The authors propose the theory of normal forms of vector fields to the auxiliary dynamic system. This methodology is tested on a 4-bus power system.

Bel-Air for the residents to residents free of charge on the ring bus service, the predecessor of the new bus line M49 line and auxiliary line in the vicinity of the Cyberport low patronage.

The electric auxiliary system sometimes has condenser motor loads, and the starting of inductor motors can cause bus voltage fluctuation problem.