ENERCON. Wind Farms with Power Plant Capabilities. Tokyo, October 27 th Werner Bohlen / Eckard Quitmann

Transcription

1 ENERCON Wind Farms with Power Plant Capabilities Tokyo, October 27 th 2009 Werner Bohlen / Eckard Quitmann Slide 1

2 Subjects: 1. ENERCON technical concept 2. Operational ranges (U, f) 3. Steady state reactive power capability and how to use it 4. Power frequency control Slide 2

3 ENERCON Technology ENERCON Gearless drive and variable speed Advantages: Direct Drive Concept No Gearbox Variable speed operation Low wear due to slow machine rotation Low machine stress due to high level of speed variability Yield-optimised control High hub heights for increased steady yield High level of grid compatibility and compliance with advanced grid codes FACTS Capabilities Slide 3

4 ENERCON Technology Concept: Gearless drive and variable Speed Generator: Stator Rotor Rectifier Excitation control G E N E R A T I O N Slide 4

5 ENERCON Technology Concept: Full scale power electronics Inverters UPS (optional) Control cabinet MV-Switchgear Level 2 Level 1 C O N V E R S I O N Transformer LV Switchgear Level 0 Slide 5

6 ENERCON Technology Structure electrical system Ring Generator Rectifier = ENERCON serial product : = = project specifically: Transformer Circuit Breaker DC- Link Inverter = Control System Filter Seen from the grid the performance is defined by the inverters Excitation Controller Seen from the grid the ENERCON WEC is mainly a symmetrical source of current. As long as frequency and voltage at the WEC terminals are within the specified ranges, the WEC injects the maximum possible current. The individual WEC controls the power factor (or reactive power) but not the voltage. The entire wind farm can be equipped with voltage control, if required. Slide 6

7 Operation Ranges Frequency and voltage Only with UVRT Option: Max. 5 seconds per event max. 60 sec. Normal continuous operation Only with UVRT Option Max. 5 seconds per event Frequency f [Hz] f R + 7 Hz Voltage U [% U R ] f R 80% 90% 100% 110% 120% 145% f R -7 Hz Older ENERCON WECs have slightly smaller operation ranges: continously: U R ±10%, max. 60s: U R ±20% Slide 7

8 FACTS Capabilities of Wind Energy Converters Reactive power capability ENERCON WEC has no need for reactive power. Each ENERCON WEC has capability to provide or to absorb reactive power. Continously operation, very fast dynamics. PQ range is basis for the ENERCON Voltage Control System (VCS) on wind farm level Export from the WEC to the grid ( lag, overexcited, raising the voltage) 1 p.u. P Import from the grid to the WEC ( lead, underexcited, lowering the voltage) Optional: ENERCON WEC operation as a STATCOM Q export Q import Slide 8

9 PQ range of wind farm To be undoubtedly defined by the system operator 20kV 400V 400V To be defined: Reference point for that PQ-range The minimum PQ-range required (incl. tolerances) Operational voltage range in which the PQ-range shall be available How PQ-range shall be used (steady state operation) Active power 20kV Example: required range 0.95 exp... cosφ imp 400V 20kV At the 400V terminals of the WEC PoC PoC? (example) Result at PoC QExport QImport Qoffset due to WF-cabling Slide 9

10 ENERCON Voltage Control System (VCS) Example: Wind farm in Corsica U Point of Reference Example: VCS on Aja Wind Farm in Corse 6 MW installed capacity: 10 x E kw Weak electric system, resulting challenges: voltage control, ride through system faults P wind farm Reference point: Point of connection 2,5km far from wind farm VCS off UCTE VCS on network Q wind farm Slide 10

11 Voltage profile within wind power plant To be planned carefully Voltage profile within the wind power plant must be carefully planned, as injection of P and Q will influence voltage on each WEC, as well as on the PoC. Boundary conditions for steady state operation: 400V +20% -10% ZL Z C Un ZL Z C U3 ZL Z C U2 UPoC +X% -Y% U1 ZL Z C 400V +20% -10% U1 = U2 = = Un = UPoC ZL UPoC Slide 11

12 Future needs of the power system Contribution of WECs during frequency disturbances Basic: All modern WECs operate with variable speed, designed for max. active power at any time. Consequence: If any dependency Power = f(frequency) is desired, it has to be implemented artificially through the control of the WEC. For wind energy the requirements about power and frequency must distinguish between: Incidents of overfrequency versus underfrequency Frequency disturbances during strong wind versus low wind Permanent requirements (minutes, hours) versus temporary (sec) Slide 12

13 ENERCON Technology Power reduction for overfrequency incidents 1. Overfrequency: - Relatively easy to respond to - WEC must reduce active power - Detailed dynamic parameters to be determined - Economical consequences negligible f > f n P electric = f(frequency) P(f) curve is adjustable Slide 13

14 ENERCON Technology Power reserve for underfrequency incidents 2. Underfrequency: P availible P limited Active power f low normal frequ. range f rated f high Active power reserve f max f If system tends to become critical, signal can be sent to wind farms: reduce active power! (temporarily for precaution) If system frequency really falls below f low, wind farm increases active power Economical disadvantage for WF only acceptable, if it is limited to a few h/a Response time is typical for primary control P rated P rated x% P reserve as percentage of P actual wind speed Technology is available, but economical aspect must be adressed! Slide 14

15 Thank you Slide 15

16 Why Fault-Ride-Through? Possible consequences of simple grid faults Spain has a relatively weak electrical connection to rest of Europe Today: Pload_min 40 GW Pwind 14 GW Expected: Pwind 40 GW Slide 16

17 Why Fault-Ride-Through? Possible consequences of simple grid faults Several 1000 MW wind power is abruptly disconnected and off for several minutes Spain has weak electrical connection to rest of Europe (UCTE power system) Example: Grid fault in the north of Spain Voltage collapses around the failure location funnel-shaped According to the old requirements of the grid operator all WEC in this zone disconnect The active power generation of the disconnected generators is suddenly missing after the fault Collapse down to 320 kv = 80% U N => Risk of total blackout (generation load) Slide 17

18 ENERCON Fault Ride Through Capability Resumed Ride through for up to 5s per event Active power coming from the generator may not be fully fed into the grid dissipated in choppers Capability to ride through symmetrical and asymmetrical faults Different FRT-modes for optimum performance, adressing different power system characteristics (physical needs) Ability to ride through faults down to zero volts at WEC terminals Measurement example of an ENERCON E-70 E4 running at 2MW / 3-phase fault Voltage U [V] Current [ka] Fault Ride Through capability may increase the capacity of a power system to integrate more wind power Slide 18