DC Voltage Source Research Articles

A Useful Experiment for Teaching Resistance of a Wire as a Function of Temperature

We have developed a new simple experiment for the students where they can get a quantitative measure of how the resistance of a wire depends on the temperature of the wire. The only materials required are a copper wire coil, a DC voltage source, a digital ohmmeter, and a calorimeter with an analog thermometer. The students discover a linear relationship between temperature and resistance. The temperature coefficient is easily calculated from the slope of the graph and compared with the standard values. The experiment, although simple to perform and feasible with minimal equipment, does provide reasonable results and is appropriate for either high school students or an undergraduate physics laboratory. Also, the work would be of interest to teachers in an introductory-level physics course.

Dynamics of the Rotating Arm of an Electromechanical System Subjected to the Action of Circularly Placed Magnets: Numerical Study and Experiment

This paper considers the experimental and numerical study of an electromechanical arm powered by a DC motor and subjected to the action of permanent magnets. The magnetic torques arise from permanent magnets mounted at the free end of the arm and along a circle. The electrical subsystem is powered by two forms of input signal (DC and AC voltage sources). For each case, we determine the condition for complete rotation of the mechanical arm versus the parameters of the system such as the arm length, the number of magnets, and the frequency of the external signal. The nonlinear dynamics of the system is examined by means of time-histories, bifurcation diagrams, Lyapunov exponents and phase portraits. Chaotic and periodic dynamics are detected numerically and confirmed experimentally.

実験値とデータシート値と近似式から構築した電力変換器の損失モデルの実機検証

This paper proposes a losses-analysis model of a DC-output converter based on the approximated equations from measurements and a datasheet. Target verification circuit consists of a DC-voltage source, a smooth capacitor, two half bridge legs, and a load inductor connected to the midpoints of the half bridge legs, which controls the continuous average DC current of the load inductor. A use of self-measured data, compared with the use of datasheet values, enables expanding the ranges of the considerable target parameters. Hence, lesser order approximated equations can deal with more target parameters with less calculation period than that in a conventional time domain simulation. In this study, calculation flow of losses from losses of power devices and an inductor to circuit losses was developed. Subsequently, a semiconductor losses model and inductor losses model were developed via the linear least square method. Finally, a 400V experimental system was developed to verify the accuracy of the circuit losses at 16 specified operating conditions by varying three verification parameters, switching frequency, gate resistance, and inductance. The result shows that the losses calculated using the proposed model has good accuracy with an error of 1.9% to 10.6% to the measured result.

Space Vector Modulation for Induction Motor on ARM-based Microcontroller

This article presents the review and the implementation of Space Vector Modulation (SVM) in a low-cost microcontroller-based motor drive system. The output three-phase voltages are obtained from a reference voltage vector in the polar coordinate system using the PWM technique; these voltages can reach up to the level of the DC voltage source (experimentally 16 VDC or practically 237 V with an inverter module). The article also provides a detailed presentation of the pre-calculations and the computations required for SVM on a STM32F1 ARM-based microcontroller. For achieving high frequency precision, a novel method for vector rotation based on the fixed-point arithmetic is proposed and tested. The experimental results highlight that the presented implementation including vector rotation can reach 1 Hz without significant error and it requires only 0.684 MIPS at 5 kHz computation rate for a 72 MIPS 32-bit microcontroller with single-cycle multiplication. The maximum instantaneous output phase-to-phase voltages could be as high as the DC voltage source.

A Novel MPPT Technique Based on Combination between the Incremental Conductance and Hysteresis Control Applied in a Standalone PV System

A new Maximum Power Point Tracking (MPPT) method, consisting in combining the Incremental Conductance (INC) algorithm with the Hysteresis control, was developed and applied to a standalone photovoltaic (PV) system to generate the maximum power of the PV array. The INC allows one to search for the Maximum Power Point (MPP). The hysteresis improves the accuracy of tracking the MPP very fast even after severe changes in weather conditions and has no oscillations around the MPP. The five-level S-Packed U Cells (SPUC5) inverter is used to transform the produced DC voltage to AC voltage; it generates five-level output voltage with a small number of switches and only DC source voltage. The capacitors of the SPUC5 are controlled by the Pulse Width Modulation (PWM) in order to balance their voltages. The proposed PV system was established and trained in the MATLAB/Simulink environment under various irradiation conditions. A comparison between different MPPT methods, INC-PWM and INC-PI, was investigated in order to examine the effectiveness of the developed MPPT technique in particular, and of all the PV system components. The results of the simulation validate the effectiveness of the suggested MPPT algorithm as well as the used SPUC5 inverter.

Multilevel Inverter from a New Basic Unit

This research makes a novel suggestion for a cascaded single-phase multilevel inverter. The suggested basic unit is connected in series with this inverter, which can only create positive levels at the output. So, the recommended inverter is expanded upon by an H-bridge. This inverter is referred to as a developed cascaded multilevel inverter, and it allows the output of the architecture to have both even and odd voltage levels. Having fewer driver circuits, DC voltage sources and power switches is a benefit of the single-phase cascaded multilevel inverter that is built. In turn, this lowers the inverter’s cost as well as the size on installation. These features are acquired when comparing the proposed inverter with the conventional inverter.

Decolorization of Dyes in the Bioelectrochemical System Depending on the Immobilization of <i>Shewanella oneidensis</i> MR-1 Cells on the Anode Surface and Electrical Stimulation of the External Circuit

The effect of the polarity of the electrical stimulation of the external circuit of the bioelectrochemical systems, as well as the immobilization of Shewanella oneidensis MR-1 cells containing the DyP peroxidase gene on the rate of discoloration of dyes of different types was found. For the crystal violet triphenylmethane dye, the maximum decolorization rate by suspended S. oneidensis MR-1 cells 2.05 ± 0.07 μM/h was noted in the case of connecting a 1.2 V direct polarity DC voltage source. One of the minimum rates was observed in the case of reverse polarity of the connection. In the case of cells immobilized on the anode, the rate was higher, reaching 2.91 ± 0.09 μM/h and did not decrease with increasing substrate concentration. The lowest values were also noted for the reverse connection of the voltage source. In case of the azo dye congo red, the maximum rate was found for a source with direct connection and an open circuit (0.26 ± 0.01 and 0.29 ± ± 0.02 μM/h, respectively), the minimum value is 0.11 ± 0.02 μM/h for reverse connection. For the crystal violet decolorization products, a significant decrease in the intensity of the main absorption peak at 590 nm band was found, with no notable hypsochromic shift. The qualitative changes in the decolorization products composition are indicated by the appearance, in case of a direct polarity of the ionistor connection, of a new absorption maximum in the region of 360 nm. The results may be of interest for the development of new methods of bioelectrochemical cleaning.

Seven Level Symmetric Cascaded H-Bridge Multilevel Inverter for Solar Photovoltaic System

Among different types of Non-Conventional Energy Sources, Solar Power has become highly prominent with exhausting suitable to innovation in Power Electronic Systems. The primary intention of the advised performance must limit the number of switches to enhance the output waveforms with a preferred harmonic profile. This topology moderates the estimate about switches, isolated DC origin, expenditure, and intensity of the circuit substantially as correlated to other topologies. The proposed method uses the MPPT approach to exploit the maximum energy from solar photovoltaic to load entirely. The Proposed method provides almost sinusoidal output waveforms by developing a few power switches. The SPV arrangement was simulated and constitution through SPV arrays, a DC-DC buck converter, and a sliding mode MPPT regulation. Based on the cascaded H-Bridge multilevel converters, The strong constraint enforced confined DC voltage sources considering separately Cascaded H-Bridge. This constitution converter worth along with diminishing the constancy based on the system. The system gives boosting voltages with improves the harmonic profile. Performance of the arrangement demonstrated in MATLAB SIMULINK as well as PROTEUS.

An Effective Transformerless PUC7-Based Dynamic Voltage Restorer Using Model Predictive Control

This paper investigates the performance of a seven-level Packed U Cell (PUC7) inverter-based transformerless Dynamic Voltage Restorer (DVR) topology under short-time voltage variations (voltage sags and swells). Unlike the existing multilevel inverter (MLI)-based DVR solutions, the proposed structure requires only one DC voltage source (suitable for PV-based DVR systems), one capacitor, and six switching devices to generate seven-level output voltage. Moreover, the studied topology is characterized by reduced cost and size due to the elimination of the injection transformer. The PUC7 inverter is controlled using a multi-objective (filtering current, compensating voltage, and PUC capacitor voltage controls) Model Predictive Control (MPC) strategy. Simulation and implementation tests are carried out to demonstrate the high performance of the proposed DVR at steady-state and during transient conditions, while keeping the load voltage unaffected by the disturbances in the grid voltage.

Quasi-Z-Source-Fed Switched-Capacitor Multilevel Inverters Without Inrush Charging Current

In switched-capacitor (SC) based multilevel inverters (MLIs), capacitors are usually replenished by a dc voltage source or other capacitors, inrush charging current are found at switching instants. In order to solve this issue, this article presents a new type of step-up MLIs, which is implemented by using a front-side quasi-Z-source unit to feed SC-based multilevel circuits. As a result, the charging current variation of capacitors is effectively limited by the quasi-Z-source impedance. Moreover, the charging voltage can be regulated by controlling the duty ratio of shoot-through states of the quasi-Z-source unit, and the total voltage gain of the new MLI is enhanced as both SC and quasi-Z-source units have boost capability. Structurally, the two units share a common switch network so that the new MLI has simple structure. Topologies for single- and three-phase configurations, operation, and modulation, as well as the parameter design are analyzed in detail. Finally, the feasibility of the new MLI is verified experimentally by a downscale three-phase prototype.

A Modular Cascaded Multilevel Converter With High Configurability: Design, Analysis, and Optimization Study

This article introduces a new modular cascaded multilevel inverter (MLI) that is composed of a cascaded connection of submodules (SMs). The combination of basic cells (BCs) with polarity changer H-bridge produces the SMs, which is the basis of the introduced inverter. Due to its high modularity, the proposed inverter can be extended to reach higher voltage levels. Hence, two extensions are suggested: 1) extension based on cascading more BCs within each SM and 2) extension based on cascading more SMs. Using a set of algorithms, the magnitude of dc voltage sources is determined to synthesize the proper ac-side voltage waveform. Furthermore, the proposed topology is optimized in different ways to achieve the desired purposes, such as maximizing the number of voltage levels, minimizing the number of switches and dc sources, and providing the least total standing voltage on the switches. Therefore, in each of the mentioned optimization goals, the optimal structure is obtained. A prototype of the presented MLI is defined and its performance is verified through several simulation studies in MATLAB/Simulink and experimental tests. Besides, a comprehensive comparison is made with the best performance of the existing alternatives to demonstrate the merits and superiorities of the proposed MLI.

Active-Arm Bridge with Two-Channel DC Voltage Source for Comparison of High-Resistance Standards in 1:1 Ratio

In this paper, a guarded active-arm bridge for high-resistance standards with programmable two-channel source of DC voltage is described. Both channels of this source are controlled from a common reference voltage. This ensures a high stability of the voltage ratio of both source channels. The presented results of tests of this source show that its use in the active bridge is more advantageous than the use of the two independent DC voltage sources. The bridge allows high accuracy in the comparison of the high-resistance standards in 1:1 ratio. The current state of knowledge about active-arm bridges is presented, the basics of the bridge operation are given, the two-channel DC voltage source used in the bridge and its test results are described, the measurement process that does not require transposition of the compared resistance standards is described, sample measurement results, and a plan for further work are given. The bridge is used in the resistance standard calibration system at the Central Office of Measures (GUM), Poland, in the range from 100 MΩ to 100 TΩ.

Challenges and potential solutions of grid-forming converters applied to wind power generation system—An overview

As the capacity of wind power generation increases, grid-forming (GFM) wind turbine generators are deemed as promising solutions to support the system frequency for future low inertia power grids. So far, the GFM converter with a nearly ideal dc voltage source has been studied thoroughly. However, when the GFM converter is applied to wind power applications, there are some realistic problems and challenges, such as coordinating wind turbine control and GFM control, limited energy to support the grid, variable wind speed, etc. These problems still need more discussion. In this paper, an overview of challenges and potential solutions of GFM converters applied to wind power generation systems are provided, where different energy reserving schemes, GFM control schemes, and overcurrent protection schemes are compared and discussed. Finally, a few perspectives on future trends are shared according to the authors’ knowledge.

Influence of rotor excitation source model in electromagnetic field–circuit coupling analysis model of tubular hydro‐generator on no‐load voltage waveform and damper winding loss calculation results

AbstractIn this study, a 34‐MW tubular hydro‐generator was selected as the study example. For the electromagnetic field–circuit coupling analysis model, the effects of the ideal DC voltage and current sources (i.e. two models of the rotor excitation power supply) on the no‐load voltage waveform quality and the damper winding loss calculation results were studied by considering the influence of the electromagnetic induction of the rotor excitation winding. The obtained results provide direct and effective theoretical support and technical reference for improving the accuracy and rationality of the calculation results of the electromagnetic performance parameters and the analysis, design, manufacturing and operating level of such generators.

Power Quality Enhancement of Grid-Connected Renewable Systems Using a Matrix-Pencil-Based Active Power Filter

Power electronic converters are used for integrating renewable energy sources such as wind and photovoltaic into the grid. This integration gives rise to many challenges in power systems, especially regarding power quality. Indeed, integrated systems generate a non-linear current full of harmonics, which degrades power quality. Active power filters are usually used to compensate for these harmonics at the point of common coupling. In the control of active power filters, harmonics need to be extracted from the non-linear current. In this paper, the matrix pencil method―a model-based technique for estimating parameters of exponentially damped or undamped sinusoids in noise―is proposed to extract the reference signal in shunt active power filter applications. The performance of the proposed matrix pencil method is studied for current harmonic compensation and power factor correction under different modulation schemes and two DC links: an external DC voltage source and a capacitor. Using a capacitor for the DC link requires not only including a proportional-plus-integral controller to maintain a constant capacitor voltage, but also accounting for the loss current in the formulation of the matrix pencil method. Compared with the instantaneous reactive power theory and synchronous reference frame, results obtained from simulated data using MATLAB/Simulink under different loading conditions show that the proposed method corrects the power factor and affords a lower source current total harmonic distortion and fast response.

Modified Structure 9-Level Inverter (MS9LI) With Reduced On-State Switches

This article describes a modified structure 9-level inverter (MS9LI) with a dual dc link and eight switches. The dual dc links are different dc voltage sources with a 1:3 ratio. To generate high-quality nine-level output, the alternative phase opposition and disposition pulsewidth modulation (APODPWM) technique has been used. Most reported reduced device multilevel inverters (MLIs) include several underutilized dc sources and much more active switches. The designed MS9LI is more efficient since it uses fewer conducting switches. The proposed configuration furthermore does not need a backend H-bridge, and voltage stress is not more than the input dc voltage. A series connection of the proposed configuration can also be used to extend the topology. To prove the superior performance of the proposed MS9LI configuration, a detailed comparison with the foremost configurations in terms of the essential number of sources, switches, and drivers is made. In order to confirm the viability and functionality of the MS9LI configuration, various simulation and experimental findings are presented.

A New Model for Remote Calibration of Voltage Source Based on GPS Common-View Method

A remote calibration system of dc voltage source based on global positioning system (GPS) common-view method is proposed in this article. The system realizes remote calibration by installing the standard in the laboratory instead of the calibrated site and solves the problem of additional errors introduced by the standard at the calibrated site. By researching the relationship between voltage, frequency, and time, a new model for remote calibration of voltage source based on the GPS common-view method is built. The model reflects the mathematical relationship between calibration results and parameters measured by the calibration system. The accuracy of the model is a prerequisite to ensure the reasonableness of the calibration results of the entire calibration system. Based on the model, the voltage value of the standard side and the calibrated side can be compared remotely by measuring the time deviation between the pulse signal converted from voltage and the GPS synchronous clock signal. The voltage difference between the two sides is obtained and the remote calibration of dc voltage sources is implemented. By experiments, the voltage difference derived by the remote calibration model and measured by the traditional calibration method can be obtained when the calibration point is 0–1 V. The discrepancy between the results of the two methods is within <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7.4244\times 10^{-5}$ </tex-math></inline-formula> V. The verification results of the two methods for the same dc voltage source are consistent in the evaluation of the accuracy level. It verifies the efficiency of the proposed system and the accuracy of the calibration model.

A Five-Level Switched-Capacitor Based Transformerless Inverter With Boosting Capability for Grid-Tied PV Applications

Transformerless grid-connected inverters have attained a lot of research interest in renewable energy interface applications, due to certain promising properties like greater efficiency, light weight, affordable price, and tolerable power density. Among various types of transformerless grid-tied photovoltaic (PV) inverters, multilevel inverters (MLIs) are mostly popular due to their ability to transmit reactive power, small filter size for reducing total harmonic distortion (THD) and their common-ground (CG) configuration to mitigate the detrimental leakage current due to the parasitic capacitances of the PV array. Again, among different types of MLIs for PV systems, switched-capacitor (SC) based multilevel inverter topologies are the burning topic in current decades due to their single source requirements for producing multilevel output voltage. However, for mostly used single-phase five-level inverters, most of the existing SC based topology requires at least two SCs for power conversion. In this paper, a five-level transformerless inverter based on a single SC is proposed, requiring only seven switches, no diode, a single capacitor, and one dc voltage source. The proposed transformerless MLI also has auto-boosting capability. Notably, the number of power switches operating at high frequency is limited to three, which lowers down the switching losses of the inverter. Rather than a new single SC based five-level transformerless inverter topology, a control scheme is also presented to inject a precisely regulated current into the grid that can govern both the active and reactive power support modes. In-depth comparisons between the proposed and cutting-edge MLIs are also provided. All these claims are validated through MATLAB/Simulink and PLECS computer simulation environments. A laboratory-scaled prototype is also built and tested to support the simulated claims further and validate the effectiveness and feasibility of the proposed five-level transformerless inverter topology.

Simulation and analysis of transition processes in linear electrical circuits using MatLab software package

The research work considers the simulation and analysis of transition processes in linear electrical circuits using the MatLab software package. The transition processes occurring in the following linear electrical circuits were analyzed: RL equivalent circuit in case of connecting the relay control winding to a DC voltage source; RC equivalent circuit in case of connecting a capacitor through a limiting resistor to a DC voltage source and disconnecting it from the source; RLC equivalent circuit in case of capacitor discharge to an inductor; this capacitor shall be pre-charged from a DC voltage source; a branched electrical circuit of the first order where its topology changes after switching. As a result of the research, the transition process graphs were obtained for which the simulated completion time of the transient process does not differ from the calculated values with an error of less than 2%. The analysis of transition processes revealed the following: the winding inductance effect on the time of relay switching; the effect of the additional resistance value on the charge (discharge) of the capacitor; the effect of the resistance value change when the capacitor is discharged in a circuit with two reactive elements; the effect of changes in the topology of the electrical circuit on the intensity of the transient process after switching.

A DC TO AC CONVERTER WITH A HIGH FREQUENCY LEVEL

Two block diagrams of DC-AC converters with a voltage curve of a given frequency close to the sinusoidal shape without a high-frequency section and with a high-frequency section are considered. In the converter circuit without a high-frequency link, an autonomous voltage inverter (AVI) is used, and in the converter circuit with a high-frequency link, a high-frequency AVI (AVI HF) and a direct frequency converter with quasi-single-band modulation (DFC QF) are used. In both of these converter circuits, for electromagnetic isolation between the DC voltage source and the load, a power transformer is envisaged, to match the input and output voltages. To improve, ensure and obtain on the load the output voltage curve close to the sinusoidal shape, filters are used, which is the simplest way of improvement without a selective elimination of distorting harmonics of non-sinusoidal periodic voltage with multiple switching of valves, without pulse-width modulation, and so on with the complication of voltage inverter and DFC control systems. At the same time, in the first converter circuit, one filter is used: connected between the output of the inverter and the input of the output transformer, and in the second converter circuit, two filters are used, one of which is connected between the output of the AVI HF and the high-frequency transformer, and the other - between the output of the DFC with the QF load. Since the output voltages of AVI and DFC are non-sinusoidal periodic functions, using the methods of harmonic analysis and switching functions, mathematical descriptions of the output voltages of AVI and DFC are obtained in the form of a trigonometric Fourier series. A numerical assessment of the weight and size parameters of transformers and filters in relative units is carried out. It is shown that the use of a converter with a high-frequency link based on AVI HF and DFC with QF allows to significantly reduce the mass and dimensions of power electromagnetic elements.