Stability analyses of step changed loads on a multimachine power system

This paper presents the analyzed results of step changed loads on the stability of a typical multimachine power system. The step changed loads would occur in large industrial hot strip steel mills containing several large-capacity synchronous motors. These large motors would simultaneously stop when the procedure for rolling and pressing a steel plate is just finished and the large active power absorbed from the power source suddenly drops to nearly zero. Such large active-power variation makes the system frequency to be significantly increased during winter midnight in the Taiwan Power System. The eigenvalue method and nonlinear model simulation are both employed to determine the power system stability before and after the addition of step changed loads. Besides, the system-frequency variation coefficient (m) and governor´s speed regulation (R) will also be examined to clearly study the stability of a multimachine power system subject to sudden injection of step changed loads