Estimation of External Dynamic Equivalents of a Thirteen-Machine System

Dynamic equivalents of external system are estimated from measurements within the study system. An equivalent model with damping and inertia explicitly expressed is chosen. An intentional disturbance of pulsed excitation is applied and the dynamic interaction between the external system and the study system is intensified for the estimation. The effect of intentional disturbance is restricted to the safe volatge regulation limit, yet much larger than that due to normal load fluctuations. To reduce the computational requirement, a least-squares algorithm with an adapted step-size scheme is used. The technique is applied to athirteen-machine electric power system, and the dynamic equivalents is given several short-circuit tests. The estimated equivalnets are unique for the model chosen, and the test results of the original system and the equivalent system are in good agreements.