Showing papers on "Capacitor published in 2019"

Ultrahigh–energy density lead-free dielectric films via polymorphic nanodomain design

Abstract: Dielectric capacitors with ultrahigh power densities are fundamental energy storage components in electrical and electronic systems. However, a long-standing challenge is improving their energy densities. We report dielectrics with ultrahigh energy densities designed with polymorphic nanodomains. Guided by phase-field simulations, we conceived and synthesized lead-free BiFeO3-BaTiO3-SrTiO3 solid-solution films to realize the coexistence of rhombohedral and tetragonal nanodomains embedded in a cubic matrix. We obtained minimized hysteresis while maintaining high polarization and achieved a high energy density of 112 joules per cubic centimeter with a high energy efficiency of ~80%. This approach should be generalizable for designing high-performance dielectrics and other functional materials that benefit from nanoscale domain structure manipulation.

Enhanced energy-storage performance with excellent stability under low electric fields in BNT–ST relaxor ferroelectric ceramics

Abstract: Relaxor ferroelectrics are promising candidates for pulsed power dielectric capacitor applications because of their excellent energy-storage properties. Different from most relaxor ferroelectrics whose energy-storage density was improved by increasing the breakdown strength and reducing the remanent polarization, in this study, anti-ferroelectric (AFE) AgNbO3 (AN) was used to partially substitute the relaxor ferroelectric 0.76Bi0.5Na0.5TiO3–0.24SrTiO3 (BNT–ST) of morphotropic phase boundary (MPB) composition to reduce the remanent polarization while maintaining large maximum polarization. In this way, a large recoverable energy-storage density (2.03 J cm−3) was obtained in the BNT–ST–5AN ceramics under lower electric field of 120 kV cm−1, which is superior to other lead-free energy-storage materials under similar electric fields. Moreover, excellent temperature (25–175 °C) and frequency (1–100 Hz) stabilities are achieved. This performance demonstrates that the BNT–ST–5AN ceramics form a promising class of dielectric capacitive material for high-temperature pulsed power capacitors with large energy-storage density.

Unveiling the double-well energy landscape in a ferroelectric layer

Abstract: The properties of ferroelectric materials, which were discovered almost a century ago1, have led to a huge range of applications, such as digital information storage2, pyroelectric energy conversion3 and neuromorphic computing4,5. Recently, it was shown that ferroelectrics can have negative capacitance6-11, which could improve the energy efficiency of conventional electronics beyond fundamental limits12-14. In Landau-Ginzburg-Devonshire theory15-17, this negative capacitance is directly related to the double-well shape of the ferroelectric polarization-energy landscape, which was thought for more than 70 years to be inaccessible to experiments18. Here we report electrical measurements of the intrinsic double-well energy landscape in a thin layer of ferroelectric Hf0.5Zr0.5O2. To achieve this, we integrated the ferroelectric into a heterostructure capacitor with a second dielectric layer to prevent immediate screening of polarization charges during switching. These results show that negative capacitance has its origin in the energy barrier in a double-well landscape. Furthermore, we demonstrate that ferroelectric negative capacitance can be fast and hysteresis-free, which is important for prospective applications19. In addition, the Hf0.5Zr0.5O2 used in this work is currently the most industry-relevant ferroelectric material, because both HfO2 and ZrO2 thin films are already used in everyday electronics20. This could lead to fast adoption of negative capacitance effects in future products with markedly improved energy efficiency.

Multivalent metal ion hybrid capacitors: a review with a focus on zinc-ion hybrid capacitors

Abstract: Multivalent metal ion hybrid capacitors have been developed as novel electrochemical energy storage systems in recent years. They combine the advantages of multivalent metal ion batteries (e.g., zinc-ion batteries, magnesium-ion batteries, and aluminum-ion batteries) with those of supercapacitors, and are characterized by good rate capability, high energy density, high power output and ultralong cycle life. Herein, after a brief introduction to supercapacitors and multivalent metal ion batteries, we reviewed the recent progress in research on multivalent metal ion hybrid capacitors, with a focus on zinc-ion hybrid capacitors, from the perspectives of design concept, configuration, electrochemical behavior and energy storage mechanism. An outlook of the future research regarding multivalent metal ion hybrid capacitors was also presented. This review will be beneficial for researchers around the world to have a better understanding of multivalent metal ion hybrid capacitors and develop novel electrochemical energy storage systems to meet the demands of rapidly developing electric vehicles and wearable/portable electronic products.

Achieving high discharge energy density and efficiency with NBT-based ceramics for application in capacitors

Abstract: High-performance capacitors, which have high energy storage density as well as high discharge efficiency, are desired. In this study, we have designed and prepared novel and high quality (1 − x)(0.65Bi0.5Na0.5TiO3–0.35Bi0.1Sr0.85TiO3)–x(K0.5Na0.5NbO3) [(1 − x)(BNT–BST)–xKNN, x = 0, 0.04, 0.06, 0.08, and 0.10] ceramics that demonstrated a remarkable energy storage capability, high efficiency, and ultrafast discharge speed. Particularly, the 0.94(BNT–BST)–0.06KNN ceramic possessed an excellent stored energy storage density (Ws = ∼3.13 J cm−3) and recoverable energy storage density (Wr = ∼2.65 J cm−3), and maintained a relatively high efficiency (η = ∼84.6%) at a relatively low electric field of 180 MV m−1, which is superior to those of the lead-free BNT-based energy-storage materials. Moreover, excellent temperature (20–120 °C) and frequency (1–100 Hz) stabilities of the 0.94(BNT–BST)–0.06KNN ceramic were also achieved. More importantly, the 0.94(BNT–BST)–0.06KNN ceramic exhibited an ultrafast discharge rate (τ0.9 = ∼1.01 μs), a high level of discharge energy density (Wd −1.21 J cm−3), and excellent reliability in energy storage performance by consecutive cycling. Moreover, this study also provides an effective approach to attain large energy-storage capability along with high efficiency in BNT-based ceramics for application in pulsed power capacitors.

Assembling 2D MXenes into Highly Stable Pseudocapacitive Electrodes with High Power and Energy Densities.

Abstract: Electrochemical capacitors (ECs) that store charge based on the pseudocapacitive mechanism combine high energy densities with high power densities and rate capabilities. 2D transition metal carbides (MXenes) have been recently introduced as high-rate pseudocapacitive materials with ultrahigh areal and volumetric capacitances. So far, 20 different MXene compositions have been synthesized and many more are theoretically predicted. However, since most MXenes are chemically unstable in their 2D forms, to date only one MXene composition, Ti3 C2 Tx , has shown stable pseudocapacitive charge storage. Here, a cation-driven assembly process is demonstrated to fabricate highly stable and flexible multilayered films of V2 CTx and Ti2 CTx MXenes from their chemically unstable delaminated single-layer flakes. The electrochemical performance of electrodes fabricated using assembled V2 CTx flakes surpasses Ti3 C2 Tx in various aqueous electrolytes. These electrodes show specific capacitances as high as 1315 F cm-3 and retain ≈77% of their initial capacitance after one million charge/discharge cycles, an unprecedented performance for pseudocapacitive materials. This work opens a new venue for future development of high-performance supercapacitor electrodes using a variety of 2D materials as building blocks.

Ultrahigh β-phase content poly(vinylidene fluoride) with relaxor-like ferroelectricity for high energy density capacitors.

Abstract: Poly(vinylidene fluoride)-based dielectric materials are prospective candidates for high power density electric storage applications because of their ferroelectric nature, high dielectric breakdown strength and superior processability. However, obtaining a polar phase with relaxor-like behavior in poly(vinylidene fluoride), as required for high energy storage density, is a major challenge. To date, this has been achieved using complex and expensive synthesis of copolymers and terpolymers or via irradiation with high-energy electron-beam or γ-ray radiations. Herein, a facile process of pressing-and-folding is proposed to produce β-poly(vinylidene fluoride) (β-phase content: ~98%) with relaxor-like behavior observed in poly(vinylidene fluoride) with high molecular weight > 534 kg mol−1, without the need of any hazardous gases, solvents, electrical or chemical treatments. An ultra-high energy density (35 J cm−3) with a high efficiency (74%) is achieved in a pressed-and-folded poly(vinylidene fluoride) (670-700 kg mol−1), which is higher than that of other reported polymer-based dielectric capacitors to the best of our knowledge. Dielectric materials are candidates for electric high power density energy storage applications, but fabrication is challenging. Here the authors report a pressing-and-folding processing of a dielectric with relaxor-like behavior, leading to high energy density in a polymer-based dielectric capacitor.

Realizing high comprehensive energy storage performance in lead-free bulk ceramics via designing an unmatched temperature range

Abstract: The study of lead-free dielectric ceramics for capacitors has become one of the most active academic research areas in advanced functional materials owing to the environmental regulations. A large recoverable energy storage density (Wrec), a high energy storage efficiency (η) and good temperature stability in lead-free dielectric ceramics are highly desired simultaneously to meet the requirements of light weight and integration of dielectric capacitors in pulsed power devices. Unfortunately, a large Wrec of lead-free dielectric ceramics is usually achieved at the cost of η, and vice versa, hindering their practical applications. More importantly, despite the considerable efforts made so far to develop a large amount of lead-free bulk ceramics for dielectric capacitor applications, there is still a lack of scientific and feasible guidelines on how to design new material systems with a large Wrec, a high η and excellent thermal stability. Herein, we propose a new strategy to tailor the temperature region between the temperature corresponding to the maximum dielectric permittivity (Tm) and the Burns temperature (TB) of relaxor ferroelectrics to room temperature via composition optimization, to explore lead-free bulk ceramics with high comprehensive energy storage properties. A large Wrec of 3.51 J cm−3 and a high η of 80.1% are simultaneously obtained in 0.86NaNbO3–0.14(Bi0.5Na0.5)HfO3 (0.86NN–0.14BNH) ceramics under an electric field of 350 kV cm−1, leading to an excellent comprehensive energy storage performance in lead-free bulk ceramics. Furthermore, both the Wrec and η of 0.86NN–0.14BNH ceramics show good temperature stability over 20 °C to 200 °C at 280 kV cm−1, which is superior to that of other lead-free bulk ceramics. Most importantly, this work provides significant guidelines for designing new high-performance bulk ceramics for electrical energy storage applications.

Ultrahigh-Sensitivity Microwave Sensor for Microfluidic Complex Permittivity Measurement

Abstract: The conventional resonant-type microwave microfluidic sensors made of planar resonators suffer from limited sensitivities. This is due to the existence of several distributed capacitors in their structure, where just one of them acts as a sensing element. This article proposes a very high-sensitivity microwave sensor made of a microstrip transmission line loaded with a shunt-connected series LC resonator. A large sensitivity for dielectric loadings is achieved by incorporating just one capacitor in the resonator structure. Applying sample liquids to the microfluidic channel implemented in the capacitive gap area of the sensor modifies the capacitor value. This is translated to a resonance frequency shift from which the liquid sample is characterized. The sensor performance and working principle are described through a circuit model analysis. Finally, a device prototype is fabricated, and experimental measurements using water/ethanol solutions are presented for verification of the sensing principle.

A 13-Levels Module (K-Type) With Two DC Sources for Multilevel Inverters

Abstract: This paper presents a new reconfiguration module for asymmetrical multilevel inverters in which the capacitors are used as the dc links to create the levels for staircase waveforms. This configuration of the multilevel converter makes a reduction in dc sources. On the other hand, it is possible to generate 13 levels with lower dc sources. The proposed module of the multilevel inverter generates 13 levels with two unequal dc sources (2 V DC and 1 V DC). It also involves two chargeable capacitors and 14 semiconductor switches. The capacitors are self-charging without any extra circuit. The lower number of components makes it desirable to be used in wide range of applications. The module is schematized as two back-to-back T-type inverters and some other switches around it. Also, it can be connected as a cascade modular which leads to a modular topology with more voltage levels at higher voltages. The proposed module makes the inherent creation of the negative voltage levels without any additional circuit (such as H-bridge circuit). Nearest level control switching modulation scheme is applied to achieve high-quality sinusoidal output voltage. Simulations are executed in MATLAB/Simulink and a prototype is implemented in the power electronics laboratory in which the simulation and experimental results show a good performance.

Harmonic State-Space Based Small-Signal Impedance Modeling of a Modular Multilevel Converter With Consideration of Internal Harmonic Dynamics

Abstract: The small-signal impedance modeling of a modular multilevel converter (MMC) is the key for analyzing resonance and stability of MMC-based power electronic systems. The MMC is a power converter with a multifrequency response due to its significant steady-state harmonic components in the arm currents and capacitor voltages. These internal harmonic dynamics may have great influence on the terminal characteristics of the MMC, which, therefore, are essential to be considered in the MMC impedance modeling. In this paper, the harmonic state-space (HSS) modeling approach is first introduced to characterize the multiharmonic coupling behavior of the MMC. On this basis, the small-signal impedance models of the MMC are then developed based on the proposed HSS model of the MMC, which are able to include all the internal harmonics within the MMC, leading to accurate impedance models. Besides, different control schemes for the MMC, such as open-loop control, ac voltage closed-loop control, and circulating current closed-loop control, have also been considered during the modeling process, which further reveals the impact of the MMC internal dynamics and control dynamics on the MMC impedance. Furthermore, an impedance-based stability analysis of the MMC-high-voltage direct current connected wind farm has been carried out to show how the HSS-based MMC impedance model can be used in practical system analysis. Finally, the proposed impedance models are validated by both simulation and experimental measurements.

Switched-Capacitor-Based Single-Source Cascaded H-Bridge Multilevel Inverter Featuring Boosting Ability

Abstract: Cascaded multilevel inverter (CMI) is one of the most popular multilevel inverter topologies. This topology is synthesized with some series-connected identical H-bridge cells. CMI requires several isolated dc sources which brings about some difficulties when dealing with this type of inverter. This paper addresses the problem by proposing a switched-capacitor (SC)-based CMI. The proposed topology, which is referred to as switched-capacitor single-source CMI (SCSS-CMI), makes use of some capacitors instead of the dc sources. Hence, it requires only one dc source to charge the employed capacitors. Usually, the capacitor charging process in a SC cell is companied by some current spikes which extremely harm the charging switch and the capacitor. The capacitors in SCSS-CMI are charged through a simple auxiliary circuit which eradicates the mentioned current spikes and provides zero-current switching condition for the charging switch. A computer-aid simulated model along with a laboratory-built prototype is adopted to assess the performances of SCSS-CMI, under different conditions.

Tunable Negative Permittivity in Flexible Graphene/PDMS Metacomposites

Abstract: The flexible metacomposites with tunable negative permittivity have great potential in wearable cloaks, stretchable sensors, and thin-film capacitors, etc. In this paper, the flexible graphene/poly...

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

Abstract: 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.

Large electrocaloric effects in oxide multilayer capacitors over a wide temperature range

Abstract: Heat pumps based on magnetocaloric and electrocaloric working bodies—in which entropic phase transitions are driven by changes of magnetic and electric field, respectively—use displaceable fluids to establish relatively large temperature spans between loads to be cooled and heat sinks1,2. However, the performance of prototypes is limited because practical magnetocaloric working bodies driven by permanent magnets3–5 and electrocaloric working bodies driven by voltage6–16 display temperature changes of less than 3 kelvin. Here we show that high-quality multilayer capacitors of PbSc0.5Ta0.5O3 display large electrocaloric effects over a wide range of starting temperatures when the first-order ferroelectric phase transition is driven supercritically (as verified by Landau theory) above the Curie temperature of 290 kelvin by electric fields of 29.0 volts per micrometre. Changes of temperature in the large central area of the capacitor peak at 5.5 kelvin near room temperature and exceed 3 kelvin for starting temperatures that span 176 kelvin (complete thermalization would reduce these values from 5.5 to 3.3 kelvin and from 176 to 73 kelvin). If magnetocaloric working bodies were to be replaced with multilayer capacitors of PbSc0.5Ta0.5O3, then the established design principles behind magnetocaloric heat pumps could be repurposed for better performance without bulky and expensive permanent magnets. High-quality multilayer capacitors of a perovskite oxide show that large electric-field-driven caloric effects could improve solid-state refrigeration technology and challenge today’s standard (based on magnetocaloric effects in gadolinium).

Fabrication of core-shell structured Ni@BaTiO3 scaffolds for polymer composites with ultrahigh dielectric constant and low loss

Abstract: Dielectric composites have drawn increasing attention owing to their wide applications in electrical systems. Herein, a novel design of dielectric composites consisting of core-shell structured porous Ni@BaTiO3 scaffolds infiltrated with epoxy was developed. It is demonstrated that the dielectric constants of the composites could be as high as 6397@10 kHz, which is approximately 1777 times higher than pure epoxy matrix (er ≈ 3.6@10 kHz). Meanwhile, the dielectric loss (tanδ ≈ 0.04@10 kHz) remains comparable to that of pure epoxy (tanδ ≈ 0.01@10 kHz). It is believed that the strong charge accumulation and interfacial polarizations on the huge interfaces, especially the Ni/BaTiO3 and Ni/epoxy interfaces, give arise to the substantially enhanced er. Besides, the sintered insulating BaTiO3 coating can block the transportation of charge carriers, resulting in the low loss. The ultrahigh dielectric constants and low loss make these composites promising candidates for microstrip antennas, field-effect transistors and dielectric capacitors.

Switched Tank Converters

Abstract: This paper presents a new class of switched tank converters (abbreviated as STCs) for high-efficiency high-density nonisolated dc–dc applications where large voltage step down (up) ratios are required Distinguished from switched capacitor converters, the STCs uniquely employ LC resonant tanks to partially replace the flying capacitors for energy transfer Full soft charging, soft switching, and minimal device voltage stresses are achieved under all operating conditions The STCs feature very high efficiency, power density, and robustness against component nonidealities over a wide range of operating conditions Furthermore, thanks to the full resonant operation, multiple STCs can operate in parallel with inherent droop current sharing, offering the best scalability and control simplicity These attributes make STC a disruptive and robust technology viable for industry's high volume adoption A novel equivalent DCX building block principle is introduced to simplify the analysis of STC A 989% efficiency STC product evaluation board (4-to-1, 650 W) has been developed and demonstrated for the next-generation of 48-V bus conversion for data center servers

Multilayered hierarchical polymer composites for high energydensity capacitors

Abstract: There is an urgent need to develop advanced energy storage materials to meet the ever-increasing demands of modern electronics and electrical power systems. Polymer-based dielectric materials are one of the most promising energy materials due to their unique combination of high breakdown strength, low dielectric loss, light weight and ultrahigh power density. However, their energy densities are severely limited by their low dielectric constants (K) and thus fall short of the demands of compact and efficient energy storage devices. Remarkable efforts have been performed to improve K, and consequently, energy densities of polymers, e.g. introducing high-K inorganic fillers into the polymer matrix to form polymer composites. However, a general drawback is that the increased K is usually achieved at the cost of substantially decreased breakdown strength, thus leading to a moderate improvement of energy density. More recently, the polymer dielectrics with optimized hierarchically layered structures has become an emerging approach to resolve the existing paradox between high K and high breakdown strength in single-layered composite films, which resulted in substantial improvement in their capacitive energy storage performance. It is demonstrated that the electric field distribution, breakdown strength and capacitive performance can be readily adjusted by systematically varying the interfaces, chemical structures and ratios of the constituent layers. This review, for the first time, outlines the contemporary models and theories, and summarizes the research advances of multilayered hierarchical polymer composites (MHPCs), including inorganic particle/organic MHPCs and all-organic layered films in the field of high-energy-density capacitors. The efficient strategies for improving the energy storage performance of MHPCs have been highlighted. To conclude, the remaining challenges and the promising opportunities for the development of MHPCs for capacitive energy storage applications are presented.

Ultra-high energy-storage density and fast discharge speed of (Pb0.98−xLa0.02Srx)(Zr0.9Sn0.1)0.995O3 antiferroelectric ceramics prepared via the tape-casting method

Abstract: Inspired by the increasing demand for high energy-storage capacitors in electronic and electrical systems, the development of dielectrics with high energy-storage performance has attracted much attention recently. Here, a record-high recoverable energy-storage density of 11.18 J cm−3 and a high energy efficiency of 82.2% are realized in (Pb0.98–xLa0.02Srx)(Zr0.9Sn0.1)0.995O3 (PLSZS) antiferroelectric ceramics prepared using the tape-casting method. Sr2+-doping and the tape-casting method give rise to a colossal increase in breakdown strength and switching of the electric field between the antiferroelectric and ferroelectric phase, which are responsible for the excellent energy-storage properties. Furthermore, with respect to the discharge performance, the antiferroelectric PLSZS ceramics exhibit a high discharge energy density of 8.6 J cm−3, and fast discharge speed where 90% of the stored energy could be released in 185 ns. This study opens up a promising and feasible route for designing high energy-storage materials via an appropriate element doping and fabricating method, and more importantly, gives PLSZS antiferroelectric ceramics an unexpected role with potential for application in high-power pulsed capacitors.

A New Free-Standing Aqueous Zinc-Ion Capacitor Based on MnO 2 –CNTs Cathode and MXene Anode

Abstract: Restricted by their energy storage mechanism, current energy storage devices have certain drawbacks, such as low power density for batteries and low energy density for supercapacitors. Fortunately, the nearest ion capacitors, such as lithium-ion and sodium-ion capacitors containing battery-type and capacitor-type electrodes, may allow achieving both high energy and power densities. For the inspiration, a new zinc-ion capacitor (ZIC) has been designed and realized by assembling the free-standing manganese dioxide–carbon nanotubes (MnO2–CNTs) battery-type cathode and MXene (Ti3C2Tx) capacitor-type anode in an aqueous electrolyte. The ZIC can avoid the insecurity issues that frequently occurred in lithium-ion and sodium-ion capacitors in organic electrolytes. As expected, the ZIC in an aqueous liquid electrolyte exhibits excellent electrochemical performance (based on the total weight of cathode and anode), such as a high specific capacitance of 115.1 F g−1 (1 mV s−1), high energy density of 98.6 Wh kg−1 (77.5 W kg−1), high power density of 2480.6 W kg−1 (29.7 Wh kg−1), and high capacitance retention of ~ 83.6% of its initial capacitance (15,000 cycles). Even in an aqueous gel electrolyte, the ZIC also exhibits excellent performance. This work provides an essential strategy for designing next-generation high-performance energy storage devices.

Flexible Zinc-Ion Hybrid Fiber Capacitors with Ultrahigh Energy Density and Long Cycling Life for Wearable Electronics.

Abstract: Emerging wearable electronics require flexible energy storage devices with high volumetric energy and power densities. Fiber-shaped capacitors (FCs) offer high power densities and excellent flexibility but low energy densities. Zn-ion capacitors have high energy density and other advantages, such as low cost, nontoxicity, reversible Faradaic reaction, and broad operating voltage windows. However, Zn-ion capacitors have not been applied in wearable electronics due to the use of liquid electrolytes. Here, the first quasisolid-state Zn-ion hybrid FC (ZnFC) based on three rationally designed components is demonstrated. First, hydrothermally assembled high surface area and conductive reduced graphene oxide/carbon nanotube composite fibers serve as capacitor-type positive electrodes. Second, graphite fibers coated with a uniform Zn layer work as battery-type negative electrodes. Third, a new neutral ZnSO4 -filled polyacrylic acid hydrogel act as the quasisolid-state electrolyte, which offers high ionic conductivity and excellent stretchability. The assembled ZnFC delivers a high energy density of 48.5 mWh cm-3 at a power density of 179.9 mW cm-3 . Further, Zn dendrite formation that commonly happens under high current density is efficiently suppressed on the fiber electrode, leading to superior cycling stability. Multiple ZnFCs are integrated as flexible energy storage units to power wearable devices under different deformation conditions.

Dual-T-Type Seven-Level Boost Active-Neutral-Point-Clamped Inverter

Abstract: The conventional three-level active-neutral-point-clamped (ANPC) inverter requires high dc-link voltage at least twice the peak of ac output. To reduce the dc-link voltage, a recent topology that enhanced the voltage gain from half to unity has been presented. In this letter, an alternative ANPC topology is established by using two T-type inverters. Two floating capacitors with self-voltage balancing capability are integrated to achieve a voltage-boosting gain of 1.5. In addition, the proposed topology is capable of generating seven voltage levels. Its operation is validated through circuit analysis followed by experimental results of a prototype.

Packed E-Cell (PEC) converter topology operation and experimental validation

Abstract: This paper proposes a novel single-dc-source multilevel inverter called Packed E-Cell (PEC) topology to achieve nine levels with noticeably reduced components count, while dc capacitors are actively balanced. The nine-level PEC (PEC9) is composed of seven active switches and two dc capacitors that are shunted by a four-quadrant switch to from the E-cell, and it makes use of a single dc link. With the proper design of the corresponding PEC9 switching states, the dc capacitors are balanced using the redundant charging/discharging states. Since the shunted capacitors are horizontally extended, both capacitors are simultaneously charged or discharged with the redundant states, so only the auxiliary dc-link voltage needs to be sensed and regulated to half of the input dc source voltage, and consequently, dc capacitors' voltages are inherently balanced to one quarter of the dc bus voltage. To this end, an active capacitor voltage balancing integrated to the level-shifted half-parabola carrier PWM technique has been designed based on the redundant charging/discharging states to regulate the dc capacitors voltages of PEC9. Furthermore, using the E-cell not only reduces components count but also the proposed topology permits multi ac terminal operation. Thus, five-level inverter operation can be achieved during the four-quadrant switch fault, which confers to the structure high reliability. The theoretical analysis as well as the experimental results are presented and discussed, showing the basic operation, multi-functionality, as well as the superior performance of the proposed novel PEC9 inverter topology.