Recloser-based decentralized control of the grid with distributed generation in the Lahsh district of the Rasht grid in Tajikistan, central Asia

Small-scale power generation based on renewable energy sources is gaining popularity in distribution grids, creating new challenges for power system control. At the same time, remote consumers with their own small-scale generation still have low reliability of power supply and poor power quality, due to the lack of proper technology for grid control when the main power supply is lost. Today, there is a global trend in the transition from a power supply with centralized control to a decentralized one, which has led to the Microgrid concept. A microgrid is an intelligent automated system that can reconfigure by itself, maintain the power balance, and distribute power flows. The main purpose of this paper is to study the method of control using reclosers in the Lahsh district of the Rasht grid in Tajikistan with distributed small generation. Based on modified reclosers, a method of decentralized synchronization and restoration of the grid normal operation after the loss of the main power source was proposed. In order to assess the stable operation of small hydropower plants under disturbances, the transients caused by proactive automatic islanding (PAI) and restoration of the interconnection between the microgrid and the main grid are shown. Rustab software, as one of the multifunctional software applications in the field of power systems transients study, was used for simulation purposes. Based on the simulation results, it can be concluded that under disturbances, the proposed method had a positive effect on the stability of small hydropower plants, which are owned and dispatched by the Rasht grid. Moreover, the proposed method sufficiently ensures the quality of the supplied power and improves the reliability of power supply in the Lahsh district of Tajikistan. © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).Chinese Academy of Sciences, CAS: XDA20060303National Natural Science Foundation of China, NSFC: 41761144079Y848041Ministry of National Infrastructure, Energy and Water ResourcesFunding: This research was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road (Grant No. XDA20060303), the International Cooperation Project of the National Natural Science Foundation of China (Grant No. 41761144079), the Xinjiang Tianchi Hundred Talents Program (Grant No. Y848041), and the project of the Research Center of Ecology and Environment in Central Asia (Grant No. Y934031).Acknowledgments: The authors are thankful to the Ministry of Energy and Water Resources of the Republic of Tajikistan and the Rasht electric networks OJSHC “Barqi Tojik” for providing the data for this research work

Estimation of the operational characteristics and determination parameters of the vertical radial-axial hydraulic turbine type 400

The operational characteristic of the hydraulic turbine is an important document with the help of which would be carried out the control over the correct operation of a hydraulic turbine at a hydroelectric power station. This article presents the calculation of operational characteristic and determination of parameters of the vertical radial-axial hydraulic turbine (Francis turbine) for high heads type 400-500. In this study, the multiple mathematics used in computer which was written in Fortran language. We designed the operational characteristic and calculated the flow part of the runner. In addition, we determined the synchronous frequency of rotation of the hydraulic turbine with a one-dimensional method. The purpose of this work is to analyze the spatial structure of the flow in high-pressure hydraulic Francis turbines of the 400-500 types. Results of this computational and designing analysis can be useful for researchers to apply the present approach to calculate the operational characteristics and the parameters of the high-pressure hydraulic turbines. © Published under licence by IOP Publishing Ltd

Comparison of Mathematical Methods for Compensating a Current Signal Under Current Transformers Saturation Conditions

Current measurements from electromagnetic current transformers are essential for the construction of secondary circuit systems, including for protection systems. Magnetic core of these transformers are at risk of saturation, as a result of which maloperation of protection algorithms can possibly occur. The paper considers methods for recovering a current signal in the saturation mode of current transformers. The advantages and disadvantages of methods for detecting the occurrence of current transformers core saturation are described. A comparative analysis of mathematical methods for recovering a current signal is given, their approbation was carried out, and the most promising of them was revealed. The stability and sensitivity of recovery methods were tested by adding white noise to the measured signal and taking into account the initial flux density (remanent magnetization) in the current transformers core. Their comparison is given on the basis of angular, magnitude, and total errors at a given simulation interval. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work was supported in part by the International Cooperation Project of National Natural Science Foundation of China under Grant 41761144079, in part by the Strategic Priority Research Program of the Chinese Academy of Sciences, in part by the Pan-Third Pole Environment Study for a Green Silk Road under Grant XDA20060303, in part by the K. C.Wong Education Foundation under Grant GJTD-2020-14, in part by the CAS PIFI Fellowship under Grant 2021PC0002, in part by the Xinjiang Tianchi Hundred Talents Program under Grant Y848041, in part by the CAS Interdisciplinary Innovation Team under Grant JCTD-2019-20, in part by the project of the Research Center of Ecology and Environment in Central Asia under Grant Y934031, and in part by the Regional Collaborative Innovation Project of Xinjiang Uygur Autonomous Regions under Grant 2020E01010

Power Flows and Losses Calculation in Radial Networks by Representing the Network Topology in the Hierarchical Structure Form

This paper proposes a structured hierarchical-multilevel approach to calculating the power flows and losses of electricity in radial electrical networks with different nominal voltages at given loads and voltages of the power source. The researched electrical networks are characterized by high dimensionality, dynamism of development, but also insufficient completeness and reliability of state information. The approach is based on the representation of the initial network graph in the form of a hierarchical-multilevel structure, divided into two stages with rated voltages Unom ≤ 35 kV and Unom ≥ 35 kV, and using the traditional (manual) engineering two-stage method, where the calculation is performed in a sequence from bottom to top (stage 1) and from top to bottom (stage 2), moving along the structure of the network. The application of the above approach makes it possible to obtain an algorithm for implementation on a computer, which is characterized by universality (for an arbitrary configuration and complexity of the network), high performance and low requirements for the computer memory. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work was supported in part by the International Cooperation Project of National Natural Science Foundation of China under Grant 41761144079, in part by the Strategic Priority Research Program of the Chinese Academy of Sciences, in part by the Pan-Third Pole Environment Study for a Green Silk Road under Grant XDA20060303, in part by the K. C. Wong Education Foundation under Grant GJTD-2020-14, in part by the Research Fund for International Scientists of National Natural Science Foundation of China under Grant 42150410393, in part by the CAS PIFI Fellowship under Grant 2021PC0002, in part by the Xinjiang Tianchi Hundred Talents Program under Grant Y848041, in part by the CAS Interdisciplinary Innovation Team under Grant JCTD-2019-20, in part by the project of the Research Center of Ecology and Environment in Central Asia under Grant Y934031, and in part by the Regional Collaborative Innovation Project of Xinjiang Uygur Autonomous Regions under Grant 2020E01010

A Statistical-Based Approach to Load Model Parameter Identification

In the last few years, a great number of methods for identifying the load model parameters have been proposed. This article discusses the use of statistical approach to estimate the substation equivalent load model parameters for supplying to oil-producing industrial region. The disadvantages of existing statistical approach are the low accuracy obtained for the parameter estimates, especially when using samples size is small. To eliminate this deficiency, the current measurement data archive from SCADA system of electrical parameters for 15 months was collected. For the purpose of verifying the obtained results of statistical processing of SCADA data, a full-scale experiment was carried out in relation to the studied substation. The article describes the statistical method used to process the current SCADA measurement data, the results of archived statistical processing and experimental SCADA data. The electrical load models' parameters received from the experimental studies results are of practical importance. © 2013 IEEE.This work was supported in part by the Strategic Priority Research Program of the Chinese Academy of Sciences, in part by the Pan-Third Pole Environment Study for a Green Silk Road under Grant XDA20060303, in part by the K. C. Wong Education Foundation under Grant GJTD-2020-14, in part by the International Cooperation Project of National Natural Science Foundation of China under Grant 41761144079, in part by the CAS PIFI Fellowship under Grant 2021PC0002, in part by the Xinjiang Tianchi Hundred Talents Program under Grant Y848041, in part by the CAS Interdisciplinary Innovation Team under Grant JCTD-2019-20, in part by the project of the Research Center of Ecology and Environment in Central Asia under Grant Y934031, and in part by the Regional Collaborative Innovation Project of Xinjiang Uygur Autonomous Regions under Grant 2020E01010

Experimental Study on Performance Enhancement of a Photovoltaic Module Incorporated with CPU Heat Pipe—A 5E Analysis

As is already known, solar photovoltaic (PV) technology is a widely accepted technology for power generation worldwide. However, it is scientifically proven that its power output decreases with an increase in the temperature of the PV module. Such an important issue is controlled by adopting a number of cooling mechanisms for the PV module. The present experimental study assesses the effect of a fanless CPU heat pipe on the performance of a PV module. The experiment was conducted in June in real weather conditions in Yekaterinburg, Russian Federation. The comparative analysis of two PV panels (i.e., cooled, and uncooled) based on the electrical energy, exergy performance, economic, embodied energy and energy payback (5E) for the two systems is presented and discussed. The key results from the study are that the average temperature reduction from the cooling process is 6.72 °C. The average power for the cooled panel is 11.39 W against 9.73 W for the uncooled PV panel; this represents an increase of 1.66 W for the cooled module. Moreover, the average improvements in the electrical efficiency, and embodied energy recorded for a cooled PV panel 2.98%, and 438.52 kWh, respectively. Furthermore, the calculations of the levelized cost of energy (LCE) for the cooled PV panel indicate that it can range from 0.277–0.964 USD/kWh, while that for the uncooled PV panel also ranges from 0.205–0.698 USD/kWh based on the number of days of operation of the plant. © 2022 by the authors.Y848041; National Natural Science Foundation of China, NSFC: 41761144079, 42150410393; Chinese Academy of Sciences, CAS: 2021PC0002, XDA20060303; Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2022-0031; K. C. Wong Education Foundation: GJTD-2020-14This research was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences, the Pan-Third Pole Environment Study for a Green Silk Road (Grant No. XDA20060303), the Research Fund for International Scientists of the National Natural Science Foundation of China (Grant No. 42150410393), the International Cooperation Project of the National Natural Science Foundation of China (Grant No. 41761144079), the CAS PIFI Fellowship (Grant No. 2021PC0002), the K.C. Wong Education Foundation (Grant No. GJTD-2020-14), and the Xinjiang Tianchi Hundred Talents Program (Grant No. Y848041).The research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program) is gratefully acknowledged: Grant number: FEUZ-2022-0031

Models of Optimal Operating Modes of the Water-Economic Complex on the Basis of Hydro Resource Price Evaluation

The purpose of this article is to solve the problem of determining the cost of a water resource for the participants of the water-economic complex (WEC) on the basis of the optimal control of hydro power plants’ (HPP) functioning, taking into account their regime characteristics and requirements. In this work, a universal method, which combines an optimization method and a method for assessing marginal utility, was proposed to assess the cost of the hydro resource and control the operating modes of the WEC. The method developed by the authors involves the use of water balance, the adequate representation of the incremental rate characteristic and the determination of the cost of the hydro resource for the control of the operating modes of the WEC and HPP. Using the example of the Novosibirsk WEC, as well as HPPs and TPPs, an assessment of the energy efficiency, proposing the concept of a developed methodology for determining the price of water for HPPs and all participants in the WEC, will be obtained. Based on the results of the implementation of the developed approach at Novosibirsk HPPs, the electricity sales price competitive electricity market can be matched with the electricity sales price generated at TPP, which will be approximately 0.16 ¢/kW * h. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: This work was supported in part by the International Cooperation Project of National Natural Science Foundation of China under Grant 41761144079, in part by the Strategic Priority Research Program of the Chinese Academy of Sciences, Pan-Third Pole Environment Study for a Green Silk Road under Grant XDA20060303, in part by the K. C. Wong Education Foundation under Grant GJTD-2020-14, in part by the Research Fund for International Scientists of National Natural Science Foundation of China under Grant 42150410393, in part by the CAS PIFI Fellowship under Grant 2021PC0002, in part by the Xinjiang Tianchi Hundred Talents Program under Grant Y848041, in part by the CAS Interdisciplinary Innovation Team under Grant JCTD-2019-20, in part by the project of the Research Center of Ecology and Environment in Central Asia under Grant Y934031, and in part by the Regional Collaborative Innovation Project of Xinjiang Uygur Autonomous Regions under Grant 2020E01010

Greenhouse gas emissions drive global dryland expansion but not spatial patterns of change in aridification

Drylands play an essential role in the Earth’s environment and human systems. Although dryland expansion has been widely investigated in previous studies, there is a lack of quantitative evidence supporting human-induced changes in dryland extent. Here, using multiple observational datasets and model simulations from the Coupled Model Intercomparison Project Phase 6, we employ both correlation-based and optimal fingerprinting approaches to conduct quantitative detection and attribution of dryland expansion. Our results show that spatial changes in atmospheric aridity (i.e., aridity index defined by the ratio of precipitation to potential evapotranspiration) between the recent period 1990-2014 and the past period 1950-1974 are unlikely to have been caused by greenhouse gas (GHG) emissions. However, it is very likely (at least 95% confidence level) that dryland expansion at the global scale was driven principally by GHG emissions. Over the period 1950-2014, global drylands expanded by 3.67% according to observations, and the dryland expansion attributed to GHG emissions is estimated as ~4.5%. Drylands are projected to continue expanding, and their populations to increase until global warming reaches ~3.5°C above pre-industrial temperature under the middle and high emission scenarios. If warming exceeds ~3.5°C, a reduction in population density would drive a decrease in dryland population. Our results for the first time provide quantitative evidence for the dominant effects of GHG emissions on global dryland expansion, which is helpful for anthropogenic climate change adaptation in drylands

An analysis of translation distance of tropical cyclones over the western North Pacific

Tropical-cyclone (TC) translation distance, proportional to its duration and translation speed, basically determines the spatial extent of TC impacted marine and terrestrial areas. Although a long-term slowdown of TCs has recently been reported, changes in translation distance of TCs over the western North Pacific (WNP) and their driving mechanisms remain poorly understood. Using multiple TC datasets, here we find that the trends are opposite in over-land translation distance of landfall WNP TCs over China and excluding China, with the number of landfalls in the two groups being almost the same. However, the increase in over-land translation distance of landfall TCs over China is offset by greater decrease in that excluding China, resulting in that over-land translation distance of TCs over the WNP has declined (−4.0% per decade). The over-sea translation distance of TCs over the WNP also shows a decreasing trend (−2.4% per decade), and thus the genesis-to-demise translation distance of TCs over the WNP has significantly decreased (by 17.7%) during 1961-2019. The shorter duration and reduced translation speed of TCs directly and jointly contribute (by 76.9% and 23.1%, respectively) to their shortened translation distance. The gradual increase in westerly and northerly winds and weaker moisture transport during the days following TC generation tend to inhibit long-distance travel after TC genesis. Declining TC translation distance is likely associated with the long-term increases in genesis potential index and an anomalous cyclonic steering flow over the WNP. Our findings suggest that these changes in TC translation distance may alter regional patterns of TC-related drying and wetting of the WNP

Substantial increase in heavy precipitation events preceded by moist heatwaves over China during 1961–2019

Both moist heatwaves (HWs) and heavy precipitation events (HP) have increased in both frequency and magnitude over China in recent decades. However, the relationship between HW and HP and changes in the lagged coincidence of events (i.e., the occurrence of an HP event several days after an HW event, noted HWHP) remain unknown. We show here that HWHP events account for nearly one-third of HP events over China in summer, with high values in North China, Northeast China, and the East arid zone. HWHP events assessed using the heat index and the wet-bulb temperature methods increased by 45.25 and 23.97% from 1961 to 2019, respectively. These concurrent HWHP events tend to be spatially clustered, and the areas affected simultaneously have grown significantly. The increase in HW is the major driver of these changes in HWHP events, except in the western arid zone and North China. Our findings provide an understanding of the spatiotemporal changes in HWHP events over China and their implications for disaster mitigation