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Keywords = reactive power (Q) support

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32 pages, 10857 KiB  
Article
Improved Fault Resilience of GFM-GFL Converters in Ultra-Weak Grids Using Active Disturbance Rejection Control and Virtual Inertia Control
by Monigaa Nagaboopathy, Kumudini Devi Raguru Pandu, Ashmitha Selvaraj and Anbuselvi Shanmugam Velu
Sustainability 2025, 17(14), 6619; https://doi.org/10.3390/su17146619 - 20 Jul 2025
Viewed by 374
Abstract
Enhancing the resilience of renewable energy systems in ultra-weak grids is crucial for promoting sustainable energy adoption and ensuring a reliable power supply during disturbances. Ultra-weak grids characterized by a very low Short-Circuit Ratio, less than 2, and high grid impedance significantly impair [...] Read more.
Enhancing the resilience of renewable energy systems in ultra-weak grids is crucial for promoting sustainable energy adoption and ensuring a reliable power supply during disturbances. Ultra-weak grids characterized by a very low Short-Circuit Ratio, less than 2, and high grid impedance significantly impair voltage and frequency stability, imposing challenging conditions for Inverter-Based Resources. To address these challenges, this paper considers a 110 KVA, three-phase, two-level Voltage Source Converter, interfacing a 700 V DC link to a 415 V AC ultra-weak grid. X/R = 1 is controlled using Sinusoidal Pulse Width Modulation, where the Grid-Connected Converter operates in Grid-Forming Mode to maintain voltage and frequency stability under a steady state. During symmetrical and asymmetrical faults, the converter transitions to Grid-Following mode with current control to safely limit fault currents and protect the system integrity. After fault clearance, the system seamlessly reverts to Grid-Forming Mode to resume voltage regulation. This paper proposes an improved control strategy that integrates voltage feedforward reactive power support and virtual capacitor-based virtual inertia using Active Disturbance Rejection Control, a robust, model-independent controller, which rapidly rejects disturbances by regulating d and q-axes currents. To test the practicality of the proposed system, real-time implementation is carried out using the OPAL-RT OP4610 platform, and the results are experimentally validated. The results demonstrate improved fault current limitation and enhanced DC link voltage stability compared to a conventional PI controller, validating the system’s robust Fault Ride-Through performance under ultra-weak grid conditions. Full article
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23 pages, 20707 KiB  
Article
Research on Energy Storage-Based DSTATCOM for Integrated Power Quality Enhancement and Active Voltage Support
by Peng Wang, Jianxin Bi, Fuchun Li, Chunfeng Liu, Yuanhui Sun, Wenhuan Cheng, Yilong Wang and Wei Kang
Electronics 2025, 14(14), 2840; https://doi.org/10.3390/electronics14142840 - 15 Jul 2025
Viewed by 265
Abstract
With the increasing penetration of distributed generation and the diversification of electrical equipment, distribution networks face issues like three-phase unbalance and harmonic currents, while the voltage stability and inertia of the grid-connected system also decrease. A certain amount of energy storage is needed [...] Read more.
With the increasing penetration of distributed generation and the diversification of electrical equipment, distribution networks face issues like three-phase unbalance and harmonic currents, while the voltage stability and inertia of the grid-connected system also decrease. A certain amount of energy storage is needed in a Distribution Static Synchronous Compensator (DSTATCOM) to manage power quality and actively support voltage and inertia in the network. This paper first addresses the limitations of traditional dq0 compensation algorithms in effectively filtering out negative-sequence twice-frequency components. An improved dq0 compensation algorithm is proposed to reduce errors in detecting positive-sequence fundamental current under unbalanced three-phase conditions. Second, considering the impedance ratio characteristics of the distribution network, while reactive power voltage regulation is common, active power regulation is more effective in high-resistance distribution networks. A grid-forming model-based active and reactive power coordinated voltage regulation method is proposed. This method uses synchronous control to establish a virtual three-phase voltage internal electromotive force, forming a comprehensive compensation strategy that combines power quality improvement and active voltage support, exploring the potential of energy storage DSTATCOM applications in distribution networks. Finally, simulation and experimental results demonstrate the effectiveness of the proposed control method. Full article
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25 pages, 10850 KiB  
Review
Effective Methods for Determination of Electrical System Power Components at Transient and Steady States
by Branislav Dobrucký, Slavomír Kaščák and Jozef Šedo
Energies 2025, 18(4), 779; https://doi.org/10.3390/en18040779 - 7 Feb 2025
Viewed by 607
Abstract
This review paper describes and compares the practical methods that make it possible to calculate an average value of apparent, active, and reactive (i.e., blind and distorted) power in each calculation step. In addition to two methods, pq and [...] Read more.
This review paper describes and compares the practical methods that make it possible to calculate an average value of apparent, active, and reactive (i.e., blind and distorted) power in each calculation step. In addition to two methods, pq and ipiq, it deals with the application of the idiq method for determining power components’ mean values in a discrete step. The results are important and needed for the right dimensioning and sizing of power electronic and electrical systems (PEESs), which those power components produce. This is because the integral calculation for the mean values of the product of voltage u(t) and current i(t) always gives a value lower than the actual value of the apparent power. Using moving average and moving root mean square (rms) techniques (or digital filtering), one obtains the right values, although with a time delay. Using sliding filtering, these techniques calculate the average or rms values, respectively, of the power components in each step k. By calculating the moving average value of the power components in both transient and steady states (on/off as well), we achieve the correct design of the system. The transients for the three- and single-phase power electronic systems are modeled, simulated, and theoretically supported in this study. Any PEES can be determined and sized using the calculated data. The real-time HW simulator Plecs RT Box 1 and Matlab/Simulink 2024a simulations validate the comprehensive time waveform produced by the suggested method. Full article
(This article belongs to the Special Issue Energy, Electrical and Power Engineering: 3rd Edition)
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19 pages, 8204 KiB  
Article
Transient Synchronous Stability Analysis of Grid-Forming Photovoltaic Grid-Connected Inverters during Asymmetrical Grid Faults
by Wenwen He, Jun Yao, Hao Xu, Qinmin Zhong, Ruilin Xu, Yuming Liu and Xiaoju Li
Energies 2024, 17(6), 1399; https://doi.org/10.3390/en17061399 - 14 Mar 2024
Cited by 5 | Viewed by 1760
Abstract
Compared with the traditional grid-following photovoltaic grid-connected converter (GFL-PGC), the grid-forming photovoltaic grid-connected converter (GFM-PGC) can provide voltage and frequency support for power systems, which can effectively enhance the stability of power electronic power systems. Consequently, GFM-PGCs have attracted great attention in recent [...] Read more.
Compared with the traditional grid-following photovoltaic grid-connected converter (GFL-PGC), the grid-forming photovoltaic grid-connected converter (GFM-PGC) can provide voltage and frequency support for power systems, which can effectively enhance the stability of power electronic power systems. Consequently, GFM-PGCs have attracted great attention in recent years. When an asymmetrical short-circuit fault occurs in the power grid, GFM-PGC systems may experience transient instability, which has been less studied so far. In this paper, a GFM-PGC system is investigated under asymmetrical short-circuit fault conditions. A novel Q-V droop control structure is proposed by improving the traditional droop control. The proposed control structure enables the system to accurately control the positive- and negative-sequence reactive current without switching the control strategy during the low-voltage ride-through (LVRT) period so that it can meet the requirements of the renewable energy grid code. In addition, a dual-loop control structure model of positive- and negative-sequence voltage and current is established for the GFM-PGC system under asymmetrical short-circuit fault conditions. Based on the symmetrical component method, the composite sequence network of the system is obtained under asymmetrical short-circuit fault conditions, and positive- and negative-sequence power-angle characteristic curves are analyzed. The influence law of system parameters on the transient synchronous stability of positive- and negative-sequence systems is quantitatively analyzed through the equal area criterion. Finally, the correctness of the theoretical analysis is verified by simulation and hardware-in-the-loop experiments. Full article
(This article belongs to the Special Issue Grid-Forming Technologies for Renewable Energy Integration)
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24 pages, 9525 KiB  
Article
Time Series Optimization-Based Characteristic Curve Calculation for Local Reactive Power Control Using Pandapower-PowerModels Interface
by Zheng Liu, Maryam Majidi, Haonan Wang, Denis Mende and Martin Braun
Energies 2023, 16(11), 4385; https://doi.org/10.3390/en16114385 - 29 May 2023
Cited by 3 | Viewed by 2821
Abstract
Local reactive power control in distribution grids with a high penetration of distributed energy resources (DERs) will be essential in future power system operation. Appropriate control characteristic curves for DERs support stable and efficient distribution grid operation. However, the current practice is to [...] Read more.
Local reactive power control in distribution grids with a high penetration of distributed energy resources (DERs) will be essential in future power system operation. Appropriate control characteristic curves for DERs support stable and efficient distribution grid operation. However, the current practice is to configure local controllers collectively with constant characteristic curves that may not be efficient for volatile grid conditions or the desired targets of grid operators. To address this issue, this paper proposes a time series optimization-based method to calculate control parameters, which enables each DER to be independently controlled by an exclusive characteristic curve for optimizing its reactive power provision. To realize time series reactive power optimizations, the open-source tools pandapower and PowerModels are interconnected functionally. Based on the optimization results, Q(V)- and Q(P)-characteristic curves can be individually calculated using linear decision tree regression to support voltage stability, provide reactive power flexibility and potentially reduce grid losses and component loadings. In this paper, the newly calculated characteristic curves are applied in two representative case studies, and the results demonstrate that the proposed method outperforms the reference methods suggested by grid codes. Full article
(This article belongs to the Special Issue Control of Renewable Energy Sources in Power Systems and Smart Grids)
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15 pages, 370 KiB  
Article
Assessment of Antioxidant Stability of Meat Pâté with Allium cepa Husk Extract
by Irina Chernukha, Nadezhda Kupaeva, Daniil Khvostov, Yuliya Bogdanova, Jutta Smirnova and Elena Kotenkova
Antioxidants 2023, 12(5), 1103; https://doi.org/10.3390/antiox12051103 - 16 May 2023
Cited by 5 | Viewed by 2237
Abstract
Antioxidants play a very important role in the food industry. Recently, both science and industry have shown substantial preference for natural antioxidants, including searching for antioxidant substances from natural sources without undesirable side effects. The purpose of this study was to evaluate the [...] Read more.
Antioxidants play a very important role in the food industry. Recently, both science and industry have shown substantial preference for natural antioxidants, including searching for antioxidant substances from natural sources without undesirable side effects. The purpose of this study was to evaluate the effect of adding Allium cepa husk extract at a volume of 68 or 34 μL/g of unsalted blanched materials to replace 34% and 17% of the beef broth, respectively, which corresponded to a total antioxidant capacity (TAC) of 44.4 or 22.2 μmol-equiv. Q/100 g meat pté (i.e., 13.42 or 6.71 mg of quercetin/100 g meat pté), on the quality and safety indicators of the developed meat pté. The TAC according to a ferric reducing antioxidant power assay, thiobarbituric acid reactive substances, and physicochemical and microbiological characteristics were determined during the storage of the meat pté. Proximal and UPLC-ESI-Q-TOF-MS analyses were also performed. The addition of yellow onion husk ethanolic extract to the meat pté at both volumes allowed the maintenance of an increased content of antioxidants, which contributed to a decrease in the generation of secondary products of lipid peroxidation for 14 days of storage at 4 C. The results of the microbiological analyses showed that the developed meat ptés were safe according to all indicators of microbial spoilage within 10 days of production. The results supported the use of yellow onion husk extract in the food industry to contribute to improving the functionality of meat products, developing products for a healthy lifestyle, and providing clean-label foods without or with a minimal content of synthetic additives. Full article
(This article belongs to the Special Issue Antioxidants in Food, Food Waste, and By-Product)
15 pages, 5509 KiB  
Article
Utilization of Electric Vehicle Grid Integration System for Power Grid Ancillary Services
by Himadry Shekhar Das, Md Nurunnabi, Mohamed Salem, Shuhui Li and Mohammad Mominur Rahman
Energies 2022, 15(22), 8623; https://doi.org/10.3390/en15228623 - 17 Nov 2022
Cited by 17 | Viewed by 2243
Abstract
Electric vehicle grid integration (EVGI) is one of the most important parts of transportation electrification. However, large-scale EV charging/discharging can have an adverse effect on the distribution grid, due to a large amount of load being drawn from or fed back to the [...] Read more.
Electric vehicle grid integration (EVGI) is one of the most important parts of transportation electrification. However, large-scale EV charging/discharging can have an adverse effect on the distribution grid, due to a large amount of load being drawn from or fed back to the power grid. Additionally, the power electronics used in the grid interaction may impose additional complications, such as voltage and frequency deviation, harmonic distortion, etc. With proper control scheme designs for the grid-connected inverters, such complications can be mitigated, and several grid ancillary services, such as voltage and frequency support, reactive power support, and harmonic mitigation, can be facilitated from large-scale EVGI. In this study, a large-scale EVGI system is developed where the vector control implementation of a grid-connected inverter in the d-q reference frame is presented for providing different grid ancillary services using the EVGI system. The EVGI system is operated in different control modes to ensure multiple ancillary services of the power grid. The study is supported by the electromagnetic transient simulation performed in Matlab/Simulink of a large-scale EVGI system. The simulation shows that with the proper control mechanism of grid-connected inverters, EVGI can be used to provide several useful grid ancillary services. Full article
(This article belongs to the Section F: Electrical Engineering)
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22 pages, 10525 KiB  
Article
Finite-Control-Set Model Predictive Control for Low-Voltage-Ride-Through Enhancement of PMSG Based Wind Energy Grid Connection Systems
by Syed Wajahat Ali, Anant Kumar Verma, Yacine Terriche, Muhammad Sadiq, Chun-Lien Su, Chung-Hong Lee and Mahmoud Elsisi
Mathematics 2022, 10(22), 4266; https://doi.org/10.3390/math10224266 - 15 Nov 2022
Cited by 16 | Viewed by 2691
Abstract
Grid faults are found to be one of the major issues in renewable energy systems, particularly in wind energy conversion systems (WECS) connected to the grid via back-to-back (BTB) converters. Under such faulty grid conditions, the system requires an effective regulation of the [...] Read more.
Grid faults are found to be one of the major issues in renewable energy systems, particularly in wind energy conversion systems (WECS) connected to the grid via back-to-back (BTB) converters. Under such faulty grid conditions, the system requires an effective regulation of the active (P) and reactive (Q) power to accomplish low voltage ride through (LVRT) operation in accordance with the grid codes. In this paper, an improved finite-control-set model predictive control (FCS-MPC) scheme is proposed for a PMSG based WECS to achieve LVRT ability under symmetrical and asymmetrical grid faults, including mitigation of DC-link voltage fluctuation. With proposed predictive control, optimized switching states for cost function minimization with weighing factor (WF) selection guidelines are established for robust BTB converter control and reduced cross-coupling amid P and Q during transient conditions. Besides, grid voltage support is provided by grid side inverter control to inject reactive power during voltage dips. The effectiveness of the FCS-MPC method is compared with the conventional proportional-integral (PI) controller in case of symmetrical and asymmetrical grid faults. The simulation and experimental results endorse the superiority of the developed FCS-MPC scheme to diminish the fault effect quickly with lower overshoot and better damping performance than the traditional controller. Full article
(This article belongs to the Special Issue Dynamic Modeling and Simulation for Control Systems)
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21 pages, 5238 KiB  
Article
Linear Sensitivity Modelling Useful for Voltage Control Analysis Using Power Injections from DER
by Ulises D. Lubo-Matallana, Miguel Ángel Zorrozua and José Félix Miñambres
Energies 2021, 14(16), 4749; https://doi.org/10.3390/en14164749 - 4 Aug 2021
Viewed by 2611
Abstract
The injection of apparent power to self-consumption buses generates voltage variations during network operation, which, when properly monitored, could support voltage regulation and control. In this paper, we propose a linear sensitivity modelling, quite useful for studies of voltage regulation with distributed energy [...] Read more.
The injection of apparent power to self-consumption buses generates voltage variations during network operation, which, when properly monitored, could support voltage regulation and control. In this paper, we propose a linear sensitivity modelling, quite useful for studies of voltage regulation with distributed energy resources (DER). This modelling consists of two analytical improvement steps: first, a full formulation for the voltage deviations, and second, the influence of line capacitance as Q-injections at the points of common couplings (PCCs). Our proposal is based on the linear topological sensitivity of an existing network (as a function of the line parameters X, R, and Bc), branch power flow (active–reactive power (P-Q)), and power injections at the PCCs. Here, the linear sensitivity algorithm is applied to a modified IEEE 33-bus distribution system to demonstrate its extended effectiveness to voltage monitoring and control scenarios. Its application estimates and compensates in a better way the voltage deviations with regard to the operating desired voltage (|V|op) constraints, using distributed power injections at the PCCs. Numerical results always showed a curtailment of the relative error against common simplifications of the electrical modelling in steady-state, thus simulating two critical scenarios of operation production–consumption for the existing system response. The proposed algorithm was validated considering as reference the voltage profile outputs of the load flow analysis, using the Newton–Raphson method via DIgSILENT, in terms of its accuracy, silhouette shape along the feeder and with regard to the application of reactive compensation as an analytical case study for voltage improvement in active distribution networks. Full article
(This article belongs to the Special Issue Distribution Grids Modernization II)
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36 pages, 5196 KiB  
Concept Paper
Ancillary Services Offered by Distributed Renewable Energy Sources at the Distribution Grid Level: An Attempt at Proper Definition and Quantification
by Charis S. Demoulias, Kyriaki-Nefeli D. Malamaki, Spyros Gkavanoudis, Juan Manuel Mauricio, Georgios C. Kryonidis, Konstantinos O. Oureilidis, Eleftherios O. Kontis and Jose Luis Martinez Ramos
Appl. Sci. 2020, 10(20), 7106; https://doi.org/10.3390/app10207106 - 13 Oct 2020
Cited by 35 | Viewed by 6023
Abstract
The gradual displacement of synchronous generators driven by conventional power plants, due to the increasing penetration of distributed renewable energy sources (DRES) in distribution grids, is creating a shortage of crucial ancillary services (AS) which are vital for the frequency and voltage stability [...] Read more.
The gradual displacement of synchronous generators driven by conventional power plants, due to the increasing penetration of distributed renewable energy sources (DRES) in distribution grids, is creating a shortage of crucial ancillary services (AS) which are vital for the frequency and voltage stability of the grid. These AS, and some new ones, could now be offered by the DRES, particularly those that are converter interfaced, in a coordinated way in order to preserve the grid stability and resilience. Although recent standards and grid codes specify that the DRES exhibit some system support functions, there are no specifications on how to measure and quantify (M & Q) them both at DRES level and in aggregated form. The M & Q of AS is crucial, since it would allow the AS to be treated as tradable AS in the current and future AS markets. This paper attempts to define a number of AS that can be offered by converter-interfaced DRES and suggests methods for their M & Q. The new AS addressed are: (1) inertial response; (2) primary frequency response; (3) active power smoothing (ramp-rate limitation); (4) exchange of reactive power for voltage regulation; (5) fault-ride-through (FRT) and contribution to fault clearing; (6) voltage harmonic mitigation. Additionally, a rough estimation of the additional investment and operational cost, as well as the financial benefits associated with each AS is provided in order to form the basis for the development of business models around each AS in the near future. Full article
(This article belongs to the Special Issue Advances in Ancillary Services by DRES in Distribution Grids)
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15 pages, 936 KiB  
Article
Direct Power Compensation in AC Distribution Networks with SCES Systems via PI-PBC Approach
by Walter Gil-González, Federico Martin Serra, Oscar Danilo Montoya, Carlos Alberto Ramírez and César Orozco-Henao
Symmetry 2020, 12(4), 666; https://doi.org/10.3390/sym12040666 - 23 Apr 2020
Cited by 10 | Viewed by 3202
Abstract
Here, we explore the possibility of employing proportional-integral passivity-based control (PI-PBC) to support active and reactive power in alternating current (AC) distribution networks by using a supercapacitor energy storage system. A direct power control approach is proposed by taking advantage of the Park’s [...] Read more.
Here, we explore the possibility of employing proportional-integral passivity-based control (PI-PBC) to support active and reactive power in alternating current (AC) distribution networks by using a supercapacitor energy storage system. A direct power control approach is proposed by taking advantage of the Park’s reference frame transform direct and quadrature currents ( i d and i q ) into active and reactive powers (p and q). Based on the open-loop Hamiltonian model of the system, we propose a closed-loop PI-PBC controller that takes advantage of Lyapunov’s stability to design a global tracking controller. Numerical simulations in MATLAB/Simulink demonstrate the efficiency and robustness of the proposed controller, especially for parametric uncertainties. Full article
(This article belongs to the Special Issue Symmetry in Renewable Energy and Power Systems)
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19 pages, 1813 KiB  
Article
Predicting Water Cycle Characteristics from Percolation Theory and Observational Data
by Allen Hunt, Boris Faybishenko, Behzad Ghanbarian, Markus Egli and Fang Yu
Int. J. Environ. Res. Public Health 2020, 17(3), 734; https://doi.org/10.3390/ijerph17030734 - 23 Jan 2020
Cited by 14 | Viewed by 4075
Abstract
The fate of water and water-soluble toxic wastes in the subsurface is of high importance for many scientific and practical applications. Although solute transport is proportional to water flow rates, theoretical and experimental studies show that heavy-tailed (power-law) solute transport distribution can cause [...] Read more.
The fate of water and water-soluble toxic wastes in the subsurface is of high importance for many scientific and practical applications. Although solute transport is proportional to water flow rates, theoretical and experimental studies show that heavy-tailed (power-law) solute transport distribution can cause chemical transport retardation, prolonging clean-up time-scales greatly. However, no consensus exists as to the physical basis of such transport laws. In percolation theory, the scaling behavior of such transport rarely relates to specific medium characteristics, but strongly to the dimensionality of the connectivity of the flow paths (for example, two- or three-dimensional, as in fractured-porous media or heterogeneous sediments), as well as to the saturation characteristics (i.e., wetting, drying, and entrapped air). In accordance with the proposed relevance of percolation models of solute transport to environmental clean-up, these predictions also prove relevant to transport-limited chemical weathering and soil formation, where the heavy-tailed distributions slow chemical weathering over time. The predictions of percolation theory have been tested in laboratory and field experiments on reactive solute transport, chemical weathering, and soil formation and found accurate. Recently, this theoretical framework has also been applied to the water partitioning at the Earth’s surface between evapotranspiration, ET, and run-off, Q, known as the water balance. A well-known phenomenological model by Budyko addressed the relationship between the ratio of the actual evapotranspiration (ET) and precipitation, ET/P, versus the aridity index, ET0/P, with P being the precipitation and ET0 being the potential evapotranspiration. Existing work was able to predict the global fractions of P represented by Q and ET through an optimization of plant productivity, in which downward water fluxes affect soil depth, and upward fluxes plant growth. In the present work, based likewise on the concepts of percolation theory, we extend Budyko’s model, and address the partitioning of run-off Q into its surface and subsurface components, as well as the contribution of interception to ET. Using various published data sources on the magnitudes of interception and information regarding the partitioning of Q, we address the variability in ET resulting from these processes. The global success of this prediction demonstrated here provides additional support for the universal applicability of percolation theory for solute transport as well as guidance in predicting the component of subsurface run-off, important for predicting natural flow rates through contaminated aquifers. Full article
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16 pages, 1202 KiB  
Article
Protective Effect of Dietary Taurine from ROS Production in European Seabass under Conditions of Forced Swimming
by Chiara Ceccotti, Basim S.A. Al-Sulaivany, Omar A.M. Al-Habbib, Marco Saroglia, Simona Rimoldi and Genciana Terova
Animals 2019, 9(9), 607; https://doi.org/10.3390/ani9090607 - 26 Aug 2019
Cited by 25 | Viewed by 4389
Abstract
Taurine (Tau) is an amino sulfonic acid, which is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and few others. In the aquafeed industry, Tau is mainly used as a feed additive [...] Read more.
Taurine (Tau) is an amino sulfonic acid, which is widely distributed in animal tissues, whereas it is almost lacking in plants with the exception of certain algae, seaweeds, and few others. In the aquafeed industry, Tau is mainly used as a feed additive to promote growth in marine fish species with limited cysteine sulfinate decarboxylase activity. In particular, Tau supplementation is required in feeds in which fishmeal (FM) is substituted with high percentages of plant-derived protein sources such as soybean meals (SBM) that have much lower levels of Tau than FM. In addition to being a growth promoter, Tau exert powerful antioxidant properties being a scavenger of the reactive oxygen species (ROS). Under sustained swimming conditions, an intracellular increase in ROS production can occur in fish red muscle where the abundance of mitochondria (the main site of ROS formation) is high. Accordingly, this study aimed at investigating the effects of dietary Tau on European seabass (Dicentrarchus labrax) growth and oxidative stress response induced by swimming exercise. Individually tagged fish of 92.57 ± 20.33 g mean initial weight were fed two experimental diets containing the same low percentage of FM and high percentage of SBM. One diet was supplemented with 1.5% of Tau. Tau supplemented in the diet had a positive effect on fish growth, and enhanced swimming performance and antioxidant status. Two swim endurance tests were performed during the feeding trial. Metabolic oxygen consumption (MO2) was measured during exercise at incremental swimming speeds (0.7, 1.4, 2.1, 2.8, 3.5, and then 4.2 BL (body length) s−1, until fatigue). Fish maximal sustainable swimming speed (Ucrit) was determined too. To investigate the antioxidant effect of dietary Tau, we also measured ROS production in fish blood by RBA (respiratory burst activity) assay and quantified the expression of genes coding for antioxidant enzymes by qPCR (quantitative polymerase chain reaction) , such as SOD (superoxide dismutase), GPX (glutathione peroxidase), and CAT (catalase) in red muscle and liver. There was a significant effect of Tau upon Ucrit during exercise. Additionally, ROS production was significantly lower in fish fed with Tau supplemented diet, supporting the role of Tau as ROS scavenger. The protective effect of Tau against oxidative stress induced by forced swimming was denoted also by a significant decrease in antioxidant enzymes gene expression in fish liver and muscle. Taken together these results demonstrate that Tau is beneficial in low FM-based diets for seabass. Full article
(This article belongs to the Section Aquatic Animals)
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19 pages, 8118 KiB  
Article
Coordinated Control for Large-Scale Wind Farms with LCC-HVDC Integration
by Xiuqiang He, Hua Geng, Geng Yang and Xin Zou
Energies 2018, 11(9), 2207; https://doi.org/10.3390/en11092207 - 23 Aug 2018
Cited by 5 | Viewed by 3132
Abstract
Wind farms (WFs) controlled with conventional vector control (VC) algorithms cannot be directly integrated to the power grid through line commutated rectifier (LCR)-based high voltage direct current (HVDC) transmission due to the lack of voltage support at its sending-end bus. This paper proposes [...] Read more.
Wind farms (WFs) controlled with conventional vector control (VC) algorithms cannot be directly integrated to the power grid through line commutated rectifier (LCR)-based high voltage direct current (HVDC) transmission due to the lack of voltage support at its sending-end bus. This paper proposes a novel coordinated control scheme for WFs with LCC-HVDC integration. The scheme comprises two key sub-control loops, referred to as the reactive power-based frequency (Q-f) control loop and the active power-based voltage (P-V) control loop, respectively. The Q-f control, applied to the voltage sources inverters in the WFs, maintains the system frequency and compensates the reactive power for the LCR of HVDC, whereas the P-V control, applied to the LCR, maintains the sending-end bus voltage and achieves the active power balance of the system. Phase-plane analysis and small-signal analysis are performed to evaluate the stability of the system and facilitate the controller parameter design. Simulations performed on PSCAD/EMTDC verify the proposed control scheme. Full article
(This article belongs to the Special Issue Power Quality in Microgrids Based on Distributed Generators)
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11 pages, 18658 KiB  
Article
Photovoltaic-STATCOM with Low Voltage Ride through Strategy and Power Quality Enhancement in a Grid Integrated Wind-PV System
by Lakshman Naik Popavath and Palanisamy Kaliannan
Electronics 2018, 7(4), 51; https://doi.org/10.3390/electronics7040051 - 12 Apr 2018
Cited by 53 | Viewed by 9548
Abstract
The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind), resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the [...] Read more.
The traditional configurations of power systems are changing due to the greater penetration of renewable energy sources (solar and wind), resulting in reliability issues. At present, the most severe power quality problems in distribution systems are current harmonics, reactive power demands, and the islanding of renewables caused by severe voltage variations (voltage sag and swell). Current harmonics and voltage sag strongly affect the performance of renewable-based power systems. Various conventional methods (passive filters, capacitor bank, and UPS) are not able to mitigate harmonics and voltage sag completely. Based on several studies, custom power devices can mitigate harmonics completely and slightly mitigate voltage sags with reactive power supplies. To ensure the generating units remain grid-connected during voltage sags and to improve system operation during abnormal conditions, efficient and reliable utilization of PV solar farm inverter as STATCOMs is needed. This paper elaborates the dynamic performance of a VSC-based PV-STATCOM for power quality enhancement in a grid integrated system and low voltage ride through (LVRT) capability. LVRT requirements suggest that the injection of real and reactive power supports grid voltage during abnormal grid conditions. The proposed strategy was demonstrated with MATLAB simulations. Full article
(This article belongs to the Special Issue Grid Connected Photovoltaic Systems)
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