DC Input Research Articles

Effect of polydimethylsiloxane content on the electrothermal performance and tensile strength of laser induced graphene films: Experimental and theoretical

BackgroundSince its discovery in 2014, laser induced graphene (LIG) has gained a lot of interest from research institutions and the industry as a result of its single-step fabrication process and tailorable properties. Nonetheless, LIG's brittle nature makes it susceptible to any mechanical disturbances thus shearing off from the polyimide (PI) sheet surface. This limits its applicability in electrothermal heating and other applications requiring high flexibility. Therefore, there is a need to enhance LIG's robustness on the precursor surface. MethodsTo overcome this, LIG films were fabricated from PI using a 10.6 µm CO2 laser machine and polydimethylsiloxane (PDMS) contents were infused into the LIG structure by spin coating to form LIG/PDMS films. Furthermore, the adhesion strength of LIG/PDMS films was further improved by making micro scratches on the substrate surface by pressing the PI sheets in between the jaws of a Universal Testing Machine (UTM). The joule heating of LIG and LIG/PDMS heaters was evaluated before, during, and after mechanical testing. Theoretical models (heat balance and Ansys Finite Element, FE) were also performed to validate experimental results. Significant findingsAt an input DC voltage of 8 V, the LIG/PDMS with 50 μL PDMS and LIG heaters generated saturation temperatures of 250 and 308.86 °C, respectively. Much as the saturation temperatures were lower for LIG/PDMS heaters, their mechanical strength was enhanced in comparison with the LIG heaters. LIG/PDMS films could undergo more bending cycles (4800) than LIG films (2400). Additionally, LIG/PDMS film accommodated more stress (⁓ 0.16 Mpa) than LIG film (⁓ 0.04 Mpa) after tensile tests. Interestingly, the LIG/PDMS heater's electrothermal performance was better than that of LIG heater after tension. The heat balance equation and simulation results showed a tight match with experimental generated temperatures, verifying the approach's trustworthiness. Hence, the demonstrated effectiveness and efficiency of LIG-based heaters with high flexibility under various mechanical stresses open new possibilities for diverse electronic applications.

Multi-Terminal DC Transformer for Renewable Energy Cluster Grid Connection

An AC (alternative current) power integration of distributed energies faces multi-fold challenges such as synchronization and weak grid-induced instability. In this study, a multi-terminal DC transformer is proposed for renewable energy clusters grid connection. The DC transformer provides multiple DC input ports for renewable energy collection, while the load port is connected to the medium-voltage DC grid via a modular multilevel converter (MMC). The multi-port topology enables flexible power transfer between multiple input sources to the load without additional components. The carrier layer modulation strategy is implemented to balance the MMC module voltage; bidirectional power transmission between multiple input sources is achieved through the phase shift modulation (PSM) method. First, we provided a detailed introduction of the proposed topology and working principle. A simulation model was built using the SIMULINK, and the simulation results verified the effectiveness of the proposed converter modulation strategy and phase shift modulation method. A corresponding hardware experimental platform was designed and built, and the modulation and voltage equalization functions of modular multilevel rectifiers were presented as well as the measured results of power transmission modulation of the converter under single-input and multi-input conditions. The results indicate that the proposed transformer can achieve multiple DC inputs and has multi-channel power transmission capabilities, making it suitable for renewable energy clusters grid connection.

Multiple‐Input and Multiple‐Output–Based Cascaded Boost Hybrid Interlink Converter

ABSTRACTThe multiple‐input and multiple‐output (MIMO) DC–DC converters offer various advantages such as improved efficiency and reduced component count. However, the preference of these converters over other types of converters is dependent on the specific application and requirements. Various types of boost‐derived MIMO DC–DC converters are discussed in the literature. However, these converters are either nonisolated or isolated types. In the paper, a MIMO‐based cascaded boost hybrid interlink converter (CBHIC) has been proposed. The proposed converter includes four DC–DC boost converters that are supplied power by two input DC sources. The boosted DC output of these converters can be used independently or in a cascaded manner depending upon the requirement of the load. Further, the cascaded action of these four boost converters leads to the production of two high‐frequency AC outputs. By using bridge rectifiers and high‐frequency transformers, high‐frequency AC voltages are converted into DC. Therefore, two isolated DC output voltages can be achieved using CBHIC. The complementary operation of the cascaded boost converters results in reduction of source current ripples. The design, operating modes, and performance evaluation of the proposed CBHIC have been included in the paper. To validate the efficacy of the proposed CBHIC, a lab prototype of 400 W is prepared. The rms value of high‐frequency AC output voltage at each is isolated port is 141 V. The CBHIC exhibits an efficiency of 94.3 at 400 W. The operation of the converter during voltage control mode is further explored and its dynamic response is studies with the help of experimental results. The obtained simulation and experimental results validate the effectiveness of the proposed converter.

Transformerless Single-Phase Buck–Boost Inverter Decoupled From the Midpoint of the Input DC Capacitors

Transformerless Single-Phase Buck–Boost Inverter Decoupled From the Midpoint of the Input DC Capacitors

Self-Sensing Potential of Metashale Geopolymer Mortars with Carbon Fiber/Graphite Powder Admixtures

Multifunctional building materials with self-sensing capability have great potential for civil engineering applications. The self-sensing capability of typically calcium aluminosilicate matrices of cementitious or geopolymer materials is adopted by admixing electrically conductive admixtures in an amount that ensures optimal electrical properties and their proportionality to mechanical loading. The paper aims to evaluate the self-sensing capability of 4 metashale geopolymer mortars with graphite powder (GP) and carbon fibers (CF) in different ratios, including MGF 5/0, MGF 4.5/0.5, MGF 4/1, and MGF 3/0. The 4-probe measurements at 21 V DC input voltage on (100 × 100 × 100) mm3 samples with embedded copper-grid electrodes evaluate the gauge factor, which corresponds to the monitored changes in electrical resistivity. Despite the limitations of DC measurements, the self-sensing capability is observed for all the mixtures. The most promising response to dynamic loading with an FCR of 0.018%, is observed for the MGF 4.5/0.5 sample.

A Power Circulating Suppression Method for Parallel Transient Inverters with Instantaneous Phase Angle Compensation

A unidirectional link is typically incorporated into the DC input side of an inverter to ensure the reliability and stability of the microgrid power supply. Due to impedance and control variations among inverters, circulating currents may rapidly arise during the operation of parallel transient inverters. Nonetheless, the unidirectional power circulating in a DC unidirectional link results in energy accumulation on the DC side, causing DC bus voltage pumping and affecting MGs’ operation safety and stability. This paper proposes a non-communication-based circulation suppression strategy to suppress power circulation in parallel transients based on the local information of inverters. First, a parallel transient is modeled, and the power circulation phenomenon and its influencing factors are analyzed. Then, the instantaneous power and absorbed active energy are calculated to adjust the phase of the inverter output voltage and suppress power circulation. Moreover, the output frequency is adjusted to balance the DC-side voltage of each inverter. Then, the stability of the parallel system after adding the circulation suppression control strategy is verified using the Lyapunov function method. Finally, simulation and experimental results verify the effectiveness of the proposed power circulation suppression strategy.

Buck–Boost DC–AC converter based on coupled inductors

In this paper, a single stage buck–boost DC–AC converter based on coupled inductors is presented for renewable energy and electric vehicle applications. The proposed topology works with only three semiconductor switches, two diodes, and three coupled inductors to transfer input DC voltage to a high gain or low gain output AC voltage. A coupled inductor is used instead of normal inductors, which will reduce core and size requirements. The sinusoidal pulse width modulation strategy is used in this paper for controlling the main switch. There are many merits in the presented topology, like high gain up to five times of input voltage, compact size, less number of components, which results in reducing the overall cost, reducing switching loss, and increasing the converter efficiency. The simulation study is carried out using MATLAB/SIMULINK to simulate the operation of the proposed converter. Also, an experimental setup is built up to examine the actual operation of the proposed converter. There is a good agreement between simulation and experimental results which increases the validation and confidence of the model.

An Isolated High Gain Push Pull Type DC to DC Converter for Fuel Cell Power Generation Systems

Due to their high efficiency and low environmental impact, fuel cell power generation systems have emerged as promising alternatives to traditional energy sources. However, the integration of fuel cells into practical applications necessitates the development of efficient power conversion systems. dc-dc converters play a crucial role in optimizing the power flow between the fuel cell stack and the load. In this paper, a push-pull type high gain dc-dc converter is proposed which consists of a push-pull inverter, a rectifier circuit, and C-filter. The push pull inverter produces high frequency square wave output while the full bridge rectifier and C-filter convert this square wave output into desired dc voltage. The converter boosts the 12V dc input supply to 326 V, representing a gain factor of more than 27. The isolated coupling inductor used in push pull inverter produces high gain and provides electrical isolation. Besides, the proposed topology eliminates the use of bulky grid-connected power transformers that decreases the system size and cost. To evaluate the performance of the proposed topology, a number of simulations under varying loads were carried out in the MATLAB Simulink framework. Further-more, a scaled-down prototype of 160W at 12/326 V was developed to confirm the simulation results. The findings indicate that the suggested converter can be a viable option for the hydrogen fuel cell-based power conversion system. GUB JOURNAL OF SCIENCE AND ENGINEERING, Vol 10(1), 2023 P 37-52

Experimental Investigation of Modified Level Shift PWM with Capacitor Voltage Balancing on Single Phase Modular Multilevel Converter

Modular Multilevel Converters (MMCs) are a prominent voltage source converter topology that is rapidly gaining popularity in medium/high power/voltage applications, including high-voltage DC transmission systems and electric vehicle systems. However, MMC has the critical issue of unbalanced submodule capacitor voltages and circulating current. The MMC distributes DC-link energy evenly among its submodule capacitors, rather than storing it in a large capacitor like conventional voltage source converters. In MMC, the submodule floating capacitors interface the DC input voltage and AC output voltage. Therefore, capacitor voltages must be balanced. The existing capacitor voltage control struggles to handle many gate pulses at medium and high voltages. An effective control scheme is needed to solve the issues mentioned earlier. This paper presents a performance analysis of a 1-Φ MMC using a modified level shift PWM technique based on Universal Control Modulation Scheme (UCMS) and a sorting-based capacitor voltage balancing algorithm. MATLAB/Simulink software implements the proposed control method for a 1-Φ , seven-level MMC. The outcomes of the simulation demonstration reveal that phase disposition PWM offers less harmonic distortion of output phase voltage than the other level shift PWM techniques, such as phase disposition PWM and alternate phase disposition PWM. The simulation results also demonstrate the effective use of the sorting-based capacitor balancing algorithm to regulate the voltages of the submodule capacitors. Finally, the real-time GUI tool validates the simulation results using an experimental prototype of 1-Φ MMC with the dSPACE MicroLabBox 1202.

A modular multiport Landsman converter-driven hybrid EV charging station with adaptive power management system

This article presents the implementation of a hybrid charging station that utilizes renewable energy sources to power its operations. The core of this system is a modular multiport Landsman converter, which serves as the interface between diverse renewable sources, including photovoltaic panels, wind turbines and fuel cells. A sophisticated multi-agent-based energy management system is employed to address the intermittency of renewable energy supply throughout the day. Additionally, a fuzzy logic controller (FLC) facilitates the seamless charging of electric vehicles within the system. The FLC detects the state of charge (SoC) of the vehicle's battery and the battery present in the station, enabling efficient EV charging. The multi-agent energy management system with load shedding controller (MAEMLS) and FLC continuously monitor the power availability, power demand, charging time, and charging duration of the charging station. This approach reduces the charging rate for EV owners during peak demand periods. The proposed system is modelled and tested using MATLAB/SIMULINK software, and a laboratory prototype has been constructed. The results demonstrate that the anticipated converter is highly suitable for integrating hybrid energy sources and charging electric vehicles (EVs). Notably, this converter exhibits an efficiency ranging from 85 %-95.05 %, based on the availability of input DC sources.

Off-grid system using a converter with multiple DC inputs and three-phase, multi-level AC output

Off-grid system using a converter with multiple DC inputs and three-phase, multi-level AC output

КОМП’ЮТЕРНЕ ТА ФІЗИЧНЕ МОДЕЛЮВАННЯ БЕЗДРОТОВОГО ЗАРЯДНОГО ПРИСТРОЮ ЄМНІСНОГО ТИПУ ДЛЯ МАЛОГАБАРИТНОГО ЕЛЕКТРОТРАНСПОРТНОГО ЗАСОБУ

The work considers one of the possible approaches to the creation of a capacitive type wireless charger, which allows for non-contact charging of batteries of small-sized vehicles: electric carts, electric scooters, electric scooters. The basis of the development of such a device is the operation of the hybrid DC-DC converter circuit, which operates at a high frequency (550 kHz), transfers energy to the charging circuit using two capacitive elements and allows receiving a constant regulated voltage on the load, which can be either lower or and more input DC voltage. A prototype of such a device has been developed and the results of its experimental research are given, which confirm the possibility of using this scheme for wireless charging of the battery. A Simulink computer model of such a device has been developed, which takes into account the real values of all parameters of the developed prototype and uses the basic model of a lithium-ion battery. According to the results of the calculations, it was determined that for the developed device of the capacitive type, and the largest losses occur in the inductor coils, the value of efficiency, which characterizes the efficiency of the process of transferring electrical energy from the primary power source to the battery, at the initial stage of its charging (when the parameter of the state of the battery SOC =50%) is 80%. References 10, figures 5.

A Cascaded H-Bridge Multilevel Inverter with DC Cells Input Fault Tolerance Capability Based on PSC-PWM Control

Multilevel inverters have proven their efficiency in generating better AC voltage outputs. This functional quality is mainly due to the use of multi-source DC inputs. Despite the fact that this type of topology is generally reliable, switching faults caused by the complete loss of a switching component or DC input cell may still occur. Such incident may inflict heavy impacts to the conversion chain resulting in a permanent damage to the switching cells or the connected load. This article presents a dynamic switching control strategy capable of tolerating DC cells open-circuit input faults in basic symmetric Cascaded H-bridge multilevel inverter architectures. The proposed topology uses a control scheme to overcome the switching cells’ fault by adapting the configured level of conversion and bypassing the flawed unit with no additional switching components. Furthermore, the proposed control strategy is capable of reversing back the inverter configuration to its original functional state after the disappearance of the faut. This research article answers the need for a theorical study of a fault tolerant Cascaded H-Bridge multilevel inverter where the short circuit’s fault types are bypassed by Pulse width modulation alteration only.

Finite‐time control of DC–AC boost converter: The limit cycle approach

AbstractThis paper proposes a novel finite‐time limit cycle controller for DC to AC conversion in power boost converters. The stable limit cycle is categorized as a positive limit set. Achieving the control law, based on the concepts of set stability and finite‐time stability, is a challenging problem. To fulfill the control objective, a novel sliding manifold is suggested concerning the structure of the wanted limit cycle which facilitates conditions for the development of finite‐time stability for the limit cycle. By utilizing the sliding mode control method, a control strategy is proposed that guarantees the desired stable limit cycle is created in the phase plane of the closed‐loop system and the phase trajectories reach it in a finite time and remain on it for all future times. This ensures the finite‐time generation of the biased sinusoidal oscillations in the output of the power boost converter from a DC input source. The simulation results of a practical boost converter have validated the effectiveness and feasibility of the presented algorithm.

A new method for selecting optimum levels in asymmetric Cascaded H‐Bridge‐Multilevel Inveter with variable DC sources

SummaryIn general, cascaded H‐bridge multilevel inverters (CHB‐MLI) are typically operated with either symmetrical or asymmetrical input DC sources, set at predefined specific ratios such as binary (1:2) or trinary (1:3) in the case of asymmetry, to achieve the desired output voltage waveform. However, if any DC source fails to provide the predefined voltage magnitude, or CHB‐MLIs with unspecified DC source ratios are utilized, the output voltage waveform may exhibit unequal magnitudes between consecutive levels, thereby causing a significant increase in total harmonic distortion (THD). Conventionally, to mitigate this effect, the corresponding H‐bridge is bypassed through zero voltage switching, which leads to an additional burden on the remaining H‐bridges to serve the same load. To reduce the burden on the remaining cells and improve the THD profile of the inverter, this article proposes a novel method for CHB‐MLI with varying DC magnitudes. It aims to enhance the quality of the output voltage waveform by strategically selecting optimum voltage levels rather than utilizing all available levels when CHB‐MLI has unspecified or variable DC sources. This approach can achieve a more balanced distribution of voltage magnitudes across successive levels by eliminating redundant states. Moreover, the proposed technique can reduce switch losses and enhance the converter's efficiency. The proposed method is validated through MATLAB/Simulink software simulations, followed by experimental verification.

Design and analysis of an interleaved step-up DC–DC converter with enhanced characteristics

In this paper, an interleaved DC–DC step-up converter with improved characteristics based on a voltage multiplier rectifier is presented. The proposed converter is presented and analyzed for two different operating duty regions including operating region 1 (0 < D ≤ 0.5), and operating region 2 (0.5 ≤ D < 1). This converter can be used in various applications such as energy storage, electric vehicles, and renewable energy systems. This converter is composed of two stages: an interleaved boost stage and a voltage multiplier rectifier stage, which collectively forms its general structure. The interleaved boost stage is a type of two-phase boost converter that transforms the input DC voltage into a high-frequency AC square waveform. This waveform can be readily filtered using smaller capacitors. The square-shaped voltage waveform from the interleaved boost stage is rectified and converted to a high DC voltage by the Voltage Multiplier Rectifier (VMR) stage. The operating regions, the evaluation of the steady-state condition, the voltage gain of the proposed converter's parasitic and ideal models as well as its losses and efficiency analysis have been evaluated. The proposed converter has an efficiency of 97% at the output power of 150 W. The proposed converter is simulated to convert a voltage of 25–159.5 V and to validate the mathematical relationships and simulation results, a laboratory prototype has been developed. The simulation and experimental results show the precision of the performance of the proposed interleaved boost converter.

Photo-Electro-Thermal Textiles for Scalable, High-Performance, and Salt-Resistant Solar-Driven Desalination.

Solar-driven interfacial evaporation is an emerging desalination technology that can potentially relieve the freshwater scarcity issue. To obtain high and continuous evaporation rates for all-weather, chemically engineered structural materials have been widely explored for simultaneous photothermal and electrothermal conversion. However, many previously reported fabrication processes involve poor integration and considerable energy loss. Herein, a scalable photo-electro-thermal textile is proposed to enable high efficiency, long-term salt rejection, and solar-driven desalination. Specifically, the photo-electro-thermal yarns with a core (commercial electric wire)-shell (polypyrrole-decorated Tencel) structure realize the integration of electrothermal and photothermal conversion. The wrapping eccentricity of 1.53mm and pitch of 3Tcm-1 for the electric wire are rationally regulated to achieve a high surface temperature of over 52°C at a 3V DC input. As a result, exceptional and stable evaporation rates of 5.57kgm-2h-1 (pure water) and 4.89kgm-2h-1 (3.5wt.% brine) under 1kWm-2·radiation with a 3V input voltage are realized. Practical application shows that the textiles can achieve high water collection of over 46kgm-2d-1 over the whole day of operation. The constructed photo-electro-thermal textile-based evaporator provides an effective method for commercial and scalable photo-electro-thermal conversion to achieve high-performance and salt-resistant solar-driven desalination.

Review of DC-DC boost converter derived topologies for renewable energy applications

This paper deals with three different power converter topologies for boosting the available dc input voltage. The converters considered for the study are conventional DC-DC boost converter, quasi switched boost DC-DC converter (qSBC) and quasi Z source converter (qZSC). The converters are designed for an input voltage of 24 V to deliver a power of 200 W to a resistive load. The steady-state analysis of all three topologies is discussed to determine the key characteristics of the proposed topologies. All the converters are simulated in MATLAB/Simulink environment and the outcomes are explained in detail. The performance comparison of the converters such as switch stress, diode stress and boost factor versus duty ratio are presented. Thus, this comparison helps to choose a suitable boost converter topology for a specific application.

Performance evaluation of novel 9-level RSMLI topology for grid-tied solar-PV system

The shortage of traditional fossil fuels like coal, petrol and natural-gas are increased day-by-day, fulfills the most of energy demand. Most of engineers are trying to maximize the energy demand by employing renewable energy with existing micro-grid system. Owing to merits, the solar-PV system plays a significant alternative among all other renewable energy sources due to abundant and virtuous nature. For grid-tied solar-PV system, the cascaded H-bridge multilevel inverter is the most significant over the classical 2-level inverter due to provision of isolated input DC sources. But the cascaded H-bridge topology is designed for limited voltage levels due to its larger number of switches for higher voltage levels, high cost, large-size, and more weight. To alleviate these demerits, a reduced-switch multilevel inverter has been generally preferable for higher voltage levels. In this work, a novel 9-level reduced-switch multilevel inverter (RSMLI) topology has been proposed by utilizing low number of switching devices. The performance of proposed novel 9-level RSMLI topology has been verified in grid-tied solar-PV system by using MATLAB/Simulink tool, simulation results are presented with attractive comparisons.

Analysis, design, and control of standalone PV based boost DC-AC converter

This paper presents a new control scheme for a boost DC–AC converter which is used for solar power applications. The proposed DC-AC converter configuration can produce an AC voltage level across the output or load side greater than input DC voltage based on the operating duty cycle. Generally, the conventional DC-AC converter or voltage source inverter (VSI) generates AC voltage which is less than input DC voltage. Maintaining a constant voltage across the load with improved dynamic performance is challenging for anyone for the solar photovoltaic (PV) system. A dual-loop sliding mode control is proposed for the boost VSI to address the above issues. The proposed controller has robust in nature against the wide fluctuation in the plant or load parameters. The design, analysis and control of the boost DC-AC converter are briefly discussed in this paper. This topology can be broadly used in solar powered uninterruptible power supply (UPS) where boosting operation is essential for low voltage solar PV system. This topology eliminates the DC boosting power processing stage which leads an improved efficiency of the overall system. The MATLAB/Simulink results are presented to highlight the above issues.