Grid integration of variable renewable energies in Ghana: assessment of the impact on system stability

Abstract

This research analyses the impact of renewable energies (RE) generation in Ghana’s national interconnected transmission system (NITS) and how its stability is affected. Integrating RE, particularly solar and wind in Ghana’s power system has been discussed at the national level with the intention to diversify the energy mix and reduce the dependency on thermal energy. RE integration introduces operational and infrastructural challenges in Ghana’s network, to which novel measures are required. Using the DIgSILENT PowerFactory simulation tool and MATLAB, simulation scenarios are created to capture diverse network conditions including different RE penetration levels, load demand and infrastructural expansion for three separate years. The ‘optimum’ penetration level of RE in the NITS considering voltage and loading limits is also identified using optimization techniques. The simulation results show that the target scenario is the most prone to both static and dynamic voltage instability. The transient stability analysis however reveals the post-target scenario to be unstable. Furthermore, methods of optimization are used to determine the reactive power deficient nodes in the NITS, which serve as the basis for the stability enhancement measures. The simulations and analysis additionally indicate that implementing the proposed measures indeed enhances the stability of the NITS. Finally, this research shows that RE integration is ‘technically’ feasible in Ghana if the required network reinforcements and operational changes are accordingly considered.