1. Cheng-Ting Hsu, Huang-Shin Cheng Presenter: Cheng-Ting Hsu Transient Stability Study of the Large Synchronous Motors Starting and Operating for the Isolated Integrated Steel-Making Facility Department of Electrical Engineering Southern Taiwan University of Technology Tainan, Taiwan

2. ․ Introduction ․ System Configurations of Cogeneration Facility ․ Mathematical Modeling of Cogeneration Units and Load ․ Computer Simulation of Motor Starting and Operating by Transient Stability Analysis ․ Conclusion Outline

3. Introduction Due to the right of way and the environmental protection, the integrated-steel cogeneration system is possible to operate without supporting of the utility in the initial and second stages. This paper presents the influences of the large motor starting and the large rolling mill operation on the isolated cogeneration system by executing the transient stability analysis. The conventional step-down voltage starter and the VVVF inverter are considered in the computer simulations. Also, the operation of rolling mills has been investigated.

4. System Configurations of Cogeneration Facility

5. Mathematical Modeling of Cogeneration Units and Loads Cogeneration Unit Model Excitation System Model Governor System Model Load

6. Governor Model of Cogeneration Units

7. Load Models Static load modelStatic load model Dynamic load modelDynamic load model

8. Computer Simulation of Motor Starting and Operating Case A: executes the large synchronous motor starting by using the autotransformer starter. Case B: executes the large synchronous motor starting by using the VVVF inverter. Case C: executes the rolling mills operation in the isolated system.

9. Case A SM (16.1MW) at bus 32 is started with AT starter. When the motor approaches synchronous speed, the nominal voltage will be applied. The load demand of 11.3MW and the exciter will be added after the motor reaches its synchronous speed.

11. Case B SM (45MW) at bus 21 is started with VVVF inverter The active and reactive power consumption of the motor can be obtained as shown in the Figure

12. Case B

13. Case C The rolling mill at the steel-plate plant （ PM-2, bus 44 ） has two synchronous motors with rating capacity 7.2MW each. The power consumption of the rolling mill is shown in the figure.

15. The large synchronous motor at the oxygen plant can be started and loaded successfully by applying the autotransformer starter with tap position at 60%. The largest synchronous motor at powerhouse plant can be started well by using the VVVF inverter. The operation of rolling mill has resulted in the fluctuation of voltage and frequency. However, it is acceptable for the cogeneration facility. Conclusions