چكيده به لاتين
The aim of this research is to develop a fully decentralized robust control solution for the voltage control problem of uncertain AC microgrids in the islanded mode of operation. Microgrids are small-scale power grids that include distributed generation (DG) resources, energy storage units, and a variety of loads. Under normal conditions, microgrids are connected to the main power grid, in which case, the voltage and frequency of the microgrid are imposed on it through the main grid. However, microgrids may get disconnected from the main grid and enter the islanding mode. If the microgrid continues to use the pre-islanding control algorithm after disconnecting from the main grid, the system loses its optimum performance due to the imbalance between output power and power consumption, and the voltage and frequency can significantly get out of their nominal values or even move to instability. As a result, the provision of control solutions that control voltage and frequency after islanding is of paramount importance and is an important step towards increasing the efficiency of the DG systems. The proposed controller in this research not only provides robust stability, it also ensures the robust performance of the AC microgrid in the islanded mode of operation against various sources of uncertainty in the microgrid system, including the Plug-and-Play (PnP) functionality of DG units, microgrid topology changes, local load changes and subsequent system changes.
The microgrid studied in this research includes several DG units with a general topology. Each DG unit of is connected to its local load through an inverter, an $ RL $ filter, a step-up transformer, and a capacitor. The uncertain microgrid system is modeled as a Linear Time-Invariant (LTI) system with a polytopic type uncertainty. Then, a robust state-feedback controller based on the Linear Matrix Inequality (LMI) with Linearly Parameter-Dependent (LPD) Lyapunov matrices is implemented on the LTI polytopic islanded AC microgrid system. The controller is designed based on a decentralized strategy that does not require any communication and robust performance property of the controller eliminates the need for pre-filter design.
Simulating multiple scenarios in MATLAB/SimPowerSystems Toolbox confirms the effective performance of the proposed controller concerning voltage tracking, local load changes, PnP functionality of the DGs, topology changes, and subsequent system change.
