DC Power Supply Research Articles

A cost-effective and high-efficient EV shared fast charging scheme with hierarchical coordinated operation strategy for addressing difficult-to-charge issue in old residential communities

Charging infrastructures are being deployed widely in urban and rural areas to solve the so-called “last one-kilometer” charging problem. However, for old residential communities, the existing difficult-to-charge issue is not easily solved solely by the widespread deployment of charging infrastructure owing to limited spaces, complex reconstruction, and huge costs. In this context, this paper introduces a cost-effective and high-efficient shared fast charging scheme for old residential communities. The comprised registration-based queuing charging mechanism is proposed to schedule electric vehicle (EV) charging. An integrated and multi-stage power electronic device called smart interlinking unit (SIU) is introduced for grid reconstruction. The SIU-based charging station architecture features flexible control capability, enabling DC power supply for terminal EV chargers. For this architecture, a novel hierarchical coordinated operation strategy is designed, comprising the upper-level real-time vehicle-to-grid (V2G) dispatching and lower-level coordination strategies. Case studies demonstrate that the proposed scheme could accommodate 40 % EV penetration, while exhibiting a significant decline in system investment and occupied area compared to the slow charging scheme. Additionally, a 1.3 % improvement in average transfer efficiency is verified under this architecture. The proposed strategy is proven to realize a prominent power peak-shaving and valley-filling, effective transformer load balance, and DC voltage restoration.

Understanding Mold Wear Mechanisms and Optimizing Performance through Nico Coating: An In-Depth Analysis

This research investigates the wear mechanism of molds and examines the worn areas using high power microscopes and SEM (Scanning Electron Microscopy). In addition, EDS (Energy Dispersive Spectroscopy) and XRF (X-ray fluorescence) techniques are used to compare the worn areas with the normal areas. The results indicate that the wear mechanism of the molds is similar to adhesive wear. To address the issue of die wear, the application of Nico coating to the copper substrate surface is investigated. Two sample preparation methods, namely DC power supply and dual pulse power supply, are employed. SEM analysis shows that the sample group prepared using the dual pulse power supply has a relatively dense surface coating. The samples with a 60:40 weight ratio of Nico exhibit the highest average hardness and thickness, with minimal dispersion as indicated by the low standard deviation. The samples also show minimal roughness. Repeat tests under the same conditions confirm that the coating surface remains dense and uniform with a hardness of 467.628 hv, a thickness of 43.0665 μm and a roughness of 4.331 nm. The nanoindenter test results show that the coating has improved wear resistance (−28.7 nm) compared to the original mold (−142.4 nm), an increase of 80%.

Synthesis of graphene by electrochemical exfoliation from petroleum coke for electrochemical energy storage application

The objective of the present work was to synthesize a graphene-like structure from petroleum coke (pet coke). Graphene is a potential alternative conducting material to replace traditional electrode materials such as indium tin oxide. The phosphoric acid was used to activate the pet coke in conditions where the coke to acid ratio is varied as 1:1, 1:2, 1:3, 1:4 and 1:5. The samples were kept at different temperatures in the furnace maintained in inert atmospheric conditions at 400, 500 and 600 °C for activation time intervals of 1, 2 and 3 h. The extent of activation of pet coke samples was characterized by their yield and iodine number. For the optimized conditions (600 °C, 3 h, 1:4 coke to acid ratio), the activated pet coke was moulded and taken as the anode for electrochemical exfoliation using platinum wire as cathode, and 0.3 M H2SO4 solution as electrolyte. The electrochemical exfoliation was carried out using DC power supply at 22 V for 8 h, and the obtained exfoliated product was analysed by surface-sensitive techniques (XRD, Raman and SEM). The specific capacitance values were measured using cyclic vol­tammetry in KOH, Na2SO4 and H2SO4 electrolytes. The highest specific capacitance value of 40 F g-1 for the scanning rate of 25 mV s-1 was obtained in 1 M H2SO4. It was confirmed that graphene-like structure produced from activated pet coke can be used as an alternate material for supercapacitor applications.

ОСОБЛИВОСТІ ЗМІНИ РОБОЧИХ СТАНІВ ВИКОНАВЧИХ СТРУКТУР БАГАТОРІВНЕВИХ ВИПРЯМЛЯЧІВ

The main component of DC power supply systems are various semiconductor mostly controlled rectifiers with corresponding filter capacitors. In particular, these are multi-level rectifiers (MLRs) with a purposeful discrete-time change in the voltage transfer coefficient through a corresponding change in the operating state of its executive structure. Synthesized optimal variants of these structures are characterized by the high efficiency of the use of semiconductor switches elements. The work revealed and analyzed the peculiarities of the implementation of transitions between the specified operating states in two types of MLR – with a wide (full) and with a limited range of output voltage regulation. Taking into account these features made it possible to determine appropriate algorithms for discrete-time control of semiconductor switches elements of the MLR, which ensure an acceptable course of these transitions, during which the possibility of noticeable unwanted surges or drops in the voltage supplied to the consumer is practically excluded. The multivariate implementation of the algorithms for transitions between the output voltage levels of the MLR is another aspect of the multivariate transformer-and-switches executive structures of converters in general. References 10, tables 1, figures 5.

Full Operating Range Optimization Design Method of LLC Resonant Converter in Marine DC Power Supply System

The marine DC power supply system is the key to a ship’s power supply, which needs to convert the energy from storage batteries or distributed power generation units into stable DC voltage for electric propulsion or the ship’s electronics. The LLC resonant converter can be used as the key power conversion link in the marine DC power supply system due to its ability to realize electrical isolation in a high-power environment and soft switching within a wide load range. Aiming at the problem of sudden changes in voltage gain at a high switching frequency under light load conditions and the problem of insufficient voltage gain under heavy load conditions due to the parasitic parameters of power devices (mainly referring to the junction capacitor), this paper first proposes a full operating range performance optimization design method. By adding an auxiliary circuit that can be opened according to the operating conditions and a multi-objective particle swarm parameter optimization method that considers the converter loss and voltage gain under heavy load conditions, the performance of the LLC resonant converter can be improved in a full range of operating conditions. Finally, the effectiveness of the proposed method is verified by an experimental prototype and compared with the conventional methods and existing solutions to highlight the superiority of the proposed method in this paper.

Morphological control of electrodeposited iron for fluctuating photovoltaic electrical energy

With the Paris Agreement, the installed capacity of green power, such as photovoltaic (PV) and wind power, is growing rapidly at a rate of more than 10 % per year. The practical application of these green electrical energies is limited by the relative lag in the scale of energy storage systems. In response to the pressure on energy storage systems, we explored the feasibility of supplying DC power directly from a PV plant to an industrial electrolyzer by comparing the electrodeposition behavior of Fe2+ in a sulfuric acid system from stabilized DC and fluctuating PV power sources. We found that the factor that damages the stable operation of an iron electrodeposition system the most is the presence of hydrogen evolution reactions, where the generation of hydrogen bubbles reduces the current efficiency of the electrodeposition system and, in severe cases, destroys the surface morphology of the deposited products, causing devastating damage to the system. On this basis, we designed a simple scheme that uses heterogeneous bubble nucleation instead of homogeneous bubble nucleation for rapid bubble expulsion from the cathode surface. Benefiting from the rapid transfer of bubbles, the current efficiency of the electrodeposited iron system increases by 1.25%–10 % at different current densities, and the maximum roughness decreases by 129–2,396 nm, which considerably improves the stability of the electrodeposited iron system for PV power. This work provides useful experimental support for the transformation of the traditional steel smelting industry, which is characterized by high carbon emission and energy consumption, into an environmentally friendly industry.

A seven level fault tolerant hybrid cascaded inverter for renewable energy applications

Abstract The cascaded H-bridge (CHB) inverters are the prominent inverters used for renewable energy applications. Fault-tolerant operation is one of the foremost concerns to safeguard the continuous operation of the system under a fault on semiconductor switches and DC power supplies. A novel hybrid CHB inverter is proposed by adding a seven-level boost SLB module in cascade with the H-bridge modules. The proposed topology ensures the reliable and dynamic operation of the inverter during the occurrence of a fault. In addition to the fault-tolerant capability of the SLB inverter, the proposed design provides the voltage boosting and self-balancing of the switched capacitors. Extensive simulation results at different operating conditions substantiate the concept of the proposed novel fault-tolerant inverter structure. The prototype system is developed in the laboratory and the experimental results validate the proposed system configuration.

Study on the Formation and Controllable Movement of Polymer Liquid Columns Based on Dynamic Control of Spatial Electric Field Distribution.

Liquid deformation and motion are very common natural phenomena and of great value in various practical applications. In this study, a dielectric fluid column formation and directional flow phenomenon are presented. Dielectric fluid can grow upward to form a liquid column through a spatial electric field and realize directional and controllable operation of the liquid column by regulating spatial electric field distribution. First, the adjustable electric field space is constructed by connecting the two parallel electrodes to the high-voltage DC power supply. Then, the regional electric field distribution was adjusted by the upper plate graphic and power supply regulation to drive the polymer liquid on the lower plate electrode to form a liquid column at different positions. The results show that the polymer liquid column can be driven by the spatial electric field distributed dynamic control method and that the height and the narrowest width of the liquid column are directly controlled by the voltage. With the experiment conditions that the distance between two parallel electrodes is 5-15 mm, the formation of liquid columns with a height of 5-15 mm can be controlled. In addition, the liquid column can be driven by adjusting the on-states of different conductive regions. When the voltage is 10 kV, the liquid column directional movement speed can reach 1 mm/s. The higher the voltage, the faster the directional movement. The research results can be used as producing polydimethylsiloxane stamp, localized heating and temperature control, fabricating a pulsating heat pipe, and so on.

A novel distributing–collecting on-line insulation monitoring system and line selection technology for the DC supply system

At present, the power supply system of 5G base stations is a micro smart grid, it generally uses 240 V DC power supply with multiple branches, and leakage accidents will threaten personal and property safety, so it is vital to identify the fault line accurately and remove the faults rapidly. In this paper, the leakage phenomenon of transmission lines in the HVDC power supply system of a 5G communication base station is studied. To address the issue of multi-branch line leakage diagnosis and line selection in the 240 V DC system, a new distributed DC insulation monitoring and fault line selection technology and system are proposed. The distributed DC insulation monitoring line selection technology is used to collect the leakage current of each branch by setting a unique single-core DC leakage transformer and process the signal primarily. In addition, a high-resistance bridge switchgear is added to the bus bar. According to different leakage currents caused by the imbalance of the bridge before and after the switch, the insulation resistance of electrodes to the ground is calculated accurately, which solves the problem that the current technology cannot judge the fault of the positive and negative electrodes to the ground at the same time. Through both simulation and prototype experiments, the feasibility of this technology and system device in line insulation monitoring and line selection of the HVDC communication base station power supply system is verified.

Research on the Electrodeposition of Graphene Quantum Dots under Supercritical Conditions to Enhance Nickel-Based Composite Coatings

A graphene quantum dots (GQDs)-reinforced nickel-based composite coating was electrodeposited on the surface of a copper plate with a supercritical carbon dioxide fluid (SC-CO2)-assisted DC power supply. The effect of the current density on surface morphology, microstructure, average grain size, hardness, and corrosion resistance of the resulting coatings was investigated in detail. It was found that the GQDs composite coating showed a more compact surface, a smaller grain size, higher microhardness, and stronger corrosion resistance than the pure Ni coating produced in SC-CO2 and a texture coefficient indicative of a (111) preferred orientation. When the current density was 8 A/dm2, the surface morphology of the GQDs composite coating showed a high density, and the grain size was about 23 nm. In addition, the micro-hardness and corrosion resistance of the GQDs composite coating was greatly improved compared with those of the pure nickel coating; at the same time, its wear rate, friction coefficient, and self-corrosion current density were decreased by 73.2%, 17.5%, and 9.2%, respectively.

Ac-Dc multi pulse converter for dc power distribution system in aircraft

ABSTRACT The Transformer Rectifier Unit (TRU) in aircraft is DC power supplies. Three-phase AC power supplies are available as long as they work. DC power distribution, on the other hand, provides DC power directly to all DC users, providing input power to the emergency AC distribution system so that the static inverter can generate AC power. To the voltages produced by TRUs to be less oscillating and of higher quality, multi-pulse ones are studied and recommended for aircraft systems. In this study, Zener diode filtered multi-pulse rectifier, which can further reduce the oscillations in the output voltage, is recommended for aircraft. Three-phase half-wave rectifier design and analysis are presented to better demonstrate the effectiveness of Zener diode regulation in multi-pulse TRUs. First, the parts of the power system, which includes the rectifier circuit of a two-engine aircraft and fed by this rectifier, are given. The circuit structure and working order of the rectifier are given with mathematical explanations. In the application phase, low oscillating output voltages and currents are obtained by creating currents and voltages on the load for different Zener voltages. Conventional rectifiers and the proposed rectifier are tested on the same loads, and comparisons are done.

A Study on the Influence of the Electroplating Process on the Corrosion Resistance of Zinc-Based Alloy Coatings

A comprehensive analysis was conducted to examine the crystal phase composition, surface and cross-section morphology, elemental composition, thickness, and corrosion resistance of coatings. X-ray diffraction (XRD) was employed to investigate the texture and crystal phase of the materials while scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were utilized to assess the surface and cross-section structure. Additionally, electrochemical techniques were employed to evaluate the corrosion performance. Compared to DC electroplating, the corrosion potential of pulsed galvanized ferroalloy alloy coating increased from −1031 mV to −1008 mV, and the corrosion current density decreased from 3.122 × 10−5 A∙cm−2 to 0.321 × 10−5 A∙cm−2. Moreover, the corrosion rate value of the coating obtained by the pulse rectifier (0.386 × 10−5 g m−2 h−1) was lower than that obtained by the DC power supply (3.75 × 10−5 g m−2 h−1). Additionally, pulsed electrodeposition reduced the iron content of the coating by 0.7%, thereby enhancing its corrosion resistance and flatness. The impedance parameters of the zinc–iron alloy coating acquired through the 30% duty cycle monopulser process exhibit superior performance compared to DC electroplating. Evidently, the monopulse coating’s structure enhances crystal packing density, augments coating thickness, improves adhesion to the substrate interface, and optimizes grain distribution uniformity. These factors are crucial determinants of the corrosion behavior exhibited by Ze–Fe coating.

Multi-objective optimization of two-stage AC–DC power supply for reliability and efficiency using NSGA-II and meta-heuristic honey bee algorithms

This paper introduces a novel approach to simultaneously optimize the reliability and efficiency of a switching power supply (SPS) using the Non-dominated Sorting Genetic Algorithm (NSGA-II) and Honey Bee Algorithm (HBA). The proposed method uses a Markov model to evaluate the reliability of the converter and maximizes objective functions, including efficiency and reliability, using optimization algorithms to identify the optimum values of the converter parameters. The optimization algorithm determines the optimal values for converter parameters, such as switching frequency, transformer turn ratio, and DC-link voltage. It also fine-tunes circuit components, such as the power factor correction inductor, DC-link capacitor, and output filter components. A sensitivity analysis is carried out to assess the impact of various parameters on the multi-objective functions of the converter. The converter’s reliability and mean time to failure (MTTF) are evaluated using the Markov reliability model, considering all components’ short and open circuit faults. The failure rates of converter components are calculated using the MIL-HDBK-217 methodology. The results obtained from the NSGA-II and HBA are compared to identify the superior algorithm with the best-optimized parameters. Simulation results indicate that the proposed optimization technique enhances the converter’s reliability performance while maintaining its efficiency. Furthermore, this paper presents comprehensive analyses, comparisons, and experimental findings to demonstrate the converter’s fault-tolerant capability. The multi-objective optimization approach offers a practical and effective strategy for optimizing switching power supplies for efficiency and reliability

Catalyst-free synthesis of ammonia using dc-driven atmospheric-pressure plasma in contact with water

Atmospheric-pressure plasma, generated using a dc power supply, in contact with water was investigated as a green, catalyst-free method for the ammonia synthesis. Stable nitrogen plasmas were generated inside bubbles which were obtained by inserting a dielectric tube with the gas flow into water. A higher production rate was obtained at a higher discharge current, a higher flow rate of nitrogen, and a lower conductivity of water. In addition, the production rate when the water worked as the cathode of the discharge was higher than that with the inverted polarity of the dc power supply. The maximum production rate of ∼0.98 µmol min−1 was realized at the optimized discharge condition, which is higher than the literature value obtained using a dc discharge in contact with water (Hawtof et al 2019 Sci. Adv. 5 eaat5778). We also discussed the possible reaction fields for the ammonia synthesis in the experimental condition.

Development of DC Power Supply for Plasma Activated Water Using Gliding Arc Discharge

Development of DC Power Supply for Plasma Activated Water Using Gliding Arc Discharge

A low-voltage MOS translinear loop, biased using FVF and its applications in realizing square-rooter and squarer circuits

In this paper, a new MOS Translinear Loop (MTL), biased using Flipped-Voltage-Follower, has been presented and its use in the CMOS Current-Mode (CM) realization of the non-linear functional circuits namely, square-rooting and squaring has been demonstrated. The new MTL facilitates the low-voltage operation of the proposed CMOS CM circuits while maintaining all the MOSFETs operating in strong inversion mode. The workability of both the proposed circuits has been validated by simulations carried out on Cadence Virtuoso software using 0.18 μm CMOS technology at a DC power supply voltage of 0.85 V and the results of the same have been presented. Furthermore, temperature and corner analyses have been performed to verify the robustness of the proposed circuits in the practical environment.

Research on the Modulation and Control Strategy for a Novel Single-Phase Current Source Inverter

Compared to the voltage source inverter, the current source inverter (CSI) can boost voltage and improve filtering performance. However, the DC side of CSI is not a real current source, and the DC input current comprises a DC power supply and an inductor. In the switching process, the DC-link inductor is charged or discharged and is in an uncontrollable state. This paper proposes a novel CSI topology containing five switching tubes and a modulation strategy based on the hysteresis control strategy of the DC-link current. Due to the conduction and switching loss being positive to the DC-link current, the calculation method for the least reference value of the DC-link current is derived to meet power requirements. By constructing a virtual axis, we then present the control strategy of the output voltage in a two-phase rotating reference frame. Finally, we carry out the simulation and experiment are to validate the proposed topology, modulation, and control strategy.

PERANCANGAN KUNCI PINTU RUMAH OTOMATIS MENGGUNAKAN E-KTP BERBASIS ARDUINO

Currently, cases of theft are still relatively high, because of this, tools or door locks with a more sophisticated security system are needed, such as the use of an e-KTP system. The door of the house is the main access to enter the house, but the security system at home used today is still relatively common and very vulnerable to theft or robbery. It is also very dangerous for the life of the home owner in the event of theft. So it takes a high level of security system to open or enter the door of the house. A system that can be implemented to improve security is one of them is a microcontroller-based electronic circuit system, this system makes it possible to design a home entrance security system with RFID to read e-KTP codes and manual passwords based on Arduino Mega 2560 and Arduino Nano. This system is designed with ±5V DC power supply, LCD, RFID, LED and ±12V DC solenoids. Arduino Mega 2560 and Arduino Nano as microcontrollers and solenoids and LCD as their outputs. Based on the test results, it can be concluded that the designed door security system works well and works optimally. With the help of a system that is made to open the door of the house automatically with RFID which reads the ID contained in the registered e-KTP or password, so as to minimize the occurrence of crime, especially cases of theft and burglary at the door of the house.

A Novel Microwave Noise Generator Using Multiple Zener Diodes Connected in Series

A novel microwave noise generator circuit using multiple Zener diodes connected in series was designed and tested. Measurements are presented up to 6 GHz. It is presented in this letter that when the number of series Zener diodes increases, the amount of noise power generated also increases across the band of interest. However, the increase of noise power from one-zener to two-zener configuration and from two-zener to three-zener configuration is not uniform. Measurements were limited to three zeners connected in series due to available high-voltage dc power supply.

Modified Roll-Type Electrostatic Separator for the Processing of Polymer Mixtures Containing Brominated Flame Retardants

The aim of the present paper is to study the efficiency of a new configuration of a roll type electrostatic separator in selectively sorting granular polymers containing brominated flame retardants (BFRs) from the same BFR-free polymers. The peculiarity of this configuration is that the “standard” grounded roll electrode is covered by a thin layer of insulating material, which is charged by corona discharge at a polarity opposite to that of the static electrode, to increase the intensity of the electric field in the active zone of the separator. The study was conducted on a mixture composed of equal quantities of BFRs-containing Polypropylene (PP) and BFR-free PP mm-size granules. The mixture was first tribocharged in a fluidized bed device, the walls of which were made of PS, and was then introduced in the corona-charged-insulating-roll-type electrostatic separator, to be selectively sorted under the action of electrical and mechanical forces. The best separation results were obtained in the case where the high-voltage static electrode was connected to a positive DC power supply and the insulating-roll-electrode was charged using a negative corona discharge. With this configuration, when mixed with PP with granules containing 40000 ppm of Br, 70% of the BFR-free PP granules were recovered in a concentrate having a purity of about 80%. The outcome of the electrostatic separation was even better, with purities approaching 93%, for mixtures composed of 50% BFR-free PP and 50% PP granules containing 2000 ppm of Br.