Voltage Build-up Research Articles

Comprehensive Analysis and Solution of Voltage Build-Up Failure in Aircraft PM-Assisted Reluctance Starter/Generator System

Permanent magnet assisted reluctance (PMAREL) machine possesses the potential as the aircraft starter/generator (S/G) for its high power density, high efficiency and tolerance to short-circuit faults. For aircraft S/G systems, the voltage build-up is a prerequisite for power generation. However, the voltage build-up of the PMAREL S/G system may fail if the initial DC-link voltage is low and the control is fast-response. In this paper, the mechanism of the voltage build-up failure is clarified. The conduction feature of power devices in the power electronic converter when the DC-link voltage is clamped at 0 V are explored. Conditions for clamping the DC-link voltage at 0 V all the time is determined. An integrated control method is proposed to cope with the voltage build-up failure as well as improve the dynamic performance of the S/G system. Based on a prototype of PMAREL S/G system, the correctness of the analysis and the effectiveness of the proposed method are verified through experiments.

Persistent Voltage Control of a Wind Turbine-Driven Isolated Multiphase Induction Machine

The growing concern about the energy crisis and environmental protection has caused a growing interest in wind power generation systems. Researchers and engineers urgently need to create new multiphase induction machines for the production of wind energy, since they are essential parts of wind turbines. This study offers control and stability analysis of a multiphase induction machine based on the entropy stability requirements for its linearized model. The generated model was used to assess the on-load properties of the multiphase induction machine and calculate its steady-state parameters under each operating circumstance. According to the analysis, the eigenvalues depend on the machine parameters, with the excitation capacitance and speed variation being the most important. Stabilization of the multiphase induction machine is the main focus of the singular values, which vary according to its variables. The simulated results include an examination of a multiphase induction machine steady state for voltage build-up at various types of load.

Validation Approach for a Spatially and Temporally Resolved Fault Arc Model

This paper presents a method to validate arc models for fault arc applications by examining the effect of changed boundary conditions on arc parameters, e.g. voltage and pressure build-up. The study shows the impact of ignition location on arc voltage and pressure build-up and prediction accuracy of the presented model. The results indicate insufficient accuracy in predicting arc voltage during dynamic phases, while the pressure build-up prediction aligns well with the experimental results.

The Modeling and SOC Estimation of a LiFePO4 Battery Considering the Relaxation and Overshoot of Polarization Voltage

A triple polarization (TP) model is proposed based on the second-order RC hysteresis equivalent circuit model, in order to more precisely reflect the dynamic and static characteristics of a LiFePO4 (LFP) battery, considering the long relaxation time and overshoot of its polarization voltage. The TP model introduces an RC link, whose time constant varies with changes in the battery operating status to represent the fast build-up and slow relaxation of the polarization voltage. Specifically, such an RC link evolves into an RLC parallel link during charging to reveal the overshoot characteristic. In this way, the external characteristics of LFP batteries, considering the complex phase transition process, are simulated by a simple equivalent circuit. Constant-current pulse tests are performed to verify the proposed model. For application, a state-of-charge (SOC) estimation is implemented on the basis of the TP model, with the use of a transformed cubature Kalman Filter (TCKF). The experimental results show that the TP model is able to represent the dynamic and static characteristics, as well as estimate the SOC of an LFP battery with a good accuracy.

Research on induction generators for isolated rural applications: State of art and experimental demonstration

-Asynchronous machines/Induction machines are one of the leading machines in the electrical sector and which are well suitable for the motoring and generating applications of a few kilowatts rating to megawatt ratings. Research on induction machines for generating applications is drawing attention among the researchers due to its low cost, rugged construction, brushless arrangement and all. The operation of induction generator (IG) is quite interesting and which is different for grid and off-grid mode of operation. The IG for the off-grid applications (so called self-excited induction generator, SEIG) requires an additional reactive power supply for the successful build-up of voltage and as well as for supplying the electric loads. On the other hand, load power balance is also one the challenges since off-grid systems are directly connected to the loads. In this context, many researches have been reported the different approaches and techniques for the successful and economical operation of IG for small scale off-grid power generation. In this paper, an exclusive analytical study is presented on the excitation requirement and load balance phenomena of self-excited induction generator (SEIG). Further, a basic experimental setup of renewable energy source driven SEIG system and its operation for the electric power generation is demonstrated and the same is simulated by using MATLAB/Simulink.

A Low-Power Recursive I/Q Signal Generator and Current Driver for Bioimpedance Applications

This brief presents a power-efficient quadrature signal generator and current driver application-specific integrated circuit (ASIC) for bioimpedance measurements in an electrical impedance tomography system for monitoring lung function. The signal generator is realized by a digital recursive signal oscillator with the ability of generating quadrature signals over a wide frequency range. The generated in-phase signal is applied to a current driver. It uses a balanced current-mode feedback architecture that monitors the output current through a feedback loop to minimize common-mode voltage build-up at the injection site. The quadrature signals can be used for I/Q demodulation of the measured bioimpedance. The ASIC was designed in TSMC 65 nm technology occupying an area of 0.21 mm2. The current driver can generate up to 0.7 mA <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {p-p}}$ </tex-math></inline-formula> current up to 200 kHz and consumes 2.7 mW power using ±0.8 V supplies.

Ionic Seebeck coefficient and figure of merit in ionic thermoelectric materials

Ionic thermoelectric (i-TE) materials have attracted much attention due to their large ionic Seebeck coefficients, but the basic relations between the property parameters and operation performances are still open questions. We derive the ionic Seebeck coefficient, Std, and the dimensionless ionic figure of merit, ZtdT, from the view of field evolutions of temperature, voltage, and ionic concentration. Different from traditional knowledge, only ionic Eastman entropies determine Std, while ionic diffusion coefficients can only affect the speed of the voltage to reach the steady state. The figure of merit for electronic thermoelectric materials is inapplicable for i-TE materials as the voltage build-up is dominated by the temperature field evolution instead of the capacitor constant. By combining the net charge storage and dimensionless response time, the proposed ZtdT can embody the transient and average efficiencies in i-TE materials, which also opens new windows for the optimization of i-TE materials.

Conformable Fractional Order Controller Design and Implementation for Per-Phase Voltage Regulation of Three-Phase SEIG Under Unbalanced Load

Self-excited induction generators (SEIGs) usage is an effective way to generate electrical power in off-grid locations. This study aims to performance improvement for voltage regulation of the SEIG in wind turbine systems. To achieve this, a fixed-capacitor with thyristor controlled-reactor based per-phase voltage controller is designed with a conformable fractional order proportional integral (CFOPI) method. The SEIG system is modeled based on small signal analysis by using the input-output data, experimentally. To do this, system identification toolbox of Matlab is used. The proposed controller is established on conformable fractional integral approach proposed by Khalil et al. in 2014. Proposed CFOPI controller parameters Kp , Ki and γ are optimized using particle swarm optimization (PSO) according to minimization of integral time absolute error (ITAE). To validate the success of proposed scheme, CFOPI, traditional fractional order PI (TFOPI) and integer order PI (IOPI) controllers are tested under same experimental setup and results are compared. Three experiments, after voltage build-up process, under balanced and unbalanced load are done for each controller. Experimental results demonstrate that proposed voltage regulator improves the performance of SEIG systems. Moreover, robust voltage regulation is ensured thanks to independent control loops created for each phase.

Positron charge sensing using a double-gated graphene field effect transistor

We utilize a high-mobility double-gated graphene field-effect transistor to measure the accumulated charge created by positron annihilation in its back-gate. The device consists of an exfoliated graphene flake stacked between two hexagonal boron nitride flakes placed on a 1 cm2 substrate of 500 μm thick conducting p-doped Si capped by 285 nm-thick SiO2. The device is placed in close proximity to a 780 kBq 22Na positron source emitting a constant flux of positrons. During the measurement, positrons annihilate within the back-gate, kept floating using a low-capacitance relay. The accumulated positive charge capacitively couples to the graphene device and builds a positive voltage, detectable through a shift in the top-gate dependent graphene resistance characteristic. The shift in the position of the top-gate Dirac peak is then used for extracting the exact voltage buildup and quantitative evaluation of the accumulated charge. Reaching a positron current sensitivity of ∼1.2 fA/Hz, detected over 20min, our results demonstrate the utility of two-dimensional layered materials as probes for charging dynamics of positrons in solids.

Central Carbon Metabolism, Sodium-Motive Electron Transfer, and Ammonium Formation by the Vaginal Pathogen Prevotella bivia.

Replacement of the Lactobacillus dominated vaginal microbiome by a mixed bacterial population including Prevotella bivia is associated with bacterial vaginosis (BV). To understand the impact of P. bivia on this microbiome, its growth requirements and mode of energy production were studied. Anoxic growth with glucose depended on CO2 and resulted in succinate formation, indicating phosphoenolpyruvate carboxylation and fumarate reduction as critical steps. The reductive branch of fermentation relied on two highly active, membrane-bound enzymes, namely the quinol:fumarate reductase (QFR) and Na+-translocating NADH:quinone oxidoreductase (NQR). Both enzymes were characterized by activity measurements, in-gel fluorography, and VIS difference spectroscopy, and the Na+-dependent build-up of a transmembrane voltage was demonstrated. NQR is a potential drug target for BV treatment since it is neither found in humans nor in Lactobacillus. In P. bivia, the highly active enzymes L-asparaginase and aspartate ammonia lyase catalyze the conversion of asparagine to the electron acceptor fumarate. However, the by-product ammonium is highly toxic. It has been proposed that P. bivia depends on ammonium-utilizing Gardnerella vaginalis, another typical pathogen associated with BV, and provides key nutrients to it. The product pattern of P. bivia growing on glucose in the presence of mixed amino acids substantiates this notion.

Solar power based positive output super-lift Luo converter using fuzzy logic controller

Photovoltaic (PV) power generation is employed to meet the increasing demand for energy and of cleaner form. Though renewable and high energy using PV can be produced, they have certain disadvantages. PV cells have a low voltage (approx. 0.5V) rating and they have to be connected in series when higher voltage is required. These cells when connected in series should have identical electrical characteristics to avoid ripples in the output voltage and current, but it is not possible practically. To avoid this miss-match, converter circuits are employed. The major drawbacks in most power converters are reduced voltage gain and their tendency to generate harmonics in the supply system and the load circuit. To overcome these limitations, a positive output super-lift Luo converter is designed. A Positive Output Super Lift Luo converter (POSLC) is a powerful DC-DC converter where the voltage is converted from positive source voltage to positive load voltage as it produces positive voltages of comparatively higher ranges than those of conventional types. The super-lift technique also overcomes the effect of parasitic elements and thus minimizing the ripples in the output voltage and current. In addition to this, the voltage build-up can be achieved by implementing the super-lift technique where the output voltage rises in geometric progression with increased voltage transfer gain and high power density. In this paper fuzzy control is used to produce better-controlled voltage and a more refined output. The performance of POSLC with and without implementation of fuzzy control has been successfully simulated and verified using MATLAB/SIMULINK as well simulation model also developed and analyzed with Proteus package.

Analysis of a Novel Three-phase Asynchronous Generator Based on Graph Theory for Supplying Single-Phase Load

This paper presents a novel three-phase star-connected stand-alone asynchronous generator (SAG) with only two capacitors, connected in series with two stator phase windings, for supplying power to single-phase resistive load. This new scheme has excellent voltage regulation (less than 1.7%) due to the presence of these two series capacitors and does not require any separate voltage regulating device making it very simple and cheaper. The symmetrical component theory has been used to form a simplified equivalent circuit of the scheme. Graph theory has been applied to the equivalent circuit to simplify the process of obtaining two non-linear higher-order equations which are solved using the binary search algorithm (BSA) to obtain the values of per unit frequency and magnetizing reactance. Accordingly, using the magnetization characteristics of the machine and the performance equations, the steady-state performance of the SAG has been obtained. To investigate the behavior of the SAG under transient conditions, such as voltage build-up, load switching and load perturbation, a dynamic model of the generator scheme has been developed on the basis of d-q axes theory in stationary reference frame including the effect of main and cross flux saturation. The simulated results have been validated through experimentation using an induction machine rated as 2 hp, 4-pole, 415 V, 3.5 A, 3-phase, 1440 rpm, 50 Hz. The simulated results closely agree with the experimental results, indicating the efficacy of the proposed approach. This can be a promising single-phase power generation scheme for supplying power in remote rural areas.

Water Pores in Planar Lipid Bilayers at Fast and Slow Rise of Transmembrane Voltage.

Basic understanding of the barrier properties of biological membranes can be obtained by studying model systems, such as planar lipid bilayers. Here, we study water pores in planar lipid bilayers in the presence of transmembrane voltage. Planar lipid bilayers were exposed to fast and slow linearly increasing voltage and current signals. We measured the capacitance, breakdown voltage, and rupture time of planar lipid bilayers composed of 1-pamitoyl 2-oleoyl phosphatidylcholine (POPC), 1-pamitoyl 2-oleoyl phosphatidylserine (POPS), and a mixture of both lipids in a 1:1 ratio. Based on the measurements, we evaluated the change in the capacitance of the planar lipid bilayer corresponding to water pores, the radius of water pores at membrane rupture, and the fraction of the area of the planar lipid bilayer occupied by water pores.planar lipid bilayer capacitance, which corresponds to water pores, water pore radius at the membrane rupture, and a fraction of the planar lipid bilayer area occupied by water pores. The estimated pore radii determining the rupture of the planar lipid bilayer upon fast build-up of transmembrane voltage are 0.101 nm, 0.110 nm, and 0.106 nm for membranes composed of POPC, POPS, and POPC:POPS, respectively. The fraction of the surface occupied by water pores at the moment of rupture of the planar lipid bilayer The fraction of an area that is occupied by water pores at the moment of planar lipid bilayer rupture is in the range of 0.1–1.8%.

Performance characteristics and reliability assessment of self‐excited induction generator for wind power generation

The paper presents the performance analysis-based reliability estimation of a self-excited induction generator (SEIG) using the Monte-Carlo simulation (MCS) method with data obtained from a self-excited induction motor operating as a generator. The global acceptance of a SEIG depends on its capability to improve the system's poor voltage regulation and frequency regulation. In the grid-connected induction generator, the magnetizing current is drawn from the grid, making the grid weak. In contrast, in the SEIG stand-alone operation, an external capacitor arrangement is implemented to render the reactive power support. This capacitor arrangement is connected across the stator terminals during the stand-alone configuration of SEIG. The capacitor serves two purposes, which include voltage build-up and power factor improvement. Therefore, the paper deals with obtaining the minimum capacitor value required for SEIG excitation in isolated mode applications, including stand-alone wind power generation. The SEIG performance characteristics have been evaluated for different SEIG parameters. The simulation and experimental results are then compared and found satisfactory. Then, SEIG reliability is estimated considering the MCS method utilizing SEIG excitation's failure and success rates during experimental work in the laboratory. Finally, the SEIG reliability evaluation is performed considering different wind speeds.

Arc Characteristics of Ultra-Fast Opening Switching Contacts in Hybrid Breakers

A mechanical switch can be used instead of a power electronic load commutation switch in orderto reduce the losses during normal power flow in standard hybrid DC circuit breakers. The success of current commutation in such hybrid breakers depends on the arc voltage formed across the contacts in the mechanical switch. The behaviour of rapidly elongated, wall constricted arcsgenerated during the opening of an ultra-fast mechanical switch in the air is studied here. The voltage-current characteristics of the generated arcs are obtained for steady state contact opening velocities of 6, 11 and 21 m/s. It is found that the arc voltage at a given current and contact separation increases with the contact opening velocity. It is shown that stationary,zero-contact-velocity characteristics can not be used to accurately quantify the voltage build-up in fast elongating arcs in hybrid breakers. A best-fitting black-box equation for the dynamic arc characteristics is presented for the tested velocities. The obtained voltage-current characteristics are used as input to simulate the current commutation process in a 12 kV hybridDC circuit breaker case-study. Different scenarios of current commutation failure related to the arc voltage build up are identified. It is shown that these failures scenarios can be avoided by increasing the contact opening velocity.

A Capacitor Voltage Precharge Method for Back-to-Back Five-Level Active Neutral-Point-Clamped Converter

The five-level active neutral-point-clamped (5L-ANPC) converter has a great application potential in high power variable-frequency drives with high and medium voltage. However, the traditional method for capacitor voltage buildup is not applicable to the capacitors inside the back-to-back (B2B) 5L-ANPC converter. To solve this problem, the topological features of the B2B-5L-ANPC converter are fully analyzed, and a capacitor voltage precharge strategy for this converter is also proposed in this article. With this strategy, all the capacitors in the converter can be charged by controlling the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> states of switch tubes in the bridge arm, no additional hardware is needed. Moreover, the structural features of the voltage booster circuit were examined in four stages, and used to derive the capacitor voltage buildup formula in each stage. In addition, the relationship between voltage buildup rate, equivalent precharge resistor, and capacity of capacitor is identified. Finally, simulation results from a B2B-5L-ANPC simulation model which is constructed according to the actual system parameters and experimental results from a scaled-down prototype are provided to support the proposed control strategy.

A Consequent-Pole Hybrid Exciter for Synchronous Generators

In low-to-medium power generating sets, a self-powered brushless excitation system is typically employed. This solution is cost-effective, simple and compact, but it suffers from an unreliable voltage build-up at start-up, a slow dynamic response and a relatively low efficiency for the exciter. The push towards more effective, reliable and efficient products has recently led to consider excitation systems equipped with permanent magnet exciters and controlled rotating converters, but their diffusion is limited by their higher complexity and cost. This article investigates the utilization of a hybrid excitation for the exciter, aiming to join the benefits of field windings and permanent magnets. As a case study, this concept is applied to a commercial mid-size generating set adopting an industrial perspective, aiming to maximize the benefits while minimizing the required modifications in the system design. After a preliminary analysis, a consequent-pole layout with surface-mounted bonded magnets is then selected as the most effective solution. Theoretical considerations, numerical analysis and experimental validation are reported to show that the hybrid excitation concept can actually lead to a significant reduction of the exciter field losses as well as to other appreciable side benefits with a very limited impact on the present design of the generating set.

Modeling of Single-Pulse Operated Switched Reluctance Generator and Its Verification

This article proposes a mathematical model for a switched reluctance (SR) generator feeding a dc link through a power electronic converter. SR machines are operated in single-pulse mode at close to and above base speed. The SR generator is modeled as a current source, controllable with dc-link voltage $V_{\text{dc}}$ , prime mover speed $\omega _m$ , and switching angles ( $\alpha _{\text{on}}$ and $\alpha _{\text{off}}$ ) of the converter. This current source model is used to predict the dc-link dynamics for constant resistance, constant current, and constant power loads. This is further utilized to derive the voltage build-up condition for an SR generator. The generator model, dc-link dynamics and voltage build-up conditions are validated through simulations and experiments.

On the Spontaneous Build-Up of Voltage between Dissimilar Metals Under High Relative Humidity Conditions

Certain metals can surprisingly build-up charge spontaneously, when exposed to high relative humidity (RH), although they need to be isolated from the ground. We have explored this phenomenon, building on former experimental knowledge and carrying out additional experiments, to identify the parameters that could enhance this charging. We used many types of metals with different characteristics under different RH and temperature conditions. While some metals were unaffected by high RH, others, like zinc and stainless steel, did acquire charge, when RH was >60%, and charged a capacitor to a voltage of 1 V. For the first time, we also performed outdoors experiments, showing this phenomenon is also valid under similar natural ambient humid conditions. If these results can be scaled up, it may lead to the development of practical applications for regions and times of high RH conditions.

Simulation of arcs for DC relay considering different impacts

Recently DC relay has been concerned as a key component in DC power distribution, management and control systems like aircraft, new energy vehicle, IT and communication industries. Ordinarily, magnetic force and contact moving speed have great influence on arc behaviours in the breaking process. This paper focuses on the numerical investigation of arc during the contact opening process in a real 400 V/20 A DC relay product coupling with an inductive load circuit. A 3D air arc model based on the magneto-hydrodynamic theory was built and calculated. A method coupling different computational software was used to take the nonlinear permanent magnet and contact opening process into consideration simultaneously. Arc behaviours under different magnetic field and contact opening speed were presented and discussed carefully. It has been found that the increase of the magnetic field is beneficial to the quick build-up of arc length and voltage. Arc breaking duration becomes shorter with the increase in contact opening speed from 63.5 rad s−1 to 94.5 rad s−1, such reduction is less significant with an increase of opening speed from 94.5 rad s−1 to 118.5 rad s−1.