Direct Current-direct Current Research Articles

Effects of current control modes on the morphological and biological properties of graded FeCrNi metal-matrix coatings containing Al2O3 nanoparticles for cardiovascular applications

Implant coatings represent the most effective strategy to address multiple issues, ultimately increasing implant longevity and improving implant compatibility. In this study, we investigated the electrodeposition of a novel graded FeCrNi/Al₂O₃ coating on a 316L substrate for cardiovascular implants using direct current (DC) and pulsed current (PC). The effects of a current density range of 3–11 A dm⁻² and decreasing the duty cycle from 90 % to 50 % and subsequently to 10 % on the concentration of Al₂O₃ nanoparticles in the FeCrNi matrix, as well as on the microstructure and morphological properties, were studied using scanning electron microscopy (SEM). Additionally, structural characterization of the FeCrNi/Al₂O₃ films was performed using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). To assess the cytocompatibility of the samples, human coronary artery endothelial cells (HCAEC) were used. The results indicate that the PC provides a uniform microstructure and a smoother surface compared to the direct current DC. The study also reveals that the PC results in fewer defects and microcracks in the coating due to reduced formation of chromium hydrides in the layer and a significant reduction in stress during the deposition process. When using PC, an increase in particle incorporation in the coating was achieved, but no effect of changing the duty cycle was found. The highest deposition rate of Al₂O₃ was achieved at a current density of 11 A dm⁻² with an electrolyte containing 10 g L⁻¹ Al₂O₃. The FeCrNi/Al₂O₃ coatings exhibit low cytotoxicity when deposited using a high alumina content and DC, showing cell viability of over 90 %. However, only a few samples demonstrated cell viability higher than 80 % on day three. The proposed composite coating may represent an initial step towards improving implant coatings for cardiovascular stent materials.

Design of Magnetic Integrated LLC Transformer

The direct current/direct current (DC/DC) converter of the LLC (inductor-inductor-capacitor) converter is an important part of affecting the work efficiency, volume, and weight of the device. It not only has the functions of traditional transformers but is also able to solve the problems of traditional power transformers’ high price, huge volume, prodigious no-load loss, and inflexible control. This paper studies the DC/DC converter mainly, according to the given indexes, the magnetic integrated LLC resonant transformer is designed in detail. The magnetic integrated transformer greatly reduces the converter volume, and the selection of devices is completed based on parameters design. In addition, according to design parameters, losses and the efficiency of the LLC resonant transformer are calculated. The results meet the efficiency requirements. A test platform of a full-bridge LLC resonant converter is built according to theoretical research. The correctness and effectiveness of theoretical research and design methods of the DC/DC converter are verified by analyzing the experimental waveforms.

A high-efficiency transformer-in-package isolated DC-DC converter using glass-based fan-out wafer-level packaging

A transformer-in-package (TiP) isolated direct current–direct current (DC-DC) converter using glass-based fan-out wafer-level packaging (FOWLP) is proposed. By using 3-layer redistribution layers (RDLs), both the transformer and interconnections are built without an additional transformer chip, and the converter only has 2 dies: a transmitter (TX) chip and a receiver (RX) chip. The proposed solution results in a significant reduction in the cost and makes major improvements in the form factor and power density. Moreover, the transformer built by the RDLs achieves a high quality factor (Q) and high coupling factor (k), and the efficiency of the converter is thus improved. The TX and RX chips were implemented in a 0.18 µm Biopolar CMOS DMOS (BCD) process and embedded in a compact package with a size of 5 mm × 5 mm. With an output capacitance of 10 µF, the converter achieves a peak efficiency of 46.5% at 0.3 W output power and a maximum delivery power of 1.25 W, achieving a maximum power density of 50 mW/mm2.

An interleaved high step‐down coupled inductor based quadratic DC‐DC converter

AbstractA high step‐down direct current‐direct current (DC‐DC) buck converter with a coupled‐inductor in its topology is presented in this study. The switching pattern of the proposed converter is interleaved; therefore, the voltage stress on the semiconductors and the components is low since the primary high voltage will be divided between the blocking capacitors on the primary side. Thus, the voltage stress on semiconductor elements will be low. As a result, the preselected elements can be chosen with low voltage ratings. In addition, there are cells with coupled inductors utilized in the structure that helps the converter to provide improved voltage gain in its output terminal. Typically, narrow duty cycles are needed to achieve high gain in conventional buck converters, but the proposed converter has obtained a high conversion ratio even with wider duty ratios. Besides, the proposed converter has a constant equation for the voltage gain for the whole range of duty cycles. Theoretical analysis and comparison with other recent converters of similar types have been conducted to demonstrate the proposed converter performance. Furthermore, to verify the theoretical analysis, a 600 W prototype of the proposed converter with 820 V/30 V is implemented, and experimental results are presented.

Simulation model of proportional integral controller-PWM DC-DC power converter for DC motor using MATLAB

Smoothly speed range changing, easily speed controlling, and swiftly dynamic response for load torque changing are the main merits which are delivered by direct current (DC) motors. They are also distinguished by their versatility. All these characteristics make the DC motors suitable candidates for various applications. An accurate high-speed control with a good dynamic response, would be of demand for many applications of the DC motors. Controlling the speed of motors using conventional systems is one of the most important method that is adopted and it can be more efficient when used with electronic power devices to control the output voltage. Hence, this paper introduces an efficient proportional integral (PI) speed controller for DC motor fed by direct current-direct current (DC-DC) convertor, which is switched by pulse-width modulation technique. MATLAB/Simulink environment is used to build the whole system. Two operation scenarios have been conducted including constant load with variable speed and variable load with constant speed.

A rapid self-heating strategy of lithium-ion battery at low temperatures based on bidirectional pulse current without external power

Polarization is a major problem for lithium-ion batteries (LIBs) at low temperatures. To realize rapid preheating of LIBs at low temperatures, a self-heating strategy based on bidirectional pulse current without external power is proposed. Four inductances and one direct current/direct current (DC/DC) converter are applied to the system. An electrothermal coupling model of LIBs and a performance evaluation model of the system are established to investigate the effects of circuit parameters and initial state-of-charge (SOC) on the heating performance, including the heating time, SOC utilization ratio (SUR), and heating efficiency. The results show that the LIBs can be warmed up from −10 °C to 0 °C in approximately 120 s. It is concluded that reducing the discharge inductance can increase the heating rate, SUR, and heating efficiency. However, the excessive reduction of the discharge inductance would cause a significant voltage drop, which will reduce the voltage to below the cut-off voltage. In addition, a comparative study shows that when the initial SOC values of the two battery packs are different, the heating time will be reduced. A higher initial SOC for one battery pack can increase the heating speed and SUR at the expense of the heating efficiency.

Development of a comprehensive transient fuel cell-battery hybrid system model and rule-based energy management strategy

ABSTRACT In the study, a comprehensive transient fuel cell-battery hybrid power system model is established to explore the output performances and dynamic responses of fuel cell electric vehicles (FCEVs). A fuel cell system sub-model, a one-dimensional transient Li-ion battery sub-model, two direct current/direct current (DC/DC) sub-models as well as a vehicle load sub-model are integrated. The coupled heat and mass transfer processes are considered inside fuel cell system and Li-ion battery. After rigorous model validation, the overall performances under several typical China standard vehicle road conditions are investigated, including power distribution between different power units, battery state of charge (SOC), battery charge/discharge rate, fuel cell operating duration, temperature, and other key parameters. During the 100 km h−1 acceleration processes under the preliminary rule-based energy management strategy (EMS), the accelerated speed is found to be the largest in the beginning, resulting in the fact that the discharge power for battery increases sharply. The shorter the acceleration time, the larger the maximum power demand for Li-ion battery. During the combined 1300 s high-speed operating conditions under the on-off switch EMS, the total operating duration of fuel cell system is calculated to be about 531 s, and the total output power is calculated to be 11,556 kJ. In comparison, the vehicle saves about 1044 kJ energy and increases the fuel cell operation duration by 333.7% under the power-following EMS. The present study provides important guidance in terms of dynamic simulation analysis and energy management strategy for FCEVs.

System for powering autonomous solar cookers by batteries

In this paper, we propose innovative autonomous solar cookers (hot plates and box ovens) supplied by batteries. The electrical energy is produced by photovoltaic panels (PV) and stored in a battery (24 V, 520 Ah). Hence, the cookers are powered through a Direct Current /Direct Current (DC/DC) boost converter (400 W) composed of three identical cells in parallel. The power switches are controlled by a digital circuit that generates three Pulse Width Modulation (PWM) signals at 20 kHz with an adjustable duty cycle α. The experimental results show that, for electrical power of 375 W and a duty cycle α = 0.7, the average inductor current of each cell is equal to 3.8 A. Moreover, the DC voltages and currents at the input/output terminals of the converter are worth 24 V / 11.5 A, and 75 V / and 5 A, respectively. Under these conditions, the efficiency of the power supply system used in the cookers is of the order of 90% and the temperature of their thermal resistors reaches 700 °C. All the electrical quantities are in accordance with the results obtained through simulation using the Orcad Pspice environment. These innovative cookers including hot plates and box ovens are tested experimentally in different cases: heating one liter of water, cooking food (1 kg of fries), and baking bread. The obtained heating times are about 25 min, 20 min, and 30 min, respectively. Moreover, according to which cooking case, the “consumed” battery capacity is worth 4.2% - 5.52% of the capacity of the fully charged battery. All these results show, on the one hand, the proper operation of the three-cell DC/DC boost converter powered by batteries, and, on the other hand, the feasibility of heating water and cooking food using the autonomous solar cookers proposed in this work.

Bidirectional converter based on boost/buck DC‐DC converter for microgrids energy storage systems interface

SummaryIn this paper, a new bidirectional nonisolated DC‐DC (direct current–direct current) converter to interface microgrid energy storage systems is proposed. This converter is based on the classical bidirectional boost/buck converter, the most used converter in microgrids and can operate both in step‐down and step‐up modes. Besides that, this converter presents low number of components, low voltage and current stress on components, simplicity of operation, low current ripple from low‐side power supply, and two different modes of operation: synchronous and asynchronous. In addition, in this paper, the modeling, control, and power losses estimate of the proposed converter are carried out and the performance of the converter in different aspects of the microgrid application is evaluated, such as step load, abrupt power flux change, and transient analysis. A prototype of 1 kW, 144 to 400 V, is developed in the laboratory to validate the theoretical evaluations of the proposed converter. Besides that, the proposed converter is also evaluated under different dynamic condition which illustrates the effectiveness of the converter. Finally, the maximum efficiency obtained is 97.1% for 500 W working in step‐down operation.

Decentralized adaptive neuro-fuzzy dynamic surface control for maximum power point tracking of a photovoltaic system

The current work proposes a decentralized adaptive dynamic surface control approach for extracting the maximum power from a photovoltaic (PV) system and then regulating the required voltage for charging the battery. In this regard, two cascaded direct current-direct current (DC-DC) converters are utilized. The boost converter is interposed between the PV system and the load to help extract the maximum power. The buck-boost converter is then exploited to maintain the output voltage at a specified level which must meet the battery demand. Therefore, to handle the interactions between the cascaded converters, a decentralized control approach is developed. In the suggested approach, by introducing a nonlinear filter, an effective dynamic surface control (DSC) scheme is proposed with guaranteeing asymptotic tracking convergence. Further, by incorporating a nonlinear compensation term into the proposed control approach, the robustness of the resulting controller is improved. In addition, since the model of the converters is nonlinear with unknown uncertainties, the neuro-fuzzy system is used to estimate lumped uncertainties. The proposed control method has good attributes in terms of having a low tracking error, an excellent transition response, and a quick response to changes in atmospheric conditions. The stability of the whole control system is proved by the Lyapunov stability theorem. Finally, comprehensive simulation results are performed to validate the effectiveness of the suggested control approach.

Modified proportional integral controller for single ended primary inductance converter

The article highlights and optimizes a controller for the single ended primary inductance converter (SEPIC) direct current-direct current (DC-DC) converter. The SEPIC converter adjusts a range of dc input voltages and delivers a constant and stable output voltage. Three different models of the SEPIC converter are presented in order to derive its transfer function. Being a 4th order, an approximation method for the reduction of this transfer function to 2nd and 1st order is implemented. Two methods for controlling the converter are presented, the first one is based on guessing techniques and the second explains the design steps of the controller based on the internal model control (IMC). Furthermore, an improvement on the IMC controller is proposed and results were shown and discussed. IMC is based on integrating the “process model” in the control operation of the actual system. By using an approximation of the original transfer function of the system, it is expected that the IMC control will be able to achieve the desired results. Control schemes of the SEPIC will be presented and results will be shown. The response of the controller was tested with mathematical models for batteries and supercapacitors in MATLAB, as non-ideal DC-sources, and results were presented.

Backstepping global and structural stabilization of direct current/direct current boost converter

SummaryThis paper deals with the stabilization of direct current/direct current (DC/DC) boost converter and the nonlinear phenomena elimination using a constrained backstepping technique. Based on the converter averaged model, the proposed control approach is designed and the input to state stability concept is used to prove the system global stability. Furthermore, the structural stability is proven to show the efficiency of the proposed approach to suppress the nonlinear phenomena exhibited by the converter. The simulation results illustrate the different stability regions of the system as functions of the controller and the system parameters. The bifurcation diagrams are used to show the effectiveness of the proposed approach in terms of nonlinear phenomena suppression in wide regions of the system operating domains.

Optimum Tuning of Photovoltaic System Via Hybrid Maximum Power Point Tracking Technique

A new methodology is used in this paper, for the optimal tuning of Photovoltaic (PV) by integrating the hybrid Maximum Power Point Tracking (MPPT) algorithms is proposed. The suggested hybrid MPPT algorithms can raise the performance of PV systems under partial shade conditions. It attempts to address the primary research issues in partial shading conditions in PV systems caused by clouds, trees, dirt, and dust. The proposed system computes MPPT utilizing an innovative adaptive model-based approach. In order to manage the input voltage at the Maximum PowerPoint, the MPPT algorithm changes the duty cycle of the switch in the DC-DC (Direct Current-Direct Current) converter (MPP). Temperature as well as fluctuations in output power will induce alteration in PV panel operating current and voltage. MPPT is gaining a lot of interest as a key optimization sector to solve this optimization problem in PV systems. A hybrid optimization approach is utilized to produce a combination of the Cuckoo Search-Perturb & Observe (CS-PO) and incremental conductance-particle swarm optimization (IC-PSO) algorithms. After measuring the voltage and current from the solar system, this optimization computes the output power. The IC-PSO optimization achieves Maximum PowerPoint Tracking with increased efficiency of 99.5%. The proposed optimization techniques are established in the MATLAB Simulink program to validate its efficiency.

Simplified cascade multiphase DC-DC buck power converter for low voltage large current applications: part II --- output current controller

<span lang="EN-US">This paper proposes a control method for new simplified cascade multiphase direct current-direct current (DC-DC) buck power converters used for low-voltage large-current applications such as cathodic protection. To control the proposed converter, a proportional-integral (PI) controller is used to regulate the output current of the converter. The control scheme analysis is carried out by linearizing the small-signal model of the proposed converter to form the output current transfer functions. This transfer function will be analyzed by using phase and gain margin approach to obtain the control parameters (Kp, Ki, and Ti). Simulation and experiment results are included to show the validity of the proposed concept.</span>

Harnessing wind and solar PV system to build hybrid power system

Electricity is the most important consideration for individual needs. Natural crossover power architecture using photovoltaic and wind is presented in this study, together with a Cuk direct current-direct current (DC-DC) converter, third phase inverter, and an inductors capacitors (LC) filter. Due to its natural disposal and availability in India, wind power and photovoltaics are ideal for the hybrid system. Hybrid power structures, on the other hand, reduce the risk of damage to equipment in sustainable stock storage since they have a higher electrical output. MATLAB Simulink was used to demonstrate this hybrid application. Before connecting the entire DC voltage frame with the main lattice of the power frame, blocks such as the wind model, PV model, Cuk converter, inverter, and LC channel are built individually. Information limitations for participating in varying levels of irradiance and variations in wind speed. The results show that the hybrid system has a considerably more reliable standard in terms of energy efficiency than an independent framework. Furthermore, the hybrid system's Cuk DC-DC converter, three-phase standard-based inverter, and LC channel can minimise power switching power.

Comparison of PV panels MPPT techniques applied to solar water pumping system

<span lang="EN-US">This paper deals with an advanced design for a pump powered by solar energyto supply agricultural lands with water and also the maximum power point is used to extract the maximum value of the energy available inside the solar panels and comparing between techniques MPPT such as Incremental conductance, perturb & observe, fractional short current circuit, and fractional open voltage circuit to find the best technique among these. The solar system is designed with main parts: photovoltaic (PV) panel, direct current/direct current (DC/DC) converter, inverter, filter, and in addition, the battery is used to save energy in the event that there is an increased demand for energy and not to provide solar radiation, as well as saving energy in the case of generation more than demand. This work was done using the matrix laboratory (MATLAB) simulink program.</span>

Comparison of Maximum Power Point Tracking Methods Using Metaheuristic Optimization Algorithms for Photovoltaic Systems

The maximum power value that can be obtained from photovoltaic systems can change continuously due to environmental conditions such as temperature, sunlight and partial shading. Direct current-direct current (DC-DC) converters and maximum power point tracking (MPPT) algorithms are required, especially in cases of partial shading, in order for the photovoltaic systems to operate at the maximum power point, that is, to draw the maximum possible power value from the system. In this study, simulation studies has been carried out for two different partially shaded scenarios using the boost-type DC-DC converter and MPPT algorithm in the PV array consisting of 3 panels connected in series. In the simulation studies, the output powers obtained by the application of particle swarm optimization, cuckoo optimization, bat optimization and firefly optimization techniques as MPPT algorithm has been compared. In the scenarios examined, the firefly optimization algorithm reached the maximum power point faster, and it has been observed that the firefly optimization method obtained the highest average power at the end of the simulation periods.

A novel multi-input DC-DC landsman converter for plug-in hybrid electric vehicles

PurposeThe purpose of the paper is to develop high accurate and unified maximum power point tracking technique that tracks the maximum power from both the photovoltaic (PV) array and wind energy conversion system, (an unified maximum power point tracking technique implemented for both wind and solar sources to track maximum power with higher accuracy).Design/methodology/approachIn recent times, multi-input Direct Current- Direct Current (DC-DC) converter has attracted attentiveness, to conserve more energy and to achieve more efficiency. The kinetic energy of the vehicle is converted to electrical energy and further stored into the battery, during the regenerative braking (moreover, the battery gets charged during the regenerative braking process by converting the kinetic energy of the vehicle into electrical energy). During such a process, only the pulse width modulation schemes of the inverter are changed. To charge electric vehicles (EVs), two renewable resources as solar and wind are combined to produce electric power. Therefore, it was conveyed that the EV will be continuously getting power without interruption using various sources and regenerated power.FindingsThe performance and effectiveness of the proposed system are studied by extensive simulations and (are) validated using a prototype of the system. The results prove that the proposed system achieves an efficiency of 95.2%, which is higher than that of the multi-input DC-DC converters existing in the literature.Originality/valueA novel multi-input DC-DC landsman converter for powering plug-in hybrid electric vehicles (HEVs) is proposed in the research. This method proposes a new cost effective and efficient technique for HEVs with brushless DC motors. Wind power, battery and PV panel are used as the input sources for the proposed converter.

Power management control and delivery module for a hybrid electric aircraft using fuel cell and battery

Hybrid electric aircrafts using fuel cells and batteries are an option to reduce emissions in air travel. State of the art concepts either connect fuel cell and battery using a direct current/direct current (DC/DC) converter or as a direct hybrid. Converters are flexible to control but direct hybrids are lighter and easy to build. A new power control module is presented which is easier to control than a system with DC/DC converters and more flexible and efficient than a direct hybrid. The new control module was developed to assure high aircraft safety criteria due to its redundancy and additional safety measures. It includes the possibility to charge the battery passively and actively from the fuel cell or by recuperation during flight reducing the required battery size. The functionality of the system was simulated and demonstrated in flight. This new concept can be adapted to power different kinds of hybrid aircrafts and offers a guideline to long-term all-electric flights since it is scalable for different aircraft sizes including single-aisle aircrafts. It is additionally usable for all kind of hybrid drive trains using fuel cell and battery.

A New High Voltage Gain DC to DC Converter with Low Voltage Stress for Energy Storage System Application

Increasing energy demand globally has led to exploring ways of utilizing renewable resources for sustainable development. More recently, the integration of renewable distributed resources in small- and large-scale grid has been seriously researched. Development in renewable power sources and its integration with the grid require voltage level conversion to match the grid/micro-grid level. The voltage level conversion is brought about by employing Direct Current-Direct Current (DC-DC) converters with boosting features. The paper presents a wide gain range DC-DC boost converter with a low-stress on switching devices. The proposed converter’s voltage gain is high compared with the conventional quadratic boost converter and other recently developed high gain boost converters. The topology has been compared with recently proposed topologies, and comparative analysis based on various performance parameters has shown that the topology is suitable for renewable and sustainable energy storage and grid integration. The power loss analysis has been done by incorporating the switching and conduction losses. A hardware prototype of 150 W has been developed to validate the converter’s performance in steady-state as well as in dynamic conditions.