solving a system of transcendental equations. Newton Raphson is one among the heuristic techniques utilised for selective harmonic elimination. The proposed SHE strategy is simulated along with Sinusoidal Pulse Width Modulation (SPWM) technique and the harmonic distortions are measured and compared for both techniques in MATLAB/Simulink software.

A Wide Input Voltage Range Switched-Capacitor Multilevel Inverter Based on Adjustable Number of Output Levels

A Wide Input Voltage Range Switched-Capacitor Multilevel Inverter Based on Adjustable Number of Output Levels

Triple boost switched capacitor multilevel inverter (TB‐SCMLI) with reduced components and self‐voltage balance

Triple boost switched capacitor multilevel inverter (TB‐SCMLI) with reduced components and self‐voltage balance

A high boost switched capacitor multilevel inverter with reduced components

ABSTRACT Switched capacitor multilevel inverters (SCMLIs) became a popular DC-to-AC converter due to their unique features like self-capacitor voltage balancing and self-output voltage boosting abilities over conventional multilevel inverters in recent years. However, recently developed SCMLIs suffer from higher component counts, lower voltage boosting factors, higher total standing voltage, and the requirement of isolated DC sources for generating high-quality output voltage level waveform. These drawbacks make the inverter costly, complex, and bulky. To address these drawbacks of SCMLIs, a novel SCMLI is proposed in this paper. The proposed SCMLI can realise 17 output voltage levels with a higher boosting factor. In addition, the proposed SCMLI uses lower switches, driver circuits, capacitors, and diodes than similar SCMLIs. The proposed SCMLI also offers a cheaper cost function per output voltage level per boosting factor compared to others. A thorough description of the proposed inverter’s operating principle, voltage stress analysis, and capacitor selection procedure have been discussed. The proposed inverter’s cascaded form has been constructed and analysed for various DC source configurations. An extensive simulation study of 17-level SCMLI in MATLAB/Simulink platform and an experimental investigation on a 17-level laboratory prototype validate the proposed SCMLI’s merits and effectiveness.

A Multilevel Switched Capacitor Inverter with Reduced Components and Self-Balance

This paper presents a novel 13-level switched capacitor multilevel inverter, which uses less devices to achieve six-fold voltage gain. The proposed topology structure consists of twelve transistors, two diodes, and three capacitors. It is worth mentioning that characteristics as having five complementary switch pairs and self-balanced electric capacity voltages are conducive to simplifying the control strategy. Moreover, the above components constitute the switched capacitor unit and L-type unit. The inverter can acquire more voltage levels and a higher voltage gain by using multiple L-type units with fewer elements. Furthermore, the cost function is employed to comprehensively appraise the performance of the proposed inverter. The comparison with other existing 13-level inverters shows that the proposed multilevel inverter can effectively decrease the value of the cost function. Finally, the simulation and experimental results are presented to demonstrate the feasibility and effectiveness of the 13-level inverter.

Realization of an extended switched-capacitor multilevel inverter topology with self voltage balancing

Achieving high voltage levels is an important issue in the design of multi-level inverters (MLIs). In this paper, the basic unit of a new switched-capacitor (SC) topology is extended to achieve higher voltage levels with fewer components. The capacitors are charged from the single supply voltage directly by turning on appropriate switching states, which can generate a high-amplitude nearly sinusoidal output voltage. The operating principles, modulation strategy, method of determining capacitance, and power loss of the extended structure are presented in detail. Also, a comparative study with recent similar structures has been done. The extended SCMLI has the advantages of self-balancing the voltage of the capacitors, generating a bipolar output voltage, and satisfying the standard of harmonics (IEEE519). The experimental test and MATLAB simulation results of a 17-level prototype are given to verify the performance of the extended structure.

Multioutput Switched-Capacitor Multilevel Inverter With Intrinsic Elimination of the Photovoltaics Induced Leakage Current and High Boost Factor

A new multi-output switched-capacitor multilevel inverter (SCMLI) and a few trade-off solutions are proposed. It concomitantly features: a) a common input source-load ground, eliminating thus the photovoltaic cell leakage current, b) a permanent non-zero input current, c) a high boost factor, equal to that in a similar no common ground inverter, and d) the smallest number of capacitors and switches per output and per boost factor compared to their count in the available common ground SC inverters. Its basic structure is constituted by two SC sub-circuits. The originality of the proposed inverter comes from a novel operation scheme in which one of the two SC sub-circuits supplies the positive half-sinusoid of both outputs, while the other SC sub-circuit supplies the negative half-sinusoid of both outputs. The alternative solutions require a few more switches. Their new switching strategies provide an equal capacitor voltages ripple, thus leading to smaller capacitance values and less capacitor-induced losses. An original design of an input choke allows drastically reducing the input current ripple, as required in alternative energy powered applications. The new SCMLI was conceived as an inverter powered by a solar cell that supplies standalone residential ac loads of small powers. A laboratory 400W nine-level prototype is built to verify the theoretical analyses and feasibility of the proposed topology.

An Advanced Switched-Capacitor Multilevel Inverter Topology With a Robust PWM Controlling Technique and Voltage Boosting Property for the Grid-Connected Renewable Energy Applications

This paper proposes an improved switched-capacitor Multilevel Inverter that utilizes fewer components. The switched capacitors are employed with the DC sources in the proposed configuration to minimize the number of DC-Links in the structure, which keeps the structure compact and combinable. Those capacitors enjoy a self-charging susceptibility with the ability to balance naturally. The suggested structure supports the expansion process to catch up with satisfactory output power levels based on a slight increase in the components count. The targeted application for this inverter involves a renewable energy system (RES) to exploit the extracted electrical power and inject it into the grid. The paper suggests a developed PWM controller to control the system’s operation. The controlling scheme has the ability to adjust the balance in the DC-Links voltages to keep generating a regular output voltage. Furthermore, it helps in extracting the maximum available power from renewable resources. Meanwhile, the controller injects the real power component into the grid, which guarantees the unit power factor operation and enhances the grid’s performance. The simulation results for both sides of RES are carried out in MATLAB/Simulink, and these results are verified experimentally through the dSPACE-1103 hardware.

Modelling of Symmetric Switched Capacitor Multilevel Inverter for High Power Appliances

Modelling of Symmetric Switched Capacitor Multilevel Inverter for High Power Appliances

Development and Control of a Switched Capacitor Multilevel Inverter

This article offers a novel boost inverter construction with a Nine-level quadruple voltage boosting waveform. The primary drawback of conventional MLI is the need for a high voltage DC-DC converter to increase the voltage when using renewable energy sources. Consequently, the developed method, complete with a quadruple voltage boost ability, can alleviate that shortcoming by automatically increased the incoming voltage. A single DC source, two switching capacitors, and eleven switches are all that are used in the newly presented architecture. The voltage of the capacitor automatically balances. The switched capacitor MLI is distinguished by the fewer parts that are required and the substitution of a capacitor for a DC source. The switching capacitor has to be charged and discharged properly in order to produce the nine-level output voltage waveform. The SPSC unit makes these levels attainable. To achieve voltage boosting, switched capacitors are coupled in parallel and series in the conduction channel. The quality of this proposed topology has been analyzed through different parameters based on the components count, THD, and cost; the resulting efficiency reaches 97.85%. The switching order of the proposed method has been controlled by the Nearest Level Modulation Method (NLC). MATLAB and PLECS software were used to evaluate the constructed Nine-level converter.

Reduced Device Count for Self Balancing Switched-Capacitor Multilevel Inverter Integration with Renewable Energy Source

In this study, a new switched-capacitor-based seven-level inverter topology with a photovoltaic system is presented. The proposed topology requires a smaller number of devices and has the ability to self-balance the voltage across the capacitor. The proposed topology configuration is simple and has the ability to extend to higher levels of voltage. This multilevel inverter topology is suitable for low- and medium-voltage applications with photovoltaic (PV) system integration. To improve the PV system efficiency as an input of a DC–DC boost converter, a Fuzzy logic-based maximum power point controller technique is used. A PV system with a DC–DC boost converter integrates with the proposed seven-level inverter topology. The anti-predatory particle swarm optimization (APSO) technique is used to solve the non-linear transduction equations of the seven-level PV switched-capacitor-based multilevel inverter (7L−PV−SCMLI) topology. The proposed APSO is described to minimize the harmonics in the multilevel inverter (MLIs), which is a complex optimization problem involving a non-linear transcendental equation. Furthermore, APSO can be applied in order to solve non-linear transcendental equations for all symmetrical and asymmetrical MLIs that have equal and non-equal DC sources. The APSO-based selected harmonic elimination (SHE) technique obtained the best switching angle value, and the optimized obtained switching angles reduced the total harmonic distortion (THD) of 7L−PV−SCMLI.