| Power balance is the foundation of stable operation in power system. Once generator or power imbalance occurs in the system because of disturbance, units or internet systems may have oscillations, which will threat the stability of power system, even will lead to serious large area power outage, bringing significant economic losses and serious social impact. Using energy storage technology to control the power system is a new idea for its stability. Energy storage devices can dynamically adjust both active and reactive power, which can control voltage sag and low-frequency power oscillation effectively, and improve power system stability. Also, such devices have mature operating experience and can be installed and adjusted easily, so they could become an ideal power controller in power system.This thesis focuses on two problems, first is using energy storage devices to inhibit voltage sag, and second is using energy storage devices to inhibit low-frequency power oscillation.For the first problem, voltage sag was defined first and corresponding control strategies were provided, then, computer simulation and dynamic simulation experiments for voltage sag in the power system with energy storage devices were made, finally, the deferent devices were compared.For the second problem, low-frequency power oscillation was defined first and then two control strategies, one for power flow balance and the other for improving system damping, were provided, finally, computer simulation experiments were made and the two strategies were analyzed and compared.The conclusions in this thesis can be guided to integrated understand the principles and control methods of energy storage systems. The simulation systems in this thesis also have reference value for choosing actual installation site of energy storage systems.
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