Direct Current Source Research Articles

Design a Perturb & Observe MPPT Algorithm for PV System Based Asymmetric Cascaded HalfBridge Multilevel Inverter

Objectives/methods: This research proposes a Perturb and Observe (P&O) algorithm to extract maximum power point for photovoltaic (PV) system which then used as a direct current (DC) source for an asymmetrical cascaded half-bridge (ACHB) multilevel inverter (MLI). The whole system is modelled in MATLAB/SIMULINK. An approach is used to give input DC sources to asymmetrical cascaded halfbridge MVI with two PV systems. For PV system, a P&O maximum power point tracking (MPPT) algorithm is used to control the duty cycle of DC to DC boost converter for maintaining the constant output voltage. The switching pattern of MLI done by using pulse width modulation (PWM) technique. Findings: The proposed switching sample based on Multi Carrier (MC) PWM which reduces the voltage of components, decrease size, cost and also switching losses. ACHB MLI is attractive for its features as it gives higher level of output voltage by using fewer number of switching devices. Finally, two PV systems of different output voltages are integrated with asymmetrical cascaded half-bridge MVI. The results of the proposed model are verified in MATLAB/SIMULINK. Novelty: Dual P&O MPPT algorithms based PV system is used as input DC source for asymmetric cascaded half-bridge MLI which provides higher level output voltage as compared to conventional two-level inverter. Keywords: P&O, MPP, Photovoltaic, Asymmetric Cascaded HalfBridge Multilevel Inverter.

Повышение искробезопасности в системах импульсного питания потребителей в сравнении с системой питания постоянным током

The purpose of the work is to evaluate the magnitude of the arc sparking energy during switching in the wires of a pulsed power supply system when compared with the energy when powered from a direct current source and to determine the flammable currents of the methane-air mixture to improve intrinsic safety. Methodology. The research methodology is based on the fundamental principles of the application of the theory of electrical engineering, the theory of planning a scientific experiment, computer and simulation modelling. The experimental data were obtained in the laboratories of the Kremenchuk Mykhailo Ostrohradskyi National University using certified metrological measuring instruments. The system was modelled using the software packages Matthcad, Microsoft. EXCEL. StatGraphik. Results. Conducted theoretical and experimental studies of the magnitude of arc sparking prove that the energy of sparking with a pulsed current is less than with a constant one and can be used as the basis for reducing the ignition of gas in mines and other explosive industries. Scientific novelty. The useful use of the consumer’s reactive energy has been substantiated if the supply line or the current source is shut off for the duration of the pause and at the same time the consumer is shunted. Practical significance. The obtained results are recommended to be used in power supply systems of consumers that operate in a pulsed mode to increase their energy efficiency and explosion and fire safety of operation.

Characteristic of Electrical Power Dissipation of Oil Palm Fruits during Storage Time

Among oil-producing plants, the oil palm produces a high-yield vegetable oil. After the oil palm fruit is harvested as a fresh fruit bunch six to eight months after the flower bloom, the fresh fruit bunch is stored for several days to be collected and transported for manufacture. This storage time can influence the quality and maturity level of the fruit, affecting the yield of crude palm oil. Currently, several methods exist to detect the grade and maturity level of oil palm fruit, such as optical spectroscopy-based and electromagnetic-induced. However, these methods need improvement as they are limited in terms of practical use as well as accuracy. This study proposes a simple four-point probe for the characterization of oil palm fruit during five days when stored under ambient conditions. A direct current power source from a low-voltage battery (~9 V) was applied to produce electric potential in the oil palm fruit. The voltage response shows a distinguished result, directly indicating different storage period. Furthermore, the dissipated power of the first four days dramatically increased from 0.01 to 1.25 µW, and a drop to 0.09 µW was recorded on the fifth day. The estimated capacitance also demonstrates a dropping time, pointing to a change in the internal molecule and cell wall. This result, then, can be employed to detect the level of freshness of the oil palm fruit after harvesting.

MULTI-LEVEL SVM FOR SIX-PHASE MULTI-LEVEL INVERTERS TO DRIVE DUAL STATOR INDUCTION MACHINE

This article proposes a new six-phase multi-level space vector modulation (SVM) method to control a six-phase induction machine (SPIM) driven by a multi-level separate direct current (DC) source (SDCS) inverter.

Adoption of Multilevel Inverter based Dynamic Voltage Restorer for Power Quality Improvement with Adjustable DC-Link

Dynamic Voltage Restorer (DVR) is a method of overcoming voltage sag and swell in electrical power distribution. To boost up voltage levels on load side on power disturbances DVR can be used so as the equipment connected will have good voltage profile In this Pulse Width Modulation inverter is in solid-state electronic switching device were employed along with Integrated Gate Bipolar Transistor by the DVR, the alternating current voltage is controllable at real and reactive powers which are made independently. The MLI; is organized as the cascaded H-bridge inverter units. The function of Multilevel Inverter; is to arrange the voltages from a significant direct current source. Here in the DVR, there is no need for external output filters. In the planned DVR, a dc-dc converter is combined with an MLI. By considering the voltage sag magnitude of a dc-dc converter can regulate the dc-link voltage. Hence the output voltage of the multilevel inverter; always has a last number of levels. Instead of using the PWM based technique, the fundamental frequency method can be used in the multilevel inverter. The proposed DVR operation range of mathematical analysis is specified in detail. The simulation results are prepared by using Simulink/MATLAB.

Selective harmonic elimination (SHE) based 3-phase multilevel voltage source inverter (VSI) for standalone applications

The breakthroughs in power electronics semiconductor technology have led to the raised in popularity of Multi-level Voltage Source Inverters, which is the reason industries and researchers are relentlessly working towards extending it to both medium and high-power applications. Consequently, this paper presents a modified Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM) controlled three-phase 5-level Multi-level Inverter (MLI) topology. The work is an extension of a single-phase topology proposed by the authors. The uniqueness of the proposed topology is that it comprises of six Cascaded H-bridge modules (two modules per phase) that are powered through a single direct current (DC) source, hence eliminating the need for multiple DC sources. In addition, conventional 5-level MLI has two switching angles (n = 2), which restricts its harmonic elimination capability to one (n = 1) lower order harmonics. This study removes that restriction by utilising the concept of multiple switching per step, resulting in the superimposing of 12 notches (n = 12) on the output voltage at the 3/9 distribution ratio. With the fundamental switching SHE-PWM, twelve non-linear, transcendental equations are generated, and they are optimally solved using the Hybrid Coded Genetic Algorithm to eliminate 11 (n − 1) lower-order harmonics. The low-switching frequency results in less electromagnetic interference as well as reduced switching loss, which improves the overall inverter efficiency. The topology has less output Total Harmonics Distortion, fewer components, and lower weight and cost than conventional topologies. The circuit was designed and validated through simulations performed in PSIM software.

Modulation and Voltage Balancing of a Five-Level Series-Connected Multilevel Inverter With Reduced Isolated Direct Current Sources

The series connection of low-power modules is an alternative solution to realize a multilevel inverter. Unlike a cascade connection, the series connection approach significantly reduces the number of isolated dc sources, thereby the design complexity, cabling of the transformer, and overall system cost become low. In this article, the operation of the series-connected multilevel inverter is presented for a five-level operation, and it is realized by using two three-level half-bridge diode clamp converter modules per phase. Hence, each phase of the series-connected multilevel inverter requires a single isolated dc source. In the series-connected multilevel inverter, the net dc-bus voltage will be equally distributed between four dc-bus capacitors. Therefore, the converter generates a multilevel voltage waveform with uniform steps and ensures equal voltage stress on the semiconductor devices. To achieve these objectives, a space vector pulsewidth modulation scheme with an additional voltage balancing approach is employed. The feasibility of series-connected multilevel inverter is validated through simulations and a scaled-down laboratory prototype under steady-state and transient conditions.

Review of Multilevel Voltage Source Inverter Topologies and Analysis of Harmonics Distortions in FC-MLI

We review the most common topology of multi-level inverters. As is known, the conventional inverters are utilized to create an alternating current (AC) source from a direct current (DC) source. The two-level inverter provides various output voltages [(Vdc/2) and (−Vdc/2)] of the load. It is a successive method, but it makes the harmonic distortion of the output side, Electromagnetic interference (EMI), and high dv/dt. We solve this problem by constructing the sinusoidal voltage waveform. This is achieved by a “multilevel inverter” (MLI). The multilevel inverter creates the output voltage with multiple DC voltages as inputs. Many voltage levels are combined to produce a smoother waveform. During the last decade, the multilevel inverter has become very popular in medium and high-power applications with some advantages, such as the reduced power dissipation of switching elements, low harmonics, and low EMIs. We introduce the information about several multilevel inverters such as the diode-clamped multilevel inverter (DC-MLI), cascaded H-bridge multilevel inverter (CHB-MLI), and flying-capacitor multilevel inverter (FC-MLI) with Power systems CAD (PSCAD) simulation. It is shown that THD is 28.88% in three level FC-MLI while THD is 18.56% in five level topology. Therefore, we can decrease the total harmonic distortion adopting the higher-level topology.

Numerical simulation and experimental investigation of air cooling system using thermoelectric cooling system

Efficient air-conditioning inside the cars is a challenge in automobile industry. Thermoelectric is one of the new methods for air cooling. It has many advantages such as non-moving parts, small size, low weight, fluid less functions, and dealing with direct current source. This research aimed to determine the amount of air chamber cooling using three thermoelectrics. For this purpose, air cooling system was initially developed and then simulated by ANSYS CFX software. The system was tested at three different airflow (0.18, 0.35 and 0.7 m s−1) and three different inlet air temperatures (31, 40 and 50 °C). The temperatures of the four points were recorded. The results of numerical simulation were compared with the experimental ones. This research demonstrated that thermoelectrics can be a good choice for air cooling. However to improve the performance of this system, it is recommended to change the layout of the heat sinks. Furthermore, the mean difference between the result of the numerical simulation and that of the experimental tests was 8.5% indicating that this simulation can be promising with sufficient confidence.

Electrocoagulation Treatment for Landfill Leachate using Stainless Steel Electrode

Electrocoagulation (EC) process uses direct electric current source between metal electrode submerged in the effluent that results in electrode dissolution, with a suitable pH, metal ion can form a wide range of metal hydroxide and coagulated species that destabilized and dissolved contaminants absorbed. Electrocoagulation (EC) has been working for the percentage removal of BOD (Biochemical oxygen demand)/ chemical oxygen demand (COD) ratio, Color and COD on leachate in a batch Electrocoagulation reactor using stainless steel (SS) electrode. EC technology depends on so many factors such as electrode material, initial pH, applied voltage, inter-electrode distance, and electrolysis time. From the experimental work, results reveal that the maximum percentage of removal achieved were COD and Color 73.5% and 65.0% respectively and increasing BOD/COD ratio 0.11 to 0.62. The optimum inter-electrode distance 1cm with electrode surface area 35 cm2 and optimum electrolysis time of 120 min at optimum applied voltage 12V, stirring speed 250 rpm and pH 9.8. These results proved that the EC process is an appropriate and proficient approach for treating the landfill leachate.

Considering reactive power coordinated control of hybrid multi‐infeed HVDC system research into emergency DC power support

According to the characteristics of line-commutated converter high-voltage direct current (LCC-HVDC) and voltage source converter high-voltage direct current (VSC-HVDC), respective additional emergency DC power support (EDCPS) controllers are designed, and a coordinated control strategy based on a hybrid multi-infeed HVDC system for EDCPS is proposed. Considering the differences in system recovery performance between LCC-HVDC and VSC-HVDC in providing EDCPS, the emergency power support priority issues and power allocation schemes for LCC-HVDC and VSC-HVDC are discussed in detail. To maintain the stability of the receiving-end AC system during boosting power process and to ensure the active power is raised to the specified value, this study also designs an additional reactive power controller that can make full use of the ability of VSC-HVDC to support the reactive power of the AC system. Finally, a hybrid three-infeed HVDC system consists of two parallel LCC-HVDCs and one VSC-HVDC is built on PSCAD/EMTDC and simulated. The effectiveness of the proposed approach is verified based on this hybrid three-infeed HVDC system.

Development of Pico-ESI-MS for Single-Cell Metabolomics Analysis.

In this chapter, we introduced a Pico-ESI strategy for metabolomics analysis with picoliter-level samples. This Pico-ESI strategy was technically achieved by pulsed direct current electrospray ionization source (Pulsed-DC-ESI). This source could collect MS signals for a few minutes from a cell, enabling us to obtain large-scale MS2 data of metabolite IDs in single-cell analysis. Further identification of the single-cell metabolome such as the database match and chemical modification to metabolome was thereby achieved. Technically, this source could ionize sample with no need of sample and electrode contact, which can be potentially applied for high-throughput analysis. We also introduced several strategies related to Pico-ESI to reduce the matrix interference especially for extremely small samples developed in our group, including step-voltage nanoelectrospray, picoliter sample desalting method, droplet-based microextraction method, and probe-ESI, etc. All these strategies have been successfully applied to single-cell analysis.

Rapid Electroformation of Biopolymer Gels in Prescribed Shapes and Patterns: A Simpler Alternative to 3-D Printing.

We demonstrate the use of electric fields to rapidly form gels of the biopolymer alginate (Alg) in specific three-dimensional (3-D) shapes and patterns. In our approach, we start with a gel of the biopolymer agarose, which is thermoresponsive and hence can be molded into a specific shape. The agarose mold is then loaded with Ca2+ cations and placed in a beaker containing an Alg solution. The inner surface of the beaker is surrounded by aluminum foil (cathode), and a copper wire (anode) is stuck in the agarose mold. These are connected to a direct current (DC) power source, and when a potential of ∼10 V is applied, an Alg gel is formed in a shape that replicates the mold. Gelation occurs because the Ca2+ ions electrophoretically migrate away from the mold, whereupon they cross-link the Alg chains adjacent to the mold. At low Ca2+ (0.01 wt %), the Alg gel layer grows outward from the mold surface at a steady rate of about 0.8 mm/min, and the gel stops growing when the field is switched off. After a gel of desired thickness is formed, the agarose mold can be melted away to leave behind an Alg gel in a precise shape. Alg gels formed in this manner are transparent and robust. This process is particularly convenient to form Alg gels in the form of hollow tubes, including tubes with multiple concentric layers, each with a different payload. The technique is safe for encapsulation of biological species within a given Alg layer. We also create Alg gels in specific patterns by directing gel growth around selected regions. Overall, our technique enables lab-scale manufacturing of alginate gels in 3-D without the need for an expensive 3-D printer.

Effect of electrocoagulation on MBR under different power supply conditions

The impact of electrocoagulation (EC) on membrane bioreactor (MBR) under different power supply conditions was investigated in this study, which included constant voltage/current of 1 V, 3 V, 5 V and 0.15 A from direct current (DC) power source and undulate voltage from 18 V/10 W solar panel. The EC actuated by constant current of 0.15 A from DC power source and undulate voltage from 18 V/10 W solar panel could mitigate the membrane fouling obviously with 14 and 20 days of operation times, respectively, as results of sludge bulking inhibition and specific resistance to filtration (SRF) reduction after effective EC. When the EC was applied, the suitable power supply condition could inhibit the sludge bulking caused by filamentous bacteria well. The protein and polysaccharide reduced from SMP and LB-EPS of sludge and filter cake was another reason for membrane fouling mitigation. The application of EC in MBR could also improve the removal efficiency of pollutants, especially for phosphate (PO43−). The maximum removal efficiency of PO43− was 92.45% under 5 V condition with influent PO43− of 26.20 ± 0.11 mg/L. The community diversity could be maintained well although community richness was reduced in EC-MBR during operation. The EC could embed the filamentous bacteria inside sludge particle and then eliminate its effect on membrane fouling.

The role of electrical anisotropy and effective conducting thickness in understanding and interpreting static resistance measurements in CFRP composite laminates

This study is focused on (i) the experimental characterization of the anisotropic electrical resistivity of carbon fiber reinforced polymer (CFRP) composites and (ii) the development and experimental validation of predictive finite element (FE) models of the electrical response in CFRP laminates based on the concept of the effective conducting thickness. Two experimental methods have been developed to characterize the anisotropic electrical resistivities in three principle directions for the CFRP composite laminates using a direct current source. One method utilizes a traditional 6-probe resistance scheme and the alternative point-type 4-probe method is based on a handheld probe device similar to the JIS K7194 standard for homogenous plastics. An extensive experimental study has been conducted to characterize the anisotropic electrical resistivities of 16-ply unidirectional and 16-ply symmetric cross-ply IM7/977-2 and 32-ply unidirectional IM7/977-3 composites using the developed methods. Exploiting the concept of the effective conducting thickness, which describes the effective depth of current penetration through the thickness of an electrically anisotropic material, a unique methodology is developed for constructing FE models of these highly anisotropic CFRP materials. The concept of effective conducting thickness was identified as a critical component in achieving accuracy of the FE results as well as recovery of experimental resistivity from the alternative point-type 4-probe method. The FE models have been validated using the experimental results on the CFRP specimens of varying layup and thickness, and the techniques developed in this work may lead to advancements in non-destructive techniques in the areas of electrical characterization and damage sensing.

PWM controlling of a new multi DC-DC converter circuit

The design and development of DC-DC converter circuits are important for increasing and decreasing the direct current energy sources at operating the loads and systems. In this study, a multi DC-DC converter structure is described. The purpose of creating this circuit structure is to create a more effective circuit by offering a different circuit structure. For the proposed DC-DC converter, a circuit structure with five switches is created. This circuit structure is described by mathematical models according to the operation of the four parts PWMs in different time periods. After the mathematical analysis of the circuit structure, the proposed circuit and conventional circuit are operated in the Matlab Simulink. The obtained results are compared. According to the comparisons, the proposed circuit produces a higher output voltage than the traditional one and has a higher performance. Additionally, the circuit is operated for values of different loads using different switching times. Finally, voltages and currents are observed on loads.

High Speed Test System of Current Pulse for Phase Change Memory Devices

The high-speed test system of current pulses for T-shaped phase change memory (PCM) cells has been studied. This system, which is able to provide the narrowest width of 500 ns, can apply direct current source pulses to the PCM device to do SET and RESET operation. The reliability of the system has been verified through the fixed resistor and the real PCM cells. The test results are presented and analyzed.

A new structure of three‐phase five‐level inverter with nested two‐level cells

SummaryThis paper presents a new structure of three‐phase five‐level inverter with a single direct current (DC) source for low‐ and medium‐voltage applications. The proposed configuration is built with a cascade connection of two‐level cells in a nested form and owns the advantages of a reduced number of passive components, total blocking voltage of the switches, and isolated DC sources. In order to make this topology attractive, a comparison is made with five‐level inverter topologies proposed for low‐ and medium‐voltage applications in recent years. The proposed circuit is powered using a single DC source and an auxiliary voltage‐balancing circuit (AVBC) to maintain the desired DC‐link capacitor voltages. A sinusoidal pulse width modulation (SPWM) scheme is implemented in field‐programmable gate array (FPGA), using Xilinx blocks developed in MATLAB/SIMULINK environment, to control the inverter switches. The performance of the proposed topology is verified through MATLAB simulation and prototype model for a step change in load. Finally, the experimental results are presented to validate the effectiveness of the proposed topology.

Design and Implementation of a Hybrid Single T-Type Double H-Bridge Multilevel Inverter (STDH-MLI) Topology

Multilevel inverters are proficient in achieving a high-quality staircase output voltage waveform with a lower amount of harmonic content. In this paper, a new hybrid multilevel inverter topology based on the T-type and H-bridge module is presented. The proposed topology aims to achieve a higher number of levels utilizing a lower number of switches, direct current (dc) voltage sources, and voltage stresses across different switches. The basic unit of the proposed single T-type and double H-bridge multilevel inverter (STDH-MLI) produces 15 levels at the output using three dc voltage sources. The proposed topology can be extended by connecting a larger number of dc voltage sources in the T-type section. The nearest level control (NLC) switching technique is used to generate gate pulses for switches to achieve a high-quality output voltage waveform. In addition, a simplified way to achieve NLC is also described in the paper. A detailed comparison with other similar topologies is provided to set the benchmark of the proposed topology. Finally, experimental work is carried out to validate the performance of the proposed topology.

Effect of Ti-Al cathode grain size on plasma generation and thin film synthesis from a direct current vacuum arc plasma source

Herein, we investigate the influence of powder metallurgical manufactured Ti0.5Al0.5 cathode grain size (45-150 μm) on the properties of a DC arc discharge, for N2 pressures in the range 10-5 Torr (base pressure) up to 3x10-2 Torr. Intermetallic TiAl cathodes are also studied. The arc plasma is characterized with respect to ion composition, ion charge state, and ion energy, and is found to change with pressure, independent on choice of cathode. Scanning electron microscopy, X-ray diffraction, and Energy-dispersive X-ray spectroscopy of the cathode surfaces and the concurrently deposited films are used for exploring the correlation between cathode-, plasma-, and film composition. The plasma has a dominating Al ion content at elevated pressures, while the film composition is consistent with the cathode composition, independent on cathode grain size. Cross-sections of the used cathodes are studied, and presence of a converted layer, up to 10 μm, is shown, with an improved intermixing of the elements on the cathode surface. This layer is primarily explained by condensation of cathode material from the melting and splashes accompanying the arc spot movement, as well as generated plasma ions being redeposited upon returning to the cathode. The overall lack of dependence on grain size is likely due to similar physical properties of Ti, Al and TiAl grains, as well as the formation of a converted layer. The presented findings are of importance for large scale manufacturing and usage of Ti-Al cathodes in industrial processes.