Control of voltage source converters for distributed generation in microgrids
- Autores: Jordi Pegueroles Queralt
- Directores de la Tesis: Oriol Gomis Bellmunt (dir. tes.), Fernando Bianchi (dir. tes.)
- Lectura: En la Universitat Politècnica de Catalunya (UPC) ( España ) en 2015
- Idioma: inglés
- Tribunal Calificador de la Tesis: Milan Prodanovic (presid.), Daniel Montesinos Miracle (secret.), Pavol Bauer (voc.)
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Microgrids are the near future candidate to reduce the dependence on the carbon-based generation, towards a more environmentally friendly and sustainable energy paradigm. The popularization of the use of renewable energy sources has fostered the development of better technologies for microgrids, particularly power electronics and storage systems. Following the improvements in microgrid technologies achieved in the last decade, a new challenge is being faced: the control and management of microgrids for its operation in islanded mode, in addition to its large scale integration into the current electrical power system. The unregulated introduction of distributed generation based on renewable energy sources into the power system could cause as many problems as it would solve. The unpredictability of the generated power would introduce large disturbances into the electric system, making it difficult to control, and eventually resulting in an unstable system. To overcome these issues, the paradigm of microgrids has been proposed: a small power system, able to operate islanded from the main grid, which will permit the large scale introduction of renewable energy sources interfaced with power electronic converters together with energy storage systems into the distribution grids. Microgrids¿ ability to allow their users to operate islanded from the utility grid, brings the potential to offer a high quality of service. It is in the islanded operation mode, particularly in microgrids with a high proportion of renewable based generation, where the major technical challenges are found. This thesis focuses in three of the main challenges of islanded and weak electrical grids: the power converter control of electrical storage systems, its decentralized control design, and also the improvement of power quality in grids disturbed by renewable generation. These topics are addressed from a control point of view, that is, to tackle the electrical problems, modelling them and proposing advanced control strategies to improve performance of microgrids. Energy storage system are a vital element to permit the islanded operation of microgrids, either in the long or short term. New control strategies are proposed in this thesis for the improvement of the converters¿ performance. In addition to the control of the converter, the management and control of different energy storage systems for microgrids are also studied. In particular, supercapacitors and batteries have been considered for the short and long term operation, respectively. Then, the control of islanded microgrids is addressed. Typical controls for islanded microgrids are analysed and new tools for designing stable controllers are proposed. Also, methodologies to analytically obtain the operating point (power flow) of droop controlled grids are studied and proposed. The high penetration of renewable energy sources in weak low-voltage grids results in undesirable electrical disturbances. This problematic in power quality is tackled and innovative solutions to mitigate it are proposed. In particular, a novel power smoothing scheme with simultaneous state of charge regulation of the ESS and power filtering. The new power smoothing scheme, along with the proposed control strategies for storage systems have been experimentally validated in a laboratory test bench, using a supercapacitor bank and a high power lithium-ion battery available at IREC's facilities.
