Inverter Control Strategy to Reduce the Synchronous Machine Rotor Angle Excursions

The increase in electricity generation from wind and solar sources brings important changes in the operational and dynamic characteristics of the power system when it is subjected to major disturbances. One important technical problem is the risk of losing transient stability by progressively replacing of conventional generation with energy sources connected to the system through electronic converters, reducing the overall system inertia. However, the converters could potentially bring new opportunities of fast control to give support to synchronous generators connected to the power system in response to a disturbance. In this paper, a control strategy for the inverter is proposed based on the injection of the current identified as having the major participation in the variation of the synchronous machine rotor angle. The identification is based on the eigenvalue sensitivity analysis with respect to the rotor angle. The proposed method is tested in a hybrid system with a synchronous generator connected in parallel with an inverter, both connected to an infinite bus through two transmission lines. The dynamic response of the rotor angle is assessed simulating a two phase to ground fault. The results show that the inverter must absorb active power, releasing the kinetic energy stored in the rotational masses of the synchronous machine, and effectively reducing the rotor angle excursions.