Estimation of Rwanda's Power System Inertia as Input for Long-term Dynamic Frequency Response Regulation Planning

Changes in the quota between conventional generation and renewable energy sources constitute major challenges that the modern power systems have to encounter. Conventional power plants are replaced by renewable generation (e.g. wind turbines, photovoltaics) that contribute to the reduction of power system inertia. This may introduce frequency stability issues because frequency is affected by the amount of system inertia, along with the response of controllable frequency reserves and the amount of power imbalance. Therefore, the estimation and analysis of power system inertia and the frequency response assessment is essential to ensure power system stability and security. This paper proposes a novel method to estimates the inertia constant for three different periods in future, namely, 2025, 2035 and 2050 based on the produced future energy scenarios (FES) for Rwandan's power system. In addition, the paper evaluates the frequency response dynamics for each scenario. Results show that the highest progression in renewable energy resources penetration resulted to a larger reduction in the system inertia constant (from 7.2 in control area 1 to 3.83s in control area 3) and the largest frequency drop was observed during the high progression scenario in the year 2050 where the PV and imported power penetration was expected to reach more than 30% of the total installed capacity.