IEEE-PES GM 2014 – National Harbor MD
July 29, 2014
Advanced Wind Power Plant Solutions
Steven Saylors, P.E.
Senior Specialist, Electrical Engineering
Vestas ROS TSS BoP Engineering NCSA
Coauthors are :
- Manoj Gupta, Specialist: VWS TSS Grid Interconnection
- Vajira Suminda Ganepola, Lead Engineer: VWS TSS Modeling Team
DISCLAIMER
Information contained in the following expresses general views and shall
merely be viewed as a contribution to the debate on the potential of wind
turbines in general.
Information contained in the following shall not be construed as an expression
of the policies or views of Vestas or as a detailed description of the properties
or functioning of wind turbines manufactured by Vestas.
Presentation Outline
1. Grid Code Requirements
2. Grid Connection
3. Wind Plant Control Systems:
•
The wind power plant control concept
4. Plant Active Power control & Frequency support performance
•
Active Power Set-Point Control
•
Active Power control loops
5. Governor Response contribution from wind turbine generators
6. Reactive Power and Voltage control
•
Reactive Power control loops
7. Solutions through WPP-Specific Studies
8. RTDS Simulations of Protections/Controllers/Grid Interactions
9. Summary
GRID CODE REQUIREMENTS
•Steady‐State requirements
– VAR provision: P‐Q chart
– Active Power Reserves: Curtailment,
Ramp Rate, Fast Runback Scheme
•Dynamic requirements: Small Disturbance
– Voltage Response: requirements for Vstep
response, V regulation
– Frequency response: Requirements for
frequency regulation, AGC
•Dynamic requirements: Large Disturbance
– Voltage response: HVRT, LVRT
– Frequency response: Large frequency
disturbances – Primary Frequency Response
(Governor Response)
WIND POWER PLANT GRID CONNECTION
• It is important to distinguish between the PCC/POI and the PoM.
• From a control perspective, they should match to the same physical
location; however, often in large WPPs this is not the case.
• Wind power plants are composed of many numerous wind turbine units
• Thus Grid Codes should apply to the overall plant performance at the PCC
with the power grid, not necessarily to the individual wind turbine’s
performance.
Wind Power Plant
Control Concept
WIND POWER PLANT CONTROL (WPPC)
•Main purposes for having a
dedicated control platform:
– To allow connectivity to higher
system level control schemes.
– To maintain the output of the
plant as close to the required
set‐points as possible (thus
fulfilling grid codes at PCC)
– To coordinate all components
in the wind power plant.
– Higher control reliability.
WIND POWER PLANT CONTROL (WPPC)
•The Active and Reactive Power Loops
can be actuated by different regulators.
•P loop can be actuated by:
– Frequency Control
– Active Power Control
•Q loop can be actuated by:
–Power Factor Control
– Reactive Power Control
– Voltage Control
Wind Power Plant Control: features of importance
1. Power Ramp Rate Control
2. Power Spinning Reserve
3. Absolute Power Constraint (Derating)
4. Frequency Response (governor characteristics)
5. Reactive Power and Power Factor Control
6. Voltage Control
7. Fault Ride-Through
ACTIVE POWER CONTROL LOOPS
•To collaborate in the system regulation, Active Power from the wind
plants should at least be prepared for the functionalities according to
the modes represented below as a,b,c
•More advanced functions may require Energy Storage.
•Additionally, energy/power forecasting is very important for wind
power grid integration.
(a)
(b)
(c)
Active Power Set‐Point Control Modes
Frequency (Governor) Response
51.0 Hz
f [Hz]
Simulated grid frequency
excursions are fed to central plant
controller and control response
command is then distributed to all
turbines operating at the time
50.0 Hz
Individual wind turbines respond
by pitching blades and/or
controlling variable frequency
converters to produce aggregated
plant response at PCC
P [pu]
0.9 pu
0.2 pu
100s
•The main goals of Reactive Power Control and Voltage Control is the
stabilization of node voltages, and avoidance of violating maximum
and minimum voltage levels.
Reactive Power Management
•In the past , VAR/PF control is the most common way of operating
the Reactive Power of wind plants (however, not commonly used in
large plants).
Voltage Control
•However, on a transmission system, superior performance for
voltage support is clearly offered by regulating Voltage rather than
VAR/PF.
•Typically used Voltage Control law is shown below:
Plant Reactive Power Control
0.04
Reactive Power [PU]
0.03
0.02
Qref
Qmeas
0.01
0
-0.01
-0.02
Qref = -0.03pu as
-0.03
capacitor of 0.06pu is
-0.04
200.8
201
201.2 201.4 201.6 201.8
202
Time [s]
202.2 202.4 202.6 202.8
203
switched
Plant WPP Voltage Control
0.15
Qref stepped ±0.10pu
0.05
0
-0.05
-0.1
Qref
Qmeas
-0.15
0
1
2
3
4
5
6
7
8
9
10
8
9
10
Time [s]
1.045
1.04
Voltage [PU]
Reactive Power [PU]
0.1
1.035
1.03
1.025
1.02
1.015
0
1
2
3
4
5
Time [s]
6
7
Plant Voltage Control (Proportional, aka. Slope Control)
– requirements to performance
When Voltage Reference is
stepped, the Reactive Power
Response should fall within a
defined envelope.
Plant Voltage Control (Slope)
1.042
Vref
Vmeas
1.04
1.038
Voltage [PU]
1.036
1.034
1.032
1.03
1.028
1.026
1.024
1.022
1.02
300
305
310
315
320
325
Time [s]
0
Reactive Power [PU]
-0.01
-0.02
-0.03
-0.04
-0.05
-0.06
-0.07 0
306.5
1
307
307.5
2
308
Time [s]
308.5
3
309
309.5
Grid Interconnection studies provide site‐specific electrical plant
analysis for the grid code compliance, ensure optimal electrical
design for better understanding and control of wind power projects.
Yaw power backup system
Fault ride‐through
Reactive power
control
HVRT
Arc flash study
Achieve
Advanced
Wind Power
Plant
Performance
Transient stability
PPC parameter settings
Weak grid connection
BoP speification/TPS
Loss
SSR/SSCI
Plant energisation
Insulation co‐ordination
19
Grid Interconnection – HVRT
Risk of WTG overvoltage protection at 1.2 pu PCC voltage
wtg is set to pickup at 1.2 pu for 80 ms and 1.15 pu for 60 s.
Voltage Vs Distance plot with locked tap position illustrates the risk.
WTG tap adjustment, PPC in voltage control are the solution
20
Grid Interconnection – HVRT (Response at the PCC)
WTG Tap adjustment, PPC in voltage control, detailed model of the collector
network, transformer saturation are key elements to consider
21
Grid Interconnection – HVRT (Response at the WTG level)
WTG is set to pickup at 1.2 pu for 80 ms and 1.15 pu for 60 s.
22
Grid Interconnection – HVRT (Ensure no WTG trips)
Pre and Post event active power at the PCC should be same
23
APPLICATIONS OF RTDS
RELEVANT TO WTG/WPP
 PROTECTION SYSTEM VALIDATION
 CONTROL SYSTEM VALIDATION
 SMART‐GRID AND DISTRIBUTED GRID APPLICATIONS
24
PROTECTION SYSTEM TESTING
CLOSED LOOP PROTECTION RELAY TESTING
 REAL‐TIME SIMULATOR CAN BE USED TO CARRY OUT PROJECT SPECIFIC
PROTECTION STUDIES WITH REAL RELAYS
 REQUIRED REAL‐TIME SIMULATOR TO PROVIDE REALISTIC POWER
SYSTEM SIGNALS & CLOSED LOOP INTERACTIONS
25
CONTROL SYSTEM TESTING
WTG CONVERTER CONTROLLER TESTING
WTG CONVERTOR
CONTROLLER
 INTERACTIONS OF WTG CONVERTER CONTROLLER WITH THE GRID AND THE
OTHER AUXILIARY EQUIPMENT IN A SPECIFIC PROJECT CAN BE STUDIED
Summary
•Wind power plants provide high bandwidth controls of Active/Reactive Power
and wtg/wpp protections. The applications span Derating, Ramp Rates,
Frequency Response, & Voltage Control, LVRT/HVRT, O/U Frequency, Power
Oscillation Damping, Inertia/Primary/Secondary Response, etc.
•Ancillary Services markets could be developed within tariffs to incentivize
WTG/WPP controls that assist in grid reliability.
•Performance of project studies are performed to identify adequacy of default
controls parameters and strategies; and also be useful to determine project‐
specific solutions to meet not only grid code compliance – but grid reliability.
•RTDS can test wtg/wpp controllers and project control strategy solutions through
Real Time simulations of actual controller logic and hardware before operations
to ensure solutions are viable.
THANK YOU FOR YOUR ATTENTION