Frequency Stability Assessment for the Future Power System of São Vicente Island

There are several challenges along the path towards 100% renewable-based power systems. One of them is ensuring the system's frequency stability and control. Provided they are large enough; isolated power systems represent an excellent testing ground for stability-related research due to the similarity between their dynamics and those of a continental-size power system while keeping a manageable size.

In this work, the recently published Cape Verde Benchmark System is used to analyze the effects of phasing out the different thermal units on frequency stability. It is assumed that those units are substituted with wind generation, and then the possibility of keeping them running as synchronous condensers (SC) for inertia support is explored.

A relevant scenario with 70% renewable penetration is defined and analysed after a sudden load increase (10%) and a single-line short circuit fault. The results show the benefits of keeping Synchronous generators as SC, providing a certain level of inertia to support frequency stability. Additionally, the study also points out that to fulfill the replacement of the role of SGs, a primary frequency reserve needs to be implemented to coordinate with SCs for secure frequency stability in renewable-based systems.

The whole study has been implemented in an EMT Real-Time Digital Simulator (RTDS).