Unstable behaviour of pump-turbines and its effects on power regulation capacity of pumped-hydro energy storage plants

Cavazzini, Giovanna; Houdeline, Jean-Bernard; Pavesi, Giorgio; Teller, Olivier; Ardizzon, Guido

doi:10.1016/j.rser.2018.06.018

Cited by 88 publications

(36 citation statements)

References 50 publications

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“…relative discharge in channel i Q 11 unit discharge Q discharge Q BEP discharge at the best efficiency point r 2 coefficient of determination t time t ' relative time v x , v y and v z…”

Section: Nomenclaturementioning

confidence: 99%

“…These flexible operation modes and the frequent transitions between different modes demand high levels of safety and stability of PSPSs. However, the core component of most PSPSs, the reversible pump‐turbine, shows significant operational instabilities [1], especially when it goes cross the so‐called S‐shaped region in the four‐quadrant characteristics plane [2]. This type of characteristics has been proved to be responsible for many problems and accidents in PSPSs all over the world, such as large hydraulic fluctuations, difficulties in synchronising with the grid, speed surging during turbine startup, power swing in low‐head conditions, and draft‐tube water column separation in the emergency shutdown [3].…”

Section: Introductionmentioning

confidence: 99%

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Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Zhang

Cheng

Zheng

et al. 2020

IET Renewable Power Generation

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To enhance the power grid's stability and safety, pumped-storage power stations (PSPSs) have to keep themselves stable and safe strictly. However, instabilities happen frequently in some PSPSs due to the S-shaped characteristics of pumpturbines. When the operating point goes through the S-shaped region, intensive radial forces on the runner could cause shaft swing of the turbine-generator unit. In this study, the runaway transient scenarios of a pump-turbine in a model PSPS were simulated by using a one-dimensional and three-dimensional coupled computational fluid dynamics model, and the influence of the unit rotational inertia on the runner radial forces was investigated. The results show that when the pump-turbine runs in the S-shaped region, large rotational inertia is easier than a small one to induce abrupt increases in runner radial forces. The reason is that large rotational inertia gives slower changes in rotational speed and discharge, providing enough time to generate unstable and uneven flow patterns in the pump-turbine. This indicates that apart from the running away region in the characteristics plane, the running away duration is also essential for the transient instability of a pump-turbine. The finding is different from the traditional understandings and should be considered when selects the rotational inertia of a pump-turbine unit. ρ 0 initial density ρ density σ standard deviation of the relative discharges ω angular velocity at the current time-step ω p angular velocity at the previous time-step

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“…relative discharge in channel i Q 11 unit discharge Q discharge Q BEP discharge at the best efficiency point r 2 coefficient of determination t time t ' relative time v x , v y and v z…”

Section: Nomenclaturementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Zhang

Cheng

Zheng

et al. 2020

IET Renewable Power Generation

View full text Add to dashboard Cite

show abstract

“…In rated conditions of speed, head, and flow, a hydraulic machine may reach its maximum efficiency in energy conversion and a cavitation and vibration-free operation [55][56][57][58]. Figure 5 shows three types of Francis runners, namely slow, normal, and fast specific speed runners, which are suitable for high, average, and low heads, respectively, with specific rotation ranging from 70 to 400.…”

Section: Francis Turbine Operating At Variable Head and Speedmentioning

confidence: 99%

The Benefits of Variable Speed Operation in Hydropower Plants Driven by Francis Turbines

et al. 2019

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Climate change and environmental degradation has resulted in a reduction in water inflow at hydropower plants, as well as a decrease in reservoir levels. Existing hydropower plants suffer from water head reduction, mainly with decrease in efficiency of energy conversion in hydro turbines. This paper showcases the benefits of operations with variable speed in existing hydropower plants, when working at a lower water head than the rated one. Theoretical analyses and tests were performed in a special constructed laboratorial setup aiming at evaluating the amount of efficiency recovery with variable speed operation. Connection alternatives for a constant frequency grid and applications of the learned concepts in an existent hydropower plant are presented. The investigations were applied to the Furnas hydropower plant. The results point out that economic feasibility of the application can be achieved.

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“…Poulain et al 7 have performed a numerical analysis to research the environmental impact of the pumped energy storage system. Cavazzini et al 8 have conducted a study to determine the effect of unstable behavior of pump‐turbines and its effects on the power regulation capacity of pumped‐hydroenergy storage plants. Ko et al 9 have performed an economic analysis of pumped energy storage for Korea.…”

Section: Introductionmentioning

confidence: 99%

Development and assessment of geothermal‐based underground pumped hydroenergy storage system integrated with organic Rankine cycle and district heating

Erdemir

2020

Int J Energy Res

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This study develops a geothermal-based underground pumped hydroenergy storage system (UPHES) integrated with an organic Rankine cycle (ORC) and district heating. The ORC has been integrated into the system for contributing the power demand of the pump used during the charging period to pump the water from the underground to the upper reservoir. District heating has been performed by geothermal. Heat recovered from the ORC has been used for the preheating of water used in district heating before entering the upper reservoir. With this proposed integrated system, both the peak energy demand has been shifted to off-peak hours and district heating has been performed. An ORC has also been included in the system to contribute to the energy demand of the UPHES pump. In order to evaluate the system's performance, thermodynamic analysis has been performed base on energetic and exergetic efficiencies. In the base case study, 60 MWh of electricity has stored by the UPHES. Also, a 2.8 MW of heating demand of 100 houses has been met and a 1.7 MW of power has been generated by the ORC. The power of the UPHES pump has been calculated as 6.81 MW. The efficiency of the UPHES system is 73.34%. Overall energy and exergy efficiencies of the proposed integrated system have been calculated as 93.09% and 78.37%, respectively.

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Unstable behaviour of pump-turbines and its effects on power regulation capacity of pumped-hydro energy storage plants

Cited by 88 publications

References 50 publications

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

Influence of rotational inertia on the runner radial forces of a model pump‐turbine running away through the S‐shaped characteristic region

The Benefits of Variable Speed Operation in Hydropower Plants Driven by Francis Turbines

Development and assessment of geothermal‐based underground pumped hydroenergy storage system integrated with organic Rankine cycle and district heating

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