Impact of solar pv plants with synchronous power controllers on power system stability
- Autores: Daniel Remón Rodríguez
- Directores de la Tesis: Pedro Rodriguez Cortes (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2017
- Idioma: español
- Tribunal Calificador de la Tesis: Xiongfei Wang (presid.), Kathy Y. Cao (secret.), Joan Bergas Jané (voc.)
- Programa de doctorado: Programa de Doctorado en Sistemas de Energía Eléctrica por la Universidad de Málaga; la Universidad de Sevilla; la Universidad del País Vasco/Euskal Herriko Unibertsitatea y la Universidad Politécnica de Catalunya
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
The irruption of renewable energy sources with power electronics interfaces is transforming power systems. To minimize the possible adverse effects that these generating systems may have on the power grid, transmission system operators define different strategies, such as increasing the active power reserves for frequency control and power balancing purposes, and require all connected systems to comply with various rules and regulations. In an effort to better integrate these renewable sources in power systems, some power converter controllers have been proposed that aim at reproducing certain features of conventional synchronous machines. This work deals with the analysis of the impact that large power-electronics-based power plants, in the range of hundreds of megawatts, have on the stability of power systems. First, the main characteristics of these advanced controllers, sometimes referred to as virtual synchronous machines, are reviewed, and their constituting blocks are systematically classified. This classification allows performing a detailed comparison of different aspects regarding their implementation and dynamics. The proposals usually found in the literature are compared in terms of their need for ancillary synchronization systems, their ability to energize a grid, or their effectiveness to limit the current injected during a fault and keep the converters connected to the grid. Additionally, time-domain simulations comparing the response of power converters employing these controllers are carried out and analyzed. Afterwards, since the study of power system stability requires adequate models of the elements interacting with the system, the modeling of an actual 100 MW photovoltaic power plant, consisting of 100 power converters, is addressed. Thus, a detailed model of the power plant is developed, considering a single-phase equivalent for transient stability studies in balanced systems. This model includes the internal network buses, cables, and transformers, and the power converters with their control systems and primary resources. Moreover, the model is implemented in a flexible way that allows considering power converters employing conventional controllers or synchronous power controllers, and the photovoltaic resource can be replaced by a storage system. Furthermore, a method to derive an equivalent model of power plants employing these advanced controllers is developed, and three equivalent models of the power plant, with different degrees of detail, are implemented employing this method. These models allow reducing the complexity of the original model and its associated computational burden, while reproducing its dynamics with accuracy, making them more suitable for the analysis of power systems with a large number of generating units, loads, passive elements, and controllers. Finally, the stability of power systems integrating this type of generating stations is analyzed. A first analysis is carried out in a 12-bus test system, considering a simpler model of the plant where the photovoltaic characteristics are modeled only through an active power limitation, and comparing the impact of these plants as the solar penetration grows, up to a 50% level. This is followed by the analysis of the power system of northern Chile, considering the actual location of the power plant previously modeled, and including the full detail of the photovoltaic resource. Lastly, the impact of hybrid power plants consisting of a synchronous generator and a photovoltaic system, with different configurations with the possibility of curtailing the solar production or employing a storage system, is assessed. These analyses comprise the study of the eigenvalues of the system and its response to different types of events through time-domain simulation, and prove the ability of the studied controllers to increase the damping of the system , to reduce the oscillations suffered by other generators, and to limit maximum frequency deviations.
