1. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 1 Analysis of the effects of wind farms dynamic behaviour on distribution networks DFIM Wind Farms Voltage Control CIRED Barcelona 12-15 May 2003 Luis Layo (SP) Session 4 - Block 3 IBERDROLA

2. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 2 Index Voltage control strategy on DFIM Wind Farms Models developed for simulations Reactive power control tests of a wind farm from a distribution control centre Voltage control operation procedure Question 6: Are there now cost effective solutions for all the voltage control challenges of renewable generators?

3. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 3 Introduction Wind energy has turned out to be one of the most important and promising sources of renewable energy This energy source will represent a significant proportion of total installed power in the Spanish power system The expected amount of wind power establishes important challenges to distribution and transmission network planning and operation Problems related to reactive power management in wind farms and to their connection to the electric network

4. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 4 DFIM Model This kind of wound rotor machine has to be fed both from stator and rotor sides Asynchronous generator which behaves as a synchronous with variable speed. Varying rotor input signal: –Amplitude: reactive power control –Phase: active power control –Frequency: rotor speed control Rotor G AC DC AC Switch Gear Network Asynchronous Generator DFIM Doubly Fed Induction Machine

5. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 5 Reactive power can be controlled while maintaining active power generation Distributes the required reactive power of the farm in a proportional way among all the operative generators: –Each machine will work with a different power factor –Machines tend to reach the saturation state at the same time Control strategy: general features

6. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 6 Q ref Pe 2 Pe n Pe 1 Pe 3 Wind Farm Control Centre Distribution Network Control Centre q n max q 2 max q 3 max q 1 max imax q  max Q  imax q max Q ref Q isp q . q 2sp q 3sp q 1sp q nsp Control strategy: model

7. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 7 Control strategy: requirements Wind generators –Control loop changes to receive local set point Wind Farm Control Centre: –Active power of each machine – P-Q capacity curve Distribution network Control Centre –OPF: maximum reactive power available –Communications Cost-effective –Take advantage of exiting control capacity

8. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 8 Security Control: voltage monitoring Qe V Vmax normal Vmin normal Vmin trigger Vmin admisible Qe=0, V= 1 P.U. Control trigger off Qe free control Qe emergency control Control trigger off Vmax admisible Vmax trigger

9. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 9 Potencia activa en kW Evolución de las potencias activas por máquina Active power performance of each generator (wind gusts) Evolución de las potencias reactivas por máquina Potencia reactiva en kVAR Reactive power performance of each generator Reactive Power Control Simulations Inductivo Capacitivo Comportamiento del Sistema de Control de cos  Power factor performance of the wind farm

10. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 10 Salajones Wind Farm data 23 MW: 35 wind generators In service since 1999 Doubly fed induction generators DFIM 660 kW machines 66 kV network connection Wind farm -> generators: radio link Control centre -> wind farm: optical fibre link Control Centre OPF -> Q set point

11. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 11 Q control test in a real Wind Farm

12. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 12 Voltage control secondary service Transmission Network Distribution Network Q’P’  Wind Farm Power Factor 0………1 P Q tg  = P Q P-P’ Q+Q’ tg  ’ = P-P’ Q+Q’ P.O. 7.4: establishes power factor limits (Q generation and absorption bands) in the transmission-distribution border points

13. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 13 Voltage Control Proposal Required service as normal generators Softer conditions in distribution networks Perform the voltage control service based in power factor bands according to the periods of the day –Peak: reactive power generation –Off-peak: reactive power absorption –Medium: power factor of unity

14. Luis Layo (SP) Session 4 – Block 3 – Selected Paper - Question 6 Barcelona 12-15 May 2003 14 Conclusions Wind farms made up with DFIMs constitute an important tool from the voltage regulation point of view DFIMs are strongly recommended for the new wind farms from the power system viewpoint, especially in areas with a large wind generation concentration Wind farms with voltage control capacity will have a better position to be accepted in the system, in terms of planning, installation and operation The DFIM technology allows to perform voltage control in a very cost-effective way