Rising electricity demand and the need to reduce pollutant emissions highlight the importance of renewable energy, especially solar power. While most studies on photovoltaic (PV) integration focus on developed countries, least developed and developing countries such as the Democratic Republic of Congo (DRC) face particular challenges due to fragile grid infrastructure. This work evaluates the technical and operational impacts of PV integration into the western grid of the DRC using DIgSILENT PowerFactory 2021 SP2 simulations. It examines penetration levels from 10% to 50% based on a 2012 MW baseline, and evaluates power losses, short-circuit ratios (SCRs), grid stability, harmonic distortions, and voltage oscillations. Results reveal that moderate penetration levels (10–20%) reduce active power losses by 25% while maintaining stability. However, above 30% penetration, critical challenges arise, including a drop of the SCR below the minimum recommended value of 3, prolonged voltage oscillations, and increased harmonic distortions, resulting from the reduced overall inertia of the grid following the increase in PV power from inverters without inertia. These findings emphasize the need for targeted solutions like Battery Energy Storage Systems (BESSs), Static Synchronous Compensators (STATCOMs), and harmonic filters. This work provides foundational insights for PV integration in fragile grids of LDCs and developing countries.

Frequency stability in power systems is increasingly challenged by sudden generation-load imbalances. This paper proposes a novel Hybrid Droop-Adaptive Control strategy with Lead-Lag Washout (LLW) compensation for Battery Energy Storage Systems (BESS) to enhance frequency regulation during load disturbances. The control approach incorporates adaptive tuning of the droop gain, dynamic deadband adjustments, and LLW compensation based on real-time measurements of frequency deviation and Rate-of-Change-of-Frequency (RoCoF). The proposed controller was implemented and validated through dynamic simulations on the standard IEEE 14-bus test system using DigSILENT PowerFactory 2024. The study includes calculation of optimal BESS power and capacity requirements for worst-case load scenarios. Simulation results under different load disturbances including a 20% sudden load increase and an abrupt bulk load disconnection demonstrate the superiority of the proposed BESS control strategy in improving frequency nadir, reducing stress and ramping demands on synchronous generators, and better preserving spinning reserves. This indicates that our strategy significantly enhances frequency stability during load perturbations. Furthermore, it highlights that BESS effectiveness is contingent upon optimal sizing, making this a critical consideration for planning frequency support systems in modern power networks.