The Design of a robust controller to improve the frequency stability of the microgrids

نوع: Type: thesis

مقطع: Segment: PHD

عنوان: Title: The Design of a robust controller to improve the frequency stability of the microgrids

ارائه دهنده: Provider: Farhad Amiri

اساتید راهنما: Supervisors: Dr. Mohammad Hasan Moradi

اساتید مشاور: Advisory Professors:

اساتید ممتحن یا داور: Examining professors or referees: Dr. Alireza Hatami, Dr. Mohsen parsa Moghaddam, Dr. Mohammad Abedini

زمان و تاریخ ارائه: Time and date of presentation: 2022/06/22، Sunday

مکان ارائه: Place of presentation: Amphitheater, Faculty of Engineering

چکیده: Abstract: Renewable energy resources (e.g., wind turbines and photovoltaics) exchange power with the microgrid through power electronic converters. The power electronic converters have low inertia, and their existence reduces the inertia of islanded microgrids. To overcome the low inertia in the islanded microgrid, the present research discusses the concept of a virtual synchronous generator. Such a generator follows the behavior of conventional synchronous generators (power system) and improves the inertia and stability of islanded microgrid. As a significant part of the performance of the virtual synchronous generator, virtual inertia control operates as an initial stimulus when disturbances occur and improve the frequency stability in the islanded microgrid. Virtual inertia control in proposed methods related to the frequency control of islanded microgrids has been implemented in the energy storage systems. The result has been a relative improvement in frequency stability. But, if the large disturbances enter the microgrid, this method may not be affected solely. Thus, the design and implementation of virtual inertia control on renewable energy resources (e.g., wind turbines and photovoltaics) may improve the frequency stability of the islanded microgrid. Implementing virtual inertia control on the wind turbine and photovoltaic has also some disadvantages, such as the increase in settling time-related to the frequency deviations of islanded microgrid, which is not desirable for the system. Thus, in addition to designing the virtual inertia control on the wind turbine and photovoltaic, designing the virtual damping control is also addressed on these resources (i.e., wind turbine and photovoltaic) and energy storage system. The virtual damping design on these resources lowers settling time related to frequency drifts of islanded microgrid due to the disturbances. Uncertainty of islanded microgrid parameters is a factor that endangers the performance of the control method of virtual inertia and virtual damping. This parameter may also cause frequency instability. Besides, since the renewable energy resources in microgrids communicate together through telecommunication networks, the distance between sensors and operators, errors in transmission lines and control operations, filtering, and so on cause the generating time delay in microgrids. The time delay in the islanded microgrid may also cause the instability of frequency. Therefore, control of virtual inertia and virtual damping must be resistant to the uncertainty of parameters and time delays. Hence, in the structure of virtual inertia and virtual damping control, a proposed control method (robust controller on the basis of the Linear matrix inequality) has been used. Proof of stability of the proposed control method is on the basis of the Lyapunov stability criterion. This proposed method (implemented on the energy storage system) improves the performance of virtual inertia control and virtual damping control against disturbances and uncertainty of parameters, thereby enhancing the frequency stability of islanded microgrid

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