load variation
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Author(s):  
Guzel Nikishina ◽  
Evgeny Denisov

The relaxation process of lithium batteries caused by load variation is considered. It is shown that such processes have strong dependence on internal physical and chemical processes and battery technical conditions. Theoretical expressions of the relaxation process caused by a step-like load variation have been obtained for 1st and 2nd order equivalent electrical circuits. The experimental investigations show that the obtained models fit the real relaxation processes and the behavior of the identified parameters could be explained by specific features of physical and chemical processes within the lithium battery. It should be noted that the obtained results can be generalized for a different type of electrochemical power source. The proposed approach makes it possible to provide means for electrochemical power source characterization and diagnostic, the main advantages of which are good time localization of measurement procedures and inexpensive apparatus implementation.


Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 86
Author(s):  
Kuang-Hsiung Tan ◽  
Faa-Jeng Lin ◽  
Tzu-Yu Tseng ◽  
Meng-Yang Li ◽  
Yih-Der Lee

Virtual synchronous generators (VSGs) with inertia characteristics are generally adopted for the control of distributed generators (DGs) in order to mimic a synchronous generator. However, since the amount of virtual inertia in VSG control is usually constant and given by trial and error, the real power and frequency oscillations of a battery energy storage system (BESS) occurring under load variation result in the degradation of the control performance of the DG. Thus, in this study, a novel virtual inertia estimation methodology is proposed to estimate suitable values of virtual inertia for VSGs and to suppress the real power output and frequency oscillations of the DG under load variation. In addition, to improve the function of the proposed virtual inertia estimator and the transient responses of the real power output and frequency of the DG, an online-trained Petri probabilistic wavelet fuzzy neural network (PPWFNN) controller is proposed to replace the proportional integral (PI) controller. The network structure and the online learning algorithm using backpropagation (BP) of the proposed PPWFNN are represented in detail. Finally, on the basis of the experimental results, it can be concluded that superior performance in terms of real power output and frequency response under load variation can be achieved by using the proposed virtual inertia estimator and the intelligent PPWFNN controller.


2021 ◽  
Vol 1 ◽  
pp. 1-None
Author(s):  
Alexis Bénard ◽  
Hélène Henri ◽  
Camille Noûs ◽  
Fabrice Vavre ◽  
Natacha Kremer

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Andi Arifudin ◽  
I Gede Wiratmaja ◽  
I Nyoman Pasek Nugraha

This study aimed to find the effect of variations in cooling load on the performance of the prototype trainer refrigerator, which in this refrigerator prototype had never been tested performance. In this study, the experimental method was used. The values sought in this study were the rate of room cooling and the Coefficient of Performance (COP). In this study, the variation of the cooling load used started from temperatures of 300C, 350C, 400C 450C, with 15 repetitions, and the temperature performance used was 1000C. The study results showed that the highest room cooling rate occurred at 300C cooling load variation, namely 0.00265, and the smallest room cooling rate occurred at 450C cooling load variation, namely 0.00174. The highest Coefficient of Performance (COP) results occurred at a cooling load variation of 450C, namely 34.09, and the lowest Coefficient of Performance (COP) occurred at a cooling load variation of 300C, namely 29.60. From these results, it can be concluded that the cooling rate of the room was inversely proportional to the increase in cooling load because the more significant the cooling load, the longer the time obtained, resulting in a small room cooling rate. And for the results of the Coefficient of Performance (COP), it was directly proportional to the increase in the cooling load because the more significant the cooling load given, the higher the temperature at T1 and T2, resulting in a significant Coefficient of Performance (COP).


Author(s):  
Oksana Dovgalyuk ◽  
Iryna Shcherbak ◽  
Yuliia Kovalova ◽  
Volodymyr Korobka

Improving the efficiency of regulating the parameters of distribution network modes is an actual task for the energy sector, requiring a detailed analysis of the nature of the total electrical load graphs of 10/0.4 kV transformer substations. The complexity of the problem in consideration is due to the fact that the load variation of transformer substations 10/0.4 kV in residential areas occurs randomly, due to the significant number, wide range and probabilistic nature of the operating modes of connected consumers, and the lack of deterministic links between consumers of electricity. The investigated function of total load of transformer substations 10/0.4 kV on a daily interval is non-stationary, in this connection there was a necessity of allocation of stationarity areas for adjusting the process of regulation of parameters of electrical network modes. In order to solve this problem, total load graphs for 10/0.4 kV transformer substations located in a residential area were constructed based on experimental measurements of active and reactive loads. The use of these dependencies made it possible to analyse the distribution law for the active and reactive power of the total load of 10/0.4 kV transformer substations, which change in time is stochastic characterised. The use of probabilistic-statistical modelling was justified to reliably describe the load variation process of 10/0.4 kV transformer substations. The hypothesis of a normal law distribution of the functions under consideration was confirmed and parametric tests were performed. Fisher's F-criterion was used to confirm the hypothesis of variance constancy, and Student's t-criterion was used to confirm the hypothesis of mathematical expectation constancy. Using the fact of constancy of dispersions and expectations of investigated mode parameters, autocorrelation coefficients of investigated random functions were determined and autocorrelation function graphs were plotted. In order to approximate the functions under investigation, the autocorrelation function coefficients were determined using the least-squares method, and an analysis of the attenuation of the autocorrelation function was carried out. The calculations carried out have highlighted the areas of stationarity on the total load curves of the 10/0.4 kV transformer substations. These stationarity plots can be used for further modelling of load graphs and the formation of control actions to adjust the load of consumer regulators in order to equalise the overall electrical load graph, as well as for voltage regulation facilities, which will contribute to the required modes of operation of the electricity distribution networks.


Author(s):  
Xin Li ◽  
Hongfu Zuo ◽  
Pengcheng Hao ◽  
Ya Su ◽  
Haoyue Liu ◽  
...  

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