•A modified perturb-and-observe-based-MPPT method is proposed.•The proposed method (PM) is tested under step/ramp changes of irradiation level.•Tracking speed by the PM is 0.025 ms against 35–52.5 ms ...for other 18 methods.•Steady-state efficiency by the PM is 99.48% versus 83.6–98.5% for other methods.•Dynamic efficiency by the PM is 98.03% against 83–96.33% for other methods.
The present paper studies thoroughly the performance of the classical perturb-and-observe (P&O) method under fast-changing solar irradiation, including increase or decrease of the irradiation level with small or large steps, when the initial operating point lies to the right or left of the MPP. In sixteen case studies of sudden variation of solar irradiation, the classical P&O method fails to track MPP properly in four cases. The classical P&O tracker does not work properly under a ramp change of irradiation level. A modified P&O-based-MPP tracking method is proposed and tested under step and ramp changes of irradiation irrespective of the value and direction of the perturbation in irradiation level and the location of the initial operating point. The proposed method succeeds in capturing the MPP under a ramp or slow change of irradiation level. The proposed method tracks correctly the MPP in the above-mentioned case studies and shows better performance in tracking speed, steady state efficiency, dynamic efficiency and tracking accuracy when compared with the classical P&O method and other modified methods reported in the literature.
•An intensive literature review on online and offline tracking of the MPP is presented.•The proposed hybrid MPPT technique improves HC and ANFIS techniques.•The proposed technique increases energy ...gain factor when compared with HC technique.•The radiation profile does not affect the performance of the proposed technique.•The proposed technique provides robust operation with no obvious oscillations.
The development of Maximum Power Point Tracking (MPPT) techniques is continuing in order to increase the generated energy from photovoltaic (PV) generators. A variety of MPPT techniques have been proposed and classified based on three main categories: offline, online and hybrid techniques. This paper presents a review of the most popular techniques for offline and online tracking of the Maximum Power Point (MPP), which are the Adaptive Neuro-Fuzzy Inference System (ANFIS) and Hill Climbing (HC) techniques, respectively. This is in addition to a review for all hybrid techniques reported in the literature demonstrating their main merits and shortcomings. Moreover, the present paper combines the ANFIS and HC as a hybrid technique for the first time. The proposed technique involves the features of the ANFIS and HC techniques and mitigates their shortcomings in order to increase the generated PV electrical energy. The proposed technique is a combination of two stages to assess the duty ratio (control signal) being applied to a boost converter for MPP tracking. The first stage includes a set point calculation loop to estimate the duty ratio. The second stage involves a fine tuning loop to determine the exact duty ratio corresponding to the MPP. This achieves maximum power transfer to the load even under nonuniform climatic conditions using a relatively simple control system. The proposed technique has been simulated in MATLAB/SIMULINK environment and compared with some other MPPT techniques (the Constant Voltage (CV), ANFIS, HC, Incremental Conductance (IncCond) techniques) for steady state and rapidly changing climatic conditions (Ropp and sine radiation tests) as well as load variations. The results reveal that the proposed hybrid MPPT technique outperforms other MPPT techniques in term of performances indicators, which include the tracking speed, tracking accuracy and energy gain factor.
The constant voltage (CV) for maximum power point tracking (MPPT) technique is considered one of the most commonly used techniques in the photovoltaic (PV) applications. This study is aimed at ...proposing an adaptive reference voltage-based MPPT technique (ARV) to improve the performance of the CV technique by making it adaptable to weather conditions. The RV for MPPT is adapted according to the measured radiation and temperature levels. The operating range of the radiation at a given temperature is divided into number of divisions and the corresponding RV is recorded off-line in a truth table. The difference between the reference and measured PV voltages is compensated using proportional–integral controller to generate suitable duty ratio to the boost converter. Performance assessment of the CV technique after being improved covers time response, MPPT efficiency, oscillation and stability. The results present performance improvement by fast time response to reach steady-state value, more stable operation with no oscillation and high MPPT efficiency as compared with the CV technique without the proposed improvement.
This paper is aimed at presenting a numerical method for calculating the transient overvoltage across a wind turbine (WT) struck by lightning. The resulting overvoltage is determined at different ...points along the WT body using the proposed numerical method. The lightning strike has been simulated by injecting a current impulse to the tested WT. The equivalent circuits of WT components and the mathematical formulas to evaluate the circuit's parameters are presented. This makes it possible to develop π-equivalent RLC networks representing the WT components to write the nodal equations at each discrete time instant. MATLAB software package is used to solve the nodal equations and determine the transient behaviour of the WT. In the laboratory, a high impulse voltage is applied on a small-scale WT to corroborate the proposed method. The calculated overvoltage temporal variations are in good agreement with those measured at different positions along the WT for various grounding resistance values, demonstrating the validity of the proposed method. Further validation is also made by comparing the present simulation with that using PSCAD/EMTDC software package. The overvoltage values increase with the rise of the grounding resistance value. The obtained results are useful for designing WT lightning protection systems.
This paper is aimed at assessing by theory and experiment the current–voltage and power-voltage characteristics of a PV module as influenced by dust accumulation. A method is proposed in a computer ...code to follow-up an incident solar radiation through the module layers considering the reflection and transmission of radiation at the interfaces between the layers to evaluate how the incident radiation is attenuated before reaching the module. Also, absorption of radiation in the dust layer and the glass cover is considered. The evaluation of the reflectance and transmittance calls for analysis of the accumulated dust to identify its constituents using X-ray fluorescence apparatus. The refractive and absorption indices are assessed for dust constituents as well as the corresponding effective values for the sample as a whole. The current–voltage characteristic of the dusty module is calculated using Simulink with consideration of module parameters after being corrected according to the incident radiation received by the solar cell and the ambient temperature where the module is installed. The calculated current–voltage and power-voltage characteristics of the dusty module agreed reasonably with the measured ones for a 175-W module as the incident radiation decreased to 68% due to dust accumulation with a subsequent decrease of the maximum output power of dusty module by 31% when compared with the clean one. The percentage decrease of short-circuit current recorded 31% due to dust deposition against 2% for the increase of open-circuit voltage at ambient temperature of 44 °C and incident solar radiation of 1027 W/m
2
. This conforms to previous findings in the literature.
This study aims to investigate how the electrical-resistivity of different soils and grounding enhancement-materials is influenced by water-content and the dehydration under ambient and high-constant ...temperatures. The used enhancement-materials were extracted from surrounding wastes in Egyptian desert. First, waste enhancement-materials, their developed-mixture and soil samples were prepared for experimental testing. The contact-resistance between soil and enhancement-material was measured by using a designed soil-box. It was observed that adding a wood-ash as an interface-layer between the soil and enhancement-materials decreased significantly the contact-resistance. The developed-mixture and wood-ash demonstrated highest water-content retention when compared against the other enhancement-materials. This maintains their resistivity values low to serve for grounding purpose. The wood-ash has the smallest grain–size diameter among the enhancement-materials. This is why it ensures effective contact between the soil and enhancement-materials in grounding systems. The effect of varying injected-current through the soil-box on the resistance values of soils and enhancement-materials is also investigated. Finally, the effectiveness of using of these materials in reducing the resistance-to-ground of a practical copper rod buried into desert soil is evaluated.
•Developed mixture from waste-materials has higher water-content during dehydration process.•Gray loamy proved to be perfect grounding soil in absence of grounding enhancement-materials (GEM).•Experimental verification of using the wood ash as interface-layer between the soil and the mixture.•Contact-resistance reduction by using the ash layer in sandy soil reached up to 33 %.•Resistance-to-ground reduction by using the mixture in sandy soil reach up to 47.6 %.
Background and Objectives: Optimal blood pressure control is achieved by medication adherence. This will reduce the risk of associated morbidities and mortalities. The present study aimed to ...determine medication adherence and its associated factors among hypertensive patients attending different primary health centers (PHC) in Abha, Saudi Arabia (KSA). Methods: A cross-sectional study was conducted among ten different PHCs in Abha, KSA. Simple random sampling procedure was utilized to choose 400 participants. A structured anonymous questionnaire was used in the present study. Analysis of the data was done using the SPSS program, version 23. A logistic regression statistical test was applied to identify the independent associated factors of medication adherence. Furthermore, we have applied Spearman's test to find the correlation between overall B-IPQ score and medication adherence score. Results: A total of 400 hypertensive patients responded in the present survey. More than one-third of the participants (36.3%) were in the high adherence category group, while the remaining participants (63.7%) were either low or medium adherence category. The binary logistic regression analysis revealed that low and medium adherence category is significantly associated with age (adjusted odds ratio AOR = 0.96, 95% CI =0.93-0.99, p = 0.021), married participants (AOR = 0.42, 95% CI =0.33-0.58, p = 0.001), residing at village (AOR = 1.49, 95% CI =1.14-1.73, p = 0.038), and participants with monthly family income of 5000 to 7000 SAR (AOR = 3.06, 95% CI =1.62-5.79, p = 0.001). A negligible positive correlation was revealed between illness perception and medication adherence. Conclusion: The present study revealed that hypertensive patients poorly adhere to their antihypertensive medications. This low adherence is significantly associated with the age, monthly income, people living in rural areas, and married participants. The present study results recommend sustained efforts to implement health education programs and awareness-raising interventions targeted at hypertensive patients. Keywords: medication adherence, hypertension, illness perception, primary health centers, Saudi Arabia
Thirunavukkarasu A, Naser Abdullah Alshahrani A, Mazen Abdel-Salam D, et al. Patient Prefer Adherence. 2022;16:2835-2844. The authors have advised the affiliation list on page 2835 is incorrect. The ...correct author list and affiliations are shown below. Ashokkumar Thirunavukkarasu,1 Abdullah Naser Abdullah Alshahrani,1,2 Doaa Mazen Abdel-Salam,3 Ahmad Homoud Al-Hazmi,1 Bashayer Farhan ALruwaili,1 Aseel Awad Alsaidan,1 Bayapa Reddy Narapureddy,4 Aliyah Muteb AL-Ruwaili,5 Fahad Ghuwayli aljabri,6 Rahaf Khalaf Albalawi,6 Khaled Abdulrahman F Alanazi6 1Department of Community and Family Medicine, College of Medicine, Jouf University, Sakaka, Saudi Arabia; 2Department of Public Health, Asir Health Affairs, Asir Region, Saudi Arabia; 3Department of Public Health and Community Medicine, Faculty of Medicine, Assiut University, Assiut, Egypt; 4Department of Public Health, College of Applied Medical Science, King Khalid University, Abha, Saudi Arabia; 5Department of Public Health, Ministry of Health, Jouf Health Affairs, Sakaka, Aljouf, Saudi Arabia; 6College of Medicine, Jouf University, Sakaka, Saudi Arabia This error was introduced by the Editorial staff during the publication process.
This paper is aimed at investigating the nitric oxide (NO) removal using dielectric barrier discharges (DBD) in a multi-rod reactor stressed by ac and pulse high voltages. The effects of various ...parameters (the voltage amplitude, frequency, gas flow rate, use of the γ-alumina pellets and the voltage type) on the discharge power and NO removal rate have been studied experimentally in the multi-rod DBD reactor. When the reactor was filled with γ-alumina pellets, improvement in NO removal rate was observed. The pulse voltage gives higher NO removal rate in comparison with ac voltage at the same energy density. Records of the discharge photograph and the emission intensity have been made at varying voltage amplitude, frequency, and gas flow rate. The records confirm the dependency of the discharge power on these parameters.
PDF
