Optimal load management of autonomous power systems in conditions of water shortage

The issues of optimizing the operation of micro hydropower plants in conditions of water scarcity, performed by additional connection to the grid of an energy storage system and wind power turbine, as well as optimal load management, are considered. It is assumed that the load of the system is a concentrated autonomous power facility that consumes only active power. The paper presents a rigorous mathematical formulation of the problem, the solution of which corresponds to the minimum cost of an energy storage system and a wind turbine, which allows for uninterrupted supply of electricity to power facilities in conditions of water shortage necessary for the operation of micro hydropower plants (under unfavorable hydrological conditions). The problem is formulated as a nonlinear multi-objective optimization problem to apply metaheuristic stochastic algorithms. At the same time, a significant part of the problem is taken out and framed as a subproblem of linear programming which will make it possible to solve it by a deterministic simplex method that guarantees to find the exact global optimum. This approach will significantly increase the efficiency of solving the entire problem by combining metaheuristic algorithms and taking into account expert knowledge about the problem being solved

HES REŽĪMU VADĪŠANA UN TO PROGNOZĒŠANA

Hidroenerģētika ir būtiska enerģētikas sastāvdaļa. Tajā tiek izstrādāti 17% elektroenerģijas, bet jaudas ziņā tā ir pat 25% no kopējas jaudas. Hidroelektrostacijām ir augstas operatīvas īpašības, kas ļauj ātri uzņemt un samazināt slodzi. Tās piedalās frekvences un jaudas optimizācijas procesā un enerģētiskā tirgus darījumos plūsmu regulēšanā, tajās izvieto operatīvas un avārijas rezerves. Tās atvieglo citu elektrostaciju iekārtu darbu. Vienīgais hidroenerģētikas trūkums operatīvā ziņā ir lielas grūtības tās darbības prognozēšanā, kas ienes grūtības energosistēmu bilanču, tarifu, investīciju plānošanā un gadu piegādes līgumu slēgšanā. Analizējot hidroelektrostaciju vadīšanas metodes, kļūst skaidrs, ka gadu izstrādes prognozēšana ir viena no svarīgākām šīs nozares problēmām. Mēģinot atrisināt šo problēmu, darbs sākās ar Daugavas gadu caurplūdamības īpašību izpēti. Darba gaitā noskaidrojās, ka analīzei izejas datu funkcijas jāpārveido palīgfunkcijās parastās un logu, Furjē-pārveidojumu pielietošanai. Veicot analīzi ar paligfunkcijām, rezultāti jāatgriež sākotnējās koordinātēs (oriģinālos) ar funkciju diferencēšanas palīdzību. Rezultātā noskaidrojās, ka gadu caurplūdamībām ir stabilas cikliskas īpašības, ko var izteikt analītiski. Pēc determinēto komponenšu atskaitīšanas no dabīga procesa paliek “atlikuma” funkcija, kam ir augstfrekvences raksturs. Noskaidrojās, ka arī šo komponentu iespējams daļēji prognozēt. Šim nolūkam nākotnē būs jāizmanto veivlet-pārveidojums un mākslīgos neironu tīklus. Rezultātā izejas datu “troksnis” tiek novests līdz nelielam īpatsvaram. Iegūstot pētījumam hierarhisko ciparu filtru, kļuva iespējams atkārtot analoģisku analīzi, ņemot tam par pamatu jebkuras upes daudzgadīgus novērojumus. Tam varēja izmantot datus, publicētos UNESKO atskaitēs, kam pielietots Furjē-pārveidojums. Analīze tika veikta uz vairāk par 45 pasaules upju novērojumu datu pamata. Noskaidrojās, ka visu upju caurpludamībām ir līdzīgs raksturs. Vienīgi procesiem ir reģionālas fāžu atšķirības, kuru iemeslus turpmāk būtu jāizskaidro citu zinātņu ietvaros (astro-, ģeo-, atmosfēras fizikās). Uzbūvētas pasaules upju caurplūdamību fāžu kartes. Kļuva skaidrs, ka šādām globālām parādībām ir jābūt kopējam spēcīgam iemeslam. “Aizdomas” krita uz Saules intensitātes izmaiņām. Tās tika novērotas un reģistrētas sākot ar 18 g.s.. Salīdzinot caurplūdamību integrālo funkciju ar Saules intensitātes procesu, noskaidrojas, ka procesu pamatharmonikām ir līdzīgi gan zemfrekvences (simtgadu cikli), gan augstfrekvences (11-gadīgie cikli) spektrā. Noskaidrojās arī caurplūdamības retu, bet lielu amplitūdu noviržu iemesli. Izrādās, ka tie notiek 11-gadīgo Saules ciklu ekstremālu lielumu posmos, sakrītot ar tiem pēc zīmes. Noskaidrojās arī retu lielu amplitūdu caurplūdamības noviržu laiki. Izrādās, kā tās veidojas periodos, kas atbilst Saules 11-gadīgo intensitātes atvasinājuma zīmes maiņām. Caurplūdamības satur līdz pieciem dažādu frekvenču komponentu, kuri jāprognozē turpmākiem gadiem un rezultāti jāsummē kopējas prognozes iegūšanai. Noskaidrota programmatūra, kas ir nepieciešama uzdevuma risināšanai. Veiktā darba rezultātā iegūtas jaunas zināšanas, kurus var praktiski izmantot enerģētikā un dažādos tautsaimniecības nozarēs, un tās var tikt izmantotas vairāku zinātņu tālākai attīstībai

HES udens rezimu vadisana un to prognozesana

Hydroenergy is a significant component of the energy industry, accounting for 17% of the electricity produced (and even 25% of the total power). Hydro electric stations possess high performance indices, which, in particular, allow for their fast loading and unloading. They participate in the frequency and power optimisation process and in the regulation of energy market transactions concerning power flows; in these stations operative and emergency reserves are stored, which facilitate the operation of other electric stations' equipment. In the operative meaning, the only drawback of hydroenergy generation is that it is very difficult to forecast, which introduces complications into the planning of power systems' balances, tariffs, investments, and into the conclusion of supply contracts. When analyzing the methods for HES management, it becomes clear that the forecasting of annual production is one of the most important problems in this area. In an attempt to solve this problem, the research work initially concerned the properties of Daugava's waterflows. In the course of work it was clarified that for the analysis it was necessary to convert the original function data into some auxiliary functions in order that simple and log Fourier transformations could be applied. After having performed the analysis with the auxiliary functions, the results were to revert to the initial coordinates (originals) by means of function differentiation. As a result it was revealed that the annual waterflows possess stable cyclic properties which can be expressed analytically as a time function. After subtracting the determinate components from the natural process a "remainder" function is left, which possesses a high-frequency character. It was revealed that this component is also partially predictable. For this purpose in the future wavelet transformation and artificial neuron networks are to be employed. As a result, the "noise" of the initial data will be reduced to a small specific weight. Using the hierarchial digital filters it was possible to perform analysis, taking as the basis the long-term observations of riverflows reported in the UNESCO publications. The analysis has been performed based on the observation data on more than 45 world's rivers. It was found that waterflows of all the rivers possess similar character. These processess have regional phase distinctions, which in the future are to be explained in the framework of other sciences (astro-, geo-, and atmospheric physics). The global phase maps for riverflows have been built. It became clear that for such global phenomena there should be a common cause. The most probably these are variations in the Solar intensity, which have been observed and recorded since the 18th century. The comparison of the waterflow integral function with the Solar intensity process revealed that in both cases the first harmonics have similar low-frequency (centenary cycles) and high-frequency (11-year cycles) spectra. Also, the causes of high-amplitude rare waterflow deviations have been revealed. It turned out that they occur in the spans of extremum values of 11-year Solar cycles, coinciding with them by sign. It was thus found that waterflows contain up to five components of different frequency, which are to be forecast for the nearest years to come and the results are to be summed up to obtain a full forecast. The program package required for solving the task has been developed/estimated. As a result of the work performed, new knowledge has been acquired that can be employed in practice in the energy industry and other branches of national economy as well as to be used as a basis for further development of different sciences.Abstract in Latvian, English, Russian. Separate summaries in Latvian and EnglishAvailable from Latvian Academic Library / LAL - Latvian Academic LibrarySIGLELVLatvi

Application of Highly Durable Surface Forming Technology (HDST) in Power Industry

This article addresses a complex solution that allows increasing the stability of power network operation by improving efficiency of nodes and components, saving the energy as well as reducing the costs related to operating different equipment of energy industry. Based on theoretical foundation built by different state institutes, scientific research organizations and private companies during more than 20 years period of time, this article addresses the possible application of highly durable surface forming technology (HDST) in power industry, that allows to build up a metalceramic layer on top of rubbing metallic surfaces, and that, in its turn, opens new, earlier unavailable, possibilities for different types of equipment in power industry

Функциональная точность статических и динамических моделей электрических систем после исключения нелинейных нагрузок

This paper concerns the reduced static and dynamic models obtained after the Jordan elimination of nonlinear loads by replacement of the indicative form of load characteristics with approximated quadratic ones and vice versa. Carrying out of such two-way approximation causes some small error which is object of the presented study. Two kinds of approximations have been considered with any influence only of voltage. Theoretical estimation of accuracy is proved on practical examples where electrical system’s behavior before and after a reduction of corresponding model is compared

Peculiarities of Annual Flows of World’s Rivers

In this monograph authors clarified that the annual throughflow of the Latvian river Daugava has certain relationships, researched and found them also on other 50 most important rivers in the world, which opened a possibility to advance a well-grounded hypothesis of the causes of the phenomenon. The goal of the work is, based upon the experience accumulated in the management of energy systems and HPPs, to make clear the significance of the latter under the conditions of open market. Having ascertained that there was a need to improve the forecasting methods as far as the hydro energy production is concerned, it was necessary to verify the possibilities of such methods with the help of the energoinformatic discipline

An Analytical Method for Reduction of Frequency-Dependent Static and Dynamic Models of Electrical Systems

Precise representation of the loads dependant on voltage and frequency in standard power form is normally used in modern static and dynamic models of electrical systems. In this paper the method of an elimination of such loads for the purpose of reduction of model’s dimension is offered. It is carried out through appropriate approximations of the load characteristics made simultaneously on voltage and frequency. Approximation of voltage leads to preservation of the linear form of the node equations for currents that allows applying the Jordan elimination. At the same time the specific mathematical operations are involved and performed over frequencydependent elements. As a result the number of nodes decreases and new frequency-dependent connections and loads are appeared in nodes of the reduced scheme. They promote exactly the same course of considered processes

Elektromagnētiskie pārejas procesi elektriskās sistēmās

Mācību grāmatā izskatīti elektrisko sistēmu elektromagnētisko pārejas procesu fizikas pamatu teorētiskie jautājumi, ka arī trīsfāžu un nesimetrisko īsslēgumu aprēķinu praktiskās metodes. Grāmata var tikt izmantota kā mācību līdzeklis RTU Enerģētikas un elektrotehnikas fakultātes elektrozinību profila studentiem disciplīnā „Elektriskās sistēmas” , kā arī kā rokasgrāmata Elektrisko sistēmu automatizācijas specializātes inženieriem