Small Hydropower Stations Research Articles

Analysis of Safety Management Method for Electromechanical Equipment of Small Hydropower Station

Analysis of Safety Management Method for Electromechanical Equipment of Small Hydropower Station

Daily Power Generation Forecasting Method for a Group of Small Hydropower Stations Considering the Spatial and Temporal Distribution of Precipitation—South China Case Study

This paper proposes a multimodal deep learning method for forecasting the daily power generation of small hydropower stations that considers the temporal and spatial distribution of precipitation, which compensates for the shortcomings of traditional forecasting methods that do not consider differences in the spatial distribution of precipitation. First, the actual precipitation values measured by ground weather stations and the spatial distribution of precipitation observed by meteorological satellite remote sensing are used to complete the missing precipitation data through linear interpolation, and the gridded precipitation data covering a group of small hydropower stations are constructed. Then, considering the time lag between changes in the daily power generation of the group of small hydropower stations and precipitation, the partial mutual information method is used to estimate the “time difference” between the two, and combined with the precipitation grid data, a data set of the temporal and spatial distribution of precipitation is generated. Finally, using only the temporal and spatial distribution of precipitation and historical power generation data, a multimodal deep learning network based on a convolutional neural network (CNN) and multilayer perceptron (MLP) is constructed, and a highly accurate prediction model for the daily power generation of small hydropower stations is obtained. Taking the real power generation data of a group of small hydropower stations in southern China as an example, after considering the temporal and spatial distribution of precipitation, the prediction accuracy of the proposed method is as high as 93%, which is approximately 5.8% higher than before considering the temporal and spatial distribution of precipitation. In addition, compared with mainstream methods such as support vector regression (SVR) and the long–short-term memory network (LSTM) (the average accuracy is about 87%), and the average accuracy improvement of the proposed method is approximately 6%.

Optimised power generation system by the SWAT and artificial neural network based on improved farmland fertility optimisation (IFFO) algorithm

Today, due to increasing environmental considerations and efforts to reduce fossil fuel consumption, the need to develop small hydropower plants has become apparent. One way to develop hydropower is to identify places that are suitable for installing small hydropower. The objective of this study is a spatial analysis method to find suitable potential sites for the construction of small hydropower stations. Innovation in this research is a hybrid model for estimation discharge. This hybrid model is including the hydrological Soil and Water Assessment Tools (SWAT) model and Multi-Layer Perceptron (MLP) networks based on Improved Farmland Fertility Optimization (IFFO) algorithm, that called SWAT-MLP-IFFO. Using this model increases the accuracy of discharge estimation, therefore, it can help to the accuracy of power estimation. The result in the section showed that the SWAT-MLP- IFFO model can simulation the discharge closer to actual discharge. After evaluating the discharge and the calculated slope of the rivers, points of rivers that have the potential to install hydropower have been identified using GIS software. The results showed that areas with higher discharges and slopes generated more electricity. Also, the results showed that river discharge is preferable to river slope and the discharge has the most effective role.

Comparative Study on Layout Scheme of High Head Diversion Power Station----Taking the Yamu River-I Hydropower Station as an Example

The small hydropower stations on most tributaries in the middle reaches of Salween River are mostly high-head diversion hydropower stations, and the choice of hub arrangement scheme is an important content of the preliminary construction project. Taking Yamu River-I Hydropower Station as an example, this paper compares and analyzes the layout scheme of the main hub of the project from the aspects of dam site, dam type, regulation scheme, diversion route and site selection, and summarizes the optimization ideas and characteristics of the layout scheme of the main hub of the project, so as to be helpful for the preliminary design of similar hydropower stations.

Study on generation capacity of small hydropower stations in distribution network

Small hydropower station, when producing power energy to power system through the distribution network, may lead to the change of the detected current in relay protection and the protection coverage. In this paper, IEEE7 based network is formed in the platform of PSCAD/EMTDC to analyze the effects of distribution network in current protection when a small hydropower station is linked in. The running of relay protection in Section I and II is simulated to obtain the difference of current variation of network with or without small hydropower station. Also the key parameters are calculated to point out the maximum generation capacity of the small hydropower station in case of reliable and sensitive current protection.

A new method for calculating the downstream ecological flow of diversion-type small hydropower stations

Diversion-type hydropower stations play an important role in energy and power generation. However, they also substantially alter the natural hydrological situation of the river section through the formation of dewatered river sections between water-retaining structures and the power plant, which have a series of associated effects on the habitats of living organisms, thereby affecting the health of the water ecosystem. Therefore, it is of practical importance to study and analyse the ecological flow of the dewatered river section. Maintaining a certain ecological flow is considered to be an effective solution, but at the same time it can also affect the socio-economic benefits of hydropower plant operation. To reconcile the relationship between the two, this paper proposes a new method for calculating ecological flow in dewatered river sections, an optimal method for the phased habitat demand (OMPHD) of key species, in which key species are selected and explored in stages, giving priority to the key elements of each stage. Organisms have different life stages and these stages require a series of different habitats; habitats with a high geomorphological diversity have the best habitat suitability. In this study, basic data were obtained through inductive sorting, data collection, and a field survey of the Houxi River (a secondary tributary of the Yangtze River) and the endemic fish Schizothorax prenanti was selected as a key species. The hydrodynamic and fish effective habitats were calculated and simulated using relevant hydraulic formulae; a geomorphological diversity index (GDI) was introduced, and the target fish habitat area and geomorphological units, such as water depth and flow velocity, were analysed comprehensively to determine the ecological flow in the downstream dehydrated river section of the diverted small hydropower station. Flows of 17.5 m3/s and 5 m3/s were established during the spawning and non-spawning periods, respectively. This information provides a basis for the ecological restoration of river sections.

Improved Method of Local Feeder Automation Considering Small Hydro-power Connection

With the access of small hydro-power stations (SHS), the distribution system presents a multiple power supply pattern, which has a negative impact on the original local feeder automation (LFA) which is suitable for single side power supply system. In view of this effect, the phase to phase short-circuit fault (PPF) and single-phase grounding fault (SPGF) are treated differently, and an improved LFA method (IMLFA) considering SHS’s access based on low-frequency load shedding (LFLS) and high-frequency generator tripping (HFGT) is proposed. In case of SPGF, the section switch (SSW) and the outgoing circuit breaker of the substation shall be opened in sequence, and the isolated network (IN) generated in the process can be operated stably by cooperating with LFLS or HFGT while the fault is preliminary isolated. The SSW and the breaker are added with the function of no-voltage detection and synchronization detection. In case of instantaneous fault, the power supply in the fault area can be restored after a series of operations, and the IN can be connected to the grid. If it is a permanent fault, the section switches (SSWs) around the fault area will be locked to close in order to isolate the fault effectively, and the IN, not separated by the fault area from the grid, can be connected to the grid. Analysis and simulation show that the method is correct and feasible.

Impact analysis of small hydropower construction on river connectivity on the upper reaches of the great rivers in the Tibetan Plateau

Hydropower construction may alleviate regional power shortages, regulate river water volume, improve energy structure. However, extensive hydropower construction activities can reduce the river connectivity, which will further lead to biodiversity loss and ecological environment degradation. Most impact assessments of river connectivity have concentrated on large hydropower stations, while few on small ones. Through field investigation, this study identified 236 small hydropower stations on the upper reaches of the great rivers in the Tibetan Plateau, including the Yellow and Yangtze Rivers. The authors established a river connectivity impact index (RCII) model to achieve quantitative analysis of the connectivity of each river segment. Four pressure indicators, the Degree of Fragmentation (DOF), the Degree of Flow Utilization (DFU), the Degree of Obstruction (DOO), and the Density of Road (DOR), were set up based on the station’s attribute data. The results indicate that the RCII can better express the impact degree of river connectivity with a high correlation coefficient R2 between the degree of water reduction and the RCII. More than 40.33% of the river reaches were with “heavy” RCII values, indicating that the construction of small hydropower stations had some impacts on river connectivity to some extent. Also, we found that DOF and DOR had greater impacts on river connectivity in the study area. The river connectivity impact had great spatial differences, with rivers in the eastern region being the most serious. Furthermore, the greater the damage of river connectivity, the greater the potential for loss of aquatic biodiversity. A framework was set up in our work to quantitatively evaluate the impact of small hydropower station construction on river connectivity, providing strong support for the further ecological river protection and strategic planning.

Numerical and Experimental Modelling of Small Hydropower Turbine

Recently, Archimedes screw turbines have been developed to operate as small hydropower stations, because of its reliability to operate with the low head( less than 5 m) and its low cost of design and operation. In the present study, the influence of the flow rate, shaft inclination angle, and the number of blades is studied using physical model and numerical model to determine the performance of Archimedes screw turbine at Ramadi Barrages in Iraq. The physical model was made of stainless steel with the following parameters: (the radius ratio is 0.536, the pitch is 70 mm, the shaft angles are 30? ,35? ,40? ,45?). The experimental work on the physical model is achieved with different flow rates and angles .The results showing that the highest efficiency is 81.4 % At the angle of 35? and the flow rate is 1.12 l/s . The maximum energy obtained is 25.13 w at the angle of 45?, the e flow rate is 2.065 l/s, and the efficiency was 72%. Also the results show that the increase in the number of blades increases the torque and efficiency of the turbine.

Numerical and Experimental Investigations on Inflow Loss in the Energy Recovery Turbines with Back-Curved and Front-Curved Impeller Based on the Entropy Generation Theory

Pump as turbine (PAT) is one of the economical and effective energy recovery devices in small hydropower stations. A back-curved PAT and a front-curved PAT were designed, and performance characteristics were studied, the accuracy of the numerical calculation was verified by comparing with the experimental results. The entropy generation theory was used to compare performance and energy loss of PATs. The results show that the high efficiency range of front-curved PAT is significantly wider than that of back-curved PAT. Under part-load condition (0.8Qd), design flow condition (1.0Qd) and over-load condition (1.2Qd), the efficiency of the front-curved PAT is 0.6%, 5.9% and 7.9% higher than that of the back-curved PAT, respectively. The energy loss in the PAT impeller mainly comes from the turbulent entropy generation rate which is mainly concentrated on the blade leading edge and trailing edge. Flow separation and flow shock caused by the mismatch between the relative flow angle and the blade setting angle are the main mechanisms of energy loss in impeller. In addition, the loss caused by the wall friction in the front-curved impeller is less than that in the back-curved impeller. Therefore, the entropy generation theory can provide guidance for the performance optimization of PAT.

Research on the electricity-gas coupling system with P2G to absorb surplus hydropower

With the rapid development of social economy, energy shortage and environmental pollution are becoming more and more serious, and clean energy power generation has become one of the measures to implement the sustainable development strategy. A large number of small and medium-sized hydropower stations in Southwest China have a large amount of surplus water due to light load and channel blockage. In response to this problem, a method of coupling the natural gas system and the power system using P2G and gas turbines is proposed to improve the absorption capacity of hydropower and reduce the amount of surplus water. In this article, a day-ahead economic dispatch model of electricity-gas coupling system(EGCS) is established with the goal of the lowest operating cost of the whole system, considering the output characteristics of run-off hydropower stations, natural gas system operation constraints, power system AC power flow and other constraints, and solve the model using the interior point method. The analysis of the calculation example shows that compared with the independent system, the EGCS can effectively reduce the amount of surplus water, improve the utilization rate of clean energy, and reduce the operating cost of the system. The rationality and effectiveness of the model are verified.

An optimal operation method of cascade hydro-PV-pumped storage generation system based on multi-objective stochastic numerical P systems

To take full advantage of the complementary characteristics of various renewable energy sources, hybrid generation systems (HGSs) are used to accommodate the increased variability and uncertainty. In southwest China, there are many small cascade hydropower stations (CHSs) and PV power stations, which have spatial and temporal correlation characteristics and complementary characteristics. Pumped-storage units are considered as ideal large-scale energy storage elements for HGSs due to their fast response and long life. The purpose of this study is to increase the system reliability and water power utilization rate and maximize the economic benefits of a cascade hydro-PV-pumped storage (CH-PV-PS) generation system. Considering the reliability, economy, and water power utilization rate of the system, the CH-PV-PS system model with multiple objectives and multiple constraints is established. Then, a multi-objective stochastic numerical P system (MOSNP) is proposed. The external storage set and correction method in the MOSNP algorithm are introduced to ensure the diversity of the solution and improve the efficiency of the algorithm. The CH-PV-PS system is introduced in Sichuan Province, Southwest China. The simulation results show that (1) the MOSNP method can obtain robust and effective optimization results for the hybrid system; (2) the use of pumped storage units has increased the daily economy by 1018 CNY, and the total fluctuation of CHSs has been reduced by 29.3%, which makes the hybrid system safer and more economical; and (3) the uncertainty of PV and runoff will lead to frequent dispatching of CHSs, thus reducing the economic benefits of the system.

Green Development Path Analysis of Small Hydropower Based on River Chief System

River chief system is an innovative river and lake management system and model with Chinese characteristics. At present, the river chief system has achieved remarkable results in the management and protection of rivers and lakes in various regions. To promote the green development of small hydropower stations under the river chief system is not only the internal requirement of protecting water ecological environment, but also the urgent need of small hydropower stations to adapt to the green development in the new era. Based on the current situation of small hydropower development, this study establishes the evaluation system of small hydropower cleaning and rectification, evaluates the main problems existing in the green development and ecological transformation of small hydropower, and puts forward a practical development path, in order to promote the small hydropower ecological problems rectification and gradually embarking on the road of green development.

Regulation capability of small cascade hydropower stations for photovoltaic generation

The stochasticity of photovoltaic (PV) generation output makes it necessary to smooth the output using other flexible power sources to realize the scale development of PV power. Small cascade hydropower stations (SCHSs) are also widely distributed in space, like PV generation. Therefore, it is proposed to utilize the regulation capability of SCHSs to complement PV generation. Targeting the maximization of the utilization rate of outgoing lines (utilization rate for short) of the system, the minimization of the curtailment rate, and the maximization of the minimum output within a time frame, a model for exploring the capability of SCHSs for regulating PV generation was established and solved by a hierarchical optimization method. By taking two small hydropower stations (the Mupo and Yangjiawan stations) on the Fabian River with a total installed capacity of 105 MW and the surrounding PV power source in China's Sichuan Province as examples, it was found that SCHSs can regulate a certain level of PV generation through the combined operation of cascade reservoirs and reduce the fluctuations and stochasticity of the PV generation output. The results have far-reaching significance on the large-scale development of PV generation.

Application of artificial neural network and Soil and Water Assessment Tools in evaluating power generation of small hydropower stations

The objective of this study is to estimate the river’s capacity power generation and identify proper sites to install small hydropower stations The innovation in this study is estimating the river flow rate using different versions of the Soil and Water Assessment Tools (SWAT) model. Evaluating the flow rivers using different models helps to increase the accuracy of estimating river discharge and it can be effective in accurately identifying the river’s hydroelectric potential. In this investigation, an Artificial Neural Network (ANN) alongside the SWAT model has been used to increases the model’s ability to estimate streams flow. Also, an optimized algorithm called Improved the Pathfinder Optimizer (IPFO) have been utilized to reduce error during the learning process. The results of this study showed that among the three proposed models, SWAT-ANN-IPFO has the best estimate for river flow. Then, using the SWAT-ANN-IPFO model and Geographic Information system (GIS) software assessed the power potential sites along the rivers. In this study, the selection of proper sites for the installation of small hydropower stations based on physiographic and hydrological characteristics has been evaluated. Two criteria, slope and discharge for this purpose have been investigated. In this study, in total, 2,031 suitable points identified for installing hydroelectric power stations. The class 4 waterways are the most prone to installing hydroelectric power plants, and the identified sites are almost 846 because it has more discharge volume and more head differences than other order streams.

Comprehensive Evaluation Method of Virtual Power Plant Based on Hydropower Suppressing Wind Power Fluctuation

In order to assess the effects of the virtual power plants (VPP) participating in power grid regulation, this paper constructs a comprehensive evaluation index system of virtual power plants based on hydropower suppressing wind power fluctuations from three aspects: hydropower regulation ability, grid operation and dispatching, and economy of VPPs. The weight of each index is determined by the combination weighting method based on the entropy weight method (EWM) and the analytic hierarchy process (AHP). To verify the rationality and scientificity of the index and the weighting method in this paper, a regional power grid in Fujian has been taken as an example. Three VPP construction schemes including wind farms and small hydropower stations are selected and then the score of compare each index and total score of each scheme are calculated to determine the optimal scheme. The conclusion indicates that the evaluation index system and method is applied to the VPPs composed of wind power and hydropower and provides a theoretical reference for the construction and planning of VPPs in areas rich in wind and water resources.

Analysis of the overvoltage cooperative control strategy for the small hydropower distribution network

AbstractIn general, the seasonal characteristics of small hydropower (SHP) especially the power transmission during the summer flood season would lead to the steady overvoltage of the distribution network. In order to suppress this steady overvoltage, a strategy for coordinated cooperation between generator phase-in operation and shunt reactors which can be called cooperative control is proposed. The distribution network of SHP stations connected to the 35 kV Bantao substation in southern Shaanxi is taken as an example to study the mechanism of overvoltage after the SHP is connected to the grid. A distribution network model with SHP units is established. Based on the model, the effect of separately installing shunt reactors on the node voltage is studied in the case of generator lag phase operation and the influence of the operation mode of SHP unit on the node voltage is also analyzed separately. Finally, the improvement measures of cooperative control between the generator phase-in operation and the parallel reactors are analyzed by simulation. Results are presented to verify the improvement measures that can effectively restrain the overvoltage of the distribution network in the SHP area.

Complementary operation of a small cascade hydropower station group and photovoltaic power stations

Complementation with hydropower is an important solution to solve the problems of grid connection and consumption of photovoltaic generation. Considering the randomicity of photovoltaic output and runoff, hydropower station with good regulation capability is often used as a complementary power source of photovoltaic generation. However, there are only a small number of regulatory hydropower stations, which is difficult to meet complementary requirements of widely distributed photovoltaic power stations. The present study aimed to explore the feasibility of using a small cascade hydropower station group as the only complementary power source for photovoltaic generation. Based on electric energy production and output fluctuation, this study constructed a hydro-photovoltaic complementary operation model with dual-objectives of maximization of average capacity factor of the system and load rate of power generation. An algorithm coupling flower pollination algorithm with progressive optimality algorithm (coupling algorithm) was put forward to obtain solutions. The simulation results of the model showed that the fluctuation in joint operation mode is significantly lower than that in single operation mode, and the comprehensive target value on sunny day calculated by the coupling algorithm is 2.53% and 2.16% higher than the results of flower pollination algorithm and progressive optimality algorithm, respectively, verifying the reliability and rationality of the model and the algorithm.

Attention to Environmental Protection of Small Hydro-power Stations

In this paper, some problems commonly encountered in the construction and production process of small hydro-power stations in China are analyzed and explained, and the solutions are provided as well. Existing problems we have are the shortage of Eco-flow discharge, the Oil pollution in downstream river course caused by power generation production at the station, the cooling water supply of hydro-power station and the problem of eliminating pollution, electromagnetic and noise pollution of station, the resident's dispute around the power station caused by the increase and decrease of the groundwater level at the location of the station, the flood control problem of the water diversion hub, the pollution of the river channel, and the danger caused by the height of trees under the transmission line. The author, who based on many years of practical experience in hydro-power stations, and combined with relevant state policies and regulations, and puts forward practical methods and ideas to solve the problem in close connection with the actual situation of the project.

Flow alteration by diversion hydropower in tributaries to the Salween river: a comparative analysis of two streamflow prediction methodologies

ABSTRACT A multi-model approach was applied to reconstruct long-term flow records in 32 ungauged rivers developed with small diversion hydropower stations. Potential hydrologic alteration was assessed for flow records simulated by a catchment similarity model and the multi-criteria Streamflow Prediction under Extreme Data-scarcity (SPED) framework. Model validation based on limited observed data suggests that the SPED flow predictions are substantially more accurate than those generated by the catchment similarity model (NSE of 0.74 and 0.22, respectively and Correlation Coefficient of 0.87 and 0.72, respectively). Both flow prediction techniques indicated that flow signatures were altered substantially by diversion hydropower. Mean annual flows decreased by a mean of 76–86% across the 32 rivers and flow became more predictable in most rivers (47–94% mean increase in predictability). Frequency and duration of high flows decreased and duration of low flow events increased substantially. Slopes of rising hydrograph limbs and recession limbs increased respectively by a mean of 123–161% and 254–720%. While direction of detected flow alteration was similar regardless of model choice, severity of alteration was consistently greater based on the analysis of flows simulated by the multi-objective SPED model. Overall, the agreement of the multi-model analysis indicates that the signal of flow alteration by diversion hydropower in the study rivers supersedes uncertainty associated with flow prediction. While both models may be appropriate for applications such as change detection analysis, prescriptive management actions, such as establishing flow targets for environmental flow regimes, should be based on flow records generated by models adept at simulating rainfall-runoff processes targeted to individual basins, such as SPED.