Renewable energy sources are proficient in reducing greenhouse gas emission in the world. Among various renewable energy sources, solar photovoltaic (PV) generation is gaining its popularity day by day. Unlike conventional generating units, PV plants do not have inertias. Therefore, the increasing penetration of PV may impact a system's oscillations negatively as PV units add additional dynamics to power systems. Therefore, it is essential to analyze a system's behavior before replacing conventional generators by large-scale solar PV units. This chapter analyzes the impacts of increasing penetration of PV units on power systems. The effect of control mode of PV generator on the system's stability is investigated. Both static and dynamic stability analysis methods are conducted to find out the critical issues. The simulation results effectively identify the impact of high PV penetration on the stability of the studied system which show that voltage control mode of PV generator can improve the performance of a system. However, high penetration of PV can interact negatively with the system in certain cases.