Voltage Ratio Research Articles

A Multiple-Modes Resonant Switched Capacitor DC/DC Converter With Variable Voltage Ratios

High step-down DC/DC converters with high efficiency and high power density are widely used in data centers, DC distribution grids and hybrid electric vehicles. In this paper, a new resonant switched capacitor converter is proposed, which can not only realize high step-down conversion, but also operate in multiple-modes to achieve various voltage ratios. The duty cycle can be allocated to one-half and one-third, enabling the converter to operate in double-mode and triple-mode accordingly. In addition, the state of the basic resonant cell can be switched between series and parallel, which enriches the operating modes, and thus allowing the converter to achieve different voltage ratios. Furthermore, the principle and strategy of switching between operating modes with different voltage ratios and switching between operating modes with same voltage ratio are presented. With the mode switching strategy, this converter can operate in the optimal mode over the wide voltage range and the full load range, thus achieves high efficiency over the full operating range. Finally, five operating modes are selected to verify the feasibility and the correctness of the theoretical analysis.

A Universal Model Predictive Control Strategy for Dual Inverters Fed OW-PMSM Drives

This study proposed a universal model predictive control (MPC) strategy for dual inverters fed open-winding permanent magnet synchronous motor (OW-PMSM) drives where two isolated buses have arbitrary DC voltages. Diverse and unordered space vector distribution caused by different voltage ratios of DC buses that greatly increases the calculation burden for the conventional MPC algorithm is analyzed in detail. Based on this, a novel MPC strategy that is universally applicable to any voltage ratio is put forward, which could decrease the number of candidate vectors from 49 to less than 15 in every cycle. Although the computational burden is reduced, the output power quality is unaffected owing to the effective simplification of the vectors. Besides, an optimized switching algorithm is designed to adapt to the situation when the voltage ratio changes during the operation state. The experimental results are presented to verify the effectiveness of the proposed method.

Towards Full Range Zero-Voltage Switching of DAB Converters: An Improved Multi-Mode Modulation at Light Loads Under Close-to-Unity Voltage Ratio

The soft switching characteristics of ZVS are of great significance for reducing the switching loss and improving the efficiency of the converter. However, affected by non-ideal factors, the DAB converter using the three-phase-shift modulation method has an inherent non-ZVS region. This paper proposes a novel operating mode to fill the non-ZVS area with ZVS operation where the input and output voltage are close to match with. What's more, combined with the existing mixed-mode modulation method and dynamic-process modulation method, the ZVS operation of DAB in full voltage gain range and full power range under all working conditions can be realized.

Communicationless Phase Cooperative Control of Inductive Power Transfer Using Asymmetrical Modulations

Dual Side Control (DSC) of Inductive Power Transfer (IPT) generally requires communication between the system sides to coordinate the local controllers. For reduction of component count and operation in challenging environments such as underwater, communicationless DSC is beneficial. This article investigates if and how asymmetric modulations, known for their improved performance in IPT, can be applied to phase cooperative communicationless DSC. A per side separate steady-state model is derived and the selection criteria for modulation schemes to be suitable for phase cooperative control are determined. The crucial importance of bijective or unique phase behavior in modulations for this control scheme is identified and demonstrated. In comparison with phase modulation it is shown that Asymmetric Voltage Cancellation of full-bridges is not reliably applicable to phase cooperative DSC, but asymmetrical modulation of half-bridges is. Therefore, a phase cooperative half-bridge DSC system as a simplified low complexity DSC scheme is further investigated and the load step regulation boundary derived. Analysis is verified in experiment and simulation, demonstrating ZVS behavior, dynamic load step regulation, the impact of harmonics on magnetics losses for high coupling and the impact of variable voltage ratio.

The simulation analysis of stator flux droop minimization in direct torque control open-end winding induction machine

<span lang="EN-US">Direct torque control (DTC) using dual-inverter technique is one of the best topologies for electric vehicle (EV) as it offers abundant selection of voltage vectors to drive the induction machine (IM). This dual-inverter technique also more reassuring as the system still workable even any of its voltage supply is disrupted or the power pack is drained. However, during the uneven voltage supply, the movement of voltage vectors is interrupted and will move obliquely especially in medium voltage vectors. This situation will lead to the faulty movement of the voltage vectors in the default sector definitions and lead to huge flux droop, which later could impose to distort phase current. This paper proposes an optimal sector definition based on the preset voltage ratio between the two inverters. The voltage vectors can be mapped tangentially to the flux vector, minimizing the flux droop and improving the phase current waveform when the proposed sector is utilized. The effectiveness of the proposed sector is tested using MATLAB/Simulink software and the exact parameter from the induction machine.</span>

Detection and Location Approach to Incipient Grounding Defect in Transformer Winding Based on Sequence Voltage Ratios at PV Inverter Switching Frequency

Silicon Carbide (SiC) power devices are used increasingly in photovoltaic (PV) inverters, with the high switching frequency (fs) and voltage slew rate. For the SiC- based-inverter-fed transformer, the ageing of groundwall insulation is aggravated and the grounding defect should be reliably detected at incipient stage. In this paper, a novel approach based on negative and zero sequence voltage components at fs is proposed to realize comprehensive online monitoring of incipient grounding defect. At fs, the equivalent sequence circuit of the PV distribution network is built and the mechanism and characteristics of sequence voltage components are investigated in scenario of the high-resistance grounding defect. The effects are distinguished caused by defect from imbalanced operation. Two sequence voltages ratios are developed to identify the occurring phase and to evaluate the defect location and severity. The MATLAB/Simulink model and the SiC-based- inverter platform are built for simulation and online experimental validation, respectively. The proposed online approach can sensitively detect and locate the defect with grounded resistance above 1 kΩ from each winding. Due to its noninvasiveness nature and convenient implementation, the operating reliability of the PV distribution network can be enhanced effectively.

Flexible Sector Detector-Based Mismatch Supply Voltage in Direct Torque Control Doubly Fed Induction Machine: An Experimental Validation

Direct Torque Control (DTC) of Induction Motors (IMs) is popular in motor drive applications because of its robust and simple control structure. The IM winding can be controlled on both sides using dual inverter technique which more effective for Electric Vehicle (EV) with a greater number of voltage vectors. However, the battery performance of the dual inverter will deteriorate unevenly on both sides, resulting in fluctuating voltages for the EV system. This will lead to the generation of distorted stator currents and a significant droop in the stator flux, which in turn can increase the total harmonic distortion (THD) in the system. Additionally, the performance of torque may not be able to regulate effectively. This paper examines the effect of unstable voltage on voltage vector mapping performance with tilted angles and proposes new sector definitions based on voltage ratio conditions. Moreover, the proposed sector for each predefined voltage ratio is tested under three-speed conditions. The proposed technique effectiveness is validated through hardware experiments using a dSPACE 1104 controller and retuning the stator current for proper waveform. This approach improves the stator current waveform, improves stator flux droop, enhances torque regulation and minimizes the THD in the DTC system.

Dissociation Kinetics in Quadrupole Ion Traps: Effective Temperatures under Dipolar DC Collisional Activation Conditions.

Ions stored in an electrodynamic ion trap can be forced from the center of the ion trap to regions of higher radio frequency (RF) electric fields by exposing them to a dipolar DC (DDC) potential applied across opposing electrodes. Such ions absorb power from the trapping RF field, resulting in increased ripple motion at the frequency of the trapping RF. When a bath gas is present, ions undergo energetic collisions that result in "RF-heating" sufficient to induce fragmentation. DDC is therefore a broad-band (i.e., mass-to-charge-independent) means for collisional activation in ion traps with added bath gas. Under appropriate conditions, the internal energy distribution of an ion population undergoing dissociation can be approximated with an effective temperature, Teff. In such cases, it is possible to determine thermal activation parameters, such as Arrhenius activation energies and A-factors, by measuring dissociation kinetics. In this work, the well-studied thermometer ion, protonated leucine enkephalin, was subjected to DDC activation under rapid energy exchange conditions and in two separate bath gases, N2 and Ar, to measure Teff as a function of the ratio of DDC and RF voltages. As a result, an empirically derived calibration was generated to link experimental conditions to Teff. It was also possible to quantitatively evaluate a model described by Tolmachev et al. that can be used to predict Teff. It was found that the model, which was derived under the assumption of an atomic bath gas, accurately predicts Teff when Ar was used as the bath gas but overestimates Teff when N2 was the bath gas. Adjustment of the Tolmachev et al. model for a diatomic gas resulted in an underestimate of Teff. Thus, use of an atomic gas can provide accurate activation parameters, while an empirical correction factor should be used to generate activation parameters using N2.

Design and investigation of doping-less gate-all-around TFET with Mg2Si source material for low power and enhanced performance applications

Metal–oxide–semiconductor field-effect transistor (MOSFET) faces the major problem of being unable to achieve a subthreshold swing (SS) below 60 mV/dec. As device dimensions continue to reduce and the demand for high switching ratios for low power consumption increases, the tunnel field-effect transistor (TFET) appears to be a viable device, displaying promising characteristic as an answer to the shortcomings of the traditional MOSFET. So far, TFET designing has been a task of sacrificing higher ON state current for low subthreshold swing (and vice versa), and a device that displays both while maintaining structural integrity and operational stability lies in the nascent stages of popular research. This work presents a comprehensive analysis of a heterojunction plasma doped gate-all-around TFET (HPD-GAA-TFET) by making a comparison between Mg2Si and Si which serve as source materials. Charge plasma technique is employed to implement doping in an intrinsic silicon wafer with the help of suitable electrodes. A low-energy bandgap material, i.e. magnesium silicide is incorporated as source material to form a heterojunction between source and silicon-based channel. A rigorous comparison of performance between Si-based GAA-TFET and HPD-GAA-TFET is conducted in terms of electrical, radio frequency (RF), linearity, and distortion parameters. It is observable that HPD-GAA-TFET outperforms conventional Si-based GAA-TFET with an ON-state current (I ON), subthreshold swing (SS), threshold voltage (V th), and current switching ratio being 0.377 mA, 12.660 mV/dec, 0.214 V, and 2.985 × 1012, respectively. Moreover, HPD-GAA-TFET holds faster switching and is more reliable than Si-based device. Therefore, HPD-GAA-TFET is suitable for low-power applications.

Thermal-Electric Modeling: A New Approach for Evaluating the Impact of Conservation Voltage Reduction on Cooling Equipment

It has been suggested in the literature that by reducing the incoming voltage at a distribution feeder head or at the supply side of buildings, significant electricity savings can be achieved. This technique is called Conservation Voltage Reduction (CVR). Data-based analysis with and without CVR is primarily used to support such assertions, which does not explain the physics behind reduction in energy consumption with CVR. This paper presents a new approach for evaluating the impact of CVR on cooling equipment. In this approach, a thermal-electric model of the cooling process is developed in MATLAB’s SIMSCAPE toolbox that can be used to explain the physics behind energy reduction with CVR. This model includes an accurate model of a compressor coupled to an induction motor whose supply voltage can be varied to simulate CVR. Simulations performed using this model show that the Coefficient of Performance (COP) of cooling equipment improves with a reduction in supply voltage. However, the energy lost in the motor windings may nullify the impact of the improvement in the COP and render the CVR programs ineffective if the range of speed change is small over the allowable voltage change. The simulation results show an increase in energy consumption of 4% at 90% rated voltage compared to the energy consumed at the rated voltage. However, if variable frequency drives-based cooling equipment is appropriately controlled, it is possible to reduce their net energy consumption using CVR. Simulations performed keeping the ratio of the supply voltage and the frequency constant showed a reduction in energy consumption of 2.5% at 90% rated voltage compared to the energy consumed at the rated voltage. Thermal-electric modeling of building cooling equipment is, therefore, vital to accurately evaluating the benefits of CVR as smart, power electronics-based end-use equipment is globally adopted.

Efficient optical modulation in ring structure based on Silicon-ITO heterojunction with low voltage and high extinction ratio

We numerically propose a low voltage, high extinction ratio optical modulator with a tunable group delay in a resonance enhanced ring resonator based on Silicon (Si) - Indium Tin Oxide (ITO) heterojunction. This is accomplished by incorporating a thin ITO layer into a Si-ring resonator. By electrically inducing carrier changes in ITO, the epsilon-near-zero (ENZ) state of ITO is attained, resulting in a sudden change in optical absorption. The resonance condition shifts because of the ENZ state, and the transmission at the ring resonator’s through port changes dramatically. The extinction ratio (ER) of 11 dB at a low forward bias of 1 V is reported with a low energy consumption of 2.6 fJ. An optical network has a non-trivial demand for a high extinction ratio optical modulator that operates at a low driving voltage and consumes minimal energy. The proposed ring modulator with a high extinction ratio at low driving voltage outperforms conventional waveguide-based modulators in terms of energy efficiency. In addition, we report around 25 psec of electrical tuning in the group delay The current concept has favorable results in terms of exploring tunable delay lines in conjunction with optical modulation with a high extinction ratio.

100 GHz bandwidth, 1 volt integrated electro-optic Mach–Zehnder modulator at near-IR wavelengths

Integrated photonics at near-IR (NIR) wavelengths currently lacks high bandwidth and low-voltage modulators, which add electro-optic functionality to passive circuits. Here, integrated hybrid thin-film lithium niobate (TFLN) electro-optic Mach–Zehnder modulators (MZM) are shown, using TFLN bonded to planarized silicon nitride waveguides. The design does not require TFLN etching or patterning. The push–pull MZM achieves a half-wave voltage length product (V π L) of 0.8 V.cm at 784 nm. MZM devices with 0.4 cm and 0.8 cm modulation length show a broadband electro-optic response with a 3 dB bandwidth beyond 100 GHz, with the latter showing a record bandwidth to half-wave voltage ratio of 100 GHz/V and a high extinction ratio exceeding 30 dB. Such fully integrated high-performance NIR electro-optic devices may benefit data communications, analog signal processing, test and measurement instrumentation, quantum information processing and other applications.

CE-454611-1 ISOLATED HIGH SHOCK IMPEDANCE DUE TO CALCIFIED POCKET AND THE MANAGEMENT

Impedance is the ratio of voltage to current in an electrical circuit. The most common causes of high shock impedance are lead conductor fracture and lead calcification often associated with lead malfunction. We present the first two cases of isolated high shock impedance from pocket calcification in which the lead function is normal. Case 1: A 73-year-old male with ICM, EF 10%, LBBB, sever COPD and Boston biventricular (BiV) ICD in 2013 that normalized EF. Shock impedance slowly rose from 70 Ω to 122 Ω in 2019 and 189 Ω in 2021. Lead extraction with a new system was considered at the time for generator exchange; however, the patient declined. The pocket was severely calcified, with normal defibrillator lead pacing parameters (pace impedance 796 Ω, pace threshold 0.8 V @ 0.4 msec). The calcium shell was removed (Figure 1A), and the shock impedance dropped to 146 Ω, and remained 137 Ω in one year follow up. Case 2: A 65-year-old female with NICM, EF 20%, LBBB, and Boston BiV ICD in 2013 that normalized QRS (Figure 1B). Shock impedance slowly rose from 65 Ω to 138 Ω (2019) and 165 Ω (2022). At the time of generator exchange, the pocket was heavily calcified. Defibrillator lead pacing parameters were normal (pace impedance 868 Ω, pace threshold 0.6 V @ 0.4 msec). After pocket decalcification, shock impedance reduced to 128 Ω. At one month follow up, shock impedance was stable at 130 Ω. N/A High shock impedance is a result of increased impedance in the circuit which includes the can. Lead fracture or calcification will alter lead function as well as shock impedance. This is managed by extraction. In contrast, pocket calcification, which only increases shock impedance, and can be easily managed by pocket decalcification. In both cases, patients benefited greatly from keeping their functional device and avoiding lead exchange. Lead fracture often results in abrupt increase in shock impedance. Calcification at the lead tip or at the pocket causes slow impedance rise. Unipolar and bipolar pacing impedance can also be used to localize the area of calcification. Normal bipolar pacing impedance and slow isolated high shock impedance should raise the suspicion of pocket calcification. Our cases highlight the importance of recognizing pocket calcification in the context of high shock impedance. Calcium removal at the pocket significantly reduces shock impedance. This management strategy can help to avoid lead extraction, a potentially high-risk operation.

Investigating the large signal phenomenon in single photo-electron measurements of the 20-inch MCP-PMT

In this paper, we investigated a large signal phenomenon (LSP) in single photo- electron (SPE) measurement of the 20-inch MCP-PMT. The LSP will cause a long tail of the PMT output charge spectrum, and it will affect the calculation of the number of photoelectrons (PEs) collected and the gain of the PMT. To evaluate the LSP of the 20-inch MCP-PMT, a parameterization method is developed, by measurement of the LSP distribution in the full photocathode of the PMT and study of LSP variation with different voltage ratios applied for the PMT.

A Lightweight and Robust Drone MHz WPT System via Novel Coil Design and Impedance Matching

This paper proposes a comprehensive approach to address the challenges posed by the simultaneously varying dc load and coil coupling in drone wireless charging, which inevitably occur during battery charging and landing positioning. The combination of two new coil designs, a quasi-elliptic transmitting (Tx) coil and a “belt” receiving (Rx) coil, enables adequate power transfer at megahertz (e.g., 6.78 MHz) and over a large circular landing area. The on-board “belt” Rx coil (5.8 g) especially helps achieve lightweight and minimize air resistance. A load-pull-based impedance analysis is then performed to clarify the need for an impedance matching network (IMN) on both Rx and Tx sides (i.e., Rx-IMN and Tx-IMN). A new Rx-IMN explicit design is specially developed to significantly limit the range of variation in the coupling coil input impedance, thereby helping to simplify the design of the Tx-IMN to ensure an efficient power amplifier operation. With the proposed coil and IMN designs, actual drone wireless charging experiments demonstrated improved system dc-dc efficiency (max. 83.5%) and dc-dc voltage ratio stability at three representative landing positions (i.e., minimum, medium, and maximum coil coupling).

Improving the Accuracy of Digital Unbalanced Impedance Bridges

This article presents an automatic digital unbalanced impedance bridge for comparing two-port impedances: R-R, R-C and C-C. The bridge consists of a two-channel digital source of voltage sinusoidal waveforms supplying the bridge arms and a three-channel precise digitizer, by means of which the complex ratio of the source output voltages and the relative bridge unbalanced voltage are determined. The hardware implementation of the bridge is based on a relatively inexpensive universal data acquisition (DAQ) card by National Instruments, USB-6281, which contains, among others, a multi-channel 18-bit analog-to-digital converter (ADC) and two 16-bit digital-to-analog converters (DAC). Thanks to the new approach to the bridge operation algorithm, consisting in the use of the interpolation method in the comparison process, the influence of the accuracy of the measurement of the bridge unbalanced voltage and some bridge parasitic admittances on the uncertainty of the impedance comparison were minimized. This simplifies the measurement procedure and shortens its execution time. The obtained results confirmed that a relatively simple digital unbalanced bridge can compare impedance standards with an uncertainty of less than 10−5. By reducing the requirements regarding the uncertainty of the measurement, and thus its execution time, the presented bridge supplemented with impedance sensors can be used in many areas of industry.

Design and analysis of a novel low RF MEMS switch with low pull-in voltage and high capacitance ratio

Design and analysis of a novel low RF MEMS switch with low pull-in voltage and high capacitance ratio

COMPARATIVE ANALYSIS OF STEADY STATE CHARACTERISTICS OF THREE-PHASE INDUCTION MOTOR UNDER DIFFERENT SPEED CONTROL SCHEME

Induction motors are the most widely used electrical motors due to their reliability, low cost and robustness. However, induction motors is a constant speed machine; hence it speed control is difficult. Electric drive system is increasingly required to meet the higher performance and reliability requirement of motors used in industrial applications. This work presents different speed controlmethod for three-phase induction motor The steady state equation were written directly from the dynamic equations of the motor based on Parks two-axis techniques. The equations were validated in MATLAB. Amongs the selected speed control methods, the constant voltage frequency (v/f) ratio scheme with peripherial intergral (PI ) controller gave a competitive advantage over others. In this method of constant v/f ratio, by use of rectifier and pulse width modulation (PWM) inverter, the supply voltage as well as the supply frequency is varied such that the voltage and frequency ratio of the motor remains constant and the flux remains constant too. With reference speed of 1500 rpm at diiferent load, results shows that the maximum torque of the motor remains unchanged at different operating zone for various speeds and given load, the maximul torque being 2.2 Nm at steady state opration. The work was done using a three-phase, 4-pole 50Hz, 155 volts induction motor.

On determination of the complex voltage ratio using the ellipse-fitting algorithm in the case of an ill-conditioned scattering matrix

The article analyzes three modified versions of the standard ellipse fitting algorithm (EFA), which enables the determination of the complex voltage ratio (CVR) for extremely small values of the phase shift angle when the input scattering matrix of sampled data is poorly conditioned. The novelty of the method is in the use of EFA twice for the sequence of samples shifted by the same angle value, but with opposite signs. The results of the numerical simulation tests are confirmed by the results of measurements carried out in the sampling system using the NI PXI 4461 data acquisition module.

Investigation of Hydrogen Production System-Based PEM EL: PEM EL Modeling, DC/DC Power Converter, and Controller Design Approaches

The main component of the hydrogen production system is the electrolyzer (EL), which is used to convert electrical energy and water into hydrogen and oxygen. The power converter supplies the EL, and the controller is used to ensure the global stability and safety of the overall system. This review aims to investigate and analyze each one of these components: Proton Exchange Membrane Electrolyzer (PEM EL) electrical modeling, DC/DC power converters, and control approaches. To achieve this desired result, a review of the literature survey and an investigation of the PEM EL electrical modeling of the empirical and semi-empirical, including the static and dynamic models, are carried out. In addition, other sub-models used to predict the temperature, gas flow rates (H2 and O2), hydrogen pressure, and energy efficiency for PEM EL are covered. DC/DC power converters suitable for PEM EL are discussed in terms of efficiency, current ripple, voltage ratio, and their ability to operate in the case of power switch failure. This review involves analysis and investigation of PEM EL control strategies and approaches previously used to achieve control objectives, robustness, and reliability in studying the DC/DC converter-PEM electrolyzer system. The paper also highlights the online parameter identification of the PEM electrolyzer model and adaptive control issues. Finally, a discussion of the results is developed to emphasize the strengths, weaknesses, and imperfections of the literature on this subject as well as proposing ideas and challenges for future work.