Nonlinear hierarchical global controller considering wide-area information delay

A two-level hierarchical structure is proposed to improve the stability of multi-machine power systems. The scheme consists of a local controller for each generator at the secondary level associated by a wide-area controller at the first level. The wide-area controller is in charge of evaluating the global signals, such as the center of rotor angle, the center of rotor speed. And the local controller combines the local signals with the global ones to achieve the feedback control law. To eliminate the effect of global signal delays, a novel nonlinear global controller is presented with inverse system algorithm and linear matrix inequality (LMI) technique. The digital simulation demonstrates that for various time delays the nonlinear global controller quickly damps down system oscillations and enhances transient stability of multi-machine power system.