![Example of Flicker
Power system model at Ulleung Island of South Korea.
Y
DG
4.5[MW]/0.5[MW]
4.5[MVA]/0.5[MVA]
3.3[kV]/6.6[kV]
DG
1.5[MW]
1.5[MVA]
3.3[kV]/6.6[kV]
WG
0.6[MW]
0.6[MVA]
0.48[kV]/6.6[kV]
1.53+j0.790 [Ω]
1.16+j0.600 [Ω]
SMES
Ps, Qs
C 0.305 MVAR
Load 6[MW]/2[MW]
6.0[MVA]/2.0[MVA]
0.23[kV]/6.6[kV]
1.16+j0.599 [Ω]
Y
0.6[MVA]/0.1[MVA]
6.6[kV]/3.3[kV]
HG
HG
0.6[MW]/0.1[MW]
0.1[MW]
D
Y
D
Y
D
D
0.378+j0.195 [Ω]
PL, QL
VG
PWG Unit
D](https://image.slidesharecdn.com/class13-long-durationvoltagevariations-221212170509-d2c8f37e/85/Class-13-Long-Duration-Voltage-Variations-ppt-16-320.jpg)
![System Responses
Wind speed data.
0 10 20 30 40 50 60
6
8
10
12
Wind
speed
[m/s]
Time [sec]
0 10 20 30 40 50 60
58
59
60
61
62
0 10 20 30 40 50 60
0.0
0.5
1.0
1.5
2.0
2.5
Frequency
[Hz]
Time [sec]
Without Wind generator
With Wind generator
Active
power
[MW]
Time [sec]
Wind generator
Diesel generator 1&2
Hydraulic generator 1&2
Load
Responses of active power and system
frequency.](https://image.slidesharecdn.com/class13-long-durationvoltagevariations-221212170509-d2c8f37e/85/Class-13-Long-Duration-Voltage-Variations-ppt-17-320.jpg)
![System Responses with SMES
0 10 20 30 40 50 60
58
59
60
61
62
0 10 20 30 40 50 60
0.0
0.5
1.0
1.5
2.0
2.5
Frequency
[Hz]
Time [sec]
Without SMES
With SMES
Active
power
[MW]
Time [sec]
Wind generator
Transmission line
Diesel generator 1&2
Hydraulic generator 1&2
Load
Responses of active power and system frequency with SMES .](https://image.slidesharecdn.com/class13-long-durationvoltagevariations-221212170509-d2c8f37e/85/Class-13-Long-Duration-Voltage-Variations-ppt-18-320.jpg)
Class 13-Long-Duration Voltage Variations.ppt
- 2. 2 Load V2 V1 V2 I I RI jX I V1 At given pf at full load, nominal V2 R X
- 3. 3 Voltage Regulation • Definition: Voltage regulation (at point x) is the percent voltage rise caused by unloading a power system (at point x) – Assumption 1: The original power factor at point x is given – Assumption 2: The original voltage is the nominal value at point x, or a given value if not nominal; the source voltage is fixed – Assumption 3: Original system is at full load, or a given value if not full load
- 4. 4 V2,NL = V1 At no load, V2 normally rises to equal V1 V2FL % 100 V V V % 100 V V V Reg R 2 R 2 NL 2 FL 2 FL 2 NL 2 Last equality assumes full-load voltage is nominal or rated value for the system
- 5. 5 • The system inductive reactance usually causes voltage drops under normal loading • If the load pf is leading or if very long transmission lines at EHV (345 kV and up, the line charging current may be very large), then regulation may be negative
- 6. 6 Root Cause • Most long-duration voltage variations are caused by too much impedance (Zth) in the power delivery system • The power system is too weak for the load – voltage drops to a low value under heavy loads (lagging pf) – voltage rises to a high value under light loads (more leading or less lagging pf)
- 7. 7 Solutions to Improve Voltage Regulation • Add shunt capacitors to increase the load power factor (not leading however) tending to decrease the load kVA by decreasing the load kVAr • Add static var compensation or other dynamic reactive power compensation (same reason as shunt capacitor addition, but better control) • Add series capacitors to lines to cancel part of the jXI voltage drop (long transmission lines and (rarely) short lines with impact loads)
- 8. 8 Solutions to Improve Voltage Regulation • Add voltage regulators to boost V under heavy load and buck voltage under light load • Increase the size of conductors to reduce Z
- 10. 10 V sensing and gate control Source side … Load side … Electronic tap-switching voltage regulator
- 11. 11 Loads … voltage regulator set at 105% without line- drop compensation V(x) x 120 V 126 V 114 V voltage profile for light load voltage profile for heavy load
- 12. 12 Loads … voltage regulator set at 100% with line- drop compensation V(x) x 120 V 126 V 114 V voltage profile for light load voltage profile for heavy load
- 14. 14 V(x) x 120 V 126 V 114 V Voltage profile after load rejection Needs rapid runback controls
- 15. 15 Flicker Sources of flicker -Load change -Induction motor starting -Variable power generation Observable flicker is dependent on the following: -Size (VA) of potential flicker-producing source -System impedance (stiffness of utility) -Frequency of resulting voltage fluctuations
- 16. Example of Flicker Power system model at Ulleung Island of South Korea. Y DG 4.5[MW]/0.5[MW] 4.5[MVA]/0.5[MVA] 3.3[kV]/6.6[kV] DG 1.5[MW] 1.5[MVA] 3.3[kV]/6.6[kV] WG 0.6[MW] 0.6[MVA] 0.48[kV]/6.6[kV] 1.53+j0.790 [Ω] 1.16+j0.600 [Ω] SMES Ps, Qs C 0.305 MVAR Load 6[MW]/2[MW] 6.0[MVA]/2.0[MVA] 0.23[kV]/6.6[kV] 1.16+j0.599 [Ω] Y 0.6[MVA]/0.1[MVA] 6.6[kV]/3.3[kV] HG HG 0.6[MW]/0.1[MW] 0.1[MW] D Y D Y D D 0.378+j0.195 [Ω] PL, QL VG PWG Unit D
- 17. System Responses Wind speed data. 0 10 20 30 40 50 60 6 8 10 12 Wind speed [m/s] Time [sec] 0 10 20 30 40 50 60 58 59 60 61 62 0 10 20 30 40 50 60 0.0 0.5 1.0 1.5 2.0 2.5 Frequency [Hz] Time [sec] Without Wind generator With Wind generator Active power [MW] Time [sec] Wind generator Diesel generator 1&2 Hydraulic generator 1&2 Load Responses of active power and system frequency.
- 18. System Responses with SMES 0 10 20 30 40 50 60 58 59 60 61 62 0 10 20 30 40 50 60 0.0 0.5 1.0 1.5 2.0 2.5 Frequency [Hz] Time [sec] Without SMES With SMES Active power [MW] Time [sec] Wind generator Transmission line Diesel generator 1&2 Hydraulic generator 1&2 Load Responses of active power and system frequency with SMES .
- 19. 19 Source side Load Thyristor-controlled reactor One type of static var compensator 3rd 5th 7th capacitors configured as harmonic filters Flicker Mitigation Techniques -Adding series reactor
- 20. 20 Source side Load Thyristor-switched capacitor Another type of static var compensator capacitors are gated fully on in sequence