Hydroelectric Unit Research Articles

ДИНАМИЧЕСКИЕ ИССЛЕДОВАНИЯ ЧАСТОТ И ФОРМ КОЛЕБАНИЙ ПЛОТИНЫ ЧИРКЕЙСКОЙ ГЭС

The purpose of the research is to monitor the amplitude-frequency characteristics on the example of the Chirkeyskaya HPP dam for further assessment of the state of hydraulic structures and hydroelectric units of the HPP, as well as to develop an automated system for seismometric control of hydraulic structures of the Chirkeyskaya HPP. The article presents the results of modeling and calculations of dynamic test data of the Chirkeyskaya HPP dam using the primary processing of measurement results to identify the quality of information processing by existing methods. The paper presents the results of measurements to create a mathematical model of the dam of the Chirkeyskaya HPP. Methods were used based on the study of the statistical characteristics of vibrations arising under the infl uence of the dynamic effects of equipment and the external environment for the experimental determination of the frequencies and modes of natural vibrations of the hydraulic structures of the Chirkeyskaya HPP. Spatial-frequency diagrams of the vibration intensity distribution in the radial direction were constructed, an algorithm was implemented to use data for both reference points when identifying natural frequencies and dam shapes, a spatial-frequency distribution diagram was constructed, averaged over two reference points, smoothed interpolated along the dam with a uniform step the conversion factor at the ridge level.

ЕНЕРГЕТИЧНА ЕФЕКТИВНІСТЬ ВІТРОГІДРОНАСОСНОЇ СТАНЦІЇ ЗНАЧНОЇ ПОТУЖНОСТІ

Розвиток відновлюваних джерел енергії в Україні характеризується стрімкими темпами. Станом на вересень 2020 року встановлена потужність вітроелектричних (ВЕС) та фотоелектричних (ФЕС) станцій складає біля 6 ГВт, що відповідає майже 20% максимального навантаження електроенергетичної системи на чинний момент часу. Тому на сьогодні набуває актуальності задача акумулювання стохастичного надходження електроенергії ВЕС та ФЕС в електроенергетичну систему, зумовлена неузгодженістю графіків генерування та споживання потужності. Ідея застосування гідроакумулювальних електростанцій (ГАЕС) для накопичення стохастичного надходження енергії ВЕС і ФЕС починає знаходити своє практичне втілення. В Іспанії вже декілька років функціонує вітродизельна електростанція для подачі води в басейн-акумулятор ГАЕС потужністю 11 МВт. Досвід експлуатації цього комплексу засвідчив суттєве зменшення його енергетичної ефективності, зумовлене стохастичним характером надходження енергії вітру. Тому на часі вирішення задачі визначення енергетичної ефективності процесу перетворення кінетичної енергії вітру в потенційну енергію води, накопиченої в басейні-акумуляторі, з урахуванням наявності пульсацій швидкості вітру . В даній роботі виконана оцінка енергетичної ефективності потужної гідронасосної станції при електроживленні двигунів насосів від вітроелектричної установки з урахуванням пульсацій швидкості вітру та кількості гідроелектричних агрегатів у складі станції. Визначення кількісних значень оцінюваних параметрів базувалось на результатах математичного моделювання динаміки навантажувальних режимів роботи вітрогідронасосної станції з урахуванням стохастичної зміни швидкості вітру. Математична модель являє собою систему нелінійних диференційних рівнянь, що описує взаємодію двох інерційних складових єдиної аероелектрогідродинамічної системи. Визначено раціональне співвідношення кількості гідронасосів в складі насосної станції для досягнення максимальних значень коефіцієнта використання встановленої потужності вітрогідронасосної станції. Бібл. 29, рис. 6.

STUDY OF THE PROCESS OF EROSION OF A MICRO HYDROELECTRIC POWER PLANT (HPP) TURBINES IN THE FORM OF A HYDROCYCLONE

One of the severe problems of a hydroelectric power plant (HPP) is providing a hydroelectric unit with purified water with the required pressure. Otherwise, the central working bodies - hydraulic turbines - are subjected to abrasive wear and quickly fail. Abrasive wear reduces the efficiency and life of the turbine and causes problems in operation and maintenance. This research aimed to study the degree of abrasive wear (erosion rate) of the surface of a blade hydraulic turbine of a micro HPP during water purification using a hydrocyclone and to ensure its rational layout based on the studies. Investigation of damage to the turbine surface from the dynamic impact was carried out by computer modeling of the process using the Autodesk Simulation CFD program, with different versions of the hydrocyclone body and testing of an experimental sample. Additional software SolidWorks (flow simulation) was used to check the calculations. It was found that the forms of particle hardness in water significantly affect the rate and magnitude of erosion, and a different design of the treatment body in the form of a hydrocyclone in different ways ensures the separation of the flow into phases. A rational scheme for installing a hydraulic turbine inside a hydrocyclone was selected, which provides the required power characteristic of a mini hydroelectric power station and other necessary parameters. The highest degree of water purification from solid impurities (94%) was achieved using the configuration option in a cylindrical-conical design with a rotational water inlet into the hydrocyclone. The location of the hydraulic turbine inside a hydrocyclone of a certain design and the tangential supply of water to the blades of the hydraulic turbine significantly protects the surface of the unit from the effects of solid particles. Their service life can be increased without additional investment in the restoration of the unit.

Dynamic behaviour of a Francis turbine during voltage regulation in the electrical power system

Hydroelectric units can be operated in synchronous condenser mode to provide reactive power to the electrical power system (EPS) for voltage regulation. In this operating mode, the hydraulic turbine consumes active power and in case of hydroelectric units equipped with a Francis turbine, pressurized air is injected in the draft tube to decrease the tailwater level below the runner for decreasing the friction losses. Several dynamic phenomena have been recorded during full-scale hydraulic turbine operation due to the air–water mixing causing pressure and torque fluctuations which may compromise the operation and safety of both the hydraulic machine and the EPS.In this paper, the study of the dynamic response of a Francis turbine prototype during synchronous condenser mode operation is performed to evaluate the transposition of the machine behaviour from the homologous reduced scale model to the full-scale prototype. Measurements of the pressure in draft tube cone, machine vibrations, and torque are performed in both full scale prototype and reduced scale model. The analysis of the dynamic behaviour of the hydraulic turbine focuses on the critical vibrations and power fluctuations. The onset of a sloshing wave in the draft tube cone is highlighted as predicted by the reduced scale model tests. Rotor–stator interactions (RSI) are analyzed and compared to the RSI during generating mode operation. The advantages of decreasing the pressure in the vaneless gap between the runner blades and the closed guide vanes by installing a draining pipe are emphasized to limit the amplitude of the fluctuations and to avoid unwanted two-phase flow phenomena in the vaneless gap which can perturb the machine operation and safety.

Dynamic competition in electricity markets under uncertainty

Abstract We study discrete-time infinite-horizon imperfect competition between asymmetric firms producing from different technologies. Specifically, one firm produces from hydroelectric units and the others operate thermal generators. This type of structure is common in some electricity markets. What makes this research interesting is that firms have different types of constraints, face different kinds of uncertainties, need to allocate their resources over time, and yet produce strategically. For the renewable energy holder, the key issue is how to allocate water between current and future electricity generation given the thermal firms' strategic actions along with demand and/or water inflow uncertainties. We analyze equilibrium outcomes (e.g., the price distribution) and market inefficiencies stemming from both production constraints and imperfect competition. We show that equilibrium price volatility and skewness are generally lower than optimal, although average price is higher than optimal. The hydro producer under-utilizes the available water, which leads to more water being available to smooth price fluctuations. However, in the extreme case of water inflows so plentiful that the hydro firm is never constrained, prices can be more volatile than optimal. We also demonstrate that the lack of social optimality of the market outcome is tempered by the capacity constraints: the welfare loss under the oligopoly market structure is much less than would occur in the absence of water and capacity constraints. These results are demonstrated using numerical simulations of the infinite horizon game, one of which is calibrated to match the characteristics of the Ontario wholesale electricity market.

Project and financial analysis of investment potential of hydraulic test stand for repair companies and service centers

Currently, stationary domestic and foreign test stands are used for assessing the technical condition of bulk hydraulic drives in the repair enterprises and service centers. However, the used domestic stands have disadvantages associated with low accuracy and reliability of the results obtained, limited ranges of diagnostic parameters, and the inability to implement the methods of manufacturers. (Research purpose) The research purpose is in evaluating the investment attractiveness of the hydrostand for repair companies and service centers of hydroelectric unit manufacturers and make a conclusion about its competitiveness. (Materials and methods) Authors have developed a hydrostand for monitoring and evaluating the technical condition, adjustment and post-repair running-in of hydraulic units of a volumetric hydraulic drive. The article presents the estimated cost of its production. The article presents the methodology for calculation of economic efficiency of developed and implemented hydroscand. (Results and discussion) The article shows the feasibility of development by conducting a design and financial analysis of investment attractiveness in relation to the currently operating small innovative enterprise LLC "Agroservice", Saransk. The project was the implementation of designed hydroscand at site for repair of volumetric hydraulic actuators. The cost of manufacturing a new hydrostand was determined in the course of research and is of 1557910 rubles, which is 10.4 percent of the cost of foreign and 44.5 percent of the cost of domestic analogues with higher technical capabilities. (Conclusions) The analysis showed that hydrostand has a relatively low payback period, a high value of the return index and internal rate of return, and a lower cost. These indicators increase its competitiveness and attractiveness among potential consumers.

Bi-objective Optimization of Black Start Allocation for Regional Power Grid

Under the influence of extreme weather events, black start allocation is more and more important for regional power grids lack of hydroelectric units and pumped-storage aggregates. This paper proposes a bi-objective optimization model considering both the time of the whole restoration and the risk of line recovery, an improved TOPSIS method is employed to solve the problem based the non-inferior solution. The results of the Dongguan power grid verify the effectiveness of this method.

Ultrasonic Technique for Assessment of the Rim Tightness of Hydro Generator Rotor

At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free state, after “cold” tight shrinking, after “hot” tight shrinking, and after 3000 and 8000 hours of operation. The ability to evaluate the rim tightness of the rotor based on data on the redistribution of compression efforts in the wedges is demonstrated.

Analyzing the Operational Materials on Crack Formation in Blades of Francis Turbines at the Krasnoyarsk HPP

Equipment of the Krasnoyarsk HPP is considered as an example to analyze the dependence of crack formation in runner blades on the operating conditions of the turbines since their commissioning. It was established that intensive crack formation in blades in the initial (running-in) period was due to manufacturing-induced high residual stresses and internal material defects. The blade failure rate increased with water head and, hence, the output of the hydroelectric units. The absence of cracks in the blades today indicates that the lifetime of the runners has not ended yet.

(Machine) Learning from the COVID-19 Lockdown about Electricity Market Performance with a Large Share of Renewables

The negative demand shock due to the COVID-19 lockdown has reduced net demand for electricity|system demand less amount of energy produced by intermittent renewables, hydroelectric units, and net imports|that must be served by controllable generation units. Under normal demand conditions, introducing additional renewable generation capacity reduces net demand. Consequently, the lockdown can provide insights about electricity market performance with a large share of renewables. We find that although the lockdown reduced average day-ahead prices in Italy by 45%, re-dispatch costs increased by 73%, both relative to the average of the same magnitude for the same period in previous years. We estimate a deep-learning model using data from 2017{2019 and find that predicted re-dispatch costs during the lockdown period are only 26% higher than the same period in previous years. We argue that the difference between actual and predicted lockdown period re-dispatch costs is the result of increased opportunities for suppliers with controllable units to exercise market power in the re-dispatch market in these persistently low net demand conditions. Our results imply that without grid investments and other technologies to manage low net demand conditions, an increased share of intermittent renewables is likely to increase costs of maintaining a reliable grid.

A Generation Expansion Planning model for integrating high shares of renewable energy: A Meta-Model Assisted Evolutionary Algorithm approach

This study presents a complementary model for Generation Expansion Planning (GEP). A GEP problem commonly determines optimal investment decisions in new power generation plants by minimizing total cost over a mid towards long planning horizon subjected by a set of constraints. The model aims to capture operational challenges arising when a transition towards higher shares of intermittent renewable generation is considered. It embeds a computationally expensive Operational Cost Simulation Model (OCSM), which may exhibit a high level of temporal and technical representation of the short-term operation of a power system to model the unit commitment. The emerging computationally expensive integer non-linear programming constrained optimization model is solved by a problem-customized Meta-model Assisted Evolutionary Algorithm (MAEA). The MAEA employs, off-line trained and on-line refined, approximation models to estimate the output of an OCSM to attain a near-optimal solution by utilizing a limited number of computationally expensive OCSM simulations. The approach is applied on an illustrative test case for a 15 year planning period considering the short-term operation of thermal, hydroelectric and storage units and generation from renewable energy sources. Moreover, the impact of technical resolution is examined through a simple comparative study. The results reveal the efficiency of the proposed problem-customized MAEA. Moreover, the trained approximation models exhibit a low relative error indicating that they may adequately approximate the true output of the OCSM. It is demonstrated that neglecting technical limitations of thermal units may underestimate the utilization of flexible units, i.e. thermal and non-thermal units, affecting the attained investment decisions.

Research on Reverse Power Mechanism of Grid-connected Hydropower Units in Asynchronous Network

Under normal conditions, the hydropower unit is less equipped with reverse power protection. In order to solve the problem of large frequency oscillation caused by the reverse power of the hydropower unit when the hydroelectric unit is connected to the grid due to the large amplitude of the frequency oscillation, the paper passes the simulation. Through analysis and on-site comparison test, the frequency deviation range of different power plants connected to the grid is given, and the impact curve of power under different frequency differences is fitted. After the asynchronous networking of regional power grids, the theory of safe and reliable grid connection of hydropower units is provided.

Hydro energy potential considering environmental variables and water availability in Paraná Hydrographic Basin 3

Brazil’s energy matrix is based on hydroelectric plants. In the current scenario, studies must be conducted to verify the possible environmental impacts and production viability in order to determine sites most suitable for installing hydroelectric units. A process was developed to identify potential sites to install hydroelectric units using geotechnology, considering morphometric analysis of watershed obtained using python scripts, PLpgSQL, and R. This process enabled the generation of multiple regression models for flow estimates, flooded areas, and estimates of the hydropower potential of the region. From the 3899 points analyzed, 3477 points showed potential for run of river hydroelectricity-generating plants (production up to 3 MW) and 48 points showed potential for small hydroelectric plants (SHPs; production between 3 MW and 30 MW). The limiting factors were assessed by using the intersect geoprocessing tool, where points that intersected with excluding factors, such as environmental or infrastructure elements, were excluded from the analysis. In addition, an efficiency coefficient was established for the SHPs by correlating potential and flooded areas, demonstrating the best points for the implementation of SHP, and considering the potential impacts of the reservoir.

Dynamic economic dispatch with demand-side management incorporating renewable energy sources and pumped hydroelectric energy storage

This paper recommends chaotic fast convergence evolutionary programming (CFCEP) for solving real-world dynamic economic dispatch (DED) with demand-side management (DSM) incorporating renewable energy sources and pumped-storage hydroelectric unit. Here, solar–wind–thermal energy system has been considered taking into account pumped-storage hydroelectric unit and uncertainty of solar and wind energy sources. DSM programs reduce cost and boost up power system security. To investigate the upshot of DSM, the DED problem is solved with and without DSM. In the recommended technique, chaotic sequences have been applied for acquiring the dynamic scaling factor setting in FCEP. The efficiency of the recommended technique is revealed on two test systems. Simulation outcomes of the suggested technique have been matched against those acquired by fast convergence evolutionary programming (FCEP), colonial competitive differential evolution and heterogeneous strategy particle swarm optimization. It has been observed from the comparison that the recommended CFCEP technique has the ability to give better-quality solution.

A hybrid approach for measuring the vibrational trend of hydroelectric unit with enhanced multi-scale chaotic series analysis and optimized least squares support vector machine

Accurate vibrational trend measuring for hydroelectric unit (HEU) is of great significance for safe and economic operation of unit. For this purpose, a novel hybrid approach based on variational mode decomposition (VMD), singular value decomposition (SVD)-based phase space reconstruction (PSR) and least squares support vector machine (LSSVM) improved with adaptive sine cosine algorithm optimization (ASCA) is proposed. Firstly, the raw vibration signal is preprocessed into several components with different scales by VMD, while the residual of VMD is defined as an additional component. Then, SVD with median filtering is utilized to unearth the dominating characteristic ingredients of each component, with which the chaotic series analysis will be effectively implemented. Moreover, the optimal parameters of PSR for each original component are determined by applying grid search on the corresponding dominating component. Later, LSSVM improved by ASCA are established for all the components, whose inputs and outputs are obtained by performing PSR with the optimal parameters. Finally, the measuring results of vibration trend are deduced by accumulating the prediction values of all the components. Furthermore, five related methods are employed to evaluate the effectiveness of the proposed approach. The results illustrate that: (1) the VMD-based models obtained better evaluation indexes compared with the relevant models through significantly weakening the non-stationarity of the original signal; (2) the proposed SVD-based PSR enhanced efficiency of chaotic system restoration, thus to improve the measuring accuracy effectively; (3) the proposed ASCA optimization algorithm could effectively search the parameters of LSSCVM, which contributes to improving model performance.

Development of an ultra-low head siphon hydro turbine using computational fluid dynamics

Structural simplification and efficient hydraulic performance are key to effectively utilizing ultra-low head water power resources and reducing hydroelectric unit costs. In this study, a computational fluid dynamics (CFD) method was used to predict hydraulic performance of an axial turbine at the Gaoliangjian power station. CFD results agreed well with field test data. Using the same numerical method, a new siphon turbine was then designed based on the original distributor and turbine runner equipment. This study investigated the effect of different siphon outlet passage geometry parameters, runner blade shapes, and distributors on the hydraulic performance of the siphon turbine. The maximum hydraulic efficiency increased to 87.9% under a head of 2.87 m. Finally, the hydraulic performance of the turbine was compared for four different distributor designs after adding an intake sump at the turbine entrance. The bell-shaped distributor with four guide vanes resulted in the highest power output at the lowest head. Therefore, the siphon turbine is a good option for energy conversion in ultra-low water head settings.

A hydrothermal coordination model for electricity markets: theory and practice in the case of the Greek electricity market regulatory framework

The generation portfolio of the Greek Mainland Electricity System mainly consists of various types of thermoelectric (using fossil fuels: natural gas and lignite) as well as hydroelectric units (impoundment, pumped storage, run of river). Regarding their fuel consumption, thermoelectric units have a large variable cost compared to hydroelectric, which is almost zero, as derived by their advantage of fueling their operation with water. Moreover, as fossil fuel price variation does not correlate to water’s value a significant trade-off is created. Due to that trade-off the use of energy sources (natural gas, lignite or water), without consideration of cost minimization, may always lead to waste and to significant losses. Demand’s variation along with its sudden peaks, as well as the uncertainty of water availability, impose the use of a specialized mathematical model for the optimal handling of the generation portfolio. Load cover should be achieved by a non-constant portfolio over time, of hydro and thermals, coordinated by an algorithm in such a way as to achieve cost minimization. The main target of such a model is the normality of operation, safeguarded by specific technical, operational and economic constraints fulfilling the objective of cost minimization. Optimization of this type can be characterized as hydrothermal coordination problem, which in our case takes the form of a Mixed Integer Programming Model. The innovative character of this model, is that in a time efficient way, it finds the optimal solution, while keeping complexity at very low level, forcing hydroelectric units to maximize production at the peaks of the load, when marginal cost of thermal’s is at the highest point, making the most economical utilization of water resources. Such an algorithm while it achieves significant economies regarding the cash flows and the fuel-quantities (fossils, water for agricultural purposes), delivers heavy support to management for market policy and operational decision-making.

Water Column Separation at Turbine Start up Loading

According to authors knowledge this is the first case of water column separation that happened, not during load rejection, but during the turbine start and loading to full power output. To control the transient flows in water courses, the wicket gates of turbine are the primary flow regulators. The minimum pressure during transient operations of hydroelectric turbine units may cause a water column separation and the subsequent re-joining creates forces that could damage turbine runners, non-rotating parts, and the whole machine house. This condition occurs when a local pressure drops below the vapour pressure or partial pressure of gases (air). The instant pressure rises from collapse of voids have the potential to crack internal linings of water conductors and connections between steel and concrete, and may damage hydraulic machines, air valves, penstock valves, or gates. The damage may not be evident immediately but would be observed after repetitive transients. All calculations and measurements of transients must be completed for analysis of the water column separation, following existing guidelines, though there is no standards and recommendation on the subject of waterhammer and hydraulic vibrations. This paper presents an approximate analysis of water column separation based on the pressures measured on site.

Nonlinear model parameter analysis of ULFO in large-scale hydropower systems

The instability of the primary frequency regulation process of hydroelectric units has led to the occurrence of ultra-low frequency oscillations(ULFO) which frequency is less than 0.1 Hz.It mainly appears in the isolated power grid and direct current delivery system with high proportion of hydropower in recent years.So it is very important to study the influence of the main link parameters of the primary frequency regulation on ULFO including the water inertia time constant, system load frequency regulation coefficient. In this paper, a nonlinear model based on each link of primary frequency regulation process is built, and the oscillation frequency of the system under the influence of different parameters is determined by using a variety of frequency domain analysis methods. The influence of the main parameters on the frequency oscillation of the system is analyzed in detail, including the joint stability region which guarantees the stability of the system under the coupling of the governor parallel PID parameters.Nonlinear link is linearized by the method of description function.A new method to determine the parameter range of each link is proposed.

Ultrasonic Evaluation of Residual Stresses in Welded Joints of Hydroelectric Unit Rotor Frame

The applicability of the ultrasonic technique based on the acoustic birefringence for evaluation of the residual stresses in welded joints of metal structures is demonstrated. A field study of one welded joint of hydroelectric unit rotor frame was performed. Also a laboratory study of a welded plate made from the same material and had the same thickness like chosen welded joint of rotor frame was performed. Ultrasonic measurements by echo method were carried out and acoustic birefringence distributions before and after welding were received. The acoustoelastic coefficients of material were obtained by testing samples cut from the welded plate. The distribution of principal stresses difference in the welded plate in the direction perpendicular to the weld was received by the ultrasonic technique. The results of ultrasonic evaluation of the residual welding stresses in the welded plate We were verified using strain gauges measurements. Due to calibration on the welded plate the residual stresses in the welded joint of the rotor frame were estimated under operating conditions.