Wide Voltage Range Research Articles

Isolated Boost Type Resonant Converter With Fixed Frequency PWM and Load-Independent Voltage Gain

This article proposes an isolated boost type resonant converter (IBTRC) with fixed frequency pulsewidth modulation (PWM), which has load-independent gain characteristics. Only one magnetic component and two active switches are used in the proposed IBTRC. Therefore, compared with the two-stage converter and the current-fed resonant converter (CFRC), the number of magnetic components and switches of the proposed IBTRC is reduced. Moreover, with the proposed modulation, the converter obtains the benefits of load-independent voltage gain characteristics. Under wide load and voltage range, all switches can realize zero-voltage switching (ZVS) and all diodes can realize zero-current switching (ZCS). The operation mode, characteristics, and parameters design process of the proposed solution are also described in detail. Finally, a 600-W prototype is built to verify the validity and the advantages of the proposed scheme.

Preparation of three-dimensional ordered macro-/mesoporous SnO2 nanomaterials for electrocatalytic CO2 reduction

Herein, three-dimensional ordered macro-/mesoporous (3DOM/m) SnO 2 catalysts are synthesized at different calcination temperatures. The optimized catalyst 3DOM/m SnO 2 -450 shows excellent electrocatalytic performance in CO 2 -saturated 0.5 M KHCO 3 electrolyte with a current density of -25.5 mA cm -2 at -1.2 V (vs. RHE) and the maximum Faradaic efficiency of formate of 83% at -1.0 V (vs. RHE). The ordered interconnected macro-/mesoporous structure of the 3DOM/m SnO 2 promotes the mass/charge transfer across the electrode, and the mesoporous structure enables the catalyst to have more accessible reactive active sites, thus improving the catalytic selectivity and activity. This work not only offers an efficient porous tin-based catalyst for formate generation, but also provides a promising strategy for the design and fabrication of robust electrocatalysts for the electrocatalytic CO 2 reduction in the future. Data will be made available upon request. The three-dimensional ordered macro-/mesoporous SnO 2 nanomaterial shows a wide operating voltage range with the Faradaic efficiencies of over 70% for formate at -0.8 ~ -1.2 V (vs. RHE) in 0.5 M KHCO 3 solution for the CO 2 reduction reaction. • 3D ordered macro-/mesoporous SnO 2 materials are prepared by dual-templating method. • The optimized catalyst shows superior electrocatalytic CO 2 reduction performance. • The formate Faradaic efficiency can be maintained at 82% for a long time. • The unique macro-/mesoporous structure contributes to the high performance.

Rejuvenating Propylene Carbonate‐based Electrolyte Through Nonsolvating Interactions for Wide‐Temperature Li‐ions Batteries (Adv. Energy Mater. 48/2022)

Lithium-Ion Batteries In article number 2201801, Ziqi Zeng, Jia Xie, and co-workers report that the non-solvating interactions within electrolytes can be employed to tune the strength and topology of Li+-propylene carbonate (PC), which enhances the graphite compatibility of PC-based electrolytes over a wide temperature range and high voltage.

A General and Automatic RMS Current Oriented Optimal Design Tool for LLC Resonant Converters

LLC resonant converters are used in renewable energy applications to achieve high power efficiency conversions between different energy sources, buses, and energy storage elements. The traditional design methods for LLC resonant converters are based on a simple frequency-domain analysis (FDA). However, the accuracy of FDA is not satisfactory, especially at wide voltage range applications. To overcome the drawbacks of the traditional FDA method in wide-range applications, in this article, the time-domain analysis (TDA) is adopted to achieve accurate analysis of LLC converters. Efficiency is normally selected as the optimization objective, where the circuit components and accurate power loss models are required beforehand. To achieve a more general optimal design method for LLC converters, a simple root-mean-square (rms) current and TDA-based optimal design method is proposed. The optimal design is achieved by minimizing the converter rms current and ensuring some key design considerations. Moreover, an automatic design tool for the proposed rms-current-based optimal design method is developed, and advanced optimization algorithms are introduced to improve the optimization speed. A 2.5-kW experimental prototype is built using the optimal circuit parameters. Experimental results under different operating conditions are demonstrated, and the results are consistent with the theoretical analysis. Efficiency comparisons between the proposed optimal design method and conventional design method are made. The proposed optimal design method can improve the converter efficiency by a maximum value of 2.14%.

A Cost-Effective and DC-Fault Tolerant Alternate Arm Converter With Wide Range Voltage Adaptability

In this article, an enhanced three-arm alternate arm multilevel converter (AAMC), called T-type AAMC (T-AAMC), is proposed for achieving dc fault ride-through capability with reduced semiconductor power devices compared to the hybrid modular multilevel converter (MMC). The upper and lower dc arms of T-AAMC are formed by half-bridge submodules (SMs) and series devices for lower construction costs, while the ac arm uses full-bridge SMs to realize dc fault tolerance. First, the arm phase-shift conducting modulation is applied for energy balance of converter stacks under wide-range operation by adjusting the arm phase-shift angle to match ac grid voltage and power factor. Then, the SM number, power device number, and SM capacitance are evaluated for T-AAMC under optimized modulation design. Analyses illustrate that 43% SMs, 17% power devices, and 44% energy storage requirement are reduced with the proposed topology than that with hybrid MMC. Furthermore, the closed-loop control system is designed to dynamically regulate the energy sharing between dc and ac stacks. Finally, full-scale simulations and down-scaled experiments are performed to verify the feasibility of the proposed converter and the theoretical analysis of its modulation and implementation.

A self-powered PVA-based flexible humidity sensor with humidity-related voltage output for multifunctional applications

In the context of the industry that supports green energy and electronics, the development of a humidity sensor with self-powered characteristics and the ability to be worn by humans is crucial for expanding its practical applications. Here, we report a self-powered flexible humidity sensor based on a sandwich structure of polyvinyl alcohol (PVA)/nanocarbon powder (NCP)/magnesium chloride (MgCl2) moisture-sensitive composite film (PCMF) and Cu and Al conductive adhesive tape. This unique sandwich structure allows it to readily adsorb and diffuse water molecules in humid environments, greatly enhancing its responsiveness to humidity changes. The Cu/PCMF/Al sensor generates voltage corresponding to different relative humidity (RH) levels and has a unique RH-Voltage linear response characteristic (R2 = 0.9978), notable for its fast response/recovery (6/11 s), wide detection range (RH 11%−98%), long-term stability (over 30 days), and high voltage (∼0.6 V) and current (∼2.3 µA) output at RH 98%. More importantly, due to the good water solubility of PVA and MgCl2 salts, the designed sensor exhibits recyclability and reusability properties (90.31% of the original response voltage value), which can significantly minimize material waste and potentially reduce manufacturing costs. In addition, this sensor can be successfully applied to domains involving human wearables, such as being integrated into a mask for monitoring human respiration, and has excellent identification capabilities even for simple coughs and pronunciations. The demonstration of non-contact humidity sensing validates the prospective application of this sensor in non-contact switching devices. This work presents a novel design idea for the development of wearable humidity sensors with low cost, simple preparation, and high responsiveness, as well as self-powered characteristics.

Surface plasmon resonance voltage sensor based on a liquid crystal-infiltrated hollow fiber

We propose an electric field tunable nematic liquid crystal (NLC) infiltrated single-hole hollow fiber sensor for voltage measurement. Due to only an air hole, the proposed sensor got a straightforward structure, and the liquid-filling process will be uncomplicated. The addition of the gold wire successfully incorporated the surface plasmon resonance (SPR) phenomenon as a sensing methodology in the proposed sensor. Besides that, the use of metal wire instead of the metal film will reduce the complicacy associated with the acquisition of uniform film thickness. The sensor characterization and performance evaluation have been done using the finite element method (FEM) for a wide voltage range from 200V to 400V. The sensor exhibits wavelength sensitivity (WS) and linearity as high as 5 nm/V and 0.9935, respectively. In addition, maximum amplitude sensitivity (AS) and wavelength resolution (R) is attained of −353.46 RIU−1 and 0.02V, respectively. Due to its excellent performance with a wide sensing range, and a simple and compact structure, the proposed sensor can be used for voltage measurement in a sophisticated place.

An interleaved multilevel converter for onboard EV charging application

ABSTRACT This paper proposes an interleaved multilevel converter (MLC)-based charger with power rating 2.8 kW to charge on-board battery of electric vehicle (EV). It comprises two stages: (1) an interleaved multilevel ac–dc converter; and (2) an LLC-resonant dc–dc converter. The interleaved approach efficiently maintains the optimum power level. The switching scheme implemented for MLC maintains the source current sinusoidal, supports unity power factor (UPF) and has the capability to balance the capacitor voltage. The MLC maintains UPF and balances capacitor voltage without any auxiliary circuit. In addition, MLC provides lower voltage stress and reduced total harmonic distortion (THD), therefore, making it a better choice for ac–dc conversion stage in battery charging application. The dc–dc converter furnishes regulated and wide output voltage range for on-board charging system. The principle of operation, modulation technique and control strategy for both the converters are analysed. Following theoretical analysis, laboratory experiments were conducted to validate the implemented approach. The results signify that for output voltage range of 24−72 V, UPF is maintained at input, lower stress across switches and capacitor voltage is balanced. The performance of MLC is satisfactory as it attains a peak efficiency of 97% with THD of 2.07%.

Research on Bidirectional Isolated Charging System Based on Resonant Converter

This paper proposes a two-stage bidirectional isolated charging system, which can realize the bidirectional flow of electric energy, not only making the electric energy flow from the grid side to the battery side but also converting the battery’s energy into single-phase alternating current to supply other electric equipment. The charging system also has the function of power factor correction and wide-range voltage output. The front stage of the charging system is a bidirectional totem pole structure power factor correction converter with a voltage and current double closed-loop control strategy to ensure the stability of the DC bus voltage, and the rear stage is a bidirectional CLLLC resonant converter, which adopts a high-frequency soft start strategy to reduce the inrush current during start-up and ensure the safe operation of the converter. Moreover, the frequency control strategy is used to make it have a wide range of DC output characteristics. In this paper, the principle analysis and parameter calculation of the charging system is carried out, the simulation platform and hardware circuit design are built, and a test prototype is piloted to verify the bidirectional operating characteristics of the charging system. The simulation and experimental results demonstrate the correctness of the theoretical analysis and topology design.

A New Optimal Thermal-Based Adaptive Frequency Control for Bidirectional DC–DC Converter with Full-Range ZVS

A new, optimal thermal-based adaptive frequency control (OTC) for a bidirectional DC–DC converter with full-range zero-voltage switching (ZVS) is presented in this paper. The proposed OTC achieves ZVS for a bidirectional DC–DC converter without any zero-crossing detection (ZCD) circuit or current sensor. In order to ensure a ZVS over a wide voltage and load range, the optimal switching frequency was adjusted by detecting and tracking the lowest junction temperature of the semiconductor device. Because the proposed OTC does not need a ZCD circuit, the complexity of the circuit and the susceptibility of the sampling noise are reduced. Additionally, compared with the expensive current sensor, the proposed method of temperature detection by the NTC thermistor decreases the cost. In addition, the proposed OTC does not need accurate circuit parameters and voltage or current sampling results, so the dependence on the parameters is reduced. Moreover, the temperature of the switch is directly monitored in the proposed OTC, which can effectively protect the device. A prototype with 16–32 V input and 48 V output was built, and the experiment results prove the effectiveness and feasibility of it.

Efficient and Fast Active Equalization Method for Retired Battery Pack Using Wide Voltage Range Bidirectional Converter and DBSCAN Clustering Algorithm

This article presents an efficient and fast echelon battery equalization method based on wide voltage range bidirectional converter combined with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DBSCAN (density-based spatial clustering of applications with noise)</i> clustering control strategy. Thanks to the wide voltage range and bidirectional buck-boost characteristics of the four-switch bidirectional converter, the battery energy can be reasonably redistributed between the battery and the super capacitor. The converter operating in synchronous rectification mode can not only achieve bidirectional energy flow in a wide voltage range, but also has a high energy conversion efficiency. The <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DBSCAN</i> clustering algorithm is used to divide all battery cells into groups, and each group may contain one or more adjacent and nonadjacent battery cells. First, the nonadjacent single cells are balanced and integrated into adjacent group with the closest voltage. Then, the groups with different voltages are balanced by group-to-group, thereby realizing rapid balance of the entire battery pack. In order to verify the effectiveness of the proposed method, simulations and experimental verification were carried out. The experimental results show that, comparing with traditional battery balancing methods, the proposed method achieves shorter balancing time and higher balancing efficiency.

Modeling the Influence of the Electrolyte Concentration on Electrical Characteristics of an Alkaline Electrolyzer

This paper presents the results of investigations into modeling the DC and dynamic characteristics of an alkaline electrolyzer. A model of the device under consideration is proposed in the form of analytical relationships in which the coefficients depend on the concentration of the potassium hydroxide solution contained in the electrolyzer under consideration. The correctness of the proposed model is verified by comparing the calculated and measured current–voltage characteristics and the dependence of the module of the impedance of the electrolyzer on the frequency obtained at different values of the electrolyte concentration. The dependence of the time needed to produce a given portion of hydrogen on the supply current and the electrolyte concentration is also presented. Good compliance with the calculation and measurement results is obtained over a wide range of voltage and current, frequency, and concentration of the electrolyte.

Aqueous hybrid electrochemical capacitors with ultra-high energy density approaching for thousand-volts alternating current line filtering

Filtering capacitors with wide operating voltage range are essential for smoothing ripples in line-powered system, which are still unsatisfactory due to low energy density and limited working voltage scopes. Herein, we report an aqueous hybrid electrochemical capacitor with areal specific energy density of 1.29 mF V2 cm−2 at 120 Hz, greater than common aqueous ones. Interestingly, it can be easily integrated at scale to show excellent flexibility, controllable and stable filtering performance, in which an integrated device (e.g., seven units in series) exhibits fluctuation of 96 mV, 10 times smaller than an aluminum electrolytic capacitor with similar capacitance. A record-high 1,000 V can also be achieved after integrating 670 units, exceeding those reported so far, and about 1.5 times of commercial bulk aluminum electrolytic capacitors (~700 V). This work opens up a new insight for promising applications in multiple electricity transmission systems that requiring high smoothness under harsh voltage.

Interlaboratory comparison of voltage sweep methods used for the electrical characterization of encapsulated high‐efficiency c‐Si solar cells

AbstractThis work presents the comparison of measurement results for four types of encapsulated high‐efficiency c‐Si solar cells measured by 10 laboratories based in Asia, Europe and North America utilizing a wide range of voltage sweeping methods, which include well‐established procedures that represent good industry practice, as well as recently introduced ones that have not been verified yet. The aim of the round‐robin interlaboratory comparison was to examine the measurement comparability of different laboratories with respect to their measurement methods of high‐efficiency solar cells. A proficiency test was employed to examine the consistency of results and their corresponding uncertainties. The short‐circuit current (ISC) under STC measured by four accredited laboratories was firstly compared. In order to investigate the consistency related to the high device capacitance, the value of the ISC was fixed for all 10 participants. The results of all participant laboratories—compared via En number analysis—generally remained well within [−1; 1], thus indicating consistency between the measured values and the reference values within stated measurement uncertainties. The differences remained within ±1.15% in PMAX and within ±0.35% in VOC for all participants and methods applied. Correlations were observed among the PMAX, VOC, and FF differences from their weighted mean. An analysis of the effects of transient current (dQ/dt) at maximum power point caused by hysteresis effect on the measurement error of PMAX showed a significant linear correlation between error of maximum power and junction voltage sweep rate for heterojunction (HJT) solar cells. This work forms the basis to validate all applied methods and their stated measurement uncertainties.

LLC resonant converter based on PFM and secondary‐side short‐circuit control for on‐board charger

AbstractCommonly used lithium‐ion battery on‐board charger (OBC) for electric vehicles (EVs) needs a wide output voltage range, but the traditional LLC converter is hard to meet the need under the condition of high efficiency and high power density. In this paper, a resonant converter with hybrid modulation is proposed. The converter has a relatively simple topology and control method. Compared with the traditional LLC topology, only two diodes are replaced by MOSFETs on the secondary side of the transformer, and no auxiliary components are added. The primary‐side switches adopt PFM) and the secondary‐side switches adopt short‐circuit control in the proposed converter, which can realize a wide output voltage range, in a narrow switching frequency range with excellent soft‐switching performance. The proposed converter can effectively reduce the resonant current and the volume of transformer core and achieve energy delivery with high power density and high efficiency. The operation principles, voltage gain, and soft‐switching conditions of the converter are analyzed in this paper. Finally, a 3.3‐kW SiC‐based prototype with 400‐V input and 250‐ to 430‐V output is built to verify the feasibility and validity of the proposed converter.

Mitigating interfacial instability of high-voltage sodium layered oxide cathodes with coordinative polymeric structure

High operating voltage ensures high sodium utilization and high specific capacity of sodium-based layered oxides for sodium-ion batteries (SIBs), but charging to high voltage (>4.2 V vs. Na+/Na) may facilitate the irreversible phase transformation and undesirable interfacial reactions with electrolyte, resulting in severe capacity fading. Herein, we demonstrate an organic surface modification strategy to remarkably enhance the interfacial stability and electrochemical performance of high-voltage sodium-based layered oxides through a copolymer nanolayer of methacrylic acid and acrylonitrile (PMAA-AN). The copolymer nanolayer with strong electron-donating groups could anchor transition metal ions by coordinative interaction and prevent cathode materials from being corroded by electrolyte, thus slowing down interfacial structural degradation during cycling. The Na0.67Li0.16Ni0.33Mn0.67O2+δ (NLNM) coated with moderate PMAA-AN (0.5 wt%) exhibits remarkable improvement and excellent electrochemical performance with an initial capacity of 173.4 mAh g−1 and 86.0% capacity retention after 100 cycles, a superior rate capability of 100.1 mAh g−1 at 5 C within the wide voltage range of 1.5–4.5 V. This work provides new insights on the protective mechanism of polymeric coatings with coordinative structure and pave a way to advance high‐voltage layered oxides for high‐energy‐density SIBs.

Nano MnOx encapsulated pyrrole-carbazole copolymer and polyvinyl chloride/carbon-coated flexible electrodes for solid-state supercapacitor cell

Pyrrole (Py) and carbazole (Cz) monomers are polymerized simultaneously in the presence of MnOx nanoparticles synthesized chemically on a stainless steel mesh (SSM) electrode by the pulse galvanostatic method in an acetonitrile medium. The resulting p(Py-co-Cz)/MnOx composite is characterized by cyclic voltammetry EIS, GCD XPS, XRD, FESEM, BET, and TEM. Since the current is applied for short periods in the presence of both monomers, p(Py-co-Cz) copolymer chains occur in short lengths, suitable for supercapacitor electrodes. The copolymer has higher Cm and lower Rct values as well as higher porosity that improves ion transport, thus greater stability than the homopolymers. It may be due to tricyclic Cz segments located between Py segments in the chains, which inhibit degradation. During the synthesis, nano-sized MnOx is also encapsulated homogeneously into the p(Py-co-Cz) coating, where 5 % is the weight percentage of manganese. Since the composite combines the advantages of the conductive polymer and metal oxide, it has the lowest Rct and highest Cm values among the coatings here. The p(Py-co-Cz)/MnOx coating with 10 mg cm−2 exhibits a high specific capacitance of 352 F g−1 at 5 A g−1 as well as flexibility, as its specific capacitance remains nearly stable (99 %) up to a bending angle of 90°. The cathode prepared from polyvinyl chloride (PVC)/activated carbon/carbon black on SSM operates within a wide voltage range of 0 to −1.5 V at 98 % cycle stability after 1000 cycles. The asymmetric cell configuration with the flexible anode and cathode electrodes provides 38 kW kg−1 and 5.28 Wh kg−1 at 5 A g−1 at a wide potential range of 2.1 V in PVA/Na2SO4 gel electrolyte, and the cycling stability was 67 % after 1000 cycles.

An all-digital CMOS temperature sensor with a wide supply voltage range

This paper proposes a MOSFET-based all-digital temperature sensor fabricated in a standard 55-nm CMOS process. The temperature sensing elements of the sensor are composed of ring oscillators, which convert temperature information into frequency information. The frequency ratio’s proportional to absolute temperature (PTAT) feature is generated by using two separate frequency oscillators with varied temperature sensitivity. The frequency-to-digital converter (FDC) converts frequency information into digital representation without introducing any overhead reference clock. A die area of 1915µm2 is occupied, owing to the all-digital architecture. After two-point calibration, the proposed sensor achieves an error of -0.4°C∼+0.6°C throughout a temperature range of -40°C∼125°C. With the help of class-adjustable oscillators, the sensor can function in a wide supply voltage range from 0.5V to 1.2V. It obtains a resolution of 0.166°C at room temperature with a dissipation of 2.5µW.

A compact floating and grounded memristor model using single active element

Memristor with defined operational specifications is a challenging task that promotes innovation in emulation circuit modelling. This article presents a single active block based compact memristor emulator architecture which is suitable for both floating and grounded circuit topologies. It effectively operates in incremental/decremental modes in both the configurations. The proposed model utilizes only one Differential Voltage Current Conveyor Transconductance Amplifier (DVCCTA) as an active block along with a few passive components. It discourages the use of extra sub-circuit components like multiple active blocks, summers and multipliers. The circuit is intended to work at ±1 V of dc power supply and has a power consumption of 8.74 mW. The proposed emulator model exhibits all the characteristics of an ideal memristor with an operating frequency of 12.8 MHz. It has wide working voltage range of 50–500 mV. The memristor model is built and simulated using the TSMC 0.18 μm CMOS process parameter. The reliability and effectiveness of the proposed model is verified through non-ideal, Monte-Carlo, process corner, non-volatility and temperature variation analysis. Furthermore, the memristor prototype is constructed on the breadboard using discrete ICs AD844AN and CA3080. The experimental outcome is found in accordance with the simulation. The applicability of the proposed memristor model is verified by implementing a memristor based Schmitt trigger circuit.

Engineering Oxygen Vacancies on Mixed-Valent Mesoporous α-MnO2 for High-Performance Asymmetric Supercapacitors.

Intrinsically poor conductivity and sluggish ion-transfer kinetics limit the further development of electrochemical storage of mesoporous manganese dioxide. In order to overcome the challenge, defect engineering is an effective way to improve electrochemical capability by regulating electronic configuration at the atomic level of manganese dioxide. Herein, we demonstrate effective construction of defects on mesoporous α-MnO2 through simply controlling the degree of redox reaction process, which could obtain a balance between Mn3+/Mn4+ ratio and oxygen vacancy concentration for efficient supercapacitors. The different structures of α-MnO2 including the morphology, specific surface area, and composition are successfully constructed by tuning the mole ratio of KMnO4 to Na2SO3. The electrode materials of α-MnO2-0.25 with an appropriate Mn3+/Mn4+ ratio and abundant oxygen vacancy showed an outstanding specific capacitance of 324 F g-1 at 0.5 A g-1, beyond most reported MnO2-based materials. The asymmetric supercapacitors formed from α-MnO2-0.25 and activated carbon can present an energy density as high as of 36.33 W h kg-1 at 200 W kg-1 and also exhibited good cycle stability over a wide voltage range from 0 to 2.0 voltage (kept at approximately 98% after 10 000 cycles in galvanostatic cycling tests) and nearly 100% Coulombic efficiency. Our strategy lays a foundation for fine regulation of defects to improve charge-transfer kinetics.