Wide Voltage Range Research Articles

Optimized Modulation Strategy of NH3L-DAB Converter to Minimize RMS Current for Wide Voltage Range Applications

Dual active bridge (DAB) converter is one of the most popular bidirectional isolated dc/dc converters. Comparing with the two-level DAB converter, the multilevel DAB topologies take advantages of providing more control degrees of freedom to enhance the control flexibility. Therefore, these topologies are promising alternatives for wide voltage range applications. This article proposed an optimizing modulation strategy for neutral-point-clamped hybrid three-level dual active bridge (NH3L-DAB) converter to minimize the rms value of inductor current and the conduction losses. First, the basic operating principle of NH3L-DAB is analyzed comprehensively in the article. Afterward, the concept of global optimal condition is employed to derive the optimal modulation, and the corresponding analytical expressions of the control coordinates for rms current minimization are derived. By applying the optimal modulation strategy, NH3L-DAB facilitates to break the performance barriers of the prior-of-art of two-level DAB converter when the voltage transmission ratio has large variation. Finally, a bidirectional prototype with 200–450 V input and 20–28.8 V output is built to demonstrate the superior performance of the proposed optimal modulation strategy, and the detailed explanation of the experimental results is given as well.

An Enhanced Dual Active Bridge Converter With Full Domain ZVS by Utilizing a Simple Segment Control for Wide Voltage Range Applications

A dual-transformer-based enhanced dual active bridge (DAB) dc–dc converter for wide voltage range applications is introduced in this article. A power leg and transformer of the conventional DAB converter (CDABC) are split in two parts, leading to an expansion of the control freedom. Its wide voltage operating range does not rely on the small leakage inductor design and high transformer turns ratio. The root mean square value of the leakage inductor current is optimized with the ensuring of full domain zero voltage switching. The conduction losses and switching losses can be significantly reduced in buck mode compared to the CDABC. A simple segment control strategy with four control degrees of freedom is employed to avoid inrush from mode switching. The analysis and control processes are simplified, and the control loop is a simple closed voltage loop without the need for look-up table checking. The discussed converter and control strategy are verified by a 1.0 kW prototype.

Gate-controlled proximity magnetoresistance in In1−xGaxAs/(Ga,Fe)Sb bilayer heterostructures

The magnetic proximity effect (MPE), ferromagnetic coupling at the interface of magnetically dissimilar layers, attracts much attention as a promising pathway for introducing ferromagnetism into a high-mobility non-magnetic conducting channel. Recently, our group found giant proximity magnetoresistance (PMR), which is caused by MPE at an interface between a non-magnetic semiconductor InAs quantum well (QW) layer and a ferromagnetic semiconductor (Ga,Fe)Sb layer. The MPE in the non-magnetic semiconductor can be modulated by applying a gate voltage and controlling the penetration of the electron wavefunction in the InAs QW into the neighboring insulating ferromagnetic (Ga,Fe)Sb layer. However, optimal conditions to obtain strong MPE at the InAs/(Ga,Fe)Sb interface have not been clarified. In this paper, we systematically investigate the PMR properties of In1-xGaxAs (x = 0%, 5%, 7.5%, and 10%) / (Ga,Fe)Sb bilayer semiconductor heterostructures under a wide range of gate voltage. The inclusion of Ga alters the electronic structures of the InAs thin film, in particular changing the effective mass and the QW potential of electron carriers. Our experimental results and theoretical analysis of the PMR in these In1-xGaxAs/(Ga,Fe)Sb heterostructures show that the MPE depends not only on the degree of penetration of the electron wavefunction into (Ga,Fe)Sb but also on the electron density. These findings help us to unveil the microscopic mechanism of MPE in semiconductor-based non-magnetic/ferromagnetic heterojunctions.

Unravelling the Nature of the Intrinsic Complex Structure of Binary-Phase Na-Layered Oxides.

The layered sodium transition metal oxide, NaTMO2 (TM = transition metal), with a binary or ternary phases has displayed outstanding electrochemical performance as a new class of strategy cathode materials for sodium-ion batteries (SIBs). Herein, an in-depth phase analysis of developed Na1-x TMO2 cathode materials, Na0.76 Ni0.20 Fe0.40 Mn0.40 O2 with P2- and O3-type phases (NFMO-P2/O3) is offered. Structural visualization on an atomic scale is also provided and the following findings are unveiled: i) the existence of a mixed-phase intergrowth layer distribution and unequal distribution of P2 and O3 phases along two different crystal plane indices and ii) a complete reversible charge/discharge process for the initial two cycles that displays a simple phase transformation, which is unprecedented. Moreover, first-principles calculations support the evidence of the formation of a binary NFMO-P2/O3 compound, over the proposed hypothetical monophasic structures (O3, P3, O'3, and P2 phases). As a result, the synergetic effect of the simultaneous existence of P- and O-type phases with their unique structures allows an extraordinary level of capacity retention in a wide range of voltage (1.5-4.5 V). It is believed that the insightful understanding of the proposed materials can introduce new perspectives for the development of high-voltage cathode materials for SIBs.

Bidirectional Resonant Converter With Minimized Switching Loss Over Wide Operating Voltage Range

In this article, we propose a bidirectional resonant converter having minimized switching loss in a wide operating voltage range. This converter serves as a pulse-width-modulation (PWM) full-bridge resonant-boost converter in the forward operation and a PWM half-bridge resonant-buck converter in the reverse operation. It can then achieve wide voltage gain range even in the reverse operation. By employing a T-type active voltage doubler, we can attain almost zero voltage switching at the turn-off instants, and so switching loss occurred at all active switches becomes negligible. Moreover, the circuit experiences very little instantaneous reactive current under wide voltage variations. Therefore, the proposed converter can accomplish a wide range of voltage gains in both power flow directions and high efficiency over a wide range of operating voltages. We present circuit operation and steady-state analysis in detail. We built a 3.3-kW/400-V prototype that copes with 250~415 V inputs and tested to demonstrate the superior quality of its circuit design.

The enhancement of cyclability of Ni‐rich LiNi 0 . 9 Co 0 . 05−x Mn 0 . 05 Zn x cathode materials by the substitution of Zn for Co

In the development of LiNixCoyMnzO2 (NCM) cathode active materials in lithium-ion batteries (LIBs) for electric vehicles, it is widely accepted that Ni-rich and Co-free NCM is the best candidate for the promotion of electric vehicle deployment. Inspired by the fact that Zn is an element that can be incorporated in regenerated NCM in the LIB recycling, Zn is doped into NCM from an impurity level in the leachate from spent LIBs to a level where Co is completely replaced by Zn. LiNi0.9Co0.05Mn0.05O2 (NCM955), LiNi0.9Co0.0495Mn0.05Zn0.0005O2 (NCMZ-0.05), LiNi0.9Co0.045Mn0.05Zn0.005O2 (NCMZ-0.5), and LiNi0.9Mn0.05Zn0.05O2 (NMZ955) are synthesized by a co-precipitation method. It is confirmed that Zn, which has a similar radius to Li+ and Ni2+, is incorporated into both Li and transition metal layers. An optimum cation mixing on the Zn-doped NCM surface and the expanded NCM lattice due to Zn doping lead to improved cyclability and rate capability. For example, the optimized NCMZ-0.5 exhibits enhanced capacity retention of 91.7% compared to NCM955 (69.8%) after 80 cycles. The cyclability improvement of Zn-doped NCM is ascribed to better reversibility as well as lower overvoltage than NCM955. In particular, NMZ955 displays outstanding capacity retention in cycling tests with a wide voltage range, which implies that Co-free NMZ has a competitive edge in cyclability compared to NCM. This work not only elucidates the positive effect of Zn doping in regenerated NCM, but also further provides a practical approach to designing a Co-free Ni-rich cathode for higher energy density.

An oversized Ku-band Cerenkov oscillator with pure TM01 mode output

An oversized Ku-band Cerenkov oscillator with pure TM01 mode output is proposed. By utilizing a separated slow-wave structure (SSWS), the resonant characteristic of the operating mode is preserved, whereas the resonant characteristics of the high order electromagnetic modes are destroyed. As a result, only the expected mode can be stimulated, and undesired beam–wave interactions are suppressed effectively. In terms of an oversized Cerenkov oscillator, the usage of SSWS shows great potential for obtaining pure operating mode output. By utilizing particle-in-cell simulation, microwaves with an output power of 4.5 GW and frequency of 14.1 GHz are obtained, when the beam voltage is 0.9 MeV, and the beam current is 12.9 kA. The percentage of the operating mode is up to 99.5% and exceeds 99% in a wide range of the beam voltage.

A Resonant Push–Pull DC–DC Converter With an Intrinsic Current Source Behavior for Radio Frequency Power Conversion

In this article, a resonant push–pull dc–dc converter suitable for switching frequencies in the MHz-range is investigated. Despite a simple design procedure with no need of multiresonant tuning, the converter topology is capable of providing a constant output current over a wide output voltage range in unregulated operation. Based on an analytical solution of steady-state operation, normalized dependencies of converter behavior are determined and used to formulate generalized design considerations. In order to verify the theoretical analysis, the design procedure of a 300-W prototype operating at a switching frequency of 6.78 MHz is described considering the impact of circuit parasitics on converter operation. The prototype provides a stable operation within the full output voltage range of 0–150 V and reaches a peak efficiency of 93% at the nominal output voltage. A rapid transient response of the converter is demonstrated by applying a closed-loop <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> / <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> -control to the prototype.

A Novel LLC Resonant Converter With Configurable Capacitors in Output Stage for Wide Output Voltage Range Operation

The traditional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter with variable switching frequency achieves wide output voltage range operation, but it is companied by the issues of reduced efficiency and difficult magnetic component design. To overcome these issues, a novel <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> converter with configurable capacitors in the output stage is proposed. It realizes two-times adjustment of output voltage by simply arranging the configurable capacitors in parallel or series in pulsewidth modulation manner. As compared to prior art, it reduces the output inductor, power losses, and switch capacity by 50%, 15.6%, and 5.7%, respectively. The experimental results obtained from a 100-V 1.5-kW setup verify the feasibility of the proposed converter.

Modified LLC Resonant Converter With LC Antiresonant Circuit in Parallel Branch for Wide Voltage Range Application

In this article, a modified <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> antiresonant circuit in parallel branch is proposed. The proposed converter is derived by placing <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> antiresonant circuit on parallel branch. In comparison with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter, the equivalent inductance of parallel branch of the proposed converter decreases along with switching frequency within regulating frequency range. This advantageous property contributes for that the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> current and circulating conduction loss in the primary side can be reduced at unity voltage conversion ratio due to large impedance of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> antiresonant circuit. Moreover, by optimizing resonant parameters design of parallel branch based on time-domain analysis, the magnetizing current is in close proximity to a sine wave and the conduction loss in the secondary side will be reduced, especially in the light load. A higher voltage conversion ratio can be achieved at low switching frequency due to decreased impedance in parallel branch. In addition, a design flowchart and a design practical case are given to help to implement an efficiency optimization algorithm to decide five resonant design parameters. Finally, a 2 kW 250 V—400 V-input and 48 V-output prototype is built, and the main experimental results are provided to verify the feasibility of the proposed converter and compare with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLC</i> resonant converter. Comparative state-plane trajectories are depicted to compare their characteristics and to verify the model-domain analysis.

Power quality improvements in a zeta conveter for brushless dc motor drives

&#x0D; &#x0D; &#x0D; An isolated Zeta converter is proposed as a power factor correction (PFC) converter with DC link voltage control for speed control of a induction motor (3 IM). The voltage source inverter (VSI). The proposed converter performs the PFC action and DC link voltage control in single stage using only one controller. The current multiplier approach with average current control is used for operation of the isolated Zeta converter in continuous conduction mode (CCM). A rate limiter in the reference DC link voltage is designed for the control of current and torque in 3 PHASE IM. The designed PFC converter results in an improved power quality at AC mains in a wide range of speed control and input AC voltage&#x0D; &#x0D; &#x0D;

Design and implementation of a single-phase buck-type inverter via an efficient hybrid control technique

PurposeThis paper aims to present the design and implementation of a new general-purpose single-phase buck-type inverter.Design/methodology/approachThe operation of the proposed inverter is based on the general-purpose buck converter. The proposed buck-type inverter topology is designed with reduced numbers of passive and active elements to minimize design cost and complexity. Also, an efficient hybrid control technique based on the proportional‐integral‐derivative (PID) supported by open-loop control signal is offered for the control of the proposed inverter. The proposed hybrid control method improves the performance of the PID controller during the change of inverter operation parameters. A close to single-phase sine wave output voltage with low total harmonic distortion (THD) can be produced by the proposed inverter in a wide range of voltage and frequency lower than the inverter input voltage value.FindingsSimulation and experimental test studies are applied to the proposed inverter. The experimental laboratory setup is built for 0–50 Hz, 0–100 Vp, 0.5 kW. Both the simulation and the experimental test results show that the single-phase inverter can produce close to sine wave output voltage with THD level under 5% in a wide range of frequency for various operating conditions and for different loads.Originality/valueIn this paper, a new topology and a new hybrid control technique that are patented by the corresponding author are implemented for a single-phase buck-type inverter through a scientific project. The operating results of the study reveal the efficient operating capability with a simple topology structure.

Observability of negative capacitance of a ferroelectric film: Theoretical predictions

We theoretically explore mechanisms that can potentially give rise to the steady-state and transient negative capacitance in a uniaxial ferroelectric film stabilized by a dielectric layer. The analytical expressions for the steady-state capacitance of a single-domain and polydomain states are derived within the Landau-Ginzburg-Devonshire approach and used to study the state stability vs the domain splitting as a function of dielectric layer thickness. Analytical expressions for the critical thickness of the dielectric layer, polarization amplitude, equilibrium domain period, and susceptibility are obtained and corroborated by finite element modeling. We further explore the possible effects of nonlinear screening by two types of screening charges at the ferroelectric-dielectric interface and show that if at least one of the screening charges is very slow, the total polarization dynamics can exhibit complex time- and voltage-dependent behaviors that can be interpreted as an observable negative capacitance. In this setting, the transient negative capacitance effect is accompanied by almost zero dielectric susceptibility in a wide voltage range and low frequencies. These results may help to elucidate the observation of the transient negative capacitance in thin ferroelectric films, and identify materials systems that can give rise to the behavior.

Multifunctional Dual Gated Coupling Device Using Van Der Waals Ferroelectric Heterostructure

Abstract2D ferroelectric materials have long attracted attention because of their switchable electrical polarization. However, it is still difficult to control the stability of the ferroelectric polarization. Here, ReS2, h‐BN, and 2D ferroelectric material α‐In2Se3 are combined to construct van der Waals heterostructure. The dual‐gated coupling configuration polarizes the ferroelectric α‐In2Se3 stably and effectively, allowing it to act as high‐performance nonvolatile memory, programmable rectifier, and negative capacitance field‐effect transistor. As nonvolatile memory, the device exhibits a large memory window (77%), large on/off ratio (&gt;106), ultralow programming state current (≈10‐13 A), and long data retention (&gt;104 s). As a programmable rectifier, the device can regulate rectification in a wide range of gate voltages with a large rectification ratio (3 × 105). When used as field‐effect transistor, the device demonstrates hysteresis‐free, the minimum sub‐threshold swing of 24.5 mV dec‐1 at room temperature. These results may inspire further development of ferroelectric van der Waals heterostructure devices.

Electronic Mechanism of In Situ Inversion of Rectification Polarity in Supramolecular Engineered Monolayer.

This Communication describes polarity inversion in molecular rectification and the related mechanism. Using a supramolecular engineered, ultrastable, binary-mixed self-assembled monolayer (SAM) composed of an organic molecular diode (SC11BIPY) and an inert reinforcement molecule (SC8), we probed a rectification ratio (r)-voltage relationship over an unprecedentedly wide voltage range (up to |3.5V|) with statistical significance. We observed positive polarity in rectification at |1.0V| (r = 107), followed by disappearance of rectification at ∼|2.25V|, and then eventual emergence of new rectification with the opposite polarity at ∼|3.5V| (r = 0.006; 1/r = 162). The polarity inversion occurred with a span over 4 orders of magnitude in r. Low-temperature experiments, electronic structure analysis, and theoretical calculations revealed that the unusually wide voltage range permits access to molecular orbital energy levels that are inaccessible in the traditional narrow voltage regime, inducing the unprecedented in situ inversion of polarity.

A Sharing-Branch Modular Multilevel DC Transformer With Wide Voltage Range Regulation for DC Distribution Grids

As the key equipment in dc distribution grids, dc transformer (DCT) suffers from low power density caused by a large number of submodules (SMs). Hence, this article proposes a novel DCT for the interconnection of medium-voltage dc (MVdc) and low-voltage dc (LVdc) distribution grids, which adopts a series-connected half-bridge SM branch (SSB) on MV-side to achieve low voltage stress of devices and reduce the number of SMs. Quasi square wave modulation strategy and phase-shifted control are employed to realize bidirectional power transmission control and zero-voltage switching (ZVS) for all switches. Furthermore, in order to ensure low current stress and ZVS within wide voltage range, a certain number of SMs are constantly inserted or bypassed to achieve voltage matching. Besides, smooth transition control strategy is employed to avoid current spikes caused by abruptly bypassing or inserting SMs. Based on the theoretical analysis, design consideration and control strategy are elaborated. Finally, a 500&#x00A0;kW&#x002F;6&#x2013;12&#x00A0;kV&#x002F;750&#x00A0;V simulation model and a 2&#x00A0;kW prototype are built to verify the proposed DCT.

A Novel Hybrid DC Transformer Combining Modular Multilevel Converter Structure and Series-Connected Semiconductor Switches

A hybrid dc transformer (DCT) combining the features of modular multilevel converter (MMC) and series-connected semiconductor switches (SSs) is proposed in this article, which is suitable for interconnection between medium-voltage dc networks and low-voltage dc networks. Compared with the conventional MMC-based DCT, the number of submodules (SMs) of the proposed DCT can be reduced under the same device voltage stress. A quasi-square-wave modulation is employed, which can ensure the high-reliability drive of SSs with the realization of zero voltage switching in a wide power and MV voltage range. The voltage self-balancing characteristic of the SM capacitor can be achieved in the proposed DCT, with no requirement of voltage sensor or specific modulation pattern. All the SSs are turned <small>on&#x002F;off</small> at zero voltage, the dynamic voltage balancing of the SSs is ensured naturally. Based on the analysis of the operation principle, the control scheme and parameters design are elaborated. The theoretical analysis is verified by the simulation and a downscaled 4-kW prototype experiment.

Insights into Highly-Efficient CO2 Electroreduction to CO on Supported Gold Nanoparticles in an Alkaline Gas-Phase Electrolyzer

Electrochemical conversion of CO2 to fuels powered by renewable energy is an attractive technology for carbon emission reduction and renewable energy utilization elevation. Here, electrochemical reduction of CO2 to selectively produce CO using a homemade electrolyzer and Au nanocatalyst was investigated. Au nanoparticles were uniformly anchored on N-doped carbon to improve catalytic activity, and the C/N ratio and operating temperature were adjusted to elevate catalytic selectivity. The resulting Au catalyst exhibited a current efficiency for CO production higher than 90% in a wide full cell voltage range (1.8 ∼ 3.0 V), a high mass activity of 900 A gAu −1, and a total current density of 200 mA cm−2 under 3.0 V cell voltage at room temperature. A scale-up 3 × 3 cm CO2 electrolyzer was constructed and tested at 1 A, the current efficiency for CO production reached 93% but decreased within a few hours due to the potassium carbonate precipitation phenomenon at the cathode. The important influence of an unideal ion transport pathway during electrolysis on CO2 electrolyzer performance was revealed, and its stability can be greatly improved by using deionized water instead of KOH solution.

High-Voltage Stabilization of O3-Type Layered Oxide for Sodium-Ion Batteries by Simultaneous Tin Dual Modification.

O3-type layered oxide materials are considered to be a highly suitable cathode for sodium-ion batteries (NIBs) due to their appreciable specific capacity and energy density. However, rapid capacity fading caused by serious structural changes and interfacial degradation hampers their use. A novel Sn-modified O3-type layered NaNi1/3Fe1/3Mn1/3O2 cathode is presented, with improved high-voltage stability through simultaneous bulk Sn doping and surface coating in a scalable one-step process. The bulk substitution of Sn4+ stabilizes the crystal structure by alleviating the irreversible phase transition and lattice structure degradation and increases the observed average voltage. In the meantime, the nanolayer Sn/Na/O composite on the surface effectively inhibits surface parasitic reactions and improves the interfacial stability during cycling. A series of Sn-modified materials are reported. An 8%-Sn-modified NaNi1/3Fe1/3Mn1/3O2 cathode exhibits a doubling in capacity retention increase after 150 cycles in the wide voltage range of 2.0–4.1 V vs Na/Na+ compared to none, and 81% capacity retention is observed after 200 cycles in a full cell vs hard carbon. This work offers a facile process to simultaneously stabilize the bulk structure and interface for the O3-type layered cathodes for sodium-ion batteries and raises the possibility of similar effective strategies to be employed for other energy storage materials.

Design and Control of a Three-Level Rectifier in LCC/S-Compensated IPT for Wide Output Voltage Regulation over Various Magnetic Couplings

Conventional inductive power transfer (IPT) employs primary control via phase shift, frequency tuning, or voltage tuning, whereas closed-loop control requires real-time wireless feedback communication. However, the long propagation delay results in small bandwidth. In this paper, a three-level (TL) rectifier is studied to implement secondary control and wide output voltage regulation in an inductor–capacitor–capacitor/series (LCC/S)-compensated IPT system over various magnetic couplings. The periodical operation behavior is analyzed, and a generic analytical expression of the system voltage gain including the TL rectifier is derived based on the Fourier series. A control strategy of an optimal control trajectory is proposed to maximize the power factor in the TL rectifier. The control variables are the duty cycles of the zero-level and one-level voltage in the TL rectifier. Either one remains at zero, while another one is utilized to modulate the output voltage in the proposed control strategy. A 2 kW prototype is designed and built to validate the theoretic analysis. The wide output voltage range between 100 V and 200 V under different magnetic coupling coefficients (0.16 and 0.23), a peak efficiency of 95.8% at 100 V and misaligned position, as well as a faster response of 1.3 ms are experimentally validated.