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The demand for energy storage systems is rising together with the proportion of renewable energy sources (RES) in power systems. The highest capacity among the various energy storage systems in power systems is provided by pumped-storage hydropower (PSH). In this paper, the ability of the real-time digital simulator (RTDS), e.g., dSpace–SCALEXIO, to emulate a complex pumped-storage hydropower plant with four units, two common penstocks, a surge tank, and a long headrace tunnel is investigated. The RTDS is the smart brain of an advanced lab setup called power hardware in the loop (PHIL), which is an extremely safe and useful lab system for electrical power system research and testing hardware and methods under various conditions. In this research, the capability of an RTDS to emulate the behavior of a pumped-storage hydropower plant including four Francis pump-turbines, four short penstocks, two common penstocks, a surge tank, and a long headrace tunnel is evaluated. Francis pump-turbines are modelled based on the hill chart-based interpolation and waterways including penstocks and headrace tunnel are modelled based on the polynomial approximation of a hyperbolic function. Finally, the results from the RTDS are presented and discussed. According to the results of the paper, we confirm that the RTDS can accurately emulate the hydraulic, mechanical, and electrical transients of a pumped-storage hydropower plant with a complex configuration. [ABSTRACT FROM AUTHOR]

This paper analyses the economic viability of twelve pumped-storage hydropower plants equipped with different fixed-speed and variable-speed units and with and without considering hydraulic short-circuit operation. The analysed plants are assumed to participate in the day-ahead energy market and in the secondary regulation service of the Iberian power system. A deterministic day-ahead energy and reserve scheduling model is used to estimate the maximum theoretical income of the plants assuming perfect information of the next day prices, the residual demand curves of the secondary regulation reserve market and the percentages of the real-time use of the committed reserves. An estimate of the minimum theoretical pay-back period is obtained from the maximum theoretical income as a result of the scheduling model. Results indicate that the economic viability with and without variable speed units and operating or not in hydraulic short-circuit mode is not discarded if the plants also participate in the secondary regulation service, and that the minimum theoretical pay-back periods can be reduced significantly when the plant is equipped with variable speed units and/or operates in hydraulic short-circuit mode. In addition, the maximum theoretical income obtained with the used optimization model and the proposed pumped-storage hydropower plants are significantly higher than the real income obtained by plants that are currently operating in the Iberian system. [ABSTRACT FROM AUTHOR]

The paper aims at demonstrating that the consideration of constant start-up costs and ramps of the thermal generating units for assessing the contribution of pumped-hydro energy storage to reduce the scheduling costs of hydrothermal power systems with high wind penetration, may yield unrealistic results. For this purpose, an isolated power system is used as a case study. The contribution of a pumped-storage hydropower plant to reduce the system scheduling costs is assessed in the paper by using a hydrothermal weekly unit commitment model. The model considers different start-up costs and ramps of the thermal generating units as a function of the start-up type. The effects of including pumped hydro energy storage in the system on the integration of wind energy, and on the start-ups and capacity factors of the thermal generating units are also evaluated. The results of the paper demonstrate that the consideration of constant start-up costs and ramps of the thermal generating units yields unrealistic results, and that the pumped-storage hydropower plant may help reduce the system scheduling costs by 2.5–11% and integrate wind power and may allow dispensing with some inflexible thermal generating units. [ABSTRACT FROM AUTHOR]

The increasing penetration of renewable energy sources (RESs) in the power system has highlighted the benefits of being able to store energy in a more efficient manner, and the need of holding additional operating reserves to manage the system under more demanding conditions due to the inherent uncertainty and variability of wind and solar power. Pumped hydroelectric energy storage (PHES) is by far the most established technology for energy storage at a large-scale. PHES units have also participated in the active power-frequency control for years, and last technical developments in PHES have been oriented to improve their capability of providing regulation reserves by means of variable speed design or by hydraulic short-circuit configurations. This fact, together with the impact of RES on spot-market energy and ancillary services prices, is changing the operation and market conditions faced by PHES plants. The aim of this paper is to review the current trends in the PHES operation, to discuss why current practices should be re-examined, and to present the main challenges faced by PHES operators who will need to adapt their scheduling and bidding models to optimize jointly the operation in the energy and in the ancillary services markets. [ABSTRACT FROM AUTHOR]

In this paper, the contribution of a hydraulic short-circuit pumped-storage power plant (HSCPSPP) to the load-frequency regulation (LFR) of an isolated power system has been further analyzed by means of simulations. For this purpose, a simulation model has been developed that considers the AGC system and both the synchronized thermal units' and the HSCPSPP's response to frequency deviations and power set-point signals sent by the AGC system. The frequency deviation of the power system and the electromechanical behavior of the HSCPSPP have been modeled by using commonly accepted approaches for studies on long-term dynamics of power systems. The behavior of the penstock has been considered through an elastic water column model. The simulations results demonstrate that the HSCPSPP has a large flexibility and that can contribute to a great extent to the LFR of the system, while fulfilling the requirements established by the TSO and preserving the plant safety. [ABSTRACT FROM AUTHOR]