Showing papers on "Switched capacitor published in 2022"

A Single-Source Nine-Level Boost Inverter With a Low Switch Count

Abstract: Switched-capacitor-based multilevel inverters for boost-type dc–ac power conversions usually exhibit a trade-off between the switch count and switch-voltage rating, i.e., a reduction of one necessitating an increase of the other. Such a dilemma is well addressed in this article by proposing a novel single-phase nine-level inverter based on a switched-capacitor network with a single switch. The proposed inverter then reduces the number of switches while generating a boosted dc-link voltage. A unique six-switch full-bridge cooperating with a low-frequency half-bridge further steps-up the output voltage with a quadruple gain. The voltage stresses on the power devices are, however, maintained low even under the boosted high output voltage, as all the switches/diodes can be clamped to any of the low-voltage capacitors. Consequently, low-voltage power devices can be utilized, reducing the overall power loss. Detailed theoretical analysis, calculations, and design considerations of the proposed inverter are provided. Comparisons with the prior-art inverters illustrate its advantages. Simulations and experimental tests on a 1-kVA inverter prototype verify the above-claimed benefits.

Switched-Capacitor Multilevel Inverters: A Comprehensive Review

Abstract: Multilevel inverters (MLIs) with switched-capacitor (SC) units have been a widely rehearsed research topic in power electronics since the last decade. Inductorless/transformerless operation with voltage-boosting feature and inherent capacitor self-voltage balancing performance with a reduced electromagnetic interference make the SC-MLI an attractive converter over the other available counterparts for various applications. There have been many developed SC-MLI structures recently put forward, where different basic switching techniques are used to generate multiple (discrete) output voltage levels. In general, the priority of the topological development is motivated by the number of output voltage levels, overall voltage gain, and full dc-link voltage utilization, while reducing the component counts and stress on devices for better efficiency and power density. To facilitate the direction of future research in SC-MLIs, this article presents a comprehensive review, critical analysis, and categorization of the existing topologies. Common fundamental units are generalized and summarized with their merits and demerits. Ultimately, major challenges and research directions are outlined leading to the future technology roadmap for more practical applications.

Self-Balanced Switched-Capacitor Thirteen-Level Inverters With Reduced Capacitors Count

Abstract: This letter describes two improved 13-level inverters based on switched-capacitor. Compared with their original structure, which is published recently, one less high-voltage capacitor is required in the proposed inverters and the blocking voltage of their inverting half-bridge is reduced by half. In addition, the new inverters inherit various advantages of the original structure, such as a high boost factor of 6, self-balanced capacitor voltages, and reduced voltage ripples. Circuit description, operation principle, hybrid PWM modulation, and capacitor voltage ripples are analyzed and the feasibility of the proposed inverters is finally verified by experimental results.

A 13-Level Switched-Capacitor Multilevel Inverter With Single DC Source

Abstract: In this article, a novel 13-level inverter single source, switched-capacitor multilevel inverter (SSC-MLI) is proposed. This topology is suitable for renewable energy applications using less input voltage source magnitude. This structure is capable of boosting the input voltage six times with the help of switched capacitors. The capacitors are automatically balanced without any control algorithms, complex circuits, or closed-loop controllers. The advantages of the proposed structure are high-power density and high efficiency by the use of only switches. Since, there are no diodes there is no forward conduction loss, and no reverse recovery delay. The maximum blocking voltage across the individual switch is three times the input voltage. The functionality of the SSC-MLI is described in detail. The capacitance calculation and optimum value of capacitors are discussed. A suitable comparison is presented for the proposed structure with the existing literature to check the inverter performance. The power loss for exiting a 13-level inverter is presented. The simulation is carried out for both pure resistive and inductive load. Later, the experimental results are presented for variation in frequency, dynamic change in load, variation in modulation index, and step-change in input voltage to validate the proposed topology performance and feasibility.

A Switched-Capacitors-Based 13-Level Inverter

Abstract: The merit of switched-capacitors-based multilevel inverters (SCMLIs) is generally quantified in terms of a “cost function” (CF) that incorporates parameters such as voltage gain, component count, total standing voltage (TSV), and number of levels. In this article, a 13-level inverter is proposed with the aim of achieving a low value of CF. The proposed single-stage SCMLI uses one input source and three capacitors to attain a voltage gain of 3. It requires 13 power switches, of which the peak inverse voltage (PIV) of nine switches is restricted to the source voltage. The remaining four switches have PIV equal to twice the source voltage and they operate at low frequency. Thus, for all switches, the PIV is less than the amplitude of the output voltage. Moreover, the capacitors are self-balanced at all regions of modulation index values. The proposed inverter is validated through simulation and experimental results. A comparison of the proposed topology with other contemporary SCMLIs shows that it is highly competent in terms of CF, PIV and TSV requirements, waveform resolution, and capability to achieve voltage balancing of capacitors at low values of modulation index.

Self-Balanced Switched-Capacitor Thirteen-Level Inverters With Reduced Capacitors Count

Abstract: This letter describes two improved 13-level inverters based on switched-capacitor. Compared with their original structure, which is published recently, one less high-voltage capacitor is required in the proposed inverters and the blocking voltage of their inverting half-bridge is reduced by half. In addition, the new inverters inherit various advantages of the original structure, such as a high boost factor of 6, self-balanced capacitor voltages, and reduced voltage ripples. Circuit description, operation principle, hybrid PWM modulation, and capacitor voltage ripples are analyzed and the feasibility of the proposed inverters is finally verified by experimental results.

Vertical Stacked LEGO-PoL CPU Voltage Regulator

Abstract: This article presents a 48–1 V merged-two-stage hybrid-switched-capacitor converter with a linear extendable group operated point-of-load (LEGO-PoL) architecture for ultrahigh-current microprocessors, featuring 3-D stacked packaging and coupled inductors for miniaturized size, fast speed, and vertical power delivery. The architecture is highly modular and scalable. The switched-capacitor circuits are connected in series on the input side to split the high input voltage into multiple stacked voltage domains. The multiphase buck circuits are connected in parallel to distribute the high output current into multiple parallel current paths. It leverages the advantages of switched-capacitor circuits and multiphase buck circuits to achieve soft charging, current sharing, and voltage balancing. The inductors of the multiphase buck converters are used as current sources to soft-charge and soft-switch the switched-capacitor circuits, and the switched-capacitor circuits are utilized to ensure current sharing among the multiphase buck circuits. A 780-A vertical stacked CPU voltage regulator with a peak efficiency of 91.1% and a full load efficiency of 79.2% at an output voltage of 1 V with liquid cooling is built and tested. The switched capacitor circuits operate at 286 kHz and the buck circuits operate at 1 MHz. It regulates output voltage between 0.8 and 1.5 V through the entire 780-A current range. This is the first demonstration of a 48–1 V CPU voltage regulator to achieve over 1-A/mm $^\text{2}$ current density and the first to achieve 1000-W/in $^3$ power density.

A Three-Winding Coupled Inductor-Based Interleaved High-Voltage Gain DC–DC Converter for Photovoltaic Systems

Abstract: In this article, an interleaved high-voltage gain dc–dc converter is proposed for use with photovoltaic (PV) systems. By integrating two three-winding coupled inductors (CIs) with switched capacitor cells, the voltage gain is further extended. Through passive diode-capacitor clamp circuits, the energy stored in the leakage inductances is absorbed; additionally, the voltage stress of the power switches is clamped to a value far lower than the output voltage, which enables designers to select switches with low-voltage ratings. Due to the interleaved structure of the proposed converter, the input current has a small ripple, which leads to the increased lifespan of the PV panels. In addition, the current stress on the components is reduced. Thanks to the leakage inductances of the CIs, the zero-current switching condition is intrinsically provided for the diodes; accordingly, the adverse impact of the diodes’ reverse-recovery is alleviated. The operating principles, steady-state analyses, and design considerations of the proposed converter are presented in this article. A comparison with other similar converters is carried out to verify the merits of the proposed converter. Finally, the theoretical analyses are confirmed through the experimental results of a 400-W prototype with an output voltage of 400 V.

Neutral-Point-Clamped Five-Level Inverter With Self-Balanced Switched Capacitor

Abstract: In this article, a new five-level inverter is developed by inserting a switched-capacitor (SC) unit into the traditional three-level neutral-point-clamped (NPC) inverter phase leg. The SC unit consists of two capacitors and one bidirectional switch, all of which withstand a quarter of the dc input voltage. While increasing the output levels, the performance is also improved in terms of power loss, common-mode voltage, switching stress dv/dt , and output filter. Compared to other five-level inverters like the conventional NPC and active NPC five-level topologies, the new solution not only reduces the number of components and simplifies the design but also has the advantage of self-balanced capacitor voltages. The analysis, simulation, and experiment indicate that the proposed inverter is suitable for a wide range of applications like renewable source grid-connected interfaces and motor drivers. Simulation and experimental results of grid-connected operation verify that the new inverter is capable of providing both active and reactive power to the grid. Its excellent performance is also experimentally evaluated by a 1.2-kW prototype and the measured efficiency is above 97% for a wide range of load.

A Switched-Capacitors-Based 13-Level Inverter

Abstract: The merit of switched-capacitors-based multilevel inverters (SCMLIs) is generally quantified in terms of a “cost function” (CF) that incorporates parameters such as voltage gain, component count, total standing voltage (TSV), and number of levels. In this article, a 13-level inverter is proposed with the aim of achieving a low value of CF. The proposed single-stage SCMLI uses one input source and three capacitors to attain a voltage gain of 3. It requires 13 power switches, of which the peak inverse voltage (PIV) of nine switches is restricted to the source voltage. The remaining four switches have PIV equal to twice the source voltage and they operate at low frequency. Thus, for all switches, the PIV is less than the amplitude of the output voltage. Moreover, the capacitors are self-balanced at all regions of modulation index values. The proposed inverter is validated through simulation and experimental results. A comparison of the proposed topology with other contemporary SCMLIs shows that it is highly competent in terms of CF, PIV and TSV requirements, waveform resolution, and capability to achieve voltage balancing of capacitors at low values of modulation index.

Modeling and Comparison of Passive Component Volume of Hybrid Resonant Switched-Capacitor Converters

Abstract: Hybrid and resonant switched-capacitor (SC) convertersenable efficient utilization of both active and passive components, and have the potential to achieve higher efficiency and higher power density than conventional SC and magnetic-based converters. One or more added inductors offer an additional degree of freedom in the design space. It is of great interest to understand the tradeoffsbetween capacitor and inductor size and volume allocation. In this article, we analyze the reactive energy processed by the passive components and use it to calculate the total passive component volume. It is shown that the total passive component volume of resonant SC (ReSC) converters can be expressed as a function of flying capacitor voltage ripple, and the optimized capacitor voltage ripple that minimizes the total volume is dependent on topology specific parameters and the relative energy density ratio between capacitors and inductors. Moreover, we also demonstrate through theoretical analysis and experimentation that ReSC converters use significantly less passive component volume than conventional SC and buck converters for the same amount of power converted. Next, to compare different ReSC topologies, a normalized passive volume parameter is proposed for simple and fair comparison. This can be used along with a normalized switch stress parameter (based on switch VA ratings) to create a framework to showcase the relative performance of different topologies. This framework can be used to visualize and compare the passive and active component utilization among different topologies. Additionally, the proposed reactive power analysis is extended to hybrid converters with regulation capability.

Nine-Level Nine-Switch Common-Ground Switched-Capacitor Inverter Suitable for High-Frequency AC-Microgrid Applications

Abstract: Voltage source multilevel inverters with reduced leakage current, single-stage voltage step-up feature, compact design, and an efficient performance are a promising technology for high-frequency ac (HFac) microgrids feeding through renewable energy sources. This article proposes a novel single-source common-grounded (CG) step-up nine-level (9L) inverter, which can be applied in HFac microgrid applications. The proposed CG-based boost inverter is comprised of only nine switches (9S) and three self-balanced capacitors. Using the switched-capacitor (SC) technique, a double voltage boosting feature within a single power processing stage is achieved, while the leakage current concern is eliminated due to a CG-based configuration between the input dc source and the null of the grid. With the help of an LC input filter, the input current profile is free from large discontinuous inrush spikes. The working principles of the proposed 9L9S-CGSC inverter are discussed in this article. The modulation and closed-loop control strategy, as well as a comparative study, are presented. Finally, the open and closed-loop grid-tied performances of the proposed topology are evaluated by both simulation and experimental results obtained from a 1.2-kW laboratory-built prototype.

Common-Ground Grid-Connected Five-Level Transformerless Inverter With Integrated Dynamic Voltage Boosting Feature

Abstract: A single-phase common-ground five-level (5L) inverter with a dynamic voltage conversion gain and capability of operating in a wide input voltage range and a single-stage energy conversion configuration is presented in this article. The proposed topology requires nine active power switches and is comprised of an integrated switched-boost (SB) module connected in series to a switched-flying-capacitor (SFC) cell. Two self-balanced capacitors with a single boost inductor in the integrated SB module are employed to generate a 5L output voltage waveform with a dynamic voltage conversion gain. The current stress profile of all the active and passive elements is kept within a permissible input current range. By adopting an extra diode-capacitor-inductor network into the integrated SB module and with the utilization of the same SFC cell, the proposed topology is extended to achieve a quadratic voltage conversion gain while retaining the quality of ac voltage waveform. Theoretical analysis, closed-loop control/modulation principles, design guidance, comparative study, and relevant experimental results obtained from a 1.5-kW laboratory-built prototype are presented to ascertain the operation and feasibility of the proposed system.

A New Single-Source Nine-Level Quadruple Boost Inverter (NQBI) for PV Application

Abstract: Multi-level inverters (MLIs) with switched capacitors are becoming popular due to their utilization in AC high-voltage applications as well as in the field of renewable energy. To achieve the required magnitude of output voltage, the switched capacitor (SC) technique employs a lesser number of DC sources in accordance with the voltage across the capacitor. Designing an efficient high-gain MLI with fewer sources and switches needs a rigorous effort. This paper introduces a prototype of a nine-level quadruple boost inverter (NQBI) topology powered by one solar photo-voltaic source using fewer capacitors, switches, and diodes when compared to the other SC-MLIs topology. The suggested NQB inverter produces nine levels of voltage in its output by efficiently balancing the voltages of the two capacitors. The various SC-MLIs are compared in order to highlight the benefits and drawbacks of the proposed nine-level quadruple boost inverter (NQBI) topology. To validate the efficacy of the proposed solar photovoltaic based NQBI without grid connection, detailed experimental results are presented in a laboratory setting under various test conditions.

A Bidirectional Five-Level Buck PFC Rectifier With Wide Output Range for EV Charging Application

Abstract: AC-to-DC conversion is integral to the two-stage charging interface of electric vehicle (EV) batteries. For such chargers, the use of multilevel rectifiers (MLRs) reduces voltage ratings of power switches, while achieving a high-quality input voltage waveform. Balancing of capacitors in MLRs, however, is an important challenge. In this work, a power factor correction (PFC) five-level rectifier with self-balanced switched capacitors is proposed. Each leg of the presented topology comprises five power switches and one switched capacitor, where the voltage ratings of power switches are equal to the output dc voltage. It does not require an additional filter capacitor on the dc side, as the load appears in parallel always with a switched capacitor of one of the legs. The five-level operation with continuous conduction leads to the elimination of the capacitive filter on the ac-side and inductive filter on the dc-side. This article presents the operating principle, modulation strategy, closed-loop control, and design aspects of the proposed rectifier. The proposed topology is validated through experimental results and a comparison is made with other topologies. Following three features of the proposed topology make it suitable for EV battery charging applications—buck operation with a wide output regulation, the possibility of bidirectional flow of power needed for vehicle-to-grid systems, and easy realization of its three-phase version by simply adding one more leg. These features too have been demonstrated with experimental results.

Five-Level Switched Capacitor Inverter for Photovoltaic Applications

Abstract: This paper proposes a switched-capacitor based single-phase five-level inverter configuration that operates under boost operation and generates a voltage that is more than the DC source voltage. The proposed five-level inverter uses a capacitor and boots the output voltage. In this proposed inverter, capacitor gets charged in parallel while it discharges in series connections so that output voltage may attain higher magnitude than the DC source voltage. Sinusoidal Pulse Width Modulation-based techniques are considered to produce the required gate pulses for operating the switching devices of the inverter. The five-level switched-capacitor inverter is combined with the PV system via DC–DC boost converters to extract the maximum power using MPPT algorithm. To verify its capability, the PV-based system is further integrated to the utility grid. The operation and performance of the suggested switched-capacitor inverter coupled with the grid-connected PV system are also analyzed by developing its model in MATLAB/Simulink environment.

Particle Swarm Optimization-Based Bandpass Filter Using Switched-Fractional Capacitors

Abstract: A new approach to designing a fractional bandpass filter using switched-fractional capacitors has been reported for the first time. This is achieved using four fractional-capacitors (FC1,FC2,FC3, and FC4) with orders α, β, δ, and λ, respectively, where 0<α,β,δ,λ≤1. The presented work deals with designing a fractional bandpass filter using switched capacitors and switched-fractional capacitors in place of resistors. The stability and the speed of response of the proposed filter have been investigated by computing the filter parameters analytically. Filter parameters such as settling-time (ts), peak-overshoot (Mp), and rise-time (tr) improve compared with their integer-order counterpart. Furthermore, detailed comparative studies on different design parameters have also been carried out through simulation studies and experimentations. The particle swarm optimization (PSO) technique is used for getting the optimal values of the orders of the switched-fractional capacitors to improve the response of the proposed filter.

A Novel and High-Gain Switched-Capacitor and Switched-Inductor-Based DC/DC Boost Converter With Low Input Current Ripple and Mitigated Voltage Stresses

Abstract: High voltage gain DC-DC boost converters are widely used in grid-connected applications through integration with the Renewable Energy Sources (RESs). Photovoltaic (PV) arrays or Fuel Cells (FCs) generate a limited value of the DC voltages and then for high power and high voltage applications, at the first stage, these voltages should be increased. This study presents a high gain, single-switched, and efficient DC-DC boost converter using the switched-capacitor and switched-inductor cells. These blocks easily can enhance the voltage and present an input current with the least values of the ripples. This will be done through replacing the location of the input inductors and by applying a switched-inductor block. Magnetizing in parallel and demagnetizing in series for the inductors present the smaller input current stresses. A single switch is used for the proposed boost converter that directly decreases the complexity of the control circuit for obtaining a fixed DC voltage at the output side for flexible input voltages or loads. More voltages will be presented by the used switched-capacitor cell simply by adding several diodes and capacitors. A deep and detailed mathematical analysis will be presented for continuous (CCM) and discontinuous conduction modes (DCM) and a 200 W laboratory-scaled prototype is presented. The results of the hardware tests confirm the correctness of the theoretical analysis and simulation results.

A Dickson-Squared Hybrid Switched-Capacitor Converter for Direct 48 V to Point-of-Load Conversion

Abstract: More energy-efficient and power-dense solutions to 48 V to point-of-load (PoL) power conversion are required for modern and future data center power delivery. This paper proposes a Dickson-squared hybrid switched-capacitor (SC) con-verter for direct 48 V-to-PoL conversion with high efficiency and high power density. The proposed topology comprises a 9-to-1 SC stage that can be viewed as two 3-to-1 Dickson SC converters combined together and a nine-phase interleaved buck stage. The proposed topology can achieve complete soft-charging operation with a simple control, ensure naturally balanced interleaved inductor currents, enable reduced conversion burden on the buck stage, and eliminate the need for large bus capacitors with a switching bus architecture. A 48 V-to-PoL hardware prototype is built to verify the performance of the proposed converter, achieving 93.8% peak efficiency and 360 W/in ³ power density at 1.0 V output voltage.

Compact Quadratic Boost Switched-Capacitor Inverter

Abstract: This article presents a new topology for a single-stage nine-level (9L) switched-capacitor inverter. The structure of the proposed topology is not only simple but also compact. The proposed topology is developed with self-voltage balancing and a low number of power components. The output voltage (vo) gain is four times higher than the input voltage (vin). Each mode of operation is discussed with a detailed current path. The conventional sinusoidal pulsewidth modulation technique is used to generate the gate pulses. Next, the experimental results are obtained from a 1 kW prototype setup. The proposed topology is tested under different scenarios such as load change, input voltage changes, and modulation variations. Both simulation and experimental results have good agreement in terms of efficiency. Finally, a detailed comparative study is performed with other recent 9L inverters to prove the merits of the proposed topology.

Fault-Tolerant Operation Strategy for Reliability Improvement of a Switched-Capacitor Multilevel Inverter

Abstract: The necessity of using several components in multilevel inverters jeopardizes the reliability of their operation. Hence, the aim of this article is to propose a novel single-phase fault-tolerant topology based on a switched-capacitor concept to ensure the robustness of the converter in the occurrence of a fault. The proposed single-source converter steps up the input voltage seven times with a simple control strategy. Fault tolerance of the converter is achieved by considering multiple fault cases and providing several redundant switching schemes concerning the type and location of failure. Each switching scheme is designed in a way to ensure the tolerability to both single and multiple open-/short-circuit failures. Also, self-voltage balancing of the capacitors, as well as the same amount of voltage levels and amplitude in the output, is guaranteed. Experimental analysis is carried out, and the results confirm the viability of the proposed inverter under normal and postfault operating modes.

Single-Input Quadruple-Boosting Switched-Capacitor Nine-Level Inverter With Self-Balanced Capacitors

Abstract: This paper suggests a single-input switched-capacitor Nine-level inverter configuration advantaging from quadruple voltage-boosting ability, natural voltage balancing of capacitors, and reduced components per level. Also, the single-source character of the proposed topology makes it cheaper and more compact. The cascaded version of the suggested topology has also been introduced, by which high boosting factors, as well as large number of steps, can be obtained. The proposed topology can effectively supply the resistive-inductive or pure inductive load types. The capacitors’ impulsive-charging-current issue has been solved by simple small-inductance-based inductor-diode (L-D) networks. The comparative analysis affirms the fewer device-usage in suggested configuration per equal gain or level count than existed structures, resulting in less size and cost. The usage of Nearest-Level modulation guarantees the low-frequency operation of semiconductors and reduces the switching losses. The comparative analysis and experimental outcomes affirm the competitiveness and accurate functionality of suggested configuration.

A 9- and 13-Level Switched-Capacitor-Based Multilevel Inverter With Enhanced Self-Balanced Capacitor Voltage Capability

Abstract: Boost action is required for enhancing the output voltage of the sources such as photovoltaic (PV) sources, fuel cells, and battery storage devices, which eliminates the need for additional units. For this purpose, switched-capacitor (SC)-based multilevel inverters (SC-MLIs) are widely used. The proposed SC-based single-phase MLI is able to produce 13-level output ac voltage and furnishes voltage gains of 3 and 6. The same topology is also able to produce a single-phase nine-level ac output with a voltage gain of 4. The abovementioned voltage levels and voltage gains are achieved using the proposed topology just by modifying the switching strategy used for firing the switches and do not require any modification in the proposed SC-MLI structure. The proposed configuration of single-phase MLI requires less switch count to produce 9- and 13-level ac output voltages with the abovementioned voltage gains. The switches connected in the proposed configuration undergo less voltage stress compared to the MLIs suggested in the literature. The comparison of the proposed converter topology with the existing MLIs reported in the literature is included. The validation of the performance of the proposed inverter is carried out using experimental results captured on a low-power laboratory prototype.

An Active-Neutral-Point-Clamped Switched-Capacitor Multilevel Inverter With Quasi-Resonant Capacitor Charging

Abstract: Switched-capacitor (SC) multilevel inverters (MLIs) offer various advantages over conventional series MLIs owing to the operation from a single dc source, self-balanced capacitor voltages, and inherent voltage gain. However, these advantages come at the cost of high current stress on the capacitors, associated semiconductors, and the dc source. This inrush current has limited the practical application of SC-MLIs to a fractional kilowatt rating. This article proposes a practical solution by introducing a unity gain nine-level active-neutral-point-clamped SC-MLI with an alleviated capacitor charging current. Switching loss in the SC circuit semiconductors is reduced by using a modified switching sequence that allows the charging current to flow with a minimum interruption till it is turned off at zero-current crossing. The structure also integrates protection against the detrimental effects of voltage transients across the charging inductor. The inverter exhibits a maximum efficiency of 98.03% at 583.91 W output power. Compared with similar SC-MLIs with hard-charging, the proposed inverter significantly reduces the losses and improves efficiency. Experimental results from a 2 kVA laboratory prototype validate the theoretical analysis and show the capacitor voltages stable under varying load impedance and modulation index.

Novel Control Scheme for Five-Level Hybrid Flying-Capacitor Inverters Without DC-Link Balancing Circuits

Abstract: In this article, a novel control scheme for five-level hybrid flying-capacitor inverters is proposed, which can balance the neutral-point voltages across split dc-link capacitors and simultaneously regulate the flying-capacitor voltages.Each capacitor voltage is maintained by regulating the currents that flow through the dc-link neutral points and the flying capacitors. The key components affecting these currents are analyzed to construct a control scheme based on the injection of zero-sequence voltage to the modulation voltage reference.This technique eliminates the need for the auxiliary balancing circuit, which was previously used in the conventional operating schemes to regulate the dc-link capacitor voltages and, thus, reduces the device count and converter volume. The effectiveness of the proposed method for maintaining the capacitor voltages within the allowable range has been verified under various operating conditions through the simulation and experimental results.

A Switched Capacitor and Autotransformer Hybrid Converter With DC Current in the Windings

Abstract: This article presents a hybrid converter combining soft-charged switched capacitors and an autotransformer with dc current in the windings, optimized for 4:1 fixed voltage gain conversion (DCX) for high output current. By adding an additional output inductor, it can also regulate the output voltage to lower than ¼ of the input voltage by changing the duty cycle. The switched capacitors voltage and the two winding currents in the transformer are auto-balanced. Nonresonant operation of the circuit enables dc current in the windings and simplifies both transformer and circuit design. Experimental results for 48 V–12 V DCX operation achieve 98% peak efficiency and 97.7% full load (250W) efficiency. Regulation by using the output inductor is verified experimentally up to 48–6V (8:1) voltage step down.

An extendable single‐input reduced‐switch 11‐level switched‐capacitor inverter with quintuple boosting factor

Abstract: This paper proposes a novel single-phase switched-capacitor-based inverter configuration that in its basic form can generate an 11-level staircase output voltage waveform with sinusoidal output current for Resistive-Inductive (R-L) loads. The increased levels, quintuple voltage-boosting factor, and natural voltage-balancing of capacitors are considered the main features of the proposed basic configuration. The proposed topology requires fewer components (resources, switches, driver circuits, and capacitors) than recently presented similar structures to acquire the same voltage gain and output steps. The proposed basic configuration can be extended in two ways: increasing levels and/or boosting factors with minimal devices. The employment of two half-bridges (rather than an H-bridge) for generating bipolar waveform has limited the number of switches tolerating the maximum output voltage to 2 (instead of 4), which results in reduced total blocking voltage (TBV) and accordingly reduced cost and losses. A comprehensive comparative analysis has been done and presented to verify the supremacy of the suggested structure. The experimental results of the laboratory-scaled prototype of the proposed basic topology have been provided, which approve its correct performance.

A Novel 17-Level Reduced Component Single DC Switched-Capacitor-Based Inverter With Reduced Input Spike Current

Abstract: Multilevel inverters (MLIs) have become common and resourceful as a result of the fast advancement of technology in the areas of high-voltage and high-power applications, among other things. Recently, MLIs have received a great deal of attention recently, due to the growing need to harness environmentally friendly energy. With reduced power electronics switches, diodes, and a voltage boost gain factor of 8, this article presents a single-phase 17-level switching capacitor inverter design. The proposed inverter uses single dc voltage source, two diodes, 14 power electronics switches, and three capacitors. The different mode of operation of topology is explained in detail, including their self-voltage balancing technique. Additionally, an inductor is used in the capacitor charging loop to avoid current spikes caused by the input dc source while charging the capacitor quickly, thereby increasing capacitor life expectancy significantly. Compared to previously the proposed single-input MLIs, the proposed inverter has a lower semiconductor switch count and a lower cost function value that are its distinguished feature. The performance of the topology is verified by MATLAB/Simulink, and furthermore, a laboratory prototype is utilized, which confirms the feasibility of the proposed topology.