Hydroelectric power plants use moving water to generate electricity, making up 15% of the world's electricity. Researchers studied how these plants operate, model, and control their power output. They also looked at the environmental impact and efficiency of these plants. The study found that hydroelectric power is a cheap and renewable energy source, providing a significant portion of the world's electricity. Additionally, the use of a flexible AC transmission system controller can improve the power system's performance when combined with hydroelectric power plants.