Search Results (21)

Solar photovoltaic (PV) panels are the best solution to reduce greenhouse gas emissions by fossil fuel combustion, with global capability now exceeding 714 GW due to rapid technological advances in solar panels (SPs). However, SPs’ efficiency and lifespan remain limited due to the absence of advanced fault-detection systems, and they are prone to short circuits (SC), open circuits (OC), and power degradation. Therefore, this large-scale production requires reliable, real-time fault diagnosis to maintain panel performance. However, traditional diagnostic methods implemented using MPPT, neural networks, or microcontroller-based systems often rely on complex computational algorithms and are not cost-effective. So, this paper proposes a diagnostic system composed of six functional blocks to address this issue. The proposed system was initially verified using an Intel DE-10 Lite FPGA board. Once its functionality was confirmed, an ASIC design was proposed for mass production, offering a significantly lower implementation cost and reduced hardware complexity than prior methods. Different circuit designs were developed for each of the six blocks. All designs were created using Cadence software and TSMC 180 nm technology files. The basic components used in these designs include PMOS transistors with 300 nm channel length and 2 µm width, NMOS transistors with 350 nm channel length and 2 µm width, as well as resistors and capacitors. Differential amplifiers with a gain of 40 dB were used for voltage and current sensing from the SP. The chip activation signal generator circuit was designed with an adjustable frequency and generated 120 MHz and 100 MHz signals in this work. The decision-making block, Logic Driver Circuit, was innovatively implemented using a reduced number of transistors. A custom memory block with a reset switch was also implemented to store the fault value detected at the SP. Finally, the proposed ASIC was implemented for fabrication, which is highly cost-effective in mass production and does not require complex computational stages. Full article

Transformerless inverters (TIs) are becoming increasingly popular in solar photovoltaic (PV) applications due to their enhanced efficiency and cost-effectiveness. Unlike transformer-based inverters, TIs, which lack transformers and additional components, offer significant advantages in terms of reduced weight, compactness, and lower costs. Research studies have demonstrated that multilevel TIs can achieve lower total harmonic distortion (THD), reduced switching stresses, and higher AC output voltage levels suitable for high voltage applications. However, achieving these outcomes simultaneously with maximum power ratings and the lowest switching frequencies poses a challenge for TI topologies. In light of these challenges, this research proposes the implementation of a 13-level single-source switched-capacitor boost multilevel inverter (SSCBMLI) designed for solar PV systems. The SSCBMLI consists of a single DC power source, switched-capacitor (SC) units, and a full H-bridge. Compared to other existing 13-level multilevel inverter (MLI) configurations, the proposed SSCBMLI utilizes the fewest components to minimize development costs. Moreover, the SSCBMLI offers voltage boosting and can drive high inductive loads, self-voltage-balanced capacitors, an adaptable topology structure, and reliable system performance. Simulations and experimental tests are conducted using PLECS 4.5 and SIMULINK to assess the performance of the proposed SSCBMLI under varying modulation indices, source powers, and loads. A comparative analysis is then conducted to evaluate the SSCBMLI against existing inverter topologies. Full article

Transformerless inverters have been extensively deployed in photovoltaic (PV) applications, owing to features such as high efficiency, high power quality, and low cost. However, the leakage current in such inverters due to the absence of galvanic isolation has resulted in several topological modifications. This paper introduces a single-input switched-capacitor (SC)-based multilevel inverter (MLI) that is capable of eliminating the leakage current due to its common-ground structure. Also, the proposed inverter has the capability of single-stage voltage boosting, which is essential in PV systems. The series–parallel switching facilitates the self-balancing of SCs, which, in turn, assists in voltage boosting. Moreover, the proposed MLI synthesizes a seven-level output using only eight switches. Following an in-depth analysis of the circuit operation, modulation scheme, and power losses, a detailed comparison among recently developed seven-level MLIs is carried out, which verifies the design's superiority. Extensive simulation and experimental results are presented to validate the prominent features of the seven-level MLI under dynamic operating conditions. Full article

Solar energy is one of the most suggested sustainable energy sources due to its availability in nature, developments in power electronics, and global environmental concerns. A solar photovoltaic system is one example of a grid-connected application using multilevel inverters (MLIs). In grid-connected PV systems, the inverter’s design must be carefully considered to improve efficiency. The switched capacitor (SC) MLI is an appealing inverter over its alternatives for a variety of applications due to its inductor-less or transformer-less operation, enhanced voltage output, improved voltage regulation inside the capacitor itself, low cost, reduced circuit components, small size, and less electromagnetic interference. The reduced component counts are required to enhance efficiency, to increase power density, and to minimize device stress. This review presents a thorough analysis of MLIs and a classification of the existing MLI topologies, along with their merits and demerits. It also provides a detailed survey of reduced switch count multilevel inverter (RSC-MLI) topologies, including their designs, typical features, limitations, and criteria for selection. This paper also covers the survey of SC-MLI topologies with a qualitative assessment to aid in the direction of future research. Finally, this review will help engineers and researchers by providing a detailed look at the total number of power semiconductor switches, DC sources, passive elements, total standing voltage, reliability analysis, applications, challenges, and recommendations. Full article

In order to meet the demands of desirable efficiency, transformerless DC/DC equipment with great voltage step-down are inevitable needed. This research offers a unique type of high-frequency, high-voltage-gain DC/DC converter, which comprises a switched capacitor (SC) converter and a buck converter. Thanks to the transformation of a two-stage converter to a single-stage converter, it has a considerable ratio of step-down voltage transformation and a reasonable duty cycle. In addition, it can permit low voltage stress on the switches. The simple control method and easy driving circuit implementation makes it scalable for high-power-level devices. Low cost can be realized as fewer components are needed. Under all operational circumstances, total soft-charging and low equipment voltage stresses are accomplished. Compared to those classic high-voltage-gain converters, the proposed converter exhibits merits of higher efficiency, higher flexibility, lower ripples, and lower costs. A comprehensive analysis is carried out for the converter’s steady-state operations. With a 1 MHz switching frequency, a 900 W prototype of a 20-time converter is constructed, with a peak efficiency of 92.5%. Simulations and experiments verify the effectiveness of the theoretical investigation of the converter’s operation. Full article

Network infrastructure sharing and mobile traffic offloading are promising technologies for Heterogeneous Networks (HetNets) to provide energy and cost effective services. In order to decrease the energy requirements and the capital and operational expenditures, Mobile Network Operators (MNOs) and third parties cooperate dynamically with changing roles leading to a novel market model, where innovative challenges are introduced. In this paper, a novel resource sharing and offloading algorithm is introduced based on a double auction mechanism where MNOs and third parties buy and sell capacity and roam their traffic among each other. For low traffic periods, Base Stations (BSs) and Small Cells (SCs) can even be switched off in order to gain even more in energy and cost. Due to the complexity of the scenario, we adopt the multi-objective optimization theory to capture the conflicting interests of the participating entities and we design an iterative double auction algorithm that ensures the efficient operation of the market. Additionally, the selection of the appropriate time periods to apply the proposed algorithm is of great importance. Thus, we propose a machine learning technique for traffic load prediction and for the selection of the most effective time periods to offload traffic and switch off the Base Stations. Analytical and experimental results are presented to assess the performance of the algorithm. Full article

Railway switches and crossings (S&Cs) are critical, high-value assets in railway networks. A single failure of such an asset could result in severe network disturbance and considerable economical losses. Squats are common rail surface defects of S&Cs and need to be detected and estimated at an early stage to minimise maintenance costs and increase the reliability of S&Cs. For practicality, installation of wired or wireless sensors along the S&C may not be reliable due to the risk of damages of power and signal cables or sensors. To cope with these issues, this study presents a method for collecting and processing vibration data from an accelerometer installed at the point machine to extract features related to the squat defects of the S&C. An unsupervised anomaly-detection method using the isolation forest algorithm is applied to generate anomaly scores from the features. Important features are ranked and selected. This paper describes the procedure of parameter tuning and presents the achieved anomaly scores. The results show that the proposed method is effective and that the generated anomaly scores indicate the health status of an S&C regarding squat defects. Full article

Electrostatic vibration energy transducers have a relatively high output impedance (R_ET) and open-circuit voltage (V_IN), so that voltage-down conversion is required for sensor/RF ICs. Switched-capacitor converters are the best candidate to create small-form-factor technology and are a low-cost solution because of their capability to fully integrate into sensor/RF ICs. To design switched-capacitor voltage-down converters (SC-VDCs) with a minimum circuit area for electrostatic vibration energy transducers, two steps are required. The first step requires an optimum design of DC-DC SC-VDCs driven by high R_ET with a minimum circuit area, and the second step requires an optimum design of AC-DC SC-VDCs based on the first step, to minimize the converter circuit area. This paper discusses circuit analysis and design optimization aimed at the first step. Switching frequency, the number of stages and the capacitance per stage were determined as a function of R_ET, V_IN and the output voltage (Vo) and current (Io) to the load, to achieve a minimum circuit area. The relationship between Io and the power conversion efficiency was studied as well. The performance was validated by SPICE simulation in 250 nm BCD technology. An optimum design flow was proposed to design DC-DC SC-VDCs driven by high R_ET with a minimum circuit area under conditions where R_ET, V_IN, Vo and Io were given. The second design step remains as future work. Full article

Among multilevel inverters (MLIs), two-level inverters are the most common. However, this inverter type cannot maintain total harmonic distortion (THD) due to its limited number of levels. Reductions in THD are inversely proportional to the number of levels where increased output occurs in diverse ways, and the use of fewer components with low harmonic distortion is necessary for such reductions. This work proposes a seven-level (7L) MLI design with a small number of components and low harmonic distortion. The proposed MLI is combined with switched capacitor (SC) cells to promote output levels and at the same time to boost the input voltage. The connections between the capacitor and the source are based on the series to parallel topology, where the charging and discharging of the SC cells are caused by fluctuations in their connection. The output of the SC cell is combined with an H-bridge inverter controlled by a proposed PWM controller. The simulation result of the SC 7L inverter was completed using LTspice software. A comparison of the proposed topology with that of other current MLI led to better validation results. The proposed design shows a reduction in the THD with fewer components. The cost and size of the proposed inverter is minimal due to the smaller number of components. Ohmic load and inductive ohmic load were used as loads for the system. Full article

The automobile industry and technology are putting a great significance in improving vehicles to become more fuel economical, but with incremental costs relative to conventional vehicle technologies; these new vehicles are electric vehicles (EV), plug-in hybrid electric vehicles (PHEV), and hybrid electric vehicles (HEV). However, their significant capabilities to reduce petroleum consumption and achieve efficiency over their life cycles offer economic benefits for customers, industry, carmakers, and policymakers. In this paper, an HEV concept based on renewable energy resources (RERs) is proposed. The proposed HEV design utilizes solar PV energy, wind energy, fuel cell, and a supercapacitor (PV + WE + FC + SC) which generates electrical energy via a proton exchange membrane (PEM) and an SC to cater for strong torque requirements. The vehicle incorporates a battery pack in conjunction with an SC for the power demands and an FC as the backup energy supply. An alternator connected to turbine blades runs by wind energy while the car is moving forward, which produces electricity through the alternator to charge the battery. The design aims to ensure zero carbon emission and improved energy efficiency, is lightweight, and incorporates in-wheel motors to eliminate the mechanical transmissions. Modeling and simulation were carried out for each subsystem using MATLAB^® and Simulink^® packages. ANSYS Fluent simulation was used to analyze wind energy. The standard analysis, e.g., pressure, velocity, and vector contour, were also considered while designing the final model. To regulate the power supply and demand, the selection of energy sources was controlled by a rule-based supervisory controller following a logical sequence that prioritizes energy sources with the SC as a source in-vehicle stop-and-go situations while the battery acts as the primary source, FC as a backup supply, and wind and solar power to recharge the battery. Solar charging is switched on automatically once the vehicle is parked, and the controller controls the energy flow from the alternator during that period. Full article

The battery storage system (BSS) is one of the key components in many modern power applications, such as in renewable energy systems and electric vehicles. However, charge imbalance among batteries is very common in BSSs, which may impair the power efficiency, reliability, and safety. Hence, various battery equalization methods have been proposed in the literature. Among these techniques, switched-capacitor (SC)-based battery equalizers (BEs) have attracted much attention due to their low cost, small size, and controllability. In this paper, seven types of SC-based BEs are studied, including conventional, double-tiered, modularized, chain structure types I and II, series-parallel, and single SC-based BEs. Mathematical models that describe the charge–discharge behaviors are first derived. Next, a statistical analysis based on MATLAB simulation is carried out to compare the performance of these seven BEs. Finally, a summary of the circuit design complexity, balancing speed, and practical implementation options for these seven topologies is provided. Full article

To date, most studies focus on complex designs to realize offset cancelation characteristics in nonvolatile flip-flops (NV-FFs). However, complex designs using switches are ineffective for offset cancelation in the near/subthreshold voltage region because switches become critical contributors to the offset voltage. To address this problem, this paper proposes a novel cross-coupled NMOS-based sensing circuit (CCN-SC) capable of improving the restore yield, based on the concept that the simplest is the best, of an NV-FF operating in the near/subthreshold voltage region. Measurement results using a 65 nm test chip demonstrate that with the proposed CCN-SC, the restore yield is increased by more than 25 times at a supply voltage of 0.35 V, compared to that with a cross-coupled inverter-based SC, at the cost of 18× higher power consumption. Full article

The switch and crossing (S&C) is one of the most important parts of the railway infrastructure network due to its significant influence on traffic delays and maintenance costs. Two central questions were investigated in this paper: (I) the first question is related to the feasibility of exploring the vibration data for wear size estimation of railway S&C and (II) the second one is how to take advantage of the Artificial Intelligence (AI)-based framework to design an effective early-warning system at early stage of S&C wear development. The aim of the study was to predict the amount of wear in the entire S&C, using medium-range accelerometer sensors. Vibration data were collected, processed, and used for developing accurate data-driven models. Within this study, AI-based methods and signal-processing techniques were applied and tested in a full-scale S&C test rig at Lulea University of Technology to investigate the effectiveness of the proposed method. A real-scale railway wagon bogie was used to study different relevant types of wear on the switchblades, support rail, middle rail, and crossing part. All the sensors were housed inside the point machine as an optimal location for protection of the data acquisition system from harsh weather conditions such as ice and snow and from the ballast. The vibration data resulting from the measurements were used to feed two different deep-learning architectures, to make it possible to achieve an acceptable correlation between the measured vibration data and the actual amount of wear. The first model is based on the ResNet architecture where the input data are converted to spectrograms. The second model was based on a long short-term memory (LSTM) architecture. The proposed model was tested in terms of its accuracy in wear severity classification. The results show that this machine learning method accurately estimates the amount of wear in different locations in the S&C. Full article

Railway infrastructure plays a major role in providing the most cost-effective way to transport freight and passengers. The increase in train speed, traffic growth, heavier axles, and harsh environments make railway assets susceptible to degradation and failure. Railway switches and crossings (S&C) are a key element in any railway network, providing flexible traffic for trains to switch between tracks (through or turnout direction). S&C systems have complex structures, with many components, such as crossing parts, frogs, switchblades, and point machines. Many technologies (e.g., electrical, mechanical, and electronic devices) are used to operate and control S&C. These S&C systems are subject to failures and malfunctions that can cause delays, traffic disruptions, and even deadly accidents. Suitable field-based monitoring techniques to deal with fault detection in railway S&C systems are sought after. Wear is the major cause of S&C system failures. A novel measuring method to monitor excessive wear on the frog, as part of S&C, based on fiber Bragg grating (FBG) optical fiber sensors, is discussed in this paper. The developed solution is based on FBG sensors measuring the strain profile of the frog of S&C to determine wear size. A numerical model of a 3D prototype was developed through the finite element method, to define loading testing conditions, as well as for comparison with experimental tests. The sensors were examined under periodic and controlled loading tests. Results of this pilot study, based on simulation and laboratory tests, have shown a correlation for the static load. It was shown that the results of the experimental and the numerical studies were in good agreement. Full article

The aim of this paper is to present a methodology for dimensioning an energy storage system (ESS) to the generation data measured in an operating wave energy generation plant connected to the electric grid in the north of Spain. The selection criterion for the ESS is the compliance of the power injected into the grid with a specific active-power ramp-rate limit. Due to its electrical characteristics, supercapacitor (SC) technology is especially suitable for this application. The ESS dimensioning methodology is based on a mathematical model, which takes into account the power generation system, the chosen ramp-rate limit, the ESS efficiency maps and electrical characteristics. It allows one to evaluate the number of storage cabinets required to satisfy the needs described, considering a compromise between the number of units, which means cost, and the reliability of the storage system to ensure the grid codes compliance. Power and energy parameters for the ESS are obtained from the calculations and some tips regarding the most efficient operation of the SC cabinets, based on a stepped switching strategy, are also given. Finally, some conclusions about the technology selection will be updated after the detailed analysis accomplished. Full article