Rotor Angle and Inertia Analysis in Presence of Renewable Energy Source

The increasing use of renewable energy as an alternative source of energy is getting more attention. However, with this increasing trend, it is more likely to have a major impact on the stability of the grid due to the reduction in inertia. The integration of variable renewable energy generation, converter connected generation in particular leads to synchronous conventional generation being displaced hence reducing the total inertia of the system. This in turns affects the system dynamics, modal frequency and damping of the electromechanical modes of rotor oscillations. Furthermore, during a system disturbance, generation and demand become unbalanced, resulting in a change of system frequency. Inertia will be an important parameter to be considered for the grid stability. With the increasing use of power electronics devices connecting renewable energy sources, virtual/synthetic inertia is the alternative to restore the frequency balance. However attention should be drawn that inducing inertia to the system will affect the rotor angle, which will be critical in the transient stability analysis of the power system grid. The aim of this paper is to provide an innovative method of establishing the impact of renewable energy like solar on the stability of the power grid, through modelling of the rotor angle and inertia analysis. The proposed system is adapted from IEEE 9-bus system with an adjusted frequency of 50 Hz. The proposed methodology is to compare the dynamics of the conventional system with synchronous generators to that of similar arrangement in presence of renewable energy sources. Transient stability was analysed with a 3-phase fault on the system and the variation of rotor angle was simulated on MATLAB in both case studies.