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Wave energy is one of the electric generation options based on renewable energies, especially suitable for islands due to the energy resource availability and the higher energy cost of energy in its electric grids. The oscillating nature of the wave resource is prone to produce negative impacts in these electric grids when considering scenarios of high penetration of wave energy generation. This study analyses the impact of wave energy generation on the power system frequency for the particular case study of Tenerife Island (Spain). Then, hourly data related to sea states in Tenerife, during a whole year, will be provided to generate an electric power profile, based on a model of a wave energy farm with a specific wave converter type. A previously developed dynamic simulation model of the Tenerife transmission network will be fed with these power profiles and the hourly electric generation and consumption profiles to analyse the system frequency. A complete set of analysis during the whole year will be accomplished in order to determine the number of over‐frequency events according to the grid codes. Finally, some corrective measures will be proposed as conclusions, e.g. energy storage devices, as the most reliable solution to mitigate frequency deviations. [ABSTRACT FROM AUTHOR]

This paper presents a new methodology to maximise the income and derive the optimal end of day storage of closed-loop and daily-cycle pumped-storage hydropower plants. The plants participate in the day-ahead energy market as a price-taker and in the secondary regulation reserve market as a price-maker, in the context of the Iberian electricity system. The real-time use of the committed reserves is considered in the model formulation. The operation of the plants with the proposedmethodology is compared to the ones that use an end of day storage of an empty reservoir or half of the storage capacity. Results show that the proposed methodology increases the maximum theoretical income in all the plants analysed both if they only participate in the day-ahead energy market and if they also participate in the secondary regulation service. It is also shown that the increase in the maximum theoretical income strongly depends on the size of the plant. In addition, it is proven that the end of day storages change notably in the new reserve-driven strategies of pumped-storage hydropower plants and that the proposed methodology is even more recommended if the secondary regulation service is considered. [ABSTRACT FROM AUTHOR]

The objective of this paper is to investigate the cause of several unexpected high amplitude oscillations that occurred in the surge tank water level of a real hydropower plant during secondary load-frequency control (LFC) maneuvers, after the replacement of the turbine runner, and to propose solutions that allow the power plant to continue providing secondary LFC in a safe and reliable manner. For this purpose, a simulation model has been developed and calibrated from data gathered during several on-site tests. Two different solutions are proposed in order to cope with the observed problem: using a state-dependent load change rate limiter or modifying the hydro turbine governor gains; the turbine governor remains the same as before the runner replacement. The proposed solutions are tested against a set of realistic secondary LFC signals by means of simulations and compared to each other as a function of the probability that the surge tank water level descends below a minimum safe level and the quality of the secondary LFC response. The results presented in the paper demonstrate the validity of the methodology proposed to determine the state-dependent ramp limit, as well as its effectiveness to prevent the surge tank drawdown and to provide clear insight into the trade-off between response quality and power plant safety. [ABSTRACT FROM AUTHOR]