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Steven Saylors, P.E.Senior Specialist, Electrical EngineeringVestas ROS TSS BoP Engineering NCSA
Ancillary Services Provided from Wind Power Plant Augmented with Energy Storage
IEEE‐PES GM 2014 – National Harbor MDJuly 29, 2014
2
Based on papers written for EWEA and IEEE
Coauthors are :
- Philip C. Kjær, Chief Specialist- Electrical Engineering: VWS TSS Power Conversion Systems
- Rasmus Lærke, Specialist- Plant Control Systems: VWS TSS Control System Design
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. Motivation2. Definition of features3. Control Structure4. Test ResultsA. Primary Reserve (PR)B. Inertial Response (IR)C. Power Oscillation Damping (POD)5. Market Participation Experience6. Conclusions & Perspectives
Motivation
• TSOs consider Wind Power Plants as sources of ancillary services:• Primary Reserve• Inertial Response• Power Oscillations Damping
• Traditionally supplied by Conventional Power Plants.• Increased % of wind power requires more ancillary services
for grid stability.
• For new WPPs to provide ancillary services that require active power modulation:A. Overloading turbines Redesign or increase component stressB. Curtailing operation of turbines Permanent energy loss +
Forecast errorsC. Augmenting WPPs with Energy Storage Systems
• Technical feasibility studies have only been conducted sporadically to date.
• Financial assessments from turbine curtailment or overload are largely unreported.
• Interest in what Energy Storage can do as complement.
∆P, ∆Q
Wind Power Plant with Energy Storage ‐ Utility scale
EnergyStorage
ManagementSystem
4 x 3MW1.2MW + 0.4MW x 0.25h
Definition of featuresPrimary Reserve (PR) + Inertial Response (IR)
IRP
0PPRP
maxf
0fSSf
SG Tripped
Power Oscillations Damping(POD)
AugmentedWPP + ESS
Multi‐Asset Power Plant Controller
Features Controllers
• Primary Reserve
• Inertial Response
• Power Oscillations Damping
IRP
PRP
PODPf
f
sTsT1
Wind Power Plant + Energy Storage Test Results
Down‐regulation by wind power plant
Up‐regulation by energy storage system Inertial Response +
Primary Reserve
10600
10800
11000
11200
11400
11600
11800
12000
12200
0 500 1000 1500 2000 2500 3000 3500
Pref_AWPP_kW
P_Elspec_WPP_kW
P_Elspec_WPP_kW
Power Smoothing Power oscillation damping
Test Results – Inertial Response + Primary Reserve• WPP providing IR + PR• Available wind power ~9.5MW.• Wind plant curtailed
ESS providing IR + PRWind plant producing available power
[Hz] [Hz]
[seconds] [seconds]
Output [kW] Output [kW]
0.5 Hz/s10s to Fmin
• WPP providing POD• Available wind power ~12MW.• Wind plant curtailed
ESS providing PODWind plant producing available power
0 20 40 60 80 100-1.5
-1
-0.5
0
0.5
1
1.5
Time [s]
Act
ive
pow
er [M
W]
0 20 40 60 80 100-1.5
-1
-0.5
0
0.5
1
1.5
Time [s]
Act
ive
pow
er [M
W]
∆PTest Results – Power Oscillation Damping
ΔP : POD Controller Reference Signal (to a 0.1 Hz simulated oscillation)Pout : WPP Output
Test Results – Combined Power Oscillations Damping
• Assets response
• ESS active power –frequency 1
• WPP reactive power –frequency 2
System oscillation event containing two frequencies0.1Hz + 1Hz
[seconds]
[seconds]
POD signal [kW]
Output [kW]
Output [kVAr]
Market Participation Experience fromLem Kær Wind Farm& Energy Storage System
Energy Storage Installation
14
ESS1: A123. 53’ container0.4MW / 0.25hLiFePO4BMSAir-conFire suppressionHeat exchangerPower electronic converterTransformer 0.48/10kV10kV circuit breaker
ESS2: Power electronic converterTransformer 0.48/10kVHeat exchangers
ESS2:AltairNano. 53’ container1.2MW / 0.25hLi4Ti5O12BMSAir-conFire suppression
Metering
Meter 1: ES consumptionMeter 2: ES generation
Common meter for WPP + ES
Lem Kær plant.
The potential services a Wind Power Plant augmented by embedded Energy Storage can provide
• Ancillary services– Primary Reserves– Secondary Reserves– Tertiary Reserves– Black Start
• Load Shifting – Energy Arbitrage• Transmission Curtailment• Forecast Error Reduction• Ramp Rate reduction (dp/dt control)• Voltage Control• Islanding
Results from a 2009 Vestas study on a 66MW wind plant in three different locations (electricity markets).
NPV (%) relative to best case (GFR)
Primary Reserve
Charging Strategy• Charging added to power reference when freq>49.98Hz, according to SoC.• If freq < 49.98Hz for >15 minutes, charge during 15 minutes to reach SoCref.
Danish TSO Primary Reserve Approval Test
0
200
400
600
800
1000
1200
‐2000
‐1500
‐1000
‐500
0
500
1000
1500
2000
2700 2900 3100 3300 3500 3700 3900 4100 4300 4500 4700 SoC [0/00]
Power [k
W]
Time [sec]
15 minute activation
P_Elspec_ESS1+ESS2+AUX
SOC 1
SOC 2
Power [kW]
State of Charge
>85% round-trip efficiency
Charge
Discharge
15 min 30 min0 min
90%
10%
1.4MW
-1.6MW
SoC ESS1 [%]
SoC2 ESS2[%]
0
0.5
1
1.5
2
2.5
3
3.5x 106 No samples vs. frequency (1 sec update)
Num
ber s
ampl
es
Frequency
49.86
->49.87
49.88
->49.89
49.9-
>49.9
149
.92->49
.9349
.94->49
.9549
.96->49
.9749
.98->49
.9950
.00->50
.0150
.02->50
.0350
.04->50
.0550
.06->50
.0750
.08->50
.0950
.1->5
0.11
50.12
->50.13
50.14
->50.15
Frequency data recorded at site
Up‐regulation
49.98 Hz
Operations
Investment 100%Yearly net result 14%Cost of capital 10,59%
NPVNominal power rating 1600 kWNominal storage energy capacity 400 kWhStorage discharge per day 400 kWhStorage charge per day 720 kWhAuxil iary consumption per day 400 kWhStorage efficiency 56 %Storage+auxil iary efficiency 36 %Storage util isation 2,1 %Market participation rate 96 %
Metered energy purchase 27 c/kWhMetered energy sales 6 c/kWh
Simulation power/energy ratio for primary reserve
ESS Capacity
(discharge time with
ESS full power )
PFRAV
A [%]
15 min discharge time 100,0010 min discharge time 100,007.5 min discharge time 100,006 min discharge time 100,005 min discharge time 99.944 min discharge time 99.823 min discharge time 99.062 min discharge time 95.701 min discharge time 84.630.5 min discharge time 72.260.1min discharge time 48.39 -2 0 2 4 6 8 10 12 14 16 18 20
30
40
50
60
70
80
90
100
110
120
ESS capacity [min]
PFR
ser
vice
ava
ilabi
lity
[%]
Simulations are based on 1 year grid frequency data (2012).
Conclusions and Perspectives1. It is technically possible to augment the wind power plant with energy storage to provide ancillary services with reduced need for
turbine curtailment or overload, such as for: power smoothening, synthetic inertia, power oscillation damping. Currently, none are traded.
2. A single power plant controller can host ancillary service algorithms and co-ordinate and dispatch between turbines and energy storage units.
3. Turbines / storage can be operated individually or in combination to deliver adequate ancillary service responses, within technical limits.
4. TSO has approved storage unit for Primary Reserve market participation.
5. Asymmetrical up-/down regulation bids maximize revenue per installed storage rating.
6. Storage life-time is crucial to life cycle cost – and requires field verification.
Outlook – financial / technical:
• Reductions of storage price and system price (commoditize) – but how fast (cf. Li-ion and pace of EV market)?
• Possible wider aggregation of turbines/plants with common storage facility to reduce ratings.
• Ancillary services market development (eg. ERCOT).
• Detailed technical performance specifications are necessary for any evaluation of feasibility of ancillary service provision from wind power plants - with/without storage!
Thanks to:
Thank you for your attention.