A Sequential Generation Redispatch Algorithm to Ensure Power System Small Signal Stability under Low-Frequency Oscillations

Table 2

Critical modes and their damping ratios under different operating points for IEEE 39-bus system.

Mode no.	Mode	Damping ratio
DR. (2.5∼5) %
1	−0.20 ± 7.92i	0.0250
2	−0.20 ± 6.57i	0.0308
3	−0.28 ± 8.65i	0.0318
4	−0.23 ± 7.04i	0.0330
5	−0.26 ± 6.08i	0.0425
6	−0.38 ± 8.93i	0.0432
7	−0.37 ± 8.15i	0.0455
8	−0.20 ± 4.00i	0.0490
DR. (3∼5) %
2	−0.20 ± 6.52i	0.0301
1	−0.24 ± 7.91i	0.0303
3	−0.27 ± 8.64i	0.0316
4	−0.23 ± 6.98i	0.0339
7	−0.34 ± 8.14i	0.0412
5	−0.26 ± 6.06i	0.0422
6	−0.38 ± 8.91i	0.0425
8	−0.20 ± 3.98i	0.0496
DR. (3.5∼5) %
7	−0.29 ± 8.13i	0.0351
4	−0.24 ± 6.94i	0.0353
6	−0.31 ± 8.78i	0.0358
5	−0.22 ± 6.08i	0.0358
1	−0.29 ± 7.93i	0.0361
2	−0.24 ± 6.53i	0.0362
3	−0.32 ± 8.67i	0.0370
8	−0.19 ± 3.99i	0.0487
DR. (4∼5) %
2	−0.24 ± 6.07i	0.0401
1	−0.31 ± 7.62i	0.0402
3	−0.34 ± 8.32i	0.0406
4	−0.27 ± 6.58i	0.0409
6	−0.35 ± 8.55i	0.0410
7	−0.33 ± 7.92i	0.0411
5	−0.22 ± 5.36i	0.0419
—	−0.24 ± 3.65i	0.0657
DR. (4.5∼5) %
2	−0.26 ± 5.81i	0.0453
7	−0.36 ± 7.79i	0.0460
4	−0.29 ± 6.34i	0.0463
6	−0.38 ± 8.22i	0.0467
1	−0.35 ± 7.49i	0.0468
5	−0.25 ± 5.05i	0.0498
3	−0.63 ± 7.99i	0.0786
—	−0.86 ± 9.69i	0.0888
DR. (5∼…) %
5	−0.25 ± 5.03i	0.0497
1	−0.37 ± 7.38i	0.0499
4	−0.28 ± 5.69i	0.0500
6	−0.42 ± 8.19i	0.0513
7	−0.39 ± 7.46i	0.0524
3	−0.46 ± 8.04i	0.0570
2	−0.41 ± 6.09i	0.0673
—	−0.88 ± 9.48i	0.0870