Pumped-storage Plant Research Articles

A coordination controller in variable speed pumped storage plant

With the integration of increased variable renewable energy generation, much attention has been devoted on the development of pumped storage. The variable speed pumped storage technology has become a research focus due to its wide operating range, high production efficiency and strong power regulation ability. Moreover, the coordination controller is the key component of variable speed pumped storage plant (VSPSP), it can coordinate the joint operation of governor and converter. The coordinated controller is studied in this work. Aiming at the coordinated control between governor and converter, the novel adaptive strategy of maximum efficiency point tracking is proposed. First, the optimal efficiency curves are described based on model experiment; and then the optimal operating curves of variable speed unit in the operation region is presented based on the BP neural networks; the convergence analysis of mean square error and regression analysis are applied to verify the reliability of results. Aiming at the application of adaptive strategy in the coordination controller, and ensuring the real-time performance, a new effective digital interpolation method is put forward, using programmable logic controller. The signal flows of the control system in variable speed unit are clarified. The proposed adaptive strategy could be easily applied in engineering, providing a technical means for the efficient and flexible operation of VSPSP.

Optimal scheduling of variable speed pumped storage, solar and wind energy system

ABSTRACT The entry of renewable energy sources in the power sector has significantly affected the inter-connected power system’s safety and stability as renewable energy sources tend to generate variable power. The variability of power inflicts severe challenges for the scheduling of renewable sources. A pumped storage hydro plant (PSP) can help in integrating the variable renewable energy and balance the demand and generation on a day-ahead (DA) or real-time basis through fast response generation. An optimal PSP operation schedule has been obtained to increase the power producer’s profit by formulating it as a mixed-integer problem. The mathematical problem formulation for the hybrid system with solar, wind, and PSP operation has been made, considering the next day’s market schedule. The revenue has been computed by utilizing the energy of solar, wind, and PSP. A comparative study for the profit earned depending upon the power is regulated or not, using variable speed technology, during the pumping mode has been presented. The grid power has been utilized for the pumping operation of the pumped storage plant. A penalty factor has been utilized for the mismatch in the demand and generation. The analysis shows that the variable speed operation of PSP during pumping mode has increased the net profit by and reduced the charges paid toward the pumping operation by compared to the fixed speed operation and a rise of in profit and decline in pump charges have been recorded compared to two-speed operation.

Nonlinear Model Predictive Control for Pumped Storage Plants Based on Online Sequential Extreme Learning Machine with Forgetting Factor

With renewable energy (RE) being increasingly connected to power grids, pumped storage plants (PSPs) play a very important role in restraining the fluctuation of power grids. However, conventional control strategy could not adapt well to the different control tasks. This paper proposes an intelligent nonlinear model predictive control (NMPC) strategy, in which hydraulic-mechanical and electrical subsystems are combined in a synchronous control framework. A newly proposed online sequential extreme learning machine algorithm with forgetting factor (named WOS-ELM) is introduced to learn the dynamic behaviors of the coupling system. Specifically, the initial learning parameters are optimized by prior-knowledge learning and a new self-adaptive adjustment strategy is also put forward. Subsequently, the stair-like control strategy and artificial sheep algorithm (ASA) are used in rolling the optimization mechanism to replace the existing complex differential geometric solutions. Comparative experiments are carried out under different working conditions based on a PSP in China. The results show that the influence from coupling factors can be considerable and the proposed MPC strategy indicates superiority in voltage and load adjustment as well as the frequency oscillation suppression.

Analysis of Inter-blade Vortex and Runner Blades Force of Pump Turbine during Load Rejection Period

Pumped storage unit as the most efficient energy storage equipment, it makes a great contribution to the development of renewable energy. The operating stability of pump turbine affects economical and safe operation of pumped storage plant directly, hence this study focuses on the transient process of pump turbine load rejection. Detached eddy simulation is adopted as turbulence model and dynamic mesh technique is used to achieve continuous guide vane closure. Internal fluid characteristics are presented based on the numerical analysis of inter-blade vortex and force of runner blades. The results show that:(1) Inter-blade vortex can be divided into two developing stages according to its location, which corresponds to the first and second half of guide vane closure respectively. (2) The incidence angle is the original reason that causes vortex in runner passage, which further development occupies the whole flow passage under the influence from centrifugal force and the interaction with the previous water. (3) The force distribution is aligned with the vortex zone, and the axial thrust keeps a downward tendency.

Control of Pumped Storage Plant with BLDC for Single Stage Grid Connected PV System Based Distributed Generation

In this paper a pumped storage plant with BLDC motor drive for single stage grid connected PV system based distributed generation is proposed. Grid Synchronization is done with synchronous reference frame (SRF) based control for improving grid power quality. A brushless DC motor drive without phase current sensors is used for water pumping. Hall effect sensor control is used for the speed control of BLDC motor. During day time PV feeds the load and excess power is used to pump the water from a lower reservoir to an upper reservoir for pumped storage. At night with the pumped water head BLDC generates power, pumped storage plant can be operated to feed the load and excess power is delivered to the grid. If pumping is not required, the excess PV output can be fed to the three-phase grid. fed. The utility grid will provide supply to the load if both PV output and Pumped Storage Plant outputs are insufficient. The whole system model is simulated in MATLAB/Simulink platform. The steady-state and dynamic, performance under various operating conditions are carried out and the simulation results are produced

Performance Optimisation of Coal-fired Boiler Control using Flownex® Simulation Environment and AI

ABSTRACT The inherent variability of renewable energy sources, pump storage plants and combined cycle gas turbines implies that coal-fired plants designed for continuous base load generation in South Africa must now be used for variable load. This has a negative effect on the overall efficiency and life expectancy of these plants. The challenge is, therefore, to balance the network demands with the power station operation, its thermal efficiency, availability and extended plant life expectancy. The focus of the current research is to monitor and optimise the efficiency of the boiler operation and control through modelling of the boiler subsystems during transient states. Flownex® Simulation Environment was used to model a generic boiler and a boiler control system in order to simulate thermo-fluid processes and critical boiler controllers. The developed model was evaluated based on plant data and optimised afterwards by means of PID controllers and Machine Learning algorithms. The process parameters obtained from the Machine Learning algorithms outperform that of the PID controllers for the selected controllers, such as: boiler load control and steam pressure control. Additional keywords: Power generation, boiler control, boiler modelling.

Analysis of the impact of construction and operation of pumped-storage power stations on grid companies and the formulation of electricity prices

The pumped storage power station is flexible to start, can realize effective storage of electric energy, and has superior peak and frequency modulation effects, which is beneficial to provide comprehensive benefits of the power system. But at present, the construction of pumped-storage power plants has obviously exceeded the speed of policy and market development, resulting in problems in pumped-storage power station operation and cost reduction. Aiming at this problem, this paper further expounds the influence of the construction and operation of pumped storage power station on the electricity price of power grid companies. The revenue of pumped storage power station mainly comes from the auxiliary service market. In China, the peak regulation effect of pumped storage power station is significant and the revenue is considerable. Therefore, this paper studies the formulation of time-of-use price and subsection price of pumped storage power station.

Zone-wide prediction of generating unit-specific power outputs for electricity grid congestion forecasts

The day-ahead trading of electricity necessitates that cross-border capacities limit inter-zonal exchanges. To construct trading domains, two-day-ahead congestion forecasts for the electricity grid are needed. These comprise nodal predictions for load as well as renewable and conventional power generation, from which line flows can be derived. Trading domains limit deviations from the predicted line flows to respect physical grid constraints, requiring an accurate prediction of unit-specific power outputs. This analysis explores various statistical and statistical learning methods, with the goal of adequately predicting the on/off status and power output levels of all power plants within a control zone. The methods are tested for 205 conventional generating units in Germany using forecast values of fundamental variables, namely, load, renewable energy generation and the unavailabilities of power plants. For most units, the extra trees classifier achieves classification accuracy values of over 90% and a second-step extra trees regressor results in average errors of below 10% in relation to the installed capacities. Flexible units, especially hard coal, gas and pumped-storage hydropower plants, exhibit the largest errors. An analysis of errors suggests that load and solar generation are the main drivers of prediction deviations.

Numerical simulation and stability analysis of pumping transients in the pumped-storage power plant

The pumped-storage unit (PSU) are of great significance in modern power system for its reversible operating mechanism in both power generation and water pumping directions. Aiming at the precise numerical simulation of pumping transient processes in PSU, this paper establishes a nonlinear and characteristic method-based mathematical model of the governing system of PSU in which the hydraulic behaviours of conduit pipes, surge tanks and the pump turbine as well as the mechanical-electrical characteristics of the generator-motor are taken into consideration. In this model, local hydraulic losses in model boundaries are specifically introduced to compensate for the unmodeled errors. To verify the modelling accuracy, simulation curves under both pump failure and pump shutdown conditions are compared with the practical data. Furthermore, the hydraulic oscillations in the two transient processes have been discussed specifically.

Control of Pumped Storage Plant with BLDC for Single Stage Grid Connected PV System Based Distributed Generation

Control of Pumped Storage Plant with BLDC for Single Stage Grid Connected PV System Based Distributed Generation

Increasing flexibility of the national energy system by building up hydro pumped storage plants

Increasing flexibility of the national energy system by building up hydro pumped storage plants

The software part, the fundamental and organizational structure of the software and hardware complex to ensure the safety of hydraulic and hydropower structures under the construction

Relevance. To ensure the safety of hydraulic and hydropower facilities, to organize constant monitoring of their condition, including the installation of additional control and measuring equipment is required. It is also necessary to introduce modern information and diagnostic systems that allow in real time to assess the state of both individual elements of the structure, as well as mutually influencing structures and complexes of structures. At the same time, the results presented in the article are aimed for describing the fundamental structure a new generation of information and diagnostic system building, developed within the framework of a software and hardware complex. The aims of the work. The main purpose of the proposed system is to increase the level of monitoring to ensure the safety of hydraulic structures, which have a possible impact on each other during operation and construction. The tasks of creating a unified platform for assessing the safe state of hydraulic structures during the construction and operation of hydraulic structures (hydroelectric and pumped-storage power plants) are being solved, the foundations of a unified information-diagnostic system on a modular basis are laid, which allows comparing monitoring and measuring equipment readings, statistical samples and calculated values obtained within the mathematical modeling objects. Methods. The paper presents the structure of the interaction of individual blocks included in the information-diagnostic system, the interaction of the information-diagnostic system with the user for decision-making during the operation of the hydraulic structures. Results. A modular shell has been implemented, consisting of a combined information-diagnostic system, expert and calculation modules, which allows a comprehensive approach to the issue of safety of mutually affecting hydraulic structures. Software links have been developed to assess the change in parameters that can lead to deviations/irregularities in the operation of the hydraulic structures.

Advantages of variable‐speed pumped storage plants in generating phase‐modulation mode: rapidity and stability

Advantages of variable‐speed pumped storage plants in generating phase‐modulation mode: rapidity and stability

Development and Construction Management System of Pumped-Storage Power Plants in China

Pumped-storage power plant(PSPP) is a special form of power supply. It is expected that the installed capacity of PSPP in China will reach 90GW by 2025. This paper summarizes the development of PSPP in China, and analysis the influencing factors of the configuration of PSPP, introduces the typical operation mode of PSPP and the existing problems in its development, and puts forward relevant policy suggestions for the development of PSPP.

Optimal scheduling for solar wind and pumped storage systems considering imbalance penalty

ABSTRACT The safe and stable operation of the traditional power system has been tremendously affected by the large-scale integration of various renewable energy sources, which has tendency to deliver variable power. The coordinated operation of renewable energy sources has become a hot topic of research nowadays. Utilizing complementary characteristics of solar, wind, and pumped hydro, this paper presents a mixed-integer problem to find optimal scheduling of hydro plants to enhance the market profit. Considering the market schedule for the day ahead, a mathematical formulation has been developed for the operation of a hybrid system. For this problem, the pumping operation of the pumped storage plant has been done by using grid supply during low market price hours. The overall profit can be increased by using the stored energy when the market price is high. The mismatch in the demand and generation has been curtailed by including a penalty factor in the objective function. The results obtained depict reasonable improvement in terms of economic benefits when the coordinated operation suggested is utilized. The results show that the penalty cost has been reduced by a factor of , and profit earned during solar-wind alone was negative and whereas using the Solar-Wind-PSP system (SWPS) the profit has increased and was found to be approximately of total revenue generated. The overall revenue saw an increase of nearly .

Thermal Performance Improvement in Multi-Megawatt Power Converters Serving to Asynchronous Hydro Generators Operating Around Synchronous Speed

In multi-MW three-level neutral point clamped back-to-back (3L-NPC) power converters, power semiconductor devices are considered as most vulnerable components due to its thermo-mechanical fatigue stress. Particularly, rotor side converter (RSC) in doubly fed induction machine (DFIM) experiences high thermal stress during its operation around synchronous speed. It degrades the performance of power converter and reduces the lifetime availability of the drive. In practice, stabilization of temperature fluctuation across each power semiconductor device improves the efficiency and reliability of power converter. With respect to this prime aim, this paper proposes a carrier-based active thermal control method to regulate temperature fluctuation across power semiconductor devices in a multi-MW (5 x 5 MW) 3L-NPC power converters serving to a 250 MW asynchronous hydro-generating unit. To test the proposed active thermal control method, different operating conditions of a 250 MW DFIM hydro-generating unit (to be commissioned in Tehri pumped storage plant, India) are examined in MATLAB/PLECS environment. The designed active thermal control method effectively regulates mean junction temperature and temperature fluctuation of power semiconductor devices within a safe operating limit. The practical feasibility and adoptability of proposed active thermal control is examined through a 2.2-kW DFIM laboratory prototype.

Utilization of energy storage systems in congestion management of transmission networks with incentive-based approach for investors

Electricity demand growth and other factors in the power system have increased the probability of congestion occurrence in power transmission lines. In recent years, there is more tendency for energy storage systems (ESSs) due to their high applications in the power system. One of these applications is the capability to relieve congestion. One of the main challenges of using ESSs is the high investment cost. In this paper, for expansion planning problem, a multi-objective optimization framework to relieve transmission congestion is proposed, combined with the use of new lines and ESSs. In the proposed framework, the viewpoint of the system operator and ESSs owner are simultaneously considered. Furthermore, an incentive-based approach for the investment of ESSs is suggested. The proposed method is implemented on the IEEE-RTS 24-bus system using pumped-storage hydro power plant (PSHP) and compressed-air energy storage (CAES) systems. The simulation results include a set of non-dominated optimal solutions that are obtained using the multi-objective genetic algorithm NSGA-II. The results provide optimal locations for new lines and ESSs and demonstrate the effectiveness of the incentive-based approach for selecting the best solution.

Can GNSS-R Detect Abrupt Water Level Changes?

Global navigation satellite system reflectometry (GNSS-R) uses signals of opportunity in a bi-static configuration of L-band microwave radar to retrieve environmental variables such as water level. The line-of-sight signal and its coherent surface reflection signal are not separate observables in geodetic GNSS-R. The temporally constructive and destructive oscillations in the recorded signal-to-noise ratio (SNR) observations can be used to retrieve water-surface levels at intermediate spatial scales that are proportional to the height of the GNSS antenna above the water surface. In this contribution, SNR observations are used to retrieve water levels at the Vianden Pumped Storage Plant (VPSP) in Luxembourg, where the water-surface level abruptly changes up to 17 m every 4-8 h to generate a peak current when the energy demand increases. The GNSS-R water level retrievals are corrected for the vertical velocity and acceleration of the water surface. The vertical velocity and acceleration corrections are important corrections that mitigate systematic errors in the estimated water level, especially for VPSP with such large water-surface changes. The root mean square error (RMSE) between the 10-min multi-GNSS water level time series and water level gauge records is 7.0 cm for a one-year period, with a 0.999 correlation coefficient. Our results demonstrate that GNSS-R can be used as a new complementary approach to study hurricanes or storm surges that cause abnormal rises of water levels.

An Exploratory Economic Analysis of Underground Pumped-Storage Hydro Power Plants in Abandoned Deep Coal Mines

This study researches the concept of underground pumped-storage hydro power plants in closed-down underground hard coal mines in Germany. After a review on how this could be realized technically, an economic feasibility analysis is presented, with a particular focus on the costs for the underground storage reservoir. The analysis is performed for different lower (i.e., underground) reservoir sizes and temporal arbitrage potentials (peak/off-peak electricity price spreads), and cost uncertainty is dealt with by means of a Monte Carlo simulation for two distinct head heights. The findings regarding costs and acceptability are compared with those of a classic (on-surface) pumped-storage hydro power plant in a mountainous area. Based on a techno-economic evaluation we conclude that under favorable conditions the realization of underground pumped-storage hydro power (UPSHP) plants seems both technically feasible and economically reasonable. More specifically, an extension of a tubular system seems the most promising option. A UPSHP plant in a mineshaft is probably slightly more expensive than a conventional one, an outcome that depends strongly on the feasible head height. However, the significant reduction of the adverse impacts on the landscape and on local residents, as well as a potentially large number of feasible sites in flat terrain, could make UPSHPs an interesting option for the future energy transition, not just in Germany but worldwide at sites where underground mining is being abandoned.

Investigation on optimization of self-adaptive closure law for load rejection to a reversible pump turbine based on CFD

Pumped storage plants (PSP) are operated under transient processes frequently in the case of the intermittent and unpredictable renewable energy. When PSPs are working in the load rejection process, the serious accident may be caused by the significant fluctuations of rotating speed and pressure. Seeking an appropriate law of guide vane movement in load rejection process is an approach to improve operating stability of PSP. This paper focuses on the optimization of self-adaptive closure law of pump turbine model for one Chinese PSP, based on sliding mesh technique and current closure law. Variations of speed and pressure are regarded as judgment functions. Meanwhile, detached eddy simulation(DES) is adopted to characterize internal flow field of pump turbine(PT) with adaptation of the optimized closure law. Not only the distribution of pressure and the turbulence kinetic energy in flow domains is analyzed details, but also the fluid evolution in passage is investigated. As a result, the optimized closure law is beneficial to impair the fluctuating rates of speed and pressure in transient process. It is illustrated that both the rotor-rotor and rotor-stator interaction in vaneless spaces are the sources of increased fluid instability in pump turbine. Note that the unstable flow regime emerges at the same moment in the inlet and outlet conduits, whereas their locations are opposite to the unit.