scholarly journals Impact Evaluation of Grid-Connected PV Systems on PQ Parameters by Comparative Analysis based on Inferential Statistics

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1668 ◽  
Author(s):  
German Osma-Pinto ◽  
María García-Rodríguez ◽  
Jeisson Moreno-Vargas ◽  
Cesar Duarte-Gualdrón
Keyword(s):  
Low Voltage ◽  
Pv System ◽  
Pv Systems ◽  
Load Demand ◽  
Power Injection ◽  
Wilcoxon Rank Sum Test ◽  
Point Of Common Coupling ◽  
The Mean ◽  
The Impact

The intermittent injection of power and the nature of power electronic devices used for photovoltaic (PV) systems can affect the power quality (PQ) of the grid to which they are connected. This study proposes to quantify and evaluate the impact of PV injection on the PQ of a low-voltage (LV) network by applying a statistical analysis through hypothesis testing for the mean comparison of populations of parameters with and without a PV system. The effects of PV power injection and load demand at the point of common coupling on PQ are monitored. The methodology includes the selection and monitoring of PQ, the use of a matrix for classification of data with similar load and PV power injection conditions, and the application of the Wilcoxon rank sum test. This methodology was applied to evaluate the impact of a 9.8 kWp PV system on the PQ of an LV network.

scholarly journals Performance analysis of malaysian low voltage distribution network under different solar variability days

2019 ◽  
Vol 13 (3) ◽  
pp. 1152
Author(s):  
Nur Izzati Zolkifr ◽  
Chin Kim Gan ◽  
Meysam Shamsiri
Keyword(s):  
Low Voltage ◽  
Distribution Networks ◽  
Solar Variability ◽  
Pv System ◽  
Voltage Unbalance ◽  
Pv Systems ◽  
Network Losses ◽  
Pv Penetration ◽  
The Impact ◽  
Different Levels

<span>The widespread of Photovoltaic (PV) systems as one of the distributed generation technologies could have profound impact on the distribution networks operation, particularly on network losses and network voltages fluctuations. This is mainly caused by the high PV penetrations coupled with high solar variability in the countries with large cloud cover. Therefore, this paper presents an investigation on the impact of residential grid-connected PV system by utilizing a typical low voltage (LV) network in Malaysia under various solar variability days. In this study, there are three scenarios; where, each scenario were performed with different levels of PV penetration and five different solar variability days. The impacts of PV system allocation in different scenarios and various solar variability days are assessed in term of voltage unbalance and network losses. The results propose that Scenario 1: randomly allocation of PV systems across the LV network has the lowest voltage unbalance and network losses especially during overcast day</span>

Optimal Penetration of Photovoltaic Systems in Distribution Networks

2013 ◽  
Vol 479-480 ◽  
pp. 590-594
Author(s):  
Wei Lin Hsieh ◽  
Chia Hung Lin ◽  
Chao Shun Chen ◽  
Cheng Ting Hsu ◽  
Chin Ying Ho ◽  
...  
Keyword(s):  
Power Generation ◽  
Solar Energy ◽  
Voltage Control ◽  
Distribution Networks ◽  
Solar Irradiation ◽  
Total Power ◽  
Pv System ◽  
Pv Systems ◽  
Power Injection ◽  
Distribution Feeder

The penetration level of a PV system is often limited due to the violation of voltage variation introduced by the large intermittent power generation. This paper discusses the use of an active power curtailment strategy to reduce PV power injection during peak solar irradiation to prevent voltage violation so that the PV penetration level of a distribution feeder can be increased to fully utilize solar energy. When using the proposed voltage control scheme for limiting PV power injection into the study distribution feeder during high solar irradiation periods, the total power generation and total energy delivered by the PV system over a 1-year period are determined according to the annual duration of solar irradiation. With the proposed voltage control to perform the partial generation rejection of PV systems, the optimal installation capacity of PV systems can be determined by maximizing the net present value of the system so that better cost effectiveness of the PV project and better utilization of solar energy can be obtained.

scholarly journals The Technical Challenges Facing the Integration of Small-Scale and Large-scale PV Systems into the Grid: A Critical Review

Electronics ◽  
2019 ◽  
Vol 8 (12) ◽  
pp. 1443 ◽  
Author(s):  
Abdullah Alshahrani ◽  
Siddig Omer ◽  
Yuehong Su ◽  
Elamin Mohamed ◽  
Saleh Alotaibi
Keyword(s):  
Large Scale ◽  
Distribution Network ◽  
Small Scale ◽  
Energy Access ◽  
Solar Pv ◽  
Pv System ◽  
Pv Systems ◽  
Technical Challenges ◽  
Technical Solutions ◽  
The Impact

Decarbonisation, energy security and expanding energy access are the main driving forces behind the worldwide increasing attention in renewable energy. This paper focuses on the solar photovoltaic (PV) technology because, currently, it has the most attention in the energy sector due to the sharp drop in the solar PV system cost, which was one of the main barriers of PV large-scale deployment. Firstly, this paper extensively reviews the technical challenges, potential technical solutions and the research carried out in integrating high shares of small-scale PV systems into the distribution network of the grid in order to give a clearer picture of the impact since most of the PV systems installations were at small scales and connected into the distribution network. The paper reviews the localised technical challenges, grid stability challenges and technical solutions on integrating large-scale PV systems into the transmission network of the grid. In addition, the current practices for managing the variability of large-scale PV systems by the grid operators are discussed. Finally, this paper concludes by summarising the critical technical aspects facing the integration of the PV system depending on their size into the grid, in which it provides a strong point of reference and a useful framework for the researchers planning to exploit this field further on.

scholarly journals Time-Series PV Hosting Capacity Assessment with Storage Deployment

Energies ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2524 ◽  
Author(s):  
Magdalena Bartecka ◽  
Grazia Barchi ◽  
Józef Paska
Keyword(s):  
Time Series ◽  
Energy Storage ◽  
Low Voltage ◽  
Gaussian Mixture ◽  
Variable Load ◽  
Pv Systems ◽  
Voltage Deviation ◽  
Time Series Analyses ◽  
Capacity Selection ◽  
The Impact

Europe aims to diversify energy sources and reduce greenhouse gas emissions. On this field, large PV power growth is observed that may cause problems in existing networks. This paper examines the impact of distributed PV systems on voltage quality in a low voltage feeder in terms of the European standard EN 50160. As the standard defines allowable percentage of violation during one week period, time-series analyses are done to assess PV hosting capacity. The simulations are conducted with 10-minute step and comprise variable load profiles based on Gaussian Mixture Model and PV profiles based on a distribution with experimentally obtained parameters. In addition, the outcomes are compared with “snapshot” simulations. Next, it is examined how energy storage utilization affects the hosting capacity. Several deployments of energy storages are presented with different number and capacity. In particular, a greedy algorithm is proposed to determine the sub-optimal energy storage deployment based on the voltage deviation minimization. The simulations show that time-series analyses in comparison with snapshot analyses give completely different results and change the level of PV hosting capacity. Moreover, incorrect energy storage capacity selection and location may cause even deterioration of power quality in electrical systems with high RES penetration.

scholarly journals Radiomic Analysis of Contrast-Enhanced Mammography With Different Image Types: Classification of Breast Lesions

2021 ◽  
Vol 11 ◽  
Author(s):  
Simin Wang ◽  
Ning Mao ◽  
Shaofeng Duan ◽  
Qin Li ◽  
Ruimin Li ◽  
...  
Keyword(s):  
Operating Characteristic ◽  
Characteristic Curve ◽  
High Energy ◽  
Breast Lesions ◽  
Wilcoxon Rank Sum Test ◽  
Contrast Enhanced ◽  
Malignant Breast ◽  
The Mean ◽  
Selection Operator

Objective: A limited number of studies have focused on the radiomic analysis of contrast-enhanced mammography (CEM). We aimed to construct several radiomics-based models of CEM for classifying benign and malignant breast lesions.Materials and Methods: The retrospective, double-center study included women who underwent CEM between November 2013 and February 2020. Radiomic analysis was performed using high-energy (HE), low-energy (LE), and dual-energy subtraction (DES) images from CEM. Datasets were randomly divided into the training and testing sets at a ratio of 7:3. The maximum relevance minimum redundancy (mRMR) method and least absolute shrinkage and selection operator (LASSO) logistic regression were used to select the radiomic features and construct the best classification models. The performances of the models were assessed by the area under the receiver operating characteristic curve (AUC) with a 95% confidence interval (CI). Leave-group-out cross-validation (LGOCV) for 100 rounds was performed to obtain the mean AUCs, which were compared by the Wilcoxon rank-sum test and the Kruskal–Wallis rank-sum test.Results: A total of 192 women with 226 breast lesions (101 benign; 125 malignant) were enrolled. The median age was 48 years (range, 22–70 years). For the classification of breast lesions, the AUCs of the best models were 0.931 (95% CI: 0.873–0.989) for HE, 0.897 (95% CI: 0.807–0.981) for LE, 0.882 (95% CI: 0.825–0.987) for DES images and 0.960 (95% CI: 0.910–0.998) for all of the CEM images in the testing set. According to LGOCV, the models constructed with the HE images and all of the CEM images showed the highest mean AUCs for the training (0.931 and 0.938, respectively; P &lt; 0.05 for both) and testing sets (0.892 and 0.889, respectively; P = 0.55 for both), which were significantly higher than those of the two models constructed with the LE and DES images in the training (0.912 and 0.899, respectively; all P &lt; 0.05) and testing sets (0.866 and 0.862, respectively; all P &lt; 0.05).Conclusions: Radiomic analysis of CEM images was valuable for classifying benign and malignant breast lesions. The use of HE images or all three types of CEM images can achieve the best performance.

scholarly journals The Relation of Allergic Rhinitis Classification with IL-5 on The Aller-gic Rhinitis

2019 ◽  
Vol 2 (3) ◽  
pp. 123-127
Author(s):  
Ismayani
Keyword(s):  
Quality Of Life ◽  
Clinical Symptoms ◽  
Mean Value ◽  
P Value ◽  
Significant Relation ◽  
Cross Sectional ◽  
The Mean ◽  
The Impact

IL-5 is an important role cytokine on the RA. IL-5 has an important role on eosinophils. ARIA-WHO made classification of RA based on how long the clinical symptoms and the impact on quality of life. The aim of this study was to know the classification of RA with IL-5 on RA study. This study used a cross-sectional method with 39 samples. The examination of IL-5 used ELISA. The highest classification of RA was medium-severe persistent of 43.58% with the mean value IL-5 was 56.25 pg/ml. Based on the test of Kruskal Wallis, it was obtained p-value = 0.664. Conclusion: There was no significant relation between classification RA and IL-5.  

scholarly journals Analysis of Voltage Unbalance and Energy Loss in Residential Low Voltage Distribution Systems with Rooftop Photovoltaic Systems

2020 ◽  
Vol 190 ◽  
pp. 00033
Author(s):  
Rattanaprapa Charoenwattana ◽  
Umarin Sangpanich
Keyword(s):  
Energy Loss ◽  
Distribution Systems ◽  
Low Voltage ◽  
Energy Losses ◽  
Photovoltaic Systems ◽  
Housing Estate ◽  
Voltage Distribution ◽  
Pv System ◽  
Voltage Unbalance ◽  
Pv Systems

This paper investigates effects of voltage unbalance and energy losses due to the connection of rooftop photovoltaic systems in a low voltage distribution system of a housing estate, which has light loads during daytime. The paper presents a case study of a real distribution power system of housing estate in Thailand. Voltage unbalance and energy losses were simulated by using system characteristic and load data from GIS database of PEA with the DIgSILENT Power Factory program. The key findings of our analysis are as follows. Firstly, the number of installable 1-phase rooftop PV systems varies directly with load density. Secondly, the number of installed 1-phase rooftop PV systems can be increased if the installation locations are closer to the transformer. For 3-phase rooftop PV systems, their installations do not have any effects on the voltage unbalance. Furthermore, system energy loss relates to the load density and PV system installation locations in the same way as the voltage unbalance. The key implication of our study is that the installation of 1-phase rooftop PV system should be granted based on a careful consideration of the installation location and the load density.

scholarly journals Investigating the Impact of Shading Effect on the Characteristics of a Large-Scale Grid-Connected PV Power Plant in Northwest China

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Yunlin Sun ◽  
Siming Chen ◽  
Liying Xie ◽  
Ruijiang Hong ◽  
Hui Shen
Keyword(s):  
Power Distribution ◽  
Large Scale ◽  
Northwest China ◽  
Pv System ◽  
Shading Effect ◽  
Pv Systems ◽  
Large Scale Grid ◽  
Feasible Solutions ◽  
The Impact ◽  
Scale Grid

Northwest China is an ideal region for large-scale grid-connected PV system installation due to its abundant solar radiation and vast areas. For grid-connected PV systems in this region, one of the key issues is how to reduce the shading effect as much as possible to maximize their power generation. In this paper, a shading simulation model for PV modules is established and its reliability is verified under the standard testing condition (STC) in laboratory. Based on the investigation result of a 20 MWp grid-connected PV plant in northwest China, the typical shading phenomena are classified and analyzed individually, such as power distribution buildings shading and wire poles shading, plants and birds droppings shading, and front-row PV arrays shading. A series of experiments is also conducted on-site to evaluate and compare the impacts of different typical shading forms. Finally, some feasible solutions are proposed to avoid or reduce the shading effect of PV system during operation in such region.

scholarly journals Interconnection Impact Analysis of Solar Photovoltaic Systems with Distribution Networks

2021 ◽  
Author(s):  
◽  
Michael Emmanuel
Keyword(s):  
Power Flow ◽  
Impact Analysis ◽  
Distribution Network ◽  
Solar Pv ◽  
Electric Grid ◽  
Pv System ◽  
Pv Systems ◽  
Wide Range ◽  
Distribution Feeder ◽  
The Impact

<p>As the solar PV technology continues to evolve as the most common distributed generation (DG) coupled with increasing interconnection requests, accurate modelling of the potential operational impacts of this game-changer is pivotal in order to maintain the reliability of the electric grid. The overall goal of this research is to conduct an interconnection impact analysis of solar PV systems at increasing penetration levels subject to the feeder constraints within the distribution network. This is carried out with a time series power flow analysis method to capture the time-varying nature of solar PV and load with their interactions with the distribution network device operations. Also, this thesis analyses multiple PV systems scenarios and a wide range of possible impacts to enable distribution system planners and operators understand and characterize grid operations with the integration of PV systems.  An evaluation of the operational and reliability performance of a grid-connected PV system based on IEC standards and industry guides is performed to detect design failures and avoid unnecessary delays to PV penetration. The performance analysis metrics in this research allow cross-comparison between PV systems operating under different climatic conditions. This thesis shows the significant impact of temperature on the overall performance of the PV system. This research conducts an interconnection study for spatially distributed single-phase grid-tied PV systems with a five minute-resolution load and solar irradiance data on a typical distribution feeder. Also, this research compares the performance of generator models, PQ and P |V |, for connecting PV-DG with the distribution feeder with their respective computational costs for a converged power flow solution.  More so, a method capable of computing the incremental capacity additions, measuring risks and upgrade deferral provided by PV systems deployments is investigated in this research. This thesis proposes surrogate metrics, energy exceeding normal rating and unserved energy, for evaluating system reliability and capacity usage which can be a very useful visualization tool for utilities. Also, sensitivity analysis is performed for optimal location of the PV system on the distribution network. This is important because optimal integration of PV systems is often near-optimal for network capacity relief issues as well.  This thesis models the impact of centralized PV variability on the electric grid using the wavelet variability model (WVM) which considers the key factors that affect PV variability such as PV footprint, density and cloud movement over the entire PV plant. The upscaling advantage from a single module and point irradiance sensor to geographic smoothing over the entire PV footprint in WVM is used to simulate effects of a utility-interactive PV system on the distribution feeder.  Further, the PV interconnection scenarios presented in this thesis have been modelled with different time scales ranging from seconds to hours in order to accurately capture and represent various impacts. The analysis and advancements presented in this thesis will help utilities and other stakeholders to develop realistic projections of PV systems impacts on the grid. Also, this research will assist in understanding and full characterization of PV integration with the grid to avoid unnecessary delays.</p>

scholarly journals Low-Voltage Ride-Through Capability of a Single-Stage Single-Phase Photovoltaic System Connected to the Low-Voltage Grid

2013 ◽  
Vol 2013 ◽  
pp. 1-9 ◽  
Author(s):  
Yongheng Yang ◽  
Frede Blaabjerg
Keyword(s):  
Distribution System ◽  
Single Phase ◽  
Control Method ◽  
Low Voltage ◽  
Photovoltaic System ◽  
Pv System ◽  
Pv Systems ◽  
Low Voltage Ride Through ◽  
Three Phase ◽  
Future Challenges

The progressive growing of single-phase photovoltaic (PV) systems makes the Distribution System Operators (DSOs) update or revise the existing grid codes in order to guarantee the availability, quality, and reliability of the electrical system. It is expected that the future PV systems connected to the low-voltage grid will be more active with functionalities of low-voltage ride-through (LVRT) and the grid support capability, which is not the case today. In this paper, the operation principle is demonstrated for a single-phase grid-connected PV system in a low-voltage ride-through operation in order to map future challenges. The system is verified by simulations and experiments. Test results show that the proposed power control method is effective and the single-phase PV inverters connected to low-voltage networks are ready to provide grid support and ride-through voltage fault capability with a satisfactory performance based on the grid requirements for three-phase renewable energy systems.

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