Grid Code Testing of Wind Turbines by VSC-based Test...
Transcript of Grid Code Testing of Wind Turbines by VSC-based Test...
1 of 32
VÄRLDENS SKILLNAD
Grid Code Testing of Wind Turbines by
VSC-based Test Equipment
Nicolás Espinoza, PhD Student
CHALMERS UNIVERSITY OF TECHNOLOGY
Gothenburg, Sweden.
2 of 15
Project Description • Aim of the project
– To develop methods for grid code testing of wind turbines using
VSC-based test system.
• Activities
– Grid code analysis for interconnection of wind parks.
– Control theory of WT and VSC.
– Mathematical model for stability analysis.
• Results
– Simulation of the WT and the VSC-based test equipment (TE).
– Laboratory experiment at Power System Lab in Chalmers.
– Field test of full power 4 MW WT with 8 MW HVDC system in
Göteborg harbor has started!
3 of 15
Wind Power Increase • World total installed capacity is 318 GW (117 GW are inside EU)
• 40 GW per year in the last 5 years, approximately.
Year
GW installed
4 of 15
Grid code development • Regulates the interconnection of the generating plant.
• Special requirements for wind parks.
• Steady state: voltage, power and frequency ranges.
• Dynamic: LVRT and reactive current injection (if allowed).
• Grid code harmonization: ENSTO, Nordic.
5 of 15
Low Voltage Ride Through (LVRT) • Voltage dip representation at the connection point
0
0 1
0.3
0.4
0.5
0.6
0.2
0.1
0.7
Sy
stem
Vo
ltag
e [p
u]
Time [s]
E.ON (Germany)
Energnet.dk (Denmark)
Red Eléctrica España (Spain)
0.8
0.9
1
2 30.50.25 0.75 1.25 1.5 1.75 2.25 2.5 2.75
Svenska Kraftnät (Sweden)
Nordel
EirGrid (Ireland)
National Grid (U.K.)
6 of 15
Wind Turbine Topologies
G
Output
transfomer
Full Power Converter
Coupling
inductor and
filtersAC
DC AC
DC
AC Grid
Gearbox/
Gearless
Control system
Wind turbine
Protection by DC crowbar
Generator
Full-size converter WT
• Grid synchronization
• Current during fault is fully
controlled.
• LVRT control.
DFIG WT
• Stator connected to the grid.
• High transient current during fault.
• VSC rated in 1/3 P nominal.
• Poor LVRT capability.
Output
transfomer
1/3 Power Converter Coupling
inductor and
filtersAC
DC AC
DC
AC Grid
Gearbox
Control system
Wind turbine
Protection by DC crowbar
DFIG
Protection by AC crowbar
7 of 15
Wind Turbine Modelling
Assumptions
• Physical decoupling between
Generator and grid.
• Mechanical transients are slow
compare to electromagnetic
transients.
wfR ,
wu wti , we
wfL , wfC ,
DC
AC
wDCu ,wDCi ,
wDCC ,
WT-VSC
si
GENP
crbR
To Test
equipment
crbsw
TWgwe , gwi ,
G
Output
transfomer
Full Power Converter
Coupling
inductor and
filtersAC
DC AC
DC
AC Grid
Gearbox/
Gearless
Control system
Wind turbine
Protection by DC crowbar
Generator
8 of 15
Grid Code Testing Equipment
Test Equipment: VSC in back-to-back
AC voltage
control for
LVRTInterface
impedance
AC
GridInterface
impedance
AC
DC AC
DCPCC
Coupling
transfomer
Coupling
trasnformer
DC voltage
control
• Impedance-based
• VSC-based
Z series
Z faultAC
Impedance-based
Test equipment
Grid impendace
9 of 15
Stability Analysis • Analytical model based on physical equations and control equations.
• Study of interactions between WT and Test Equipment
wfR
,
wu
wti
, we
wfL
, wfC
,
DC
AC
wDCu
,wDCi
,
wDCC
,
WT-VSC
si
AC
DC
PCC
eg
i ut
i
fC
fR
fL
Interface impedance Collector-VSC
eqR
eqL
CL vs OL voltage CTRL
Blue: P-based controller
Red: PI-based controller
Black: Open-loop Well damped area
10 of 15
Laboratory Setup
utie
1,1, , ff RL
DCu
DCC
Grid Emulator DC machine360 V
DS1103
2,2, , ff RLfC
AC voltage control for LVRT
AC
DC AC
DCwtu , wti ,
AC grid, 400 V, 50
Hz
lR
wDCC ,
wDCu ,
crbR
DS1103
Wind Turbine Model AC-link
wtwt QP ,
• Placed at the Power System Lab. at Chalmers University of Technology.
• Consisting of 2 DC-sourced VSC interfaced by an AC-link.
• 200 V, 10 kVA.
11 of 15
12 of 15
13 of 15
Field Test Results
14 of 15
Turbine
VSC
AC
DCAC
Utility Grid
Flexible VSC-based Testing Equipment
Grid VSC
DC
AC
15 of 15
Conclusions and Future Work
Conclusions
• Need for regulations for renewable energy sources.
• VSC-based T.E. is flexible
• Development of PCC voltage control and control algorithms.
Future Work
• To develop control strategies for testing of:
– Voltage control
– Power oscillation damping
– Frequency control
• Characterization of wind turbines
• To include wind turbine mechanical system
16 of 15
Thanks for your attention
Nicolás Espinoza, PhD Student
CHALMERS UNIVERSITY OF TECHNOLOGY
Gothenburg, Sweden.