Doubly Fed Induction Generator models in PSS/E

Transcription

1 1 Doubly Fed Induction Generator models in PSS/E Ian Norheim SINTEF Energy Research January 2004

2 2 DFIG system us=usqjusd isqjisd DFIG Pgen Pd,loss Pr,loss xt icqjicd ucqjucd AC DC Id Ud C Iv DC AC urqjurd irqjird m α urq urd

3 3 Some benefits of Doubly Fed Induction Generators for Wind Turbines 1. Torque pulsations are reduced 2. The system efficiency is improved (?) 3. The acoustic noise at low power operation is lowered 4. Possible reactive compensation 5. Reduced requirements to the pitch controller

4 4

5 5 Implemented PSS/E model of DFIG Programmed in Fortran Third order model, i.e the stator transients due to the stator flux are neglected Interacts with turbine models via the mechanical power and the speed The transients due to the DC-link are neglected The active power flowing into the rotor circuit equals the active power drawn from the grid by the net side converter An initialisation routine for the model has been implemented

6 6 SINTEF Energiforskning AS Implemented PSS/E model of DFIG cont. qr r m N s q N r s qs r m s d s d v x x v i x x v T v / = ' 2 ' ' 0 ' ) ( ) ( dr r m N s d N r s ds r m s q s q v x x v i x x v T v / = ' 2 ' ' 0 ' ) ( ) ( ) ( 2 1 ag gen r T T H =

7 7 Implemented PSS/E model of DFIG cont. The reactive power flowing through the net side converter depends on the terminal voltage of the DFIG V ref PI Q conv - Cc - G 1Ts Qnet vs

8 8 Implemented PSS/E model of DFIG cont. The structure of the torque controller t Tsp PI T sp () Tag G 1T s - vdr s - r iqr * xrr (xm) 2 xss - G 1Ts * vs xm xr

9 9 Implemented PSS/E model of DFIG cont. The control of reactive power delivered to the external grid via the stator Q s Qset G 1Ts - PI - v qr s - r i dr * x rr (x m ) 2 x ss

10 10 Simulation CASE 1 In this case the DFIG model was used to represent the Havøygavlen wind farm A model of the Havøygavlen wind farm was placed into a detailed PSS/E model of the Nordic system The chosen load flow in the simulated case was built on measurements performed by Statnett/SINTEF in October 2003 Disturbances in the grid were used to trigger the dynamic responses of the DFIG The simulated dynamic responses of the wind farm are analysed and compared with the measured dynamic respose The turbine torque is assumed to be constant during the simulation. The shaft is modeled with a stiffness and a damping

11 11 CASE 1 cont.

12 12 CASE 1 cont. Initial load flow, measurements: Produced power from the wind farm: 18 MW / -2 Mvar Smørfjord Lakselv/Skaidi: 8 MW /? Mvar Skaidi Hammerfest: 22 MW /? Mvar Initial load flow, simulation: Produced power from the wind farm: 18 MW / -2 Mvar Skaidi Smørfjord: 5.0 MW / -2.2 Mvar Lakselv Smørfjord: 3.2 MW / -1.1 Mvar Skaidi Hammerfest: 21.9 MW / -1.9 Mvar

13 13 CASE 1 cont. After 8 seconds of the simulation time the line Skaidi-Smørfjord was disconnected and after 22 seconds this line was reconnected. The wind farm s active power, reactive power production, and terminal voltages were monitored in both the simulation and in the measurements

14 14 CASE 1 cont Active power 15 Aktiv effekt 15 MW / Mvar 10 MW / Mvar Reactive power 0 Reaktiv effekt Time (sec) Tid (sekunder)

15 15 CASE 1 cont Mvar Reaktiv effekt (Mvar) Utkobling av Skaidi-Smørfjord Time (sec) -3 Innkobling av Skaidi-Smørfjord Tid (sekunder)

16 16 CASE 1 cont Line volta ge (kv) Linjespenninger (kv) Time (sec) Tid (sekunder)

17 17 CASE 1 cont. The uncertainty due to the distibution of active power flow on the lines Smørfjord-Skaidi and Smørfjord-Lakselv may explain some of the large difference in the transient response in active power Another factor in this may be the difference in control strategy The difference in the response of the line voltages are due to different load flow in the simulation and the measurements The chosen control strategy for the DFIG in the simulated case does work satisfactory

18 18 CASE 2 Single 2.5 MW wind turbine delivering power to a grid via a line and a transformer Simulation of the response in speed, power, and voltage from a 600 s wind series with average speed 7.9 m/s. 3P pulsations are taken into consideration through a wind field model A two mass model representation of the drive train Cp(λ,β) calculation based on turbine speed, wind speed, and pitch angle v w β Gear - box f n - f r AG f r f n Z line Power grid

19 19 CASE 2 cont. 10 Weighted average wind speed on the rotor blades m/s seconds

20 20 CASE 2 cont. 1 Generator speed pu seconds

21 21 CASE 2 cont. 1 Active power delivered to the grid MW seconds

22 22 CASE 2 cont Reactive power flowing from the stator to the grid Mvar seconds

23 23 CASE 2 cont. Terminal voltage pu seconds

24 24 Further work Make the DFIG model more user friendly (put in warning messages etc.) Improve the documentation on how to use the model Perform thorough test simulations with the DFIG model (Faults, 3P fluctuations, system damping)