DC Voltage Generator Research Articles

Study on Direct Torque Control Methods of a Doubly Fed Induction Machine Working as a Stand-Alone DC Voltage Generator

The article presents a comparison of different Direct Torque Control methods of a Stand-Alone Doubly Fed Induction DC-Voltage Generator, with classic field oriented control used as a benchmark. The system consists of a doubly fed induction generator the stator circuit of which is connected to the DC-bus with a diode rectifier, and the rotor circuit converter is connected to the same DC bus. The main problem of this power generation system are large torque oscillations caused by a nonlinear diode rectifier connected to the stator. Three direct torque control algorithms are described as a means of reduction of this drawback with simultaneous control of DC bus voltage and stator voltage frequency. The methods differ by the second variable used for control in parallel to the torque control path. The selected second variable is the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> component of the rotor current vector, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> component of the stator flux or the stator flux module.

Proton Exchange Membrane Electrolyzer Modeling for Power Electronics Control: A Short Review

The main purpose of this article is to provide a short review of proton exchange membrane electrolyzer (PEMEL) modeling used for power electronics control. So far, three types of PEMEL modeling have been adopted in the literature: resistive load, static load (including an equivalent resistance series-connected with a DC voltage generator representing the reversible voltage), and dynamic load (taking into consideration the dynamics both at the anode and the cathode). The modeling of the load is crucial for control purposes since it may have an impact on the performance of the system. This article aims at providing essential information and comparing the different load modeling.

Modeling of airgap influence on DC voltage generation in a dynamo-type flux pump

High-temperature superconducting (HTS) flux pumps are promising devices to maintain steady current mode in HTS magnets or to energize rotor windings in motors and generators in a contactless way. Among different types of flux pumps, the dynamo-type flux pump has been very common due to its simple structure and ease of maintenance. However, understanding the principle of dynamo-type flux pump has been challenging despite the recent progress. This article employs an efficient numerical model based on minimum electromagnetic entropy production method to analyze the performance of the flux pump in open-circuit mode. This model is much faster and efficient than previous works on flux pumps. In addition to the main behavior of the flux pump, this work investigates the influence of airgap and critical current density on open-circuit DC voltage of the flux pump. We compare the modeling results of open-circuit DC voltage for different airgaps to experimental ones obtained in (Bumby et al 2016 Appl. Phys. Lett. 108 122601), showing good agreement. Modelling results show that with increasing airgap, pumping voltage in the superconducting tape does not cease, but only reaches to insignificantly low values, which is not measurable via experiments. In addition, the voltage in open-circuit does not depend on the critical current density, as long as the superconducting tape is fully saturated with screening currents.

Biomedical Mechatronic Dynamometer to Support the Evaluation of the Effects of Leprosy Through the Palmar Holding Strenght and the Tweezer Holding Strenght

The hand can suffer the effects of several diseases among the most serious, leprosy stands out, which is considered infectious and can generate loss of muscle strength, atrophy, deformity and physical, mental and social disability. For the World Health Organization (WHO) and also doctors and physiotherapists, it is necessary to evaluate the diseases in an objective, reliable and early manner in order to propose appropriate treatment and follow their evolution. This research proposed a biomedical mechatronic dynamometer in order to support the evaluation of the effects of leprosy by means of palmar grip strength and grip strength of tweezers performed by hand. The experimental research was developed at the Federal University of Mato Grosso do Sul and consisted first of all in the survey of the demands of the health area in relation to the biomedical dynamometer being consulted the following databases: Medical Literature Analysis and Retrieval System Online (Medline); US National Library of Medicine National Institutes of Health (PUBMED) e Institute of Electrical and Electronic Engineers (IEEE). The mechatronic biomedical dynamometer consisted of three fundamental parts: mechanical structure, electronic signal conditioning circuitry and digital information processing. The mechanical structure was designed to withstand a strenght of up to 700 N, developed in brass because this metal has low cost, has less mass and also because it is easier to machine than steel. The oval shape of the structure contains two lateral and thin regions that measure 2 cm thick, 3 cm wide each and aim to concentrate mechanical stresses in order to sensitize the strain sensor consisting of the four linear strain gages, model N2A-XX-S5262P-350/E4 and nominal resistance of 350 Ω, from the company Micro-Measurements, which showed accuracy of 98%. The mechanical structure also has a stainless-steel support that measures 1 cm thick and 3 cm wide located at the bottom and on which was glued a cushion to support the palm of the hand. This support can be replaced by other models that also contain a cushion that considers the presence of injuries or deformities in the hand. The mechanical structure also has a upper support that also measures 1 cm thick and 3 cm wide, to which four pressure sensors developed with rosette strain gages model N2K-XX-S5294R-350/DP/E4 with a nominal resistance of 350 Ω, from the company Micro-Measurements, were fixed and which showed an accuracy of 99.5%. The deformation sensor is stimulated by the application of palmar grip strenght while the pressure sensors are stimulated by the realization of index, middle, annular and minimum finger gripping strenght. In addition, these sensors are connected to Wheatstone Bridges whose feeds and also the responses are processed by five signal conditioning circuits developed with operational amplifiers LF 356, OPA 27 and OP27 GP of the company Burr-Brown, whose structure consists of voltage oscillator, amplifier, band pass filter, buffer and peak detector that generates DC voltage that feeds the data acquisition board. The answers on this board are sent to the Inspiron 15 3000 microcomputer from Dell, which has installed Labview software from National Instruments, which processes the information, stores, plotts the palmar grip strenght and pinch grip strenght graphs and can also send the information over the Internet. This research has the potential to obtain accurate information on the effects of leprosy in the hand that can support the evaluation, diagnosis of health professionals, follow up the evolution of the disease and the treatment adopted.

Reliable DC voltage generation based on the enhanced performance triboelectric nanogenerator fabricated by nanoimprinting-poling process and an optimized high efficiency integrated circuit

Intensive research on triboelectric nanogenerators (TENGs) has been established since they were first introduced, but their application as a practical power source remains to face several challenges. Herein, we report a one-step process of thermal nanoimprinting and simultaneous electric poling to increase the total energy obtained by each cycle of a TENG with a ferroelectric thermoplastic polymer. The synergetic effect generated by the resultant formation of surface topography and the enhancement of effective dipole strength is systematically verified, and a wind energy harvester with enhanced electrical output performance is demonstrated. Furthermore, this paper also presents a novel integrated circuit (IC) that can generate reliable DC voltage even when an intermittent and irregular electrical output of the TENG is supplied. In the automatic control of the moment when the electrical output of the TENG is transferred into the electronic device, the present IC shows a conversion efficiency over 70% even when the input power is about 2.5 μW. This work intensively addresses the issues hindering the utilization of TENGs as a practical and reliable power source and thus may serve as a reference in the development of TENG-based self-powered systems in the future.

Design and Model of Series-Connected High-Voltage DC Multipliers

The generation of high dc voltages is necessary for feeding many technical applications and testing the insulation material of high-voltage dc transmission lines and ac power cables with long lengths. The article proposes a modular multiplier high-voltage dc generator with integrated Cockcroft-Walton (CW) circuits. In this new topology, CW circuits are connected in series to produce a high dc output voltage with low regulation factor (<; 2%) and a negligible ripple factor without the need for costly filters to produce a nearly constant output voltage. The modules are fed by low input ac voltage sources that have the same magnitude and frequency. Numerical simulations using MATLAB/Simulink confirm the viability of the proposed generator. The generator is finally validated by experimental tests on a kV-size prototype.

57.3: Improvement of Image Sticking for High Standard Automotive Application

As the rapid growth of LCD market, higher level of image quality is required. Image sticking is a phenomenon that a faint outline of previously displayed image remains visible on the screen as the frame is refreshed and it is an unvarying problem as the birth of LCD display. Furthermore, it has been a critical issue for high standard automotive application. In essence, the image sticking arises from the residual electric field (DC) in liquid crystal which caused by the ordered arrangement of ionic charges or dielectric polarization under the external DC offset voltage. In this paper, we will summarize the mechanism of the the residual DC voltage generation and image sticking. And an optimum Vcom setting method minimizing external DC offset voltage is introduced to improve image sticking.

P‐47: Improvement of Image Sticking for High Standard Automotive Application

As the rapid growth of LCD market, higher level of image quality is required. Image sticking is a phenomenon that a faint outline of previously displayed image remains visible on the screen as the frame is refreshed and it is an unvarying problem as the birth of LCD display. Furthermore, it has been a critical issue for high standard automotive application. In essence, the image sticking arises from the residual electric field (DC) in liquid crystal which caused by the ordered arrangement of ionic charges or dielectric polarization under the external DC offset voltage. In this paper, we will summarize the mechanism of the the residual DC voltage generation and image sticking. And an optimum Vcom setting method minimizing external DC offset voltage is introduced to improve image sticking.

Design and Analysis of Modified Diode Rectifier Circuit Suitable for Piezoelectric Energy Harvester for Biomedical Applications

Nowadays renewable energy sources play a significant role in the energy harvesting. For the past decade various energy harvesting methods have been discussed by researchers for capturing the energy from different sources. From the survey, one of the most prominent methods is the use of piezoelectric transducers for harvesting the energy. It is known that piezoelectric energy harvesting is the easiest method of energy harvesting from the various sources available such as human walking, dancing etc. Therefore this method can be implemented in system for wide variety of applications. The piezoelectric transducer AC output is of very low voltage and power and hence insufficient to drive any electrical application. Most of the small scale electrical application generally runs on the DC voltage, therefore the AC voltage obtained from the piezo transducer vibration is rectified using rectifiers to generate DC voltage. Thus in this paper, a modified rectifier AC/DC converter with the combination of an inductor is placed in the rectifier, which enhances the voltage and power from the rectifier output. In order to enhance the voltage rating, a DC/DC converter has been added at the end of a rectifier circuit. From the simulation results the proposed circuit modified rectifier has improved the output voltage as well as output current by 10.19 volts and 0.1019 amps respectively for input voltage of 5V. When compared with conventional rectifier circuit.

Automated setup to accurately calibrate electrical dc voltage generators

At National Institute of Metrological Research (INRIM), an automated setup to calibrate dc voltage generators, mainly top-level calibrators, from 1 mV to 1 kV has been developed. The heart of the setup is an INRIM-built automated precision fixed ratios dc voltage divider. It can be interconnected to a DMM characterized in linearity, to a dc voltage standard and to a dc voltage generator under calibration to manage automatically the calibration process. Novelty of the system is the employment of the divider being such an instrument not commercially available. Main results are the improvement of the reliability and the increasing of the accuracy of the calibration process saving a lot of time. In addition, it is possible to avoid several standards (still manually operating) carrying out the whole process without changing the setup configuration and without the presence of operators. The expanded uncertainties of the system span from 6.0 × 10−7 to 1.3 × 10−4 improving the previous capabilities of the INRIM laboratory for calibration of multifunction instruments. The setup concept can be transferred to secondary high-level electrical laboratories to improve and expedite their calibrations.

Automated precision DC voltage fixed ratios divider

At the National Institute of Metrological Research (INRIM), an automated precision DC voltage fixed-ratios divider allowing the division ratios 10:1 and 100:1 has been built. It is made utilizing one hundred selected bulk metal foils 10 kΩ resistors with low temperature coefficient. Being the instrument inter-connectable to a multi-meter (DMM) characterized in linearity on the 10 V range and to a DC voltage generator, it can be quickly and automatically calibrated when necessary. This calibration method has been validated by comparing it with another method involving the INRIM DC voltage ratio standard. Other achievement is that the characterization of the linearity of the DMM on the 10 V range allow considering in the uncertainties budget of the calibration of the divider, the uncertainties of the linearity characterization of the DMM instead of its much larger accuracy specifications. The expanded uncertainties of the calibration of the 10:1 and 100:1 ratios are respectively 4.6 × 10−7 and 6.6 × 10−7, suitable to employ the divider in an automated measurement setup with a DMM and a DC voltage standard to calibrate DC voltage generators as top-level calibrators, widespread in secondary electrical laboratories.

Unidirectional Spin-Wave-Propagation-Induced Seebeck Voltage in a PEDOT:PSS/YIG Bilayer

We clarify the physical origin of the dc voltage generation in a bilayer of a conducting polymer film and a micrometer-thick magnetic insulator Y_{3}Fe_{5}O_{12} (YIG) film under ferromagnetic resonance and/or spin wave excitation conditions. The previous attributed mechanism, the inverse spin Hall effect in the polymer [Nat. Mater. 12, 622 (2013)NMAACR1476-112210.1038/nmat3634], is excluded by two control experiments. We find an in-plane temperature gradient in YIG which has the same angular dependence with the generated voltage. Both vanish when the YIG thickness is reduced to a few nanometers. Thus, we argue that the dc voltage is governed by the Seebeck effect in the polymer, where the temperature gradient is created by the nonreciprocal magnetostatic surface spin wave propagation in YIG.

Power Generation for Wearable Electronics: Designing Electrochemical Storage on Fabrics

We report a new class of textiles with electrochemical functions which, when moistened by a conductive liquid (saline solution, sweat, wound fluid, etc.), generate DC voltage and current levels capable of powering wearable electronics on the go. Contrary to previously reported power generation techniques, the proposed fabrics are fully flexible, feel and behave like regular clothing, do not include any rigid components, and provide DC power via moistening by readily available liquids. Our approach entails printed battery cells that are composed of silver and zinc electrodes deposited onto a polyester fabric to generate power in the microwatt range. Electrochemical characterization of the discharge of a single printed battery cell in a 10 M NaOH electrolyte shows reproducible results with a sustained power level of ∼80 μW for over 3 hours. Scalable DC power may also be achieved by connecting multiple battery cells in series via flexible and conductive E-threads. Indeed, a series connection of two battery cells is demonstrated to boost the generated voltage from 1.4 V to 2.5 V. Notably, this in-series printed battery arrangement is shown to successfully power a digital thermometer under both 10 M NaOH, a 0.5 M NaCl solution (mimicking human sweat), and Dulbecco's Phosphate-Buffered Saline solution (DPBS) (mimicking bodily fluid electrolytes). Overall, the proposed technology is expected to be of utmost significance for healthcare, sports, military, and consumer applications, among others.

Performance Analysis of a 2 kW Wind Turbine in the Southern Beach of Bantul

This paper presents performance analysis of a 2 kW wind turbine in the Southern Beach of Bantul. The Government of the Republic of Indonesia through the Ministry of Energy and Mineral Resources targets by 2025 of at least 23% of the total national electricity supply comes from renewable energy sources. In this research, the create-designing and testing of wind power with maximum capacity of 2 kW is done. The test has been carried out on September 5 and 6, 2015 at the Baru Beach, Srandakan, Bantul. The test results on September 5, 2015 showed that the highest power generator occurred at 12:40 PM is 768.96 watts, with a wind speed of 8.76 m/s, AC voltage of generator is 40.00 volts, the DC voltage generator after rectified be 53.40 volts, and the load current is 14.40 ampere. In this condition, the 2 kW wind turbine has the efficiency of 38.4%. Furthermore, the test results dated 6 September 2015 found that the highest power generator at 10:50 PM is 842.20 watts, with a wind speed 9.53 m/s. At this peak condition resulting AC voltage of generator of 39.00 volts, the DC voltage of 49.60 volts, the load current of 17.00 amperes, and resulting in efficiency of 42.1%. The research results indicate that wind turbine is an alternative solution in the southern coastal region of Bantul for the supply of renewable energy sources.

PD detection and analysis of oil-pressboard insulation under pulsed DC voltage

HVDC transmission has been adopted widely for its large energy transport capacity, high stability and more economical in long-distance power transmission. Converter transformer is the key equipment in HVDC transmission system. The insulation of converter transformer valve side endures a composite voltage including AC, DC and pulsating component etc. Partial discharge (PD) occurring in a void surrounded by insulating material is believed to be one of the main causes of insulation breakdown and it is the main factor of electrical aging of materials. Therefore, it is important to recognize the prebreakdown phenomena and to evaluate the lifetime of insulating materials. Much research has been carried out to study the partial discharge characteristics under pure AC or DC voltage. Only a few investigations were focused on composite voltage. In order to obtain more understanding of PD characteristics under composite voltage, the PD detection and analysis of oil-pressboard insulation under pulsating DC voltage waveform are studied in this paper. The voltage waveform of converter transformer is analyzed through computer simulation. A 6-pulse DC voltage generator and PD detection system are set up. Influence of the DC component and pulsating component to the PD characteristics is studied in lab test. The experimental results show the DC component and pulsating component affect the PD inception voltage, but the pulsating component has more significant influence to PD characteristics than DC component. The study provides an experimental foundation for the converter transformer insulation breakdown mechanism analysis.

Modelling and efficiency optimisation of UHF Dickson rectifiers

This paper presents a new time-efficient modelling approach for UHF Dickson rectifiers. Due to the very low computation time, the approach can provide a quick and effective alternative to the standard transient simulations. The presented approach results in better estimation of the generated DC voltage and power conversion efficiency compared with the similar works in the literature. For the first time, an accurate mathematical relationship, including the non-zero reverse current, is expressed for finding the open load voltage of the Dickson rectifier while covering the broad range of RF amplitudes. The model uses the relation between the peak forward current and the load current to develop an input-to-output formula. Unlike the previous works, the channel length modulation is taken into consideration for the first time making the proposed model ideal for UHF Dickson rectifiers implemented with submicron CMOS transistors. Moreover, the proposed model takes secondary effects, such as the body effect and short-channel effects into account resulting in a more accurate estimation of the generated output DC voltage. Using the presented approach, a Dickson rectifier working at 900 MHz is implemented in a 0.18 µm CMOS process. Good agreement between simulation results, predicted results, and measurement results is observed.

Spin rectification induced by spin Hall magnetoresistance at room temperature

We have experimentally and theoretically investigated the dc voltage generation in the heterostructure of Pt and yttrium iron garnet under the ferromagnetic resonance. Besides a symmetric Lorenz line shape dc voltage, an antisymmetric Lorenz line shape dc voltage is observed in field scan, which can solely originate from the spin rectification effect due to the spin Hall magnetoresistance. The angular dependence of the dc voltage is theoretically analyzed by taking into account both the spin pumping and the spin rectification effects. We find that the experimental results are in excellent agreement with the theoretical model, further identifying the spin Hall magnetoresistance origin of the spin rectification effect. Moreover, the spin pumping and the spin rectification effects are quantitatively separated by their different angular dependence at particular experimental geometry.

A novel control grid bias power supply for high-frequency pulsed electron beam welding

Pulsed electron beam welding (EBW) is a novel welding process of which the welding beam current is modulated to pulsed square wave. Pulsed EBW is considered a promising method to increase the depth-width ratio and improve the mechanical property of welding joints. Pulsed beam current can be achieved by regulating the bias voltage on the control grid electrode of electron gun. For further studying the characteristics of high frequency pulsed EBW, a novel control grid bias power supply is developed with advanced inverter control technology. This power supply includes one base circuit and one pulse circuit in series. The base circuit can generate DC voltage, and the pulse circuit can generate pulsed voltage. The frequency and duty ratio of pulsed voltage can be adjusted by the designed control circuit. Carrier wave technique is used to transmit the control signal and homemade insulating transformer is used to protect the control circuit from high voltage. EBW machines equipped with the developed power supply can realize both continuous EBW and 0–20 kHz pulsed EBW. The base value, peak value and frequency of pulsed beam current all can be adjusted conveniently.

UV/ozone assisted local graphene (p)/ZnO(n) heterojunctions as a nanodiode rectifier

Here we report the fabrication of a novel graphene/ZnO nanodiode by UV/ozone assisted oxidation of graphene and demonstrate its application as a half-wave rectifier to generate DC voltage. The method involves the use of electrospinning for one-step in situ synthesis and alignment of single Gr/ZnO nanocomposite across metal electrodes. On subsequent UV illumination, graphene oxidizes, which induces p type doping and ZnO being an n type semiconductor, thus resulting in the formation of a nanodiode. The as-fabricated device shows strong non-linear current–voltage characteristic similar to that of conventional semiconductor p–n junction diodes. Excellent rectifying behavior with a rectification ratio of ~103 was observed and the nanodiodes were found to exhibit long-term repeatability in their performance. Ideality factor and barrier height, as calculated by the thermionic emission model, were found to be 1.6 and 0.504 eV respectively. Due to the fact that diodes are the basic building blocks in the electronics and semiconductor industry, the successful fabrication of these nanodiodes based on UV assisted p type doping of graphene indicates that this approach can be used for developing highly scalable and efficient components for nanoelectronics, such as rectifiers and logic gates that find applications in numerous fields.

Electric voltage generation by antiferromagnetic dynamics

We theoretically demonstrate dc and ac electric voltage generation due to spinmotive forces originating from domain wall motion and magnetic resonance, respectively, in two-sublattice antiferromagnets. Our theory accounts for the canting between the sublattice magnetizations, the nonadiabatic electron spin dynamics, and the Rashba spin-orbit coupling, with the inter-sublattice electron dynamics treated as a perturbation. This work suggests a new way to observe and explore the dynamics of antiferromagnetic textures by electrical means, an important aspect in the emerging field of antiferromagnetic spintronics, where both manipulation and detection of antiferromagnets are needed.