Issues on nonlinear control of voltage source FACTS devices

In this paper, we present three typical nonlinear control strategies for voltage source FACTS devices. The most basic device of this kind is STATCOM (STATatic COMpensators), which is powerful in providing voltage support and improving power system stability. The nonlinear control strategies discussed in the paper include the input-output linearization based on differential geometry and differential algebra as well as passivity approach. We discuss and compare these control methods from the perspectives of their dynamic performance for local voltage support, impacts on overall power system and implementation