DC Source Research Articles

Reduced Device Count for Self Balancing Switched-Capacitor Multilevel Inverter Integration with Renewable Energy Source

In this study, a new switched-capacitor-based seven-level inverter topology with a photovoltaic system is presented. The proposed topology requires a smaller number of devices and has the ability to self-balance the voltage across the capacitor. The proposed topology configuration is simple and has the ability to extend to higher levels of voltage. This multilevel inverter topology is suitable for low- and medium-voltage applications with photovoltaic (PV) system integration. To improve the PV system efficiency as an input of a DC–DC boost converter, a Fuzzy logic-based maximum power point controller technique is used. A PV system with a DC–DC boost converter integrates with the proposed seven-level inverter topology. The anti-predatory particle swarm optimization (APSO) technique is used to solve the non-linear transduction equations of the seven-level PV switched-capacitor-based multilevel inverter (7L−PV−SCMLI) topology. The proposed APSO is described to minimize the harmonics in the multilevel inverter (MLIs), which is a complex optimization problem involving a non-linear transcendental equation. Furthermore, APSO can be applied in order to solve non-linear transcendental equations for all symmetrical and asymmetrical MLIs that have equal and non-equal DC sources. The APSO-based selected harmonic elimination (SHE) technique obtained the best switching angle value, and the optimized obtained switching angles reduced the total harmonic distortion (THD) of 7L−PV−SCMLI.

Cracking failure analysis due to fatigue of the Ti-6Al-4V alloy coated with SiC layer and Cr interlayer deposited by magnetron sputtering

This work aimed to study the effects of coating a thin film of Silicon Carbide and chromium interlayer on the fatigue behavior of Ti-6Al-4V alloy and the correspondent failure evaluation. In the characterization of the layer, the roughness, thickness, and adhesion were determined. Uniaxial fatigue tests were performed under R = 0.1 and the fracture surfaces and corresponding failure mechanisms were observed and identified by SEM, respectively. In the specimens coated using the DC source the number of cycles to failure of the fatigue was increased. The fracture surfaces showed that the crack initiation occurred in the internal regions of the specimens and not superficially. In this case, the layer remained adhered to the specimens even after the tests, showing the effectiveness of the film. In specimens coated using the HiPIMS source, the number of cycles to failure decreased, the cracks were mostly superficial, and the deposited film showed low adhesion after the tests. It proved to be ineffective, worsening the material fatigue behavior.

Non-Thermal Plasma Pyrolysis of Fuel Oil in the Liquid Phase

A pulsed plasma pyrolysis reactor with an efficient control system was designed for fuel oil processing. Non-thermal plasma pyrolysis was carried out in the liquid phase at low temperatures (not higher than 100 °C) in a 300 cm3 reactor without additional reagents or catalysts. The main process parameters and characteristics of non-thermal plasma fuel oil products were investigated within the DC source voltage range of 300–700 V. An increase in the energy of pulsed discharges led to an increase in the productivity of the plasma pyrolysis process and the yield of hydrogen but reduced the yield of acetylene and ethylene. The resulting gas consisted predominantly of hydrogen (46.5–50.0 mol%), acetylene (28.8–34.3 mol%), ethylene (7.6–8.6 mol%), methane (4.2–6.2 mol%), and C3–C5 hydrocarbons. The solid-phase products were in the form of disordered graphite and multilayer nanotubes.

A Review of Single-Stage Multiport Inverters for Multisource Applications

Conventional power electronic interfaces for multisource applications always need multiple conversion stages as intermediate dc-dc power conversion stages are inevitably installed for matching the different dc voltage levels and regulating the power distribution among dc sources. Dually, single-stage multiport inverter for multisource applications enables direct connection from the dc source to ac side without an extra conversion stage and has witnessed an upward trend in recent years. The salient advantages of single-stage multiport inverters comprise fewer power losses, fewer passive filters, and higher system efficiency. To capture the advancement in the field, the article reviews various single-stage multiport inverters for multisource applications, offers a comprehensive understanding of the current development of this configuration, and provides an insightful forward look at potential research issues of single-stage multiport inverters. This article presents various state-of-art single-stage multiport topologies as well as their applications and comparisons. In addition, systemic topology derivation methods of single-stage multiport inverters are discussed to provide inspiration for exploring new topologies. Moreover, the main challenging issues of this topology such as modulation, control, and energy management strategies are analyzed and summarized. Finally, some open questions and future trends of single-stage multiport inverters are also discussed to motivate future research and explore new alternatives.

A New Integrated Multilevel Inverter Topology for Renewable Energy Transformation

This paper presents a new three-phase integrated module multilevel inverter (IMMLI) with reduced component count which is suitable for low, medium and high voltage renewable energy systems. The proposed inverter is a resultant structure of a number of integrated module and each module is configured with a number of series connected basic blocks. Each block consists of a dc voltage source, a blocking diode and a semiconductor switch. A computational combination and summation among the dc sources from different blocks results in a high number of levels within the output voltage. This task is performed by controlling the switches equipping appropriate switching algorithm. Thus, a high level of output is obtained employing reduced number of components. Since the topology owns two degree of modularity, the total stress voltage (TSV) of the system is low and distributed among the switches. Hence, the proposed topology allows to be implemented in high power systems with reduced amount of costs. The inverter also offers enhanced efficiency, as the number of simultaneously conducting switch is low. Additionally, in order to operate the presented inverter with optimum ac power quality, a multi-carrier based level shifted PWM scheme is addressed in this paper. This paper also shows how to prepare balanced dc sources that are required to implement the inverter using high-frequency magnetic-link. The operating principle of the IMMLI is explained with the help of a fifteen level (15-L) single phase unit and its performance is evaluated in MATLAB/Simulink considering different conditions. Experimental validation is also presented to support the simulation results and to evaluate its superiority over the existing.

Assessment of Multi-Phase Conversion and Modified PWM Strategy for Power Converters of Medium-Voltage Induction Motors Drive

Multi pulse and multilevel converters show great potential for use in medium voltage induction motor drive systems due to cascaded design and high-quality output. However, variable-speed medium voltage drives have demanding requirements in enhancement number of pulses with less number of DC sources and converter topologies with reduced component counts. This paper utilizes the phase displacement technique as well as the three-phase to five-phase conversion technique so that the drive system extracts 30-pulse current from the grid supply, which helps to enhance the power quality at the grid end. In this paper, a 30-pulse AC-DC converter based on a 10-pulse converter is designed and implemented to feed a power 4-level cascaded inverter through three DC sources. Apart from this, a modified carrier-based LSPWM technique is used to enhance the performance of the MLI at a low switching frequency. An indirect field-oriented control (IFOC) method is utilized to address the issues of the drive system during dynamic operations. Performance analysis through theoretical and simulation by using the full-scale model is evaluated in terms of voltage and current quality, speed and torque response, losses, and efficiency. Experimental verification is also carried out on a 7.5kW, 415V laboratory prototype using a digital signal controller for implementation of the control scheme.

Integrated Converter With G2V, V2G, and DC/V2V Charging Capabilities for Switched Reluctance Motor Drive-Train Based EV Application

The article proposes an integrated converter (IC) with driving, grid-to-vehicle (G2V), vehicle-to-grid (V2G), and DC/ vehicle-to-vehicle (V2V) charging capabilities for electric vehicle (EV) drive-train employing switched reluctance motor (SRM). During drive mode, the battery supplies the driving power, and the proposed IC independently controls the individual phases of the SRM. When EV is standstill/ idle, the proposed IC can charge the battery via standard AC and DC charging sockets. For charging the battery via a single-phase residential/public AC outlet, i.e., G2V charging, the proposed IC exhibits a power factor correction (PFC) charger. The reconfigured switches are bidirectional, facilitating the flow of power in both directions, i.e., G2V and V2G charging. For fast charging of the battery via DC source, which includes emerging DC grids, solar photovoltaic systems, and battery source of another EV, i.e., V2V charging, the proposed IC exhibits a four-quadrant DC-DC converter (FQDDC). For realizing the inductors of the PFC charger and FQDDC converter, the phase windings of SRM are reconfigured. Thus, the proposed IC eliminates the requirement of any additional non-integrated circuit, which reduces the total switch count. Also, proposed way of reconfiguring inductors results in a standstill rotor at appropriate rotor positions. The above-stated claims of the proposed IC are validated via experimental studies.

A Modular Unipolar/Bipolar High-Voltage Pulse Generator Suitable for High Resistive Load

This article presents two novel high-voltage pulse generator (HVPG) structures. These modular topologies are based on the buck-boost converter (BBC) operated in discontinuous conduction mode (DCM). The proposed generators produce unipolar and bipolar bell-shaped pulses, which can be applied for applications with high resistive loads. In these structures, the capacitors can be charged up to several times the dc input voltage, simultaneously. Accordingly, they have a high voltage (HV) gain even with a low-voltage dc (LVDC) source. This allows for a compact structure with a low number of modules (switches, diodes, capacitors, etc.). By reducing the number of modules, the total cost and power losses are reduced and the reliability is increased and its maintenance and fault detection would become easier. The other significant advantage of the proposed topologies is the voltage rating reduction of switches and diodes. Also, the series connection of switches and diodes is not required in this structure, which decreases the complexity and costs. Furthermore, due to the simultaneous charging of the capacitors, high-frequency pulses can be generated. Moreover, pulsewidth and pulse rise time are designed arbitrary parameters in nanosecond to microsecond ranges and they are completely independent of the gate driver and switch speed. In the design section, the parameters of the structure are determined based on the pulse specifications. The structures are simulated in MATLAB/SIMULINK environment. The experimental results for 1 kV output voltage confirm the performance of the proposed structures.

The Dynamic Sliding Mode Controller with Observer of Coincident Perturbations and States for Buck Converter of Fuel Cell Source

Buck converter has been widely used in the DC renewable energy system application. The Fuel Cell (FC) based DC renewable energy is offered as a high-performance and low-emission power supply, which replaces conventional DC sources. Its relevant control system has regulated the output voltage under input voltage and load resistance variations to track the desired reference signal. To control the current sensorless-based buck converter with matched and mismatched uncertainties, the system must be modeled in such a way that by measuring the output voltage, both the inductor current and system perturbations can be estimated. The purpose of the work is suggestion of a novel dynamic sliding mode controller (DSMC) based on observer of coincident perturbations and states (CSPO) to enhance its controllability and tracking performance. The significance of the work lies in low cost and reduced losses due to the inductor current measurement. Lacking an exact value for inductor current, it is not possible to estimate and compensate the perturbations caused by parametric uncertainties in the buck converter. These objectives were achieved by modeling in the canonical form. The canonical model somehow converts both the matched and mismatched perturbations into the matched perturbation, in which the system states and perturbations can be merely estimated using only an output voltage value and a CSPO. The most important results are the fastness and robustness of the DSMC to control the buck converter and compensate the effect of mismatched uncertainties and nonlinear disturbances and chattering phenomenon.

High Gain Magnetically Coupled Single Switch Quadratic Modified SEPIC DC-DC Converter

This article proposes, analyzes, and tests an improved high voltage gain dc-dc converter based on a single-ended primary-inductor converter (SEPIC). The proposed magnetically coupled quadratic modified SEPIC converter (MCQ-MSC) employs a coupled transformer with an optimized design to obtain a high voltage boost factor by controlling the transformer's turn ratio along with the switching duty cycle. Thanks to the unique structure of the coupled transformer, high voltage gain is obtained at low turns ratio, which is highly desirable for high voltage applications and the compact size of the converter. In addition to the coupled transformer, a voltage-boosting module is utilized to achieve a very high output voltage for a low switching duty cycle. The proposed inverter has a single switch with a wide control range of duty cycle (0<D<1), causing low conducting losses and high efficiency. Furthermore, a clamping circuit is successfully designed to remove the leakage inductance effects of the coupled transformer on the power switch. The proposed MCQ-MSC drains a continuous current from the input dc source, which makes it a suitable choice for renewable energy sources (RES). The hardware prototype of the proposed converter is tested to verify the mathematical expressions and theoretical results.

A Novel High-Efficiency Three-Phase Multilevel PV Inverter With Reduced DC-Link Capacitance

We present a novel three-phase multilevel inverter (MLI) design for PV applications that does not require large DC-link capacitors to buffer the 120 Hz power ripple and allows individual inverter module to process trapezoidal power instead of sinusoidal power. This new design features two inverters connected in parallel to each DC source and N inverters connected in series to each grid phase to support the grid voltage. The trapezoidal operation improves the overall system&#x2019;s efficiency by allowing the inverter module to output peak or zero power for most of the AC cycle. We present the controller design and simulate the proposed MLI system in PLECS. We demonstrate an experimental 110<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> DC input, 208 <inline-formula><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> three-phase AC output, 1kW 5-level prototype with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;95&#x0025; efficiency. With the same inverter module, we compare the efficiency of the proposed design to the conventional MLI design, where all modules share phase power evenly. We demonstrate that the proposed design consistently outperforms the conventional design in efficiency, with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;20&#x0025; loss reduction at light load conditions.

Electrical Performance Analysis of Grading Electrodes After Scaling in Converter Valves

It is necessary to take out the electrode when detecting the scaling degree of the conventional grading electrode. The steps are cumbersome and there are safety risks. In this paper, through the analysis of the equivalent circuit model before and after the scaling of the grading electrode on the cooling water manifold in the converter valve, the loop resistance model suitable for the positive and negative potential sides is obtained. The constant voltage DC source is used as the driving voltage of the circuit, and the leakage current of the circuit is measured under different temperatures and conductivity conditions of the internal cooling water. The degree of scaling of the grading electrode is determined by analyzing the leakage current. The leakage current in the non-scaling state of the grading electrode and the leakage current in the scaling failure state of the grading electrode are taken as the reference values. It is concluded that when the leakage current of the measurement circuit decreases to 68 % - 80 % of the leakage current in the non-scaling state of the grading electrode, the grading electrode can be considered to fail.

A Soft-Switched Current-Fed Dual-Input Isolated DC–DC Converter Topology

A soft-switched current-fed dual-input isolated dc-dc converter topology is proposed in this article. This converter integrates two low-voltage dc sources with similar transferred characteristics such as two PV panels or two batteries into a dc bus using a simple circuit topology and a minimum number of active and passive components. The energy transfer between the input and output ports is controlled by modulating the pulse-width of the control signals. Moreover, the soft-switching operations are discussed, and the smooth connection between the input-side inductor and the transformer leakage inductance is achieved. Furthermore, the operation of the converter in reverse power flow direction is presented to demonstrate the bidirectional operational capability of the converter. Finally, different operation modes of the proposed dual-input converter are verified by the experimental results obtained from a 250 W hardware prototype.

Online adaptive SHE algorithm for multilevel converters and implementation with embedded control system

Selective harmonic elimination pulse-width modulation (SHE-PWM) method has been widely used in various industrial multilevel converters befitting from low switching frequencies and precise elimination of low-order harmonics. Most of existing studies focus on accelerating calculation of switching angles or optimizing predictive neural networks. However, these offline methods cannot dynamically deal with the errors introduced by nonuniform dc sources of multilevel converters or biased placements of switching angles. This paper proposes an online adaptive SHE (OA-SHE) algorithm to compensate these errors. Errors caused by nonideal dc (NID) sources and leading-lagging placements (LLPs) are analyzed in detail. The error of output waveform is comprehensive result of NID sources and LLPs. By introducing feedback, the output waveform accuracy of multilevel converters can be increased greatly. Realization of the particle swarm optimization (PSO) with an embedded control system is presented to acquire good real-time performance. With the OA-SHE method, the value of particles has been higher than the initial value. High order harmonics, including 1st, 5th, 7th, 11th, and 13th components, are suppressed by the low-pass filter. Comparing to existing studies, this online algorithm does not need detailed model parameters and can be directly applied to practical applications achieving multi-objective optimization. Finally, both simulations and experiments are carried out to verify the effectiveness of this algorithm.

A single‐source switched‐capacitor based 13‐level sextuple boost inverter with reduced component count and low THD

AbstractA switched‐capacitor‐based 13‐level inverter with a lesser number of components is presented in this article. The 13‐level single‐phase AC output voltage is achieved with a voltage gain of 6 by including a single DC source, 11 switches, 4 capacitors, and 3 diodes in the proposed converter. The self‐voltage balancing is achieved for various types of load without the need for complex control schemes and auxiliary circuits. The proposed topology does not require a back‐end H‐bridge to generate negative polarity. This leads to a reduction in voltage stresses across the switches. Thus, total standing voltage (TSV) and the overall cost of the proposed topology are reduced as compared to the state‐of‐the‐art topologies reported in the literature. Furthermore, an Improved Nearest Level Modulation (INLM) scheme is used to improve the power quality of the output voltage. Using the proposed scheme, the Total Harmonic Distortion (THD) of the output voltage is reduced to 5.08%. The power loss analysis for various elements of the proposed converter is also included. A comparison with recent topologies in reference to various performance parameters is carried out. In addition to the simulation study, a laboratory prototype is prepared to validate the efficacy of the proposed converter.

Multi-harvesting smart solution for self-powered wearable objects: System-level model and transistor-level design

Internet of Things and growing popularity of connected devices are increasing the demand for wearables applications, which is driving the development of ultra-low power secure systems. Thus, having a system running at low voltage with low power consumption introduces the use of ambient energy harvesting. Besides, batteries have several limitations reducing their compatibility with wearables, including periodical need for recharge, limited life-time, heavy and large form factor and non-eco-friendly life-cycle. Therefore ambient energy harvesting technology gives a promising alternative for self-powered wearables. The integration of these solutions on the same silicon support is a real technological challenge. This paper proposes a multi-harvesting fully-integrated system architecture combining AC and DC sources. Based on a MATLAB/Simulink model, the proposed system allows the calibration of an optimal solution. It is designed and simulated in 40 nm CMOS process, demonstrating the use of an AC source as secondary input to start a harvesting system with very low DC source as main source.

Design and Development of a Low-Cost 2.4 GHz GFSK Modulation based Walkie-Talkie

A walkie-talkie device can be quite useful in the location where there is no cellphone coverage. Even in the cellphone coverage area it provides communication at very low cost. Currently the law enforcement and military personnel uses frequency modulation (FM) based walkie-talkie systems. The main goal of this research is to design and develop a lowcost walkie-talkie device that can be used by anyone other than the military and law enforcement personals. To construct the walkie-talkie system, the 2.4 GHz industrial, scientific, and medical (ISM) band and GFSK modulation technology have been chosen. In addition, the device includes transceiver module, dc power source, microphone amplifier, audio amplifier, dc-dc booster, and speaker. The coverage range of the implemented walkie-talkie system has been determined and found up to 200 meters. The gadget incorporates a li-ion battery charging system. The voltage, current and power levels at various locations of the device have been measured. It has been found that the maximum operating power consumption is 4.81W and standby power is 1mW. Moreover, the waveforms of different signals at different points of the systems have been observed on the oscilloscope. All of the development process of the system and the performance data are presented in this paper. DUJASE Vol. 7 (2) 16-20, 2022 (July)

High‐gain nine‐level switched‐capacitor multilevel inverter featuring less number of devices and leakage current

AbstractIn this article, a novel switched‐capacitor multilevel inverter (SC‐MLI) for on‐grid and off‐grid applications with PV is presented. The nine‐level proposed SC‐MLI with simple architecture is produced gain of four times across the load voltage. Further, the proposed inverter needs only 10 power switches, a single dc source, three diodes, and three capacitors. For a suitable switching operation, phase disposition pulse width modulation (PD‐PWM) was developed. Furthermore, the capacitor inrush current, which is a major shortcoming of SC‐MLI, is mitigated in the proposed topology by employing a charging inductor. Furthermore, the proposed inverter is used as a single‐stage PV grid‐tied inverter. When inverter is used for PV applications, the proposed inverter provides minimum value of leakage current. In addition, to demonstrate the superior performance of the proposed switched capacitor MLI, a comparative analysis with an existing off‐grid and existing on‐grid SC‐MLIs is performed. A fully circuit has been simulated using Matlab/Simulink to test the effectiveness and feasibility of the proposed topology. The prototype of the hardware system is designed of a nine‐level proposed topology using the dSpace 1103 controller board to validate the results.

Memristor-Based Cryogenic Programmable DC Sources for Scalable In Situ Quantum-Dot Control

Current quantum systems based on spin qubits are controlled by classical electronics located outside the cryostat. This approach creates a major wiring bottleneck, which is one of the main roadblocks toward scalable quantum computers. Thus, we propose a scalable memristor-based programmable dc source that can perform biasing of quantum dots (QDs) inside the cryostat. This novel cryogenic approach would enable to control the applied voltage on the electrostatic gates by programming the resistance of the memristors, thus storing in the latter the appropriate conditions to form the QDs. In this study, we first demonstrate multilevel resistance programming of TiO2 memristors at 4.2 K, an essential feature to achieve voltage tunability of the memristor-based dc source. We then report hardware-based simulations of the electrical performance of the proposed dc source. A cryogenic TiO2 memristor model fit on our experimental data at 4.2 K was used to show a 1 V voltage range and 100 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{V}$ </tex-math></inline-formula> resolution in situ memristor-based dc source. Finally, we simulate the biasing of double QDs (DQDs), enabling 120 s stability diagrams. This demonstration is a first step toward advanced cryogenic applications for resistive memories, such as cryogenic control electronics for quantum computers.

Dynamics of the Rotating Arm of an Electromechanical System Subjected to the Action of Circularly Placed Magnets: Numerical Study and Experiment

This paper considers the experimental and numerical study of an electromechanical arm powered by a DC motor and subjected to the action of permanent magnets. The magnetic torques arise from permanent magnets mounted at the free end of the arm and along a circle. The electrical subsystem is powered by two forms of input signal (DC and AC voltage sources). For each case, we determine the condition for complete rotation of the mechanical arm versus the parameters of the system such as the arm length, the number of magnets, and the frequency of the external signal. The nonlinear dynamics of the system is examined by means of time-histories, bifurcation diagrams, Lyapunov exponents and phase portraits. Chaotic and periodic dynamics are detected numerically and confirmed experimentally.