New and improved solutions for the configuration, management and operation of large-scale photovoltaic power plants using hybrid energy storage system

Abstract

This thesis is presented in the context of multiple efforts being made by research groups in order to disseminate and evolve the technological knowledge in the renewable energy (RE) field. The motivation of this study is based on the main disadvantages of photovoltaic (PV) solar power generation compared to conventional energy sources, such as intermittency, non-dispatchability, and unreliability. From those drawbacks, the aim is to find creative solutions to mitigate these issues with a power plant combining PV and hybrid energy storage systems (HESS). In doing so, hybrid power plants represent a very interesting option for power generation and grid integration of PV systems, since they allow increased efficiency in the energy generation, as well as storing and supporting RE generation when needed.The storage systems are particularly important to deal with the intermittent nature of solar radiation. A wide variety of storage systems exists nowadays, all of them based on different operating principles and target applications. A thorough review of the literature has exposed that, depending on the application, a certain type of storage could be preferred above others. Besides, two or more different technologies working together can present complementary features. In this sense, the HESS can accomplish higher efficiencies and improved systems for grid connection. The objective is to develop new solutions to improve the configuration, management, and operation of PV plants with energy storage, designing the necessary control techniques and validating them through real-time simulations. In this context, this thesis presents a large-scale PV power plant with HESS, through a DC/DC impedance source converter (DC/DC-ZSC), and a new simplified model (SM) of the quasi Z-source inverter with battery energy storage (qZSI-BES) attached directly to the Z-network without an extra DC/DC converter. The HESS consists of battery arrays (BES) and ultracapacitors (UC). The newly designed SM is implemented, assessed, and validated experimentally in laboratory through a TYPHOON HIL system and a dSPACE MicroLabBox control board. Three different energy management strategies are implemented, using two of them advanced control techniques based on fuzzy logic. The control loops of the active, reactive, BES, and UC power have been conveniently deployed. The results obtained are coherent with the expected responses, observing an appropriate power balance and grid energy dispatch. This thesis aims for a relevant contribution in the development of low polluting energy sources that can fulfill the growing electricity demand. Following the global trends, and recognizing the importance of this knowledge for the scientific community and for society, this thesis will provide new solutions in the field of solar PV generation. In view of the fact that research has mainly focused on small-scale hybrid power plants so far, further studies are required regarding the configuration, design, control, energy management, operation, and problems associated with large PV power plants with hybrid storage.