Direct Current Power Research Articles

Sinusoidal PWM Generation for 3 Phase Inverter and RPM Measurement using Hercules TMS570LC43xx Launchpad

This project focuses on implementing a 3 phase Sinusoidal PWM generation using the Hercules TMS570LC43xx Launchpad Development Kit (Launchpad). The primary objective is to generate synchronized Sinusoidal nature PWM signals using the onboard High-End Timer (HET) and Enhanced Pulse Width Modulation (ePWM) module, which can be given to the Inverter for conversion of Direct current (DC) power into Alternating current (AC) power. This conversion is essential in various applications where AC power is required but the power source provides DC power. It is used in Solar photovoltaic (PV) systems and other renewable energy installations. These systems generate power suitable for powering household appliances or feeding into the electrical grid. Itis alsoused in electric vehicles (EVs) to drive the electric motor with variable speed. For verification of the wave nature, we have used an external lowpass filter (LPF) to transform the dynamic PWM signals into sinusoidal waveforms, ensuring compatibility with various applications like Inverters which can be further used in equipment and machinery such as Brushless DC motors, pumps and compressors. With the addon functionality to control the signal’s frequency which will be given to the Inverter to control the speed of the motor. Additionally, the project incorporates RPM measurement of the motor using an optical encoder setup interfaced with the Enhanced Quadrature Encoder Pulse (eQEP) module on the Launchpad. This feature enables accurate measurement of rotational speeds, position and Revolution per minute (RPM), enhancing the functionality of the system in real world applications like the speed of conveyor belts and other automated transport systems. Through successful implementation, this project demonstrates wide control for the Inverter, achieving reliable synchronized 3 phase signals with its variable speed having 120-degree phase shift signals alongside precise RPM measurement. The project highlights the Launchpad’s capabilities in handling complex signal processing tasks essential for modern power electronics applications. Looking forward, this project establishes a foundation for future enhancements and innovations in power electronics.

Detection of Faulty Energizations in High Voltage Direct Current Power Cables by Analyzing Leakage Currents

The use of multi-terminal high voltage direct current (HVDC) power transmission systems is being adopted in many new links between different generation and consumption areas due to their high efficiency. In these systems, cable energization must be performed at the rated voltage. Healthy energizations at the rated voltage result in large inrush currents, especially in long cables, primarily due to ground capacitance. State-of-the-art protection functions struggle to distinguish between transients caused by switching and those associated with ground faults, leading to potential unwanted tripping of the protection systems. To prevent this, tripping is usually blocked during the energization transient, which delays fault detection and clearing. This paper presents a novel method for prompt discrimination between healthy and faulty energizations. The proposed method outperforms conventional protection functions as this discrimination allows for earlier and more reliable tripping, thus avoiding extensive damage to the cable and the converter due to trip blocking. The method is based on the transient analysis of the current in the cable shields, therefore, another technical advantage is that high voltage-insulated measuring devices are not required. Two distinct tripping criteria are proposed: one attending to the change in current polarity, and the other to the change in current derivative sign. Extensive computer simulations and laboratory tests confirmed the correct operation in both cases.

Influence of external AC transverse magnetic field on air arc oscillation patterns and its application in DC forced current zero techniques

Abstract Direct current (DC) circuit breakers are essential for maintaining the stability of the electric energy transmission and safeguarding the power equipment from the damage caused by the fault currents in DC power systems. The characteristics of the switching arc can be utilized in DC forced current zero techniques. This paper investigates the influence of an external alternating current (AC) transverse magnetic field on the oscillation characteristics of air arc. By confining the arc between two insulating walls and applying a transverse AC magnetic field, the arc exhibits "bidirectional oscillation" and "unidirectional oscillation" modes. The effects of magnetic field amplitude and frequency on the air arc oscillation characteristics are analyzed through experiments, from the aspects of the arc voltages and arc motions. It can be found that an external AC magnetic field can stabilize the arc voltage at a specific oscillation frequency. By connecting an inductor-capacitor (LC) branch in parallel with the arc and setting the LC branch's resonant frequency equal to the arc voltage oscillation frequency, a current resonance process between the arc and the LC branch can be achieved. This resonance facilitates the creation of the arc current zero-crossing point. A test platform based on the arc oscillation characteristics is established for current interruption experiments. For system currents of 1 kA and 3 kA, the arc current zero-crossing time is controlled within 0.41 ms after applying the external AC transverse magnetic field. The experimental results verify the rationality of the proposed DC breaking scheme.

Tribo-hygro-electric generator: Harnessing mechanical energy with liquid-infused porous cellulose for multiple sensing and DC power generation

This study introduces the Tribo-Hygro-Electric Generator (THEG), a novel device that harvests ambient mechanical and water-enabled energies for highly sensitive, self-powered multi-sensing. THEG employs a simple design using liquid-infused porous cellulose (LIPC), created by absorbing functional liquids such as water into porous cellulose, and metal contacts with distinct work functions (e.g., Al and Cu) to generate triboelectric charges through friction. It operates via a three-step process: generating triboelectric charges through sliding motion, establishing an internal electric field across Al/LIPC/Cu interfaces for charge separation, and directing charges to create unidirectional output electron transfer, producing direct current (DC) outputs. The principle behind THEG emphasizes the critical role of the single Schottky contact at the Al/LIPC interface in separating and directing charge transfer, as well as the conductive path formed by the hydrogen-bonded network of water molecules and cellulose’s functional groups. THEG can harvest DC power with a current density of up to 3.4 A/m² and 0.5 V, which can be increased to 2 V with four cells in series. THEG demonstrates impressive multiple-sensing capabilities, with robust linear relationships (correlation coefficients > 0.99) between output current density and stimuli such as pressure, velocity, water absorption, and ion concentration. Demonstrating practical utility, the generated energy powers devices like a commercial calculator. This technology advances mechanical energy harvesting and multiple sensing, reducing dependence on external power and enabling transformative IoT applications.

Advancing High-Performance Piezoelectric Nanogenerators: Simple Electric Field Switching for Orientated and Aligned BaTiO3/PDMS Composite.

Barium titanate (BaTiO3) is renowned for its high dielectric constant and remarkable piezoelectric attributes, positioning it as a key element in the advancement of environmentally sustainable devices. Nevertheless, the effectiveness of piezoelectric nanogenerators (PENGs) that integrate BaTiO3 nanoparticles (NPs) and poly(dimethylsiloxane) (PDMS) poses a challenge, thereby restricting their utility in energy harvesting applications. This study presents a direct approach involving the cyclic manipulation of direct current (DC) power supply terminals to achieve unidirectional alignment of BaTiO3 NPs within a PDMS matrix, aiming to enhance the performance of the PENGs. Examination of the morphology and evaluation of diffraction planes, notably (111) and (200), in the aligned BaTiO3 PENGs exhibited well-oriented structures resulting from the repetitive switching between two electrodes, leading to improved piezoelectric properties. The BaTiO3 PENGs manifested notably higher output power (∼15 V and 1.91 μA) in contrast to devices containing randomly distributed polarized BaTiO3-PDMS composite films. The generated power was sufficient to directly operate six light-emitting diodes (LEDs) connected in series, with a collective nominal voltage of around 14 V, encompassing red, green, and blue LEDs. Nanoindentation verified the enhanced piezoelectric characteristics attributed to the alignment, sensitivity to bending, and energy-cohesive effects of clustered BaTiO3 one-dimensional (1D) pillars. These findings suggest a widely applicable technique for aligning and situating nanoparticles vertically within a polymer matrix, exploiting the intrinsic dielectric properties of the nanoparticles through a straightforward electric field switching mechanism.

Design and Testing of an Electric Side-Mounted Cabbage Harvester

To address the limitations of current cabbage harvesters in China, which are often designed for a single variety and lack adaptability to different cabbage varieties, we developed an electric side-mounted cabbage harvester suitable for field operations in the Jiangsu region of China. This design is informed by the statistical analysis of the physical and agronomic parameters of major cabbage varieties. The harvester consists of key components, including an extraction device, a leaf-stripping device, a clamping and conveying device, and a root-cutting device. Powered by a 120 Ah direct current (DC) power source, it is capable of performing cabbage extraction, feeding, clamping, conveying, root cutting, and boxing in a single operation for three hours. Through theoretical analysis of the key components, specific parameters were determined, and field tests were conducted to verify the design. The results of the field experiments indicate that all components of the cabbage harvester operated effectively. Optimal performance was observed when the extraction roller speed was set between 100 and 110 RPM, the conveyor belt speed at 60 RPM, and the cutter speed between 160 and 220 RPM, resulting in a low cabbage harvest loss rate. The harvest loss rates from the three experiments were 11.3%, 13.3%, and 12%, respectively, which meets the mechanical harvesting requirements for cabbage.

Research on distributed optimal scheduling method based on consensus

Abstract With access to large-scale distributed power sources, the physical structure of the power grid system tends to be distributed. The application of traditional centralized optimal scheduling methods will lead to a surge in communication overhead and computational complexity, which will affect the performance and efficiency of the solution. In this paper, the minimum operating cost of the system is taken as the goal, and the distributed direct current optimal power flow (DC-OPF) optimization calculation of the photovoltaic-storage power generation system is considered to approximately solve the economic dispatch problem. The DC optimal power flow model with energy storage charging penalty is constructed. Then, the distributed optimization method based on the consensus alternating direction multiplier method (ADMM) is adopted. By decoupling the objective function and constraints of the whole system problem, the fully distributed DC-OPF calculation is realized by introducing the global consensus variable to deal with the boundary buses. Finally, the improved IEEE 30-bus example is used to test the method, and the simulation results verify the convergence and accuracy of the method.

Enhance Hydrogen Production from Water Using 532 Lasers

ABSTRACT: hydrogen production via water electrolysis under the influence of laser sounds fascinating with its unique properties, was particularly effective in promoting hydrogen production. The mechanism by which the laser promotes hydrogen production The electrolytic cell used in this work contains 270 ml of distilled water stimulated with different amounts of alcohol (2 ml - 4 ml - 6 ml - 8 ml - 10 ml). This chamber consists of two vertically oriented cylinders. Inside each cylinder there are graphite electrodes, each measuring 10 x 5 x 7 mm3, connected to the positive and negative terminals of a direct current power source, in addition to using a green laser source (532). An efficiency study was conducted using a green laser with a wavelength of 532 nanometers as an optical light source for water analysis through electrolysis. Results were obtained using both the standard electrolysis method and with the green laser source (532 nm). In the case of standard electrolysis, we obtained (When adding 5 ml of cohol, we get 6.63 hydrogen ), while (Adding 10 ml of ill we get 7.44 of hydrogen ) was obtained when using the laser source. The results indicate that using the laser source enhances hydrogen production significantly compared to standard electrolysis, demonstrating the laser's high effectiveness in electrolysis due to its non-absorptive property in water. This could have significant implications for renewable energy and hydrogen fuel production.

Ultra-Durable Polysilicon Based Tribovoltaic Nanogenerators for Bearing In Situ Rotational Speed Sensing.

Tribovoltaic nanogenerator (TVNG) is an emerging energy device with the advantages of direct current and high power density. At present, many TVNGs are based on single-crystal materials, which are expensive and fragile during structural processing. Here, a polysilicon-based TVNG for bearing in situ rotational speed sensing is developed, which has the same level of performance and lower cost compared to monocrystalline silicon. The defects in polysilicon can provide additional carriers, but the grain boundaries can suppress the transport process of carriers, resulting in almost the same electrical output as single crystals. The oiled sliding mode TVNG has an impressive durability of up to 1 million cycles. The friction coefficient of rolling mode TVNG is as low as 0.14. Based on rolling mode polysilicon TVNG, the tapered roller bearing, thrust ball bearing, and deep groove ball bearing are manufactured by cutting and engraving processes. Moreover, their short-circuit current and open-circuit voltage are linear with speed, and the fitting coefficient is as high as 0.99, providing favorable conditions for in situ rotational speed sensing. This work presents a structure-function integrated bearing design methodology, demonstrating the considerable potential of in situ sensing for intelligent components in the industrial Internet of Things.

Effect of Process Conditions on the Microstructure and Properties of Supercritical Ni-GQDs Plating.

The Ni-GQDs composite plating was created using direct current (DC), single-pulse, and double-pulse power supplies, with GQDs serving as additives under supercritical CO2 conditions. A comparative analysis was conducted to evaluate the effects of different electrodeposition power sources on the microstructure and properties of the Ni-GQDs composite plating. High-Resolution Transmission Electron Microscopy (HRTEM) was employed to investigate the distribution of GQDs within the composite plating as well as to analyze d-spacing and diffraction patterns. Scanning Electron Microscopy (SEM) was utilized to illustrate the surface morphology of the plating and assess its surface quality. The grain size and preferred orientation of the plated layer were examined using X-ray Diffraction (XRD), while Atomic Force Microscopy (AFM) was used to evaluate the roughness of the surface. To compare the abrasion resistance of the various plating types, wear amounts and friction coefficients were measured through friction and wear tests. Additionally, corrosion resistance tests were performed to assess the corrosion resistance of each plating variant. The results indicate that the Ni-GQDs-III composite layers produced via double-pulse electrodeposition exhibit superior surface quality, characterized by smaller grain sizes, enhanced surface flatness, reduced surface roughness, and improved resistance to wear and corrosion.

Simulation of Time-Sequence Operation Considering DC Utilization Hours of New Energy Base in Desert and Gobi Area

Direct current power transmission is a crucial method for consuming new energy in desert and Gobi regions. Given the issue of the inefficient use of transmission channels, this study develops a simulation model for the operational time sequence of new energy bases in these areas. The model integrates factors such as hours of DC power transmission, environmental impacts, economic considerations, and operational flexibility. Initially, the model addresses the significant variability and unpredictability of wind and solar energy in these regions by introducing an analysis method combining Gaussian Kernel Density Estimation (GKDE) with a Gaussian Mixture Model (GMM). Subsequently, a flexible DC power transmission operational model is formulated, taking into account different DC transmission modes. The model’s efficiency is enhanced by employing the Dung Beetle Optimization algorithm with nondominated sorting to minimize variable ranges and expedite solution times. The model’s effectiveness is demonstrated through a simulation applied to a new energy base in Gansu Province, Northwest China, confirming its validity.

Impact of cell voltage on synthesis of caproic acid from carbon dioxide and ethanol in direct current powered microbial electrosynthesis cell

Production of medium chain fatty acids (MCFAs) from CO2 through microbial electrosynthesis (MES) holds great potential. The present study investigated the effect of cathode voltages of − 0.8 V (MES-1), −1.0 V (MES-2) and −1.2 V vs Ag/AgCl (MES-3), on the production of MCFAs from CO2 and ethanol using an enriched culture. Direct current (DC) power supply was used to maintain constant cathode voltages. The highest amounts of caproic acid were produced in MES-2 at an average concentration of 1.51 ± 0.14 g/L with a maximum selectivity of 68 ± 7 %. Microbial diversity analysis showed abundance of the Clostridiaceae family that allowed chain elongation in all MES reactors. This study shows that potentiostatic control approach for MCFA synthesis, can be replaced by DC power supply in future MES setups. Using selective culture enrichment, MES efficiently produces MCFAs from CO2 and ethanol, with −1.0 V yielding the highest caproic acid.

Optimal Design of High-Power Density Medium-Voltage Direct Current Bipolar Power Cables for Lunar Power Transmission

Power systems on the lunar surface require power lines of varying lengths and capacities to connect generation, storage, and load facilities. These lines must be designed to perform efficiently in the harsh lunar environment, considering factors such as weight, volume, safety, cost-effectiveness, and reliability. Traditional power transmission methods face challenges in this environment due to temperature fluctuations, micrometeoroid impacts, and ionizing radiation. Underground deployment, although generally safer, faces challenges due to low soil thermal conductivity. At a depth of 30 cm, the lunar temperature of −23.15 °C can be advantageous for managing waste heat. This study presents a novel approach, developed using COMSOL Multiphysics, for designing bipolar MVDC cables for lunar subsurface power transmission. Kapton® MT+ is chosen as the insulating material for its exceptional properties, including high thermal conductivity and superior dielectric strength. The cables are designed for voltages of ±10 kV and ±5 kV and capacities of 200 kW (low power), 1 MW (medium power), and 2 MW (high power). Our findings indicate that aluminum conductors offer superior performance compared to copper at medium and high power levels. Additionally, elevated voltage levels (±10 kV) enhance cable design and power transfer efficiency. These specially designed cables are well-suited for efficient operation in the challenging lunar environment.

Efficient rectifier with wide input power range for 5G applications

This article presents three efficient rectifiers for radio frequency energy harvest-ing (RFEH) systems operating at the fifth generation (5G) band (3.5 GHz). Eachrectifier operates at various input power levels (high, low, and across a widepower range). The high and low-power rectifiers feature a single serial topologyusing HSMS-2860 and SMS-7630 Schottky diodes, respectively, along with mi-crostrip lines to implement the input and output filters and the impedance match-ing network. At an radio frequency (RF) power level of 15 dBm, the high-powerrectifier harvests 67.4% to direct current (DC) power with a 300Ωload resistorand an output voltage of 2.5V. The low-power rectifier achieves its maximumpower conversion efficiency (PCE) at -2 dBm, reaching 45% efficiency with a1200Ωload. The rectifier with a extended input power range comprises twobranches of subrectifiers functioning at both high and low power levels. De-pending on the power level, the considered subrectifier harvests radio frequencypower into DC power, while the other subrectifier is deactivated. Across a powerspan of 32.5 dB (ranging from -13 to 19.5 dBm), the rectifier maintains an effi-ciency above 30%. The proposed rectifiers are efficient and suitable for imple-mentation in 5G-enabled RFEH systems.

A novel cascaded H-bridge photovoltaic inverter with flexible arc suppression function

This paper presents a novel approach that simultaneously enables photovoltaic (PV) inversion and flexible arc suppression during single-phase grounding faults. Inverters compensate for ground currents through an arc-elimination function, while outputting a PV direct current (DC) power supply. This method effectively reduces the residual grounding current. To reduce the dependence of the arc-suppression performance on accurate compensation current-injection models, an adaptive fuzzy neural network imitating a sliding mode controller was designed. An online adaptive adjustment law for network parameters was developed, based on the Lyapunov stability theorem, to improve the robustness of the inverter to fault and connection locations. Furthermore, a new arc-suppression control exit strategy is proposed to allow a zero- sequence voltage amplitude to quickly and smoothly track a target value by controlling the nonlinear decrease in current and reducing the regulation time. Simulation results showed that the proposed method can effectively achieve fast arc suppression and reduce the fault impact current in single-phase grounding faults. Compared to other methods, the proposed method can generate a lower residual grounding current and maintain good arc-suppression performance under different transition resistances and fault locations.

Mitigation of the commutation failure problem in the HVDC multi-infeed scenario in Brazil using synchronized phasor measurement

This paper presents the Commutation Failure (CF) problem in the High Voltage Direct Current - Line-Commutated Converter (HVDC-LCC) scenario in Brazil through the monitoring of Short-Circuit Ratio (SCR), CF indexes, Direct Current (DC) link power, and the use of simulated synchrophasor data. The analysis was performed by training a neural network using data from the year 2020, and its robustness was verified using data from the year 2021 of the Brazilian Interconnected Power System (BIPS). Additionally, an analysis of transient instability in the North-South Transmission Corridor (NSC) will be presented right after the occurrence of CF by monitoring the Lyapunov transient instability margin, with the primary objective of bringing subsidies to the control center operation area according to the severity of the CF occurrence, preventing its propagation and mitigating it through real-time predictive actions, such as power redispatch on DC links and, thus, minimizing the occurrence of CF.

Influence of Electrolyte Concentration on Metal Removal Rate and Surface Finish Quality in Electrochemical Machining Masking

Electrochemical machining (ECM) is a specialized and precise manufacturing technique involving selective metal removal to achieve the desired shape or form. This article’s primary focus is examining the technical facets associated with the procedure. The elements mentioned encompass the system’s design and optimization, the electrolyte solution’s careful selection, and the precise control of the etching parameters. When considering the overall framework, it is essential to consider important factors such as the concentration of electrolytes, the operational voltage, and the value of the current flowing through the system. The main objective of this study is to evaluate the influence of different concentrations of sodium chloride electrolyte on the metal removal rate (MRR). This will be achieved by utilizing a direct current power supply. The present investigation used aluminum, steel, and stainless steel materials as the substrate for experimentation. These materials were selected to have identical dimensions for the anode and cathode. The main objective of this study is to evaluate the influence of varying concentrations (0.5, 1, 1.5, and 2 mole/liter) of sodium chloride electrolyte on the material removal rate and surface roughness. The findings have been disclosed, revealing the utmost removal rate for aluminum, steel, and stainless-steel materials across all levels of electrolyte concentration. The experimental information is currently presented, related to the rates of metal removal at various electrolyte concentrations of 2 moles per liter. The rates of mass loss observed in aluminum are comparatively higher when compared to those surveyed in steel and stainless steel. The roughness of a machined surface is inversely proportional to the concentration of the electrolyte.

Evaluation of cobalt removal from polycrystalline diamond compact in the coupling mechanism of acid leaching and electrolysis

Polycrystalline diamond compact (PDC) is a widely used superhard material, and its thermal stability and wear resistance are the main factors determining its performance. The residual cobalt binder content in polycrystalline diamond (PCD) has a significant impact on the thermal stability and wear resistance of PDC. Therefore, cobalt removal treatment is required to improve the performance of PDC. The current cobalt removal methods mainly include acid leaching and electrolysis. This study proposes a novel coupling method that combines acid leaching and electrolysis for cobalt removal. Cobalt removal was conducted for 10 h under the conditions of electrolytic voltage of 12 V, direct current power supply current of 0.01 A, and sulfuric acid electrolyte concentration of 9.2 mol/L. The cobalt removal effect was evaluated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The hardness and elastic modulus of PDC before and after cobalt removal were measured using nanoindentation experiments. The results indicate that the coupled electrolysis process effectively removes the cobalt phase in the PCD layer while retaining the WC phase. The hardness and elastic modulus of PDC decrease after the removal of cobalt binder, and the cobalt removal depth can reach 807 μm.

Optimal transient power sharing method for shipboard MVDC System based on segmented variable step dynamic programming

Supplying power for large pulsed power load with shipboard medium voltage direct current integrated power system has continued to be a challenge. The energy storage device configured in the system can effectively mitigate the power impact on grid and gas turbine gensets, but it also complicates the system operation, requiring advanced power sharing and control strategies for support. In this paper, the control framework of system configured with hybrid energy storage is presented, the objective function to quantify transient power disturbance on gas turbine genset is established, and the segmented variable step dynamic programming method for system transient power sharing is innovatively proposed and employed to derive the optimal transient power-sharing scheme for the rectangular and triangular large pulsed power load conditions. Compared with the conventional approach through MATLAB/Simulink simulation, the scheme derived from segmented variable step dynamic programming demonstrates enhanced utilization of the transient power compensation capability of hybrid energy storage, and leads to a reduction in the power regulation pressure on gas turbine gensets. In the assumption of two typical operating processes, as the results of the power impacts，the transient regulation rate of the genset rotor is reduced from 10.4 % to 9.9 % and from 13.7 % to 8.6 %, respectively, the fatigue damage of shaft system is decreased by 53 % and 94.4 %, respectively, and the maximum inlet relative temperature of gas generator turbine is reduced by 0.015 and 0.139, respectively.

Novel Fault Protection Method for Flexible DC Power Systems

A fault protection method is proposed for flexible direct-current (DC) power systems based on the cosine similarity of currents in current-limiting reactors. The typical characteristics of external and internal faults in a flexible DC power system were analyzed. The principles of cosine similarity and the fault current characteristics of current-limiting reactors were used to distinguish between internal and external faults. The ratio of the average positive and negative voltages of the current-limiting reactor was then used to distinguish the fault types and fault line. Finally, a simulation model of a circular flexible DC power system was constructed using MATLAB/Simulink software (2018b). The simulation results show that the proposed protection scheme can quickly and accurately identify the location and type of faults, and has a strong ability to withstand fault resistance and is less affected by distributed capacitance, noise, and communication delay.