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Investigation of Control Strategies to Mitigate the Oscillation Effects caused by Interconnected Buck Converters

Abstract:

The use of renewable energy requires the integratation between alternative energies sources and the main grid. These sources, such as solar and wind energy, are increasingly used due to their simplicity in structure, high power efficiency, low cost and high reliability. In these systems, DC-DC converters are used to ensure regulation and voltage stability. However, the dynamic behavior of the converters is a big concern due to nonlinear characteristic caused by switching operation. Thus, The linearization around the operating point is necessary to regulate the output of converters in order to preserve stability and dynamic performance of the system. On the other hand, when the converters are in series connection create another problem which, depending on the operating conditions, can destabilize the whole system. Instability in cascaded systems may occur due to the constant power load, which exhibit incremental negative resistance behavior causing a high risk of instability in interconnected converters. Aiming to effectively mitigate oscillations effects caused by the interconnection of DC-DC buck converts, this papers presents the studies and comparison of difference control techniques. It is investigated state and output feedback structures through pole-placement methods using classical tools such as solving the Diophantine equation, root locus design, in addition to other modern control tools as the use of the Riccati equation to solve the optimization control problem by using LQR. Through performance index graphs, the controllers ability, speed and effort to mitigate oscillations are observed.