Conversion systems are critically important devices in electrical systems across various environments, especially in modern times, as multiple components with different
voltage levels and sources are interconnected within a single system. Consequently, dynamic study methods of this network are examined using approaches that simplify the
network based on speed modes and switching of other conversion systems, wherein
fast systems are simplified to constant power loads (CPL). This method evaluates the
network’s stability conditions. The study reveals that CPLs act as negative incremental
resistances, and when analyzed through a linear model, it is observed that such loads
reduce system damping, thereby decreasing stability margins and potentially rendering
the system unstable. Additionally, uncertainties in the physical components of the circuit
further affect the stability and performance of microgrids. Hence, designing regulators
to mitigate oscillations caused by these effects becomes crucial to ensure the proper
performance of these systems.In this work, a robust controller is designed to handle
uncertainties and attenuate oscillations in the presence of constant power loads. This
controller is implemented in a microgrid composed of two cascaded DC-DC buck converters, one of which is modeled as a CPL. The system model is utilized for both stability
analysis and robust controller design in state space, where the compensator synthesis
is structured in the form of a linear matrix inequality, solved using system optimization tools. The controller’s results are compared with another controller based on pole
placement in both linear and nonlinear switched models, within the Matlab/Simulink
simulation platform. Transient response and control signals are evaluated graphically
and through performance indices under various operating conditions, including load
disturbances and system parameter variations.
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