Pumped Storage Hydropower Station Research Articles

Combined dam-break modes between upper and lower reservoirs of pumped storage hydropower stations and associated flood risk assessment

ABSTRACT With the increasing construction of pumped storage hydropower projects in China, dam-break risk has become a matter of great concern. Typical pumped storage hydropower stations have relatively small storage capacity but are vulnerable to complicated combinations of dam breaks between their upper and lower reservoirs. This paper provides basic principles for determining different dam-break classes that could initiate at a pumped storage hydropower station and summarizes these in terms of risk source. After idealizing the breach development process, a simple dam-break model and a planar two-dimensional depth-averaged shallow flow model are used to calculate the discharge hydrograph of the dam-break flood and simulate the temporal and spatial characteristics of downstream inundation. Taking a montane rockfill-pumped storage project as an example, 12 dam-break schemes are used to examine different types of combined flow patterns driven by upper and lower dam breaks with modes that are gradual and/or instantaneous. It is found that predicted dam-break discharge hydrographs and downstream inundation indexes under adverse schemes fit common features of dam-break floods in mountain rivers. Downstream disaster losses are evaluated and flood evacuation routes are recommended. The findings of this study should be useful in ensuring the safe management of pumped storage hydropower stations.

Unified Paradigm of Start-Up Strategy for Pumped Storage Hydropower Stations: Variable Universe Fuzzy PID Controller and Integrated Operation Optimization

Unified Paradigm of Start-Up Strategy for Pumped Storage Hydropower Stations: Variable Universe Fuzzy PID Controller and Integrated Operation Optimization

Based on the Security Control of Pumped Storage Hydropower under Extreme Fault Conditions after Grid Connection

Abstract As an important part of the new energy grid connection, pumped storage hydropower plays an important role in black start, frequency modulation and phase modulation, peak shaving and valley filling, energy storage and accident reserve. In order to ensure the security and stability of the power system under extreme fault conditions after the pumped storage hydropower is connected to the grid, it is particularly important to configure reasonable security and stability control measures. Based on the development status and operation characteristics of pumped storage hydropower stations at home and abroad, considering the need of system security and stability control, this paper takes a pumped storage hydropower station in Southwest China as an example to simulate and analyze the transient characteristics of the pumped storage hydropower after grid connection. In view of the possible extreme fault conditions, a regional security control system is designed, and the configuration, control measures and strategies of the security control device on the pumping side are studied.

The application effect of the optimized scheduling model of virtual power plant participation in the new electric power system

To build a comprehensive framework for virtual power plant (VPP) development aligned with market dynamics and to devise effective strategies to foster its growth, this study undertakes several key steps. Firstly, it constructs a VPP development framework based on market conditions, to drive the evolution of new power systems and facilitating energy transformation. Secondly, through a blend of theoretical analysis and model construction, the fundamental principles of VPP are systematically elucidated, and a decision model for the VPP development framework, focusing on price demand response, is formulated. Lastly, an optimal scheduling model for the new power system is developed, with its efficacy validated across three distinct scenarios. The findings underscore the critical importance of integrating energy storage technologies, particularly pumped storage hydropower systems, for achieving balance and optimization within new power systems. Model verification reveals that the incorporation of energy storage power stations significantly enhances system stability and efficiency, particularly in addressing the volatility associated with renewable energy sources. Additionally, the analysis indicates that while the adoption of energy storage technologies may marginally increase overall power generation costs, the total power generation cost declines with the integration of battery storage and pumped storage hydropower stations. This suggests that leveraging energy storage technologies not only enhances system operational reliability but also contributes to reducing the overall cost of power production to a certain extent. In summary, this study presents an economic and environmentally sustainable scheduling model for new power systems within the context of market trading environments. By offering both theoretical insights and practical guidance, it aims to support sustainable development and energy transformation initiatives. Ultimately, the study is poised to foster the adoption of clean energy, facilitate the establishment of smart grids, and bolster the sustainable utilization of energy resources, thereby advancing environmental conservation efforts.

Analysis of Seepage Field Characteristics of Water Diversion Power Generation System of Pumped Storage Power Station

Based on the diversion power generation system project of the Hami pumped storage Hydropower Station, the drainage substructure method is used to accurately simulate the drainage holes of the plant area, and the three-dimensional finite element model of the plant area including the main faults and reflecting the seepage characteristics of complex rock mass is established. Based on the inversion analysis of the natural seepage field, the distribution characteristics of the three-dimensional seepage field in the plant area were studied, and the rationality of the layout of the anti-seepage drainage system was evaluated. The results show that under the action of the anti-seepage drainage system, the groundwater level of the mountain is greatly reduced, and the descending funnel is formed in the three caverns, the seepage flow is controllable overall, and the permeability stability meets the engineering safety requirements.

Revealing the pressure pulsations that can cause water column separation in pump-turbine

Water column separation (WCS) can lead to a lifting-up of the rotating parts of pump-turbine and even a catastrophe in pumped-storage hydropower stations. However, the fundamental question, which pressure pulsations can trigger WCS, has not been answered. To answer this problem, we quantitatively analyzed the responses of a cavitation bubble in compressible unbounded water and cavitation cavities in a prototype pump-turbine to different pulsating pressures, using the Keller-Miksis equation and three-dimensional computational fluid dynamics. The findings reveal that a single cavitation nucleus oscillates around its initial radius when the lowest pulsating pressure is higher than the saturated vapor pressure (pv); as numerous cavitation nuclei grow to the maximum radius, they will coalesce a cavitation cavity when the lowest pulsating pressure drops to the pv and maintains 0.5Tf; the cavitation cavity can develop into a WCS when the pulsating pressure continue to maintain at the pv for about 1.0TRmax. Specifically, the lowest pulsating pressure dropping to the pv is a crucial prerequisite for WCS, and the pressure pulsations with frequencies below 0.83 Hz can make the cavitation cavity becoming a WCS in the prototype pump-turbine. This finding provides the theoretical base for the revision of the WCS criterion for pump-turbines.

Numerical Study on the Effect of Crown Clearance Thickness on High-Head Pump Turbines

In order to promote the development of new power systems and the consumption of clean energy, pumped storage hydropower stations tend to become increasingly larger in capacity and higher in head height. In this paper, a three-dimensional model of the full channel of a high-head pump turbine is established, and the influence of the gap thickness between the runner crown and the headcover on the internal flow field characteristics, pressure fluctuation characteristics and axial water thrust are studied by means of computational fluid dynamics (CFD). The results indicate that the area where the pressure and velocity vary greatly in the flow field of the crown clearance is at the seal of the labyrinth ring. In addition, the pressure balance pipe has a greater impact on the pressure and flow rate of the water passing through the clearance, and the crown clearance near the pressure balance pipe generates a vortex, resulting in energy loss. Decreasing the thickness of the clearance has no obvious effect on the pressure on the flow-passing components, and increasing the thickness of the clearance has a great change in the pressure values at the upper crown inlet, in front of the labyrinth ring of the crown and in front of the labyrinth ring of the band. The upper part of the vaneless area, the crown inlet and the lower ring inlet are close to the runner; hence, the interference from the rotating parts is the strongest. The effect of increasing the thickness of the crown clearance on the axial water thrust is greater than that of decreasing the thickness of the crown clearance. The pulsation frequency of the axial thrust on the crown, band and blade and the resultant force of the axial thrust increase with the increase in the crown clearance thickness.

A many-objective optimization strategy for unified optimal operation of pumped storage hydropower station under multiple load rejection conditions

Pumped storage hydropower stations are essential for the efficient integration of renewable energy, while frequent conditions conversion make them prone to fall into terrible transient processes, posing a stiff challenge for sustaining stable operation. Especially when simultaneous or successive load rejection happens, the hydrodynamic pressure can be tremendous because of hydraulic interference and outrageous flow changes. Researchers have actively pursued for optimal control under extreme conditions, while their concern is solely on a specific condition. The circumstance may happen that operation strategy admirable for certain condition is generally inappropriate or even highly hazardous for another. Following this idea, a many-objective optimization strategy for unified optimal operation is proposed, which intends to pinpoint the optimal strategy of turbine mode suitable for multiple load rejection conditions with marvelous transient process performance. In the first place, the model foundation of pumped storage hydropower stations characterized by one-tunnel-two-units is primarily established, which incorporates logarithmic curve projection for precise emulation on pump-turbines. Meanwhile, a novel constrained many-objective optimization strategy is proposed as optimization basis, which possesses distinguished exploration and exploitation attributes taking the merit of reference direction and ε-constraint. The effect analysis of operation scheme is conducted for a preliminary understanding of stability characteristic and dynamic quality. The calculation example applied to actual case shows that, compared with other state-of-art counterparts, the proposed many-objective optimization algorithm effectively harmony the contradictory targets under multiple load rejections, and satisfactory performance can be obtained with existence of adequate safety margin disregarding the variation of operation parameters. These results demonstrated the effectiveness and applicability of the proposed strategy for the insurance of stable operation.

Pressure fluctuation characteristics of a pump turbine in a draft tube: New insight into water column separation

The pumped-storage hydropower station is the most reliable, economic, long-term, large capacity, and mature energy storage technology in the power system, and it is an important component of renewable energy. Cavitation and water column separation of a pumped storage unit are important and widely researched factors in the safe and stable operation of a unit. This study focused on the evolution of water column separation of a pump turbine and its relationship with the pressure distribution of the cross section of a draft tube as well as the pressure pulsation characteristics of different measuring points in the cross section of the draft tube. A pumped storage experimental platform that can realize water column separation is established, and experiments with different opening angles are carried out. The results show that there are three factors that impact water column separation and cavitation: gas nucleus, vaporization pressure, and duration of vaporization pressure. Water column separation is the development and continuation of cavitation. The difference between the center pressure of the vortex rope and the wall pressure is large, reaching 2.23 m at a large opening. The pressure fluctuation amplitude of the wall measuring point is greater than that of the other measuring points in the same cross section, but the frequency characteristics are the same. In the transition process, the pressure pulsation amplitude of the liquid column bridging is the largest, and the largest pressure pulsation amplitude can reach 4.18 m at a small opening.

Evolution and influence of high-head pump-turbine cavitation during runaway transients

Pumped-storage hydropower stations (PSHSs) play irreplaceable roles in promoting the stability and flexibility of power grids. Runaway process is one of the most dangerous transients for PSHSs, and the cavitation in the pump-turbine seriously affects the stability and safety of the unit. However, the evolution and influence of pump-turbine cavitation during runaway transients are still unclear. In this study, the runaway transients of a high-head pump-turbine considering the cavitation effects were simulated by using the three-dimensional (3D) computational fluid dynamics (CFD) method. The results show that the cavitation cavities in the runner appear and disappear periodically, influenced by the backflows around the leading and trailing edges of the runner blades. The wedge-shaped cavities near the leading edges occur around the peak rotational speed moment when the pressure pulsations in the vaneless space show the peak magnitude. And the tongue-shaped shaped cavities near trailing edges appear around zero discharge moment when the hydraulic radial forces reach the peak. The two types of cavitation occur at dangerous moments, to which attention should be paid in the preliminary design stage of PSHSs.

Techno-economic optimization of grid-connected solar-wind-pumped storage hybrid energy system using improved search space reduction algorithm

With the fast paced development and integration of the renewable sources into the grid, it is essential to design and develop the storage system effectively to complement the renewable power generation so that the renewable energy system is not only reliable but also cost-effective. The pumped storage is an optimal, economically viable, and scalable solution for renewable energy integration with the grid. This paper proposes the optimal sizing of grid-connected solar–wind hybrid renewable energy systems (HRES) involving pumped storage hydro-power station (PSHS). The main goal is to determine the optimal combination of the PV-WT-PSHS hybrid system to minimize the levelized cost of energy (LCOE) subjected to the constraints which improve the system reliability and also promotes the use of maximum renewable fraction to meet the total load requirement. Further, the random inflow during the rainy season is modeled and its impact on the sizing of the HRES is also analyzed in this work. The effect of random inflow on sizing of the HRES is novel and has not been applied any optimal sizing studies in the literature. The optimal sizing is carried out by using a newly proposed algorithm called search space reduction (SSR) algorithm. Further, an improved search space reduction (ISSR) algorithm is also developed and applied to the same problem. The optimization is carried out in two scenarios; with and without including the random inflow, and the results indicate that when the random inflow is included, the cost per unit is significantly lesser. For validating the effectiveness of the ISSR algorithm, the results were compared to the other well-known algorithms such as grey wolf optimizer (GWO), teaching-learning based optimization (TLBO) the obtained also demonstrate the superiority of ISSR algorithm as it is able to achieve minimum value of objective function when compare to the other algorithms.

Research on Coal Acoustic Emission Characteristics and Damage Evolution During Cyclic Loading

The acoustic emission, energy, and damage evolution of coal samples for three kinds of uniaxial cyclic loading and unloading are deeply analyzed in this study. The evolution of total absorption energy, elastic strain energy, and dissipated energy of coal samples is related to the stress path, and the increasing amplitudes cycle loading has an obvious damage effect on coal samples. During the loading stage, the acoustic emission phenomenon is most active when loading is increasing and the Felicity and post-Kaiser phenomena appear. The acoustic emission phenomenon during constant loading does not obviously change, but rather becomes active with the increase of the equivalent load. The damage to the coal sample shows nonlinear change increasing loading and unloading and shows linear change for other stress paths. Compared to waveforms with stepwise increasing amplitudes cyclic loading, the failure process of the coal sample is more closely related to the size of the external load, which indicates that reasonable hydraulic design is beneficial to the stability of the confining pressure in the chamber of an underground pumped storage hydropower station.

Failure and protection of metal equipment in Pumped Storage Power Station

In order to ensure the safe and stable operation of pumped storage hydropower station equipment, it is very important to carry out regular maintenance of metal equipment. Because of the stress concentration, the stress state and the complex environment, the variable section of the turbine runner blade is easy to produce cracks, which endangers the safety of the equipment. By fully analyzing the characteristics, failure modes and causes of blade cracks, and putting forward effective detection, treatment and protection measures, cracks can be effectively prevented, which will play a key role in future equipment maintenance and repair.

Research and Application of Flood Regulation System Based on Visual Studio

Due to the characteristics a pumped storage power station owns, the issues it considers concerning flood regulation calculation differ from those of a regular hydropower station. Take the flood regulation system of Hongs pumped storage hydropower station as a study case, the business requirements of flood regulation for regular hydropower station reservoir and pumped storage hydropower station is analyzed. Based on Visual Studio development platform, design systematic functional structures, elaborate the design ideas of core function modules in system development, such as database management, flood regulation principles and information inquiry, etc. Finally introduce the application of the system on flood regulation in Hongs pumped storage hydropower station reservoir.

Study of Hydraulic Disturbances From Single-Unit Load Rejection in a Pumped-Storage Hydropower Station With a Shared Water Delivery System

The transient characteristics of load rejection process in pumped-storage hydropower (PSH) stations have a close relation to the safety of electric power system and hydraulic facilities. A large portion of PSHs consist of multiple units sharing one tunnel (MUSOT). In this paper, a three-dimensional numerical simulation method for hydraulic disturbance caused by single unit load rejection transition process based on the volume of fluid (VOF) two phase flow model was proposed and a filed test was carried out in a PSH station with a two units sharing one tunnel (TUSOT) setting. The power output from the unit that operates in normal condition (UNC), the pressure fluctuations of the spiral casing inlet and tailrace tunnel outlet, the water level variation and flow pattern in surge tank were obtained through the numerical simulation and field test. The results showed that the highest and lowest water level in surge tank from the numerical method agreed well with the measured data obtained in the field test. The guide vanes closing law of the unit that runs in load rejection (ULR) mainly impacts on the variation of the above parameters. To reduce the influence of single-load load-rejection hydraulic disturbance, a more elaborate guide vanes adjustment scheme of the UNC should be proposed in the next step to avoid large short-time fluctuations in the power output and pressure.

Research on Hydraulic Characteristics in Diversion Pipelines under a Load Rejection Process of a PSH Station

Transient analysis in diversion pipelines should be performed to ensure the safety of a hydropower system. After the establishment of a three-dimensional (3D) geometric model from the part upstream reservoir to the diversion pipeline end in a pumped storage hydropower (PSH) station, the hydraulic characteristics of the diversion system were solved by Reynold average Navier–Stokes (RANS) equations based on a volume of fluid (VOF) method under the condition of simultaneous load rejection of two units. The variations of the water level in the surge tank, the pressure at the pipeline end, and the velocity on the different pipeline sections with time were obtained through the calculation. The numerical results showed that the water level changing in the surge tank simulated by VOF was consistent with the field test data. These results also showed that a self-excited spiral flow occurs in the pipeline when the flow at the end of the pipeline was reduced to zero and its intensity decreased with the flow energy exhaustion. The discovery of the self-excited spiral flow in the study may provide a new explanation for the pressure wave attenuation mechanism.

3D Modeling of the Different Boiling Regimes During Spill and Spreading of Liquid Hydrogen

In a future energy generation market, the storage of energy is going to become increasingly important. Besides classic ways of storage, like pumped storage hydro power stations, etc, the production of hydrogen will play an important role as an energy storage system. Hydrogen may be stored as a liquefied gas (LH2) on a long term base as well as for short term supply of fuel stations to ensure a so called “green” mobility. The handling with LH2 has been subject to several recent safety studies. In this context reliable simulation tools are necessary to predict the spill and spreading of LH2 during an accidental release. This paper deals with the different boiling regimes: film boiling, transition boiling and nucleation boiling after a release and their modeling by means of an inhouse-code for wall evaporation, which is implemented in the commercial CFD code ANSYS CFX. The paper will describe the model, its implementation and validation against experimental data, such as the HSL LH2 spill experiments [1].

Research on Optimizing Precast Water Head on Preloading Filling Spiral Case of a Large-Scale Hydropower Station

In combination with the practice of a pumped storage hydropower station, a 3-D nonlinear finite element method on the preloading filling spiral case is carried out to compare and analyze stresses of the steel spiral case and hoop reinforcement, the stress and bearing ratio of the surrounding concrete, the contact state between the spiral case and concrete in different precast water head. The results indicate that the stress of the surrounding concrete will get better with the increasing of precast water head. But there is a distance between the spiral case and the surrounding concrete when the water head is excessive, which is unhelpful for operating of the unit. When the precast water head of the spiral case is 439m or so, it can play a greater degree of mechanical characteristics of steel and concrete under the premise of operating stably of the unit.

Proposal of a simplified method for integrating reduction of effective power of pumped storage into a generation system planning method

Pumped storage hydropower stations are extensively used as peaking and reserve power plants. The current trend in this area is to increase their power output relative to the capacity of reservoirs, which results in a shorter maximum duration of full-power operation while availability of the energy required for the pumping becomes less evident. This increases the possibility of reducing the effective power of pumped storage units in the case of a tight supply–demand balance in the power system. Although many studies have examined a role of pumped storage in generation systems, few studies have explicitly dealt with the power reduction. This paper proposes a new linear programming model that incorporates the reduction of effective power of pumped storage. The proposed model makes it possible to easily incorporate the power reduction in computations by employing hypothetical daily load curves and dispatching loads to the curves. The model also includes LNG combined cycle power generation plants that are now being intensively implemented. The developed model is applied to a power system model. The sample study reveals that the reduction of effective power considerably varies from season to season and the reduction highly affects the optimal generation mix, that is, the optimal share of pumped storage. © 2001 Scripta Technica, Electr Eng Jpn 134(4): 50–61, 2001