1. TRANSIENT STABILITY ENHANCEMENT OF A HYBRID POWER SYSTEM
D.P. KOTHARI, RAMNARAYAN PATEL and
T.S. BHATTI
Centre for Energy Studies, Indian Institute of Technology, New Delhi (India)
INTRODUCTION
ILLUSTRATIVE SYSTEM EXAMPLE
SIMULATION OF POWER SYSTEM AND CONTROL SCHEMES
RESULTS AND DISCUSSIONS
CONCLUSION

2. INTRODUCTION The Swing Equation: Generation side control:
fast valving sudden decrease in turbine mechanical power input
Load side control:
braking resistor increased generator power
output due to artificial load

3. ILLUSTRATIVE SYSTEM EXAMPLE

4. SIMULATION OF POWER SYSTEM AND CONTROL SCHEMES
Brake insertion:
immediately after fault clearing
Brake removal criterion:
i = 0 
Fig.2: Valve stroke characteristic curve

5. SIMULATION RESULTS
Fig. 3: Rotor angle swing (gen. # 3) with different control schemes, for fault at P1 and F.C.T.=0.28 sec.
Fig. 4: Rotor angle swing (gen. # 1) with different control schemes, for fault at P1 and F.C.T.=0.28 sec.

6. SIMULATION RESULTS
Fig. 5: Terminal voltage variation (gen. # 1) with different control schemes, for fault at P1 and F.C.T.=0.28 sec.
Fig. 6: Rotor angle swing (gen. # 3) with different control schemes, for fault at P2 and F.C.T.=0.26 sec.

7. SIMULATION RESULTS
Fig. 7: Rotor angle swing (gen. # 1) with different control schemes, for fault at P2 and F.C.T.=0.26 sec.
Fig. 8: Rotor angle swing (gen. # 3) with different control schemes, for fault at P3 and F.C.T.=0.17 sec.

8. SIMULATION RESULTS
Fig. 9: Terminal voltage variation (gen. # 3) with different control schemes, for fault at P3 and F.C.T.=0.17 sec.

9. CONCLUSIONS
Transient stability performance of a typical 3-generator, 9-bus hybrid power system, with one small hydro and two steam units, has been carried out
A coordinated fast valving and braking resistor control is proposed.
Control laws for the operation of fast valving and braking resistor, are fairly simple and need very less computation and measurement.
Simulation results show that the coordinated control substantially improves the fault clearing time.
The improved generator terminal voltage profile and damping of the rotor angle swings were also observed.
The coordinated control from both load and generation sides reduces the stress on the part of an individual control.