Real-time verification of new controller to improve small/large-signal stability and fault ride-through capability of multi-DER microgrids

Decentralised control methods of voltage-source inverters-based multi-distributed energy resource (DER) microgrids and microgrids hierarchical control scheme studied in earlier researches limited to primary and secondary control levels while the proposed control scheme is completely analysed so that the three hierarchical control levels modelled for both grid-connected mode and islanded modes. In this study, the proposed hierarchical control scheme adds new control loop to control the reactive power reference by a fuzzy logic controller to have the benefit of increasing the system stability margins. In addition to the small-signal events, it maintains the stability of microgrids faced with large-signal disturbances such as short circuits, line outage, heavy motor starting etc., and improves fault ride through capability. However, power sharing to loads and network is sufficiently done. To demonstrate the effectiveness of the proposed hierarchical controller, simulation studies have been performed on a microgrid consisting of four units of distributed generation with local loads and in presence of main grid using MATLAB/SIMULINK software (offline simulations) and OPAL-RT real time digital simulator for verification.