Transient Frequency Response Improvement in Microgrid Using Virtual Synchronous Machine

Abstract

Microgrid concept helps to provide reliable electric power by integrating distributed generators based on renewable energy into the power system network. Grid-connected and autonomous modes of operation of microgrids and power electronic converter-based distributed generators make the microgrids to operate in a highly flexible manner. Since many of the microgrids are dominated by converter-based generators as against the rotating synchronous generators, they have a lower amount of rotating inertia. This causes poor transient frequency response in microgrids. Virtual inertia can be provided to microgrids by virtual synchronous machine-based control of converters. In this method, the converter emulates the behaviour of a synchronous machine and provides virtual inertia with the help of the electrical energy storage. Swing equation is used to derive the equivalent power to be delivered by the inverter to the grid. Simulation of the virtual synchronous machine with the grid-connected inverter was carried out in MATLAB/Simulink platform, and the results indicate the satisfactory operation of the proposed control strategy. An experiment on the laboratory scale model of the grid-connected inverter with virtual synchronous machine control strategy was carried out. The control algorithm was implemented in OPAL-RT real-time simulator. The performance of the virtual synchronous machine is compared with droop control, and the difference in performance with the two schemes is analysed.