Generation scheduling in isolated power systems with high penetration of variable renewable generation and pumped-storage
- Autores: Daniel Fernández Muñoz
- Directores de la Tesis: Juan Ignacio Pérez Díaz (dir. tes.)
- Lectura: En la Universidad Politécnica de Madrid ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Javier García González (presid.), Ignacio Guisández (secret.), Hrvoje Pandzic (voc.), Araceli Hernández Bayo (voc.), Miguel Carrion Ruiz-Peinado (voc.)
- Programa de doctorado: Programa de Doctorado en Sistemas de Ingeniería Civil por la Universidad Politécnica de Madrid
- Materias:
- Enlaces
- Tesis en acceso abierto en: Archivo Digital UPM
- Resumen
The declared worldwide target values of variable renewable generation in power systems have been steadily increasing year after year and this trend is expected to continue in the near future. These target values will definitely bring invaluable benefits to both the society and the environment, but also operational challenges to the electric power system. Some of these challenges are already being experienced in some power systems, but some others are even difficult to foresee and will show up in the future as the variable renewable generation continues increasing.
Energy storage resources have been devised to help the power system to accommodate higher values of variable renewable energy, especially in power systems with little inertia like the islands.
This thesis deals with the operation of isolated power systems with high penetration of variable renewable generation and pumped-storage. Once the most relevant articles from the scientific and technical literature have been reviewed, the main research gaps and challenges that have been detected and suggested to be carried out in this thesis, can be summarised as follows:
1. The hierarchical coordination between the long- or medium- and short-term optimisation models to manage the energy storage in the upper reservoir of a pumped-storage hydropower plant has to be further analysed. There is a gap in the literature concerning the realistic estimation of the storage opportunity cost, i.e. water value, in isolated power systems with high penetration of both variable renewable generation and pumped-storage.
2. The contribution of flexible pumped-storage hydropower plant configurations to reduce the system’s scheduling cost and renewable energy curtailment in isolated power systems with high penetration of variable renewable generation, needs to be rigorously analysed with realistic generation scheduling models and procedures.
3. There is a research gap and a challenge in the provision of a realistic short-term generation scheduling model of an isolated power system with high penetration of variable renewable generation and pumped-storage, that simultaneously calculates the next-day scheduling cost and the storage opportunity cost while considering the intra-hourly variable renewable generation variability, with an acceptable computational time for the day to day work of the power system operator.
4. There is a lack of a comprehensive review of the regulatory changes regarding frequency control ancillary services, which have been recently implemented in some power systems worldwide or are currently under development, that aim to fairly compensate the superior capability of some energy storage systems to provide such ancillary services.
This thesis presents a two-stage stochastic linear programming optimisation model to calculate the water value with a low computational time that can be used every day by the power system's operator so as to update the storage opportunity cost in the system.
This thesis provides a novel two-stage stochastic unit commitment model based on mixed-integer linear programming that simultaneously calculates the next-day generation schedule and the storage opportunity cost while considering the intra-hourly variability of the variable renewable generation.
The model uses an approach based on the Benders decomposition technique in order to increase its computational efficiency making it useful for the daily work of a power system operator.
The results obtained with the optimisation models proposed in this thesis point to the use of optimisation models that do not assume the usual simplifications made by the traditional unit commitment models that lead to hidden inflexibilities, e.g. unfeasible generation schedules, when real-time dispatch is applied.
This thesis analyses the contribution of flexible pumped-storage hydropower plant configurations in an isolated power system with high penetration of wind generation to reduce the scheduling cost and to reduce the wind energy curtailment, among others, by means of a realistic generation scheduling procedure which considers variable start-up costs and power trajectories of the thermal generating units as a function of the time that the unit has remained off-line since the previous shut-down and the water value.
The results obtained have shown that flexible configurations of pumped-storage hydropower plants can positively contribute to increase the flexibility of isolated power systems, allowing them to reach higher levels of variable renewable energy and reducing the power system scheduling cost.
However, this contribution might not be enough to afford the investment required to build a pumped-storage hydropower plant with the current energy markets remuneration mechanisms.
This thesis provides a review of the frequency control ancillary services that value the response speed of the frequency control provider, that are currently in force or in a development phase in power systems worldwide, since the frequency control ancillary services have been pointed as an important source of income for energy storage resources.
The results obtained suggest that, with a proper design of both the frequency control ancillary services technical requirements and payments, fast-acting energy storage resources can help improve the quality of the power system’s frequency to a greater extent than conventional generation resources and decrease the total amount of frequency control reserve.
