Application of a Virtual Synchronous Machine for Undershoot Reduction of the Frequency in Microgrids with Renewable Generation

There is a change occurring in the energetic matrix, and the participation of renewable energy generation is growing daily. The increase of wind and solar (photovoltaic) generation is reaching surprising levels, something that concerns electrical system's controllers. The reduced inertia is an inherent characteristic of this new generation, which affects the system's stability, primarily in relation with the transient frequency. With this reduced inertia occurs an increase of the frequency nadir (undershoot) which occurs in the sudden increases of load, which can provoke action of the sub frequency relays. The goal of this article is to conduct a study the implement of a virtual inertia (synthetic) to the electric system, studying your characteristics and comparing to the system's performance. By using computer simulation, a test system with a low inertia traditional generator plugged to a power grid was created. It was made the modelling of a VISMA (virtual synchronous machine) to reproduce the behavior of traditional generators. A disturbance (increase of load) was simulated in the test system and the performances were compared with or without the VISMA implantation. The result of the computer simulation demonstrates that it is possible to obtain a virtual inertia helping in the electric system's stability.