Performance Improvement of Multi-DER Microgrid for Small- and Large-Signal Disturbances and Nonlinear Loads: Novel Complementary Control Loop and Fuzzy Controller in a Hierarchical Droop-Based Control Scheme

This paper presents new control scheme for a microgrid including several distributed energy resources that is completely analyzed so that the three hierarchical control levels are modeled for islanded and grid-connected modes. However, decentralized control methods of voltage-source converter (VSC)-based microgrids and microgrids’ hierarchical control scheme in the earlier research works have been limited to primary and secondary control levels. The presented hierarchical control scheme exploits new control loop to control the reactive power reference by a nonlinear fuzzy logic controller to improve performance of microgrid, not only for small signal events, but also respect to large signal disturbances such as short circuits, line outage, heavy motor starting, etc. and moreover, nonlinear loads and consequently, have the benefit of increasing the system stability margins and fault ride through capability. Besides, this control scheme can sufficiently provide power sharing to loads and network. Simulation studies are performed on a microgrid consisting of four distributed energy resources with local loads in MATLAB/Simulink environment to show the effectiveness of the proposed hierarchical control strategy.