Enhancing the Stability Margin of Microgrids through Multifaceted Control Algorithms in Damping Resistor Reduction Scenarios

Renewable energy integration with the utility grid is a great challenge. At the point of common coupling, the microgrid faces disturbances when connecting and disconnecting from the utility grid. Small signal stability analysis is often required to model the microgrid dynamics for analyzing the settling time and overshoot percentage of a distributed energy resource. Moreover, natural and anthropogenic disturbances produce high-frequency dynamics that add more challenges. An LCL filter with a damping resistor is typically used to suppress the high-frequency component when converting power from direct current mode to alternating current. The damping resistor plays an important role in dampening out the high-frequency dynamics. Normally, the high value of a damping resistor reduces the total harmonic distortion (THD) by weakening the higher-order frequency component. However, it introduces a switching delay due to internal heating loss. This manuscript proposes the design of a 2-degree-of-freedom PID controller to reduce the THD and improve the stability margin. The dynamics of the grid-tied and off-grid microgrids are modeled first, considering the participation factor. To verify the stability margin enhancement of the proposed controller, the pole placement method is used. The performance of the designed controller is tested and verified using Matlab/Simulink. The results show that the designed controller has achieved a significant reduction in THD in the absence of the damping resistor.