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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. Index. Voltage control strategy on DFIM Wind Farms Models developed for simulations
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Analysis of the effects of wind farms dynamic behaviour on distribution networksDFIM Wind Farms Voltage Control CIRED Barcelona 12-15 May 2003 Luis Layo (SP) Session 4 - Block 3 IBERDROLA
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?
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
DFIM Model Switch Gear Asynchronous Generator Network G • 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 DFIM Doubly Fed Induction Machine AC DC Rotor DC AC
Control strategy: general features • 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
q1sp q2sp q3sp qnsp Q ref = Q q q q = max isp imax imax Q . max q1 max q3 max qn max q2 max Qref Control strategy: model Wind Farm Control Centre Pe1 Pe2 Pe3 Pen Distribution Network Control Centre
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
V Control trigger off Vmax trigger Vmax admisible Qe emergency control Vmax normal Qe free control Qe Qe free control Qe=0 , V= 1 P.U. Vmin normal Qe emergency control Vmin admisible Control trigger off Vmin trigger Security Control: voltage monitoring
Comportamiento del Sistema de Control de cosj Evolución de las potencias reactivas por máquina Inductivo Capacitivo Potencia reactiva en kVAR Evolución de las potencias activas por máquina Reactive power performance of each generator Potencia activa en kW Reactive Power Control Simulations Power factor performance of the wind farm Active power performance of each generator (wind gusts)
Salajones Wind Farm data Control Centre OPF -> Q set point • 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
Q P Q+Q’ P-P’ Q+Q’ Q tg’ = tg = P-P’ P P’ Q’ Wind Farm Voltage control secondary service • P.O. 7.4: establishes power factor limits (Q generation and absorption bands) in the transmission-distribution border points Power Factor 0………1 Transmission Network Transmission Network Distribution Network Distribution Network
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
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