March 2011 Spanish TSO Operational Challenges and Solutions Dirección de Operación

March 2011

Spanish TSO Operational Challenges and Solutions

Dirección de Operación

Contents

Current Operational challenges at Spanish System facing renewables variable inputs

REE Renewables Control Center (CECRE)

Facing the future: technical and market issues

RES Integration in the Spanish Electric System

RED ELÉCTRICA DE ESPAÑA

Demand is given at a certain moment, until relevant demand side management takes place, generation must adapt to demand to maintain system equilibrium.

Adequacy to system demand profiles.

3

Influence of RES Generation in System Operation (I)

Variability influences the rest of the electric system that must compensate such variations to keep the system balanced.

Predicting this variability and awareness of uncertainties crucial for efficient operation.

Demand coverage

Variability and predictability

The combination of these two factors along with the behavior and uncertainty of the demand contribute to situations with balance feasibility difficulties due to lack of downward reserve.



4

Influence of RES Generation in System Operation (II)Generation control and supervision

Dynamic behavior during disturbances

Visibility and controlability by the SO:Real-time telemeasurementsPossibility to issue instructions and

feedback Renewable generation is more distributed

and dispersed than conventional. Awareness increases with visibility and

remedial actions must be fast and efficient.

Stability during disturbances in coordination with the rest of the system.

Voltage dip ride through capabilities. Contribution to the clearance of the

disturbance.



5

Influence of RES Generation in System Operation (III)Generation Management

Ancillary services provision

Definition of manageable generation according to Spanish legislation:Production reduction does not imply loss of

primary energy.Certainty in generation prognoses. In Spain the SO determines whether to

consider a facility as manageable or non-manageable according to tests.

Displacement of conventional generation and ancillary services providers.

Manageable RE may participate in load frequency control.

Influence on voltage control during high production situations.



6

System Balancing Reserves

Type Influence of Wind Power on ReserveDefinition

Primary Regulation Not influenced by wind powerAction of speed regulators from generator units responding to changes in system frequency

(<30 s to 15 minutes)

Secondary Regulation

Only slightly affected by wind generation ramps when these ramps are opposite to system demand. Presently, no need

to contract further reserve bands.

Automatic action of central algorithm and AGCs in the generation units that provide this service responding to changes in system frequency and

power deviations with respect to France. (≤100 s to 15 minutes)

Tertiary RegulationOnly slightly affected by wind generation ramps when these

ramps are opposite to system demand.

Manual power variation with respect to a previous program in less than 15 minutes.

(<15 min to 2 hours)

Running Reserves or Hot Reserves

Significant influence of wind power. Reserve provision must be increased to take into account wind power forecast

errors. Presently confidence intervals used and probabilistic sizing of reserve needs under study.

Manageable generation reserves that can be called upon within 15 minutes to approximately

2 hours. Include tertiary reserves and consist on the running reserves of connected thermal units

and hydro and hydro pump storage reserves. (15 min-2 hours to 4 hours)



Only slightly affected by wind generation ramps when these ramps are opposite to system demand.


errors. Presently confidence intervals used and probabilistic sizing of reserve needs under study.

Tertiary RegulationManual power variation with respect to a

previous program in less than 15 minutes. (<15 min to 2 hours)

Running Reserves or Hot Reserves

Manageable generation reserves that can be called upon within 15 minutes to approximately 2 hours. Include tertiary reserves and consist of

the running reserves of connected thermal units and hydro and hydro pump storage

reserves. (15 min-2 hours to 4-5 hours)



Only slightly affected by wind generation ramps when these ramps are opposite to system demand.


errors. Reserves are checked from day D-1 once market results are received until real time.



Cog + Other RE; 20.31%

Coal; 16.62%

Combined cycles; 35.09%

Nuclear; 16.89%

Int. Int-4.67%

Wind; 1.26%

Hydro-Power; 13.10%

Cog + Other RE; 17.65%

Pumping; -12.45%

Coal; 2.99%

Combined cycles; 6.10%

Nuclear; 31.84%

Int. Int-4.67%

Wind; 53.09%

Hydro-Power; 5.42%

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

01/11/2009 00:00:00

01/12/2009 00:00:00

01/01/2010 00:00:00

01/02/2010 00:00:00

01/03/2010 00:00:00

01/04/2010 00:00:00

01/05/2010 00:00:00

01/06/2010 00:00:00

01/07/2010 00:00:00

01/08/2010 00:00:00

01/09/2010 00:00:00

01/10/2010 00:00:00

01/11/2010 00:00:00

Maximum coverage

09/11/2010 3.35 h

Minimum coverage

03/09/2010 12.33 h

Wind production variability

Wind production record 14 962 MW

09/11/2010 14.46 h



Wind Energy CharacteristicsDEMAND vs. WIND PRODUCTION

26,000

28,000

30,000

32,000

34,000

36,000

38,000

40,000

00:00

01:00

02:00

03:00

04:00

05:00

06:00

07:00

08:00

09:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

21:00

22:00

23:00

00:00

1,400

1,900

2,400

2,900

3,400

3,900

Demand 06/02/2008 Wind Production 06/02/2008

WIND PRODUCTION DURING A YEAR

Non manageable primary energy.

Very variable production output.

Downward ramps in wind production in the mornings often increase morning ramps of conventional generation.

8

0

2.000

4.000

6.000

8.000

10.000

12.000

01/0

1/20

09

01/0

2/20

09

01/0

3/20

09

01/0

4/20

09

01/0

5/20

09

01/0

6/20

09

01/0

7/20

09

01/0

8/20

09

01/0

9/20

09

01/1

0/20

09

01/1

1/20

09

01/1

2/20

09

MW



Data corresponds to year 2009 Wind production differs sometimes from demand requirements, specially in

summer.

HOURLY PRODUCTION DISTRIBUTION

Wind Energy Characteristics

MONTHLY PRODUCTION DISTRIBUTION

9

0,00%

5,00%

10,00%

15,00%

20,00%

25,00%

30,00%

35,00%

40,00%

jan feb mar apr may jun jul aug sep oct nov dec

0%

5%

10%

15%

20%

25%

30%

35%

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

Hour



5,700.00

5,950.00

6,200.00

6,450.00

6,700.00

6,950.00

7,200.00

7,450.00

7,700.00

7,950.00

8,200.00

10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00 02:00 04:00 06:00 08:00 10:00

Wind Production 23/03/08-24/03/08

23/03/2008 24/03/2008

Wind turbines technology

Wind generation trippings if wind speed higher than 25 m/s.

Wind power variation on this day: 1 800 MW

Wind Energy Characteristics

Increase of 586 MW in 30 min. Gradient: 1172 MW/h

Decrease of 1110 MW in 1 h 25 min. Gradient: -785 MW/h

5800

6200

6600

7000

7400

7800

8200

8600

0:00

1:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:00

11:00

12:00

13:00

14:00

15:00

16:00

17:00

18:00

19:00

20:00

21:00

22:00

23:00 0:

00

Wind Production 30/03/2008

Wind production variability

10



Operational challenges of distributed generation Myriad of plants each belonging to different companies with different

policies for operation, switching and maintenance. However there is a need for planning and real-time communication.

In the past, very slow contact in case of emergency reductions, outages or maintenance planning of the transmission assets next to connection points for generation.

SO actions had to be always manual leading to longer execution times.

When actions and supervision takes longer and risks are higher, stricter limitations must be in place and planned further in advance reducing RES production and installation.

Example, there are more than 700 wind parks installed in the peninsular system.

11

Solved by grouping facilities in control centers with real-time contact with the System Operator through the CECRE.



Congestion management According to RD 661/2007 and Operational Procedure PO 3.2, in

case several plants that have a minimum of sensibility to a congestion need to be redispatched to solve the congestion the following order must be applied:

Ordinary regime. In decreasing sensibility order.

Non-renewable manageable special regime

Renewable manageable special regime

Non-renewable non-manageable special regime

Renewable non-manageable special regime

12



Impact of forecast errors in the demand coverageWind Production Forecast Errors D-1 h12

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

MW

-630 MW

In D-1 at hour 12 when the daily congestion management studies are conducted there is a 15% possibility that wind production is 630 MW lower than predicted.

Within start-up time of thermal power units (5 hours in advance) there is still a 15% possibility that wind production is 570 MW lower than predicted.

Reserves are checked within these time scopes and the uncertainties must be translated into further running reserves. Additional thermal groups might be needed to guarantee demand coverage.

Wind Production Forecast Errors H-5

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

MW

-570 MW

13



15000

0:00 0:00

0

10000

0 h 24 h

Req_min

D_min

Req_max

D_max

MW

Requirement for Manageable Generation (I)

DemandWind productionRequirement for manageable generation

Demand Ratio = D_max/D_min Requirement Ratio =

Req_max/Req_min Due to wind energy and its

behavior during peak and off-peak hours: Requirement Ratio > Demand Ratio Steeper slopes (from off-peak

hours to peak hours)

14

Monotonous curve for demand and requirement ratio in 2009

1,0

1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

3,0

3,2

0% 10% 20% 30% 40% 50% 59% 69% 79% 89% 99%R

atio

Demand ratio Requirement ratio



Requirement for Manageable Generation (III)

15

Requirement for the 5th of March 2009



15000

0:00 0:00

0

10000

0 h 24 h

Req_min

D_min

Req_max

D_max

MW

DemandWind productionRequirement for manageable generation

Requirement for Manageable Generation (II) Since there is a minimum value for

manageable generation (technical minimum power output of generating units, flowing hydro power plants…) there is a ratio over which it is necessary to shut down conventional power generation during off-peak hours to connect it back several hours later in real time (8 times since 2006).

Due to the need of keeping connected power plants during off-peak periods that are necessary for the daily peak loads (longer start up times) and to deliver ancillary services there is also a ratio above which wind power reduction is unavoidable.

16



1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

3,0

3,2

0% 10% 20% 30% 40% 50% 59% 69% 79% 89% 99%

Rat

io

2004 2005 2006 2007 2008 2009

Requirement : = Demand – Wind Generation

2004-2008: Few days with requirement ratio > 2 2009: 14% of the time requirement ratio > 2 Possible solutions: storage, wind generation providing frequency control under certain

system conditions, peaker thermal plants…17



Demand-generation balance: 2/11/2008

Low demand (~20 000 MW) and high forecasted errors (~ 3 200 MW) Running out of downward reserves:

Shut down in real time of combined cycles. As last resource, wind power reduction from 7:22 to 9:30 h.

18

0

5000

10000

15000

20000

25000

30000

0

2000

4000

6000

8000

10000

12000

Win

d P

rod

uct

ion

in M

W

Time 02/11/2008

Previsión Eólica

Producción Eólica RealPrograma MercadoDemanda

Wind reduction instructions, November 2nd 2008 (I)



19

Balance feasibility during off-peak hours (I)

High wind production during off-peak hoursMinimum demand

23 653 MW

Maximum demand 39 183 MW

Lower wind production on

peak hours

Generation mix during off-peak

March 3rd 2010

Downward tertiary reserve exhausted in hours 2:00-6:00



20

1 combined cycle units during off-peak hours

27 combined cycle units during peak

hoursMarch 3rd 2010

Balance feasibility during off-peak hours (II)



21

Example of the needed flexibility

5 combined cycle units

during off-peak hours

Minimum demand 20 638

MW

Maximum demand 36 319

MW

30 combined cycle units during peak

hours

Generation mix during off-

peak

March 1st 2010

Downward tertiary reserve exhausted in hours 3:00-9:30

and 15:00-18:00 h



22

Requirement for Manageable Gen. (I) Requirement = Demand – Wind Production Demand Ratio = Dmax / Dmin; Requirement Ratio = Reqmax / Reqmin

Due to wind energy production and its correlation with demand: Requirement Ratio > Demand Ratio Steeper ramps for manageable generation Displacement by RES of the generation that provides ancillary services

05.000

10.00015.00020.00025.00030.00035.00040.00045.000

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

MW Demand

Wind generation

Requirement

Demand Ratio = 1.70

Requirement Ratio = 2.24

March 10th 2010March 10th 2010



1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

3,0

3,2

0% 10% 20% 30% 40% 50% 59% 69% 79% 89% 99%

Rat

io

2004

2005

2006

2007

2008

2009

Measures the need for flexibility for the manageable generation. Present providers: mainly combined cycle units, hydro-pump storages and

hydro generation. Future needs: additional storage, wind generation providing frequency control

under certain system conditions, “peaker” thermal plants…23

Requirement for Manageable Gen. (II)



Renewable Energies in System Operation Facilitate the maximum possible non-managable generation integration.

Creation of the Control Centre for Renewable Energies (CECRE)

Control and supervision of special regime generation.

Maximize RES production, but always keeping the electric system in a secure state.

24



Target: achieve a greater level of integration for renewable energy sources without compromising system security.

Main function: Organise special regime electric production according to the needs of the electric system.

Be the only real time communication channel with CECOEL and with the Control Centres (RESCC), which would be the entities in charge of switching operations in the facilities.

Receive the relevant production information of generation units in real time and send it to CECOEL.

Coordinate, control and supervise all generation units by means of grouping them in Control Centres.

Contribute with security and effectiveness in System Operation.

Change zone simultaneous production hypothesis and preventive criteria (conservative) by real-time production control and therefore allowing:

Higher energy production

Higher installed power (agent decision)

CECRE: purpose and targets

25



CECRE: functional scheme

Link and telecommand

CECRE is a control centre devoted to special regime generation and specially to Wind Power:

Integrated in REE’s control structure

Communication with generation Control Centres for supervision and control instructions.

According to RD661/2007 all special regime facilities >10 MW must be connected to a RESCC.

CECRE issues generation limitations through the SCADA system to the Control Centres.

RESCC: Renewable Energy Source Control Centre

CCCONV: Control Centre for conventional generation

RESCCn

CECOEL / CECORE

CECRE

RESCC1CCCONV …


Iccp L

ink

Iccp

Lin

k

Iccp

Lin

k


26



RES power connected to the CECRE via RESCC

According to RD661/2007 all special regime facilities >10 MW must be connected to a RESCC.

Facilities that don’t comply with this requirement loose the Special Regime status regarding the prime received.

27

Wind77.0%

Solar1.8%

Mini-Hydro2.8%

Cogeneration16.9%

Biomass1.1%

Rest RE0.4%



5000

5500

6000

6500

7000

7500

8000

8500

9000

9500

0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

011

:0012

:0013

:0014

:0015

:0016

:0017

:0018

:0019

:0020

:0021

:0022

:0023

:00

0:00

Time 09/02/2009

Win

d P

rod

uct

ion

in

MW

SIPREÓLICO

Real Production

Market program

Forecasts available to the CECRE REE has an internal forecast of all wind parks: SIPREÓLICO

Hourly forecasts of next 48 hours by region or transmission system node (update 15 min.)

Total hourly forecast of next 10 days (update 1 hour).

Hourly stochastic forecast of total production: percentiles 15, 50 and 85. Wind park programs matched in the daily market. Agent’s forecast.

28


RED ELÉCTRICA DE ESPAÑAEvolution of absolute error based on production

Critical time horizons are 24 or 32 hours in advance for D-1 reserve evaluation and 5 hours for real-time evaluation.

Positive evolution in forecast error in the last years has resulted in fewer need for reserves to cover wind forecast errors, specially in D-1.

29



0

2.000

4.000

6.000

8.000

10.000

12.000

14.000

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

MW

h

25/03/2010

Wind forecast with different confidence intervals

RealPr=50%Pr=15%Pr=85%

RES forecast uncertainties increase needed provisions of reserve.o Higher levels of reserve.o Influence on downward reserve.

Example: Technical Constraints Management D-1 h12 o REE checks if there are enough available running reserves for the next day.o Probabilistic wind forecast used.

30

Influence of forecast uncertainty

Additional reserves during peak demand = 2 310 MW



5000

6000

7000

8000

9000

10000

11000

12000

0:00

1:00

2:00

3:00

4:00

5:00

6:00

7:00

8:00

9:00

10:0

011

:0012

:0013

:0014

:0015

:0016

:0017

:0018

:0019

:0020

:0021

:0022

:0023

:00

0:00

Time 23/01/2009

Win

d P

rod

uc

tio

n in

MW

SIPREÓLICOReal ProductionMarket program

Some days errors affect System Operation… On January 23rd and 24th 2009 the storm Klaus hit the Iberian peninsula. Some wind parks

recorded winds up to 220 km/h. Most turbines in the north of Spain shut down due to their over-speed protection. Difference between real and forecasted wind production was greater than 6 000 MW on

some hours, but since demands were low and thermal plants were connected in real time due to alert situation there was enough upward reserve to deal with these errors.

31



2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

MW

Time on November 15th 2009

Wind Production Wind Program Wind Forecast

32

Wind reduction to recover downward reserve On the afternoon of Sunday November 15th at 14:50 h with low demands of the year

(~24,000 MW), wind prediction error was about 2 800 MW. Fast increase in error from 12:00 to 15:00 h. Spanish system ran out of downward reserves rapidly. The only solution to balance the

system was to decrease wind production from 14:50 to 17:00 h.



3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

MW

Time on March 1st 2010

Wind Production Wind Program Wind Forecast

CECRE may issue wind generation curtailments Wind and demand forecast error during off-peak hours. System run out of tertiary reserve. Low secondary downward reserve during

some instants. Wind generation curtailments issued from 1:12 to 6:19 h.



7500

7700

7900

8100

8300

8500

8700

8900

8:15 8:45 9:15 9:45 10:15 10:45 11:15 11:45 12:15 12:45 13:15 13:45 14:15 14:45 15:15 15:45

Hora

MW

09:00 h Beginning of the

reduction instructions.

15:00 h End of the

reduction instructions

Wind power reduction due to risk of generation trip 27/03/2008

CC.AA.

ISSUED REDUCTION (MW)

9-10 h 10-11 h 11-12 h 12-13 h 13-14 h 14-15 h

Galicia 48 62 74 19 91 19

Asturias 6 35 23 11 14 5

P.Vasco 0 0 0 3 0 0

Navarra 8 0 0 0 0 0

La Rioja 0 5 2 1 0 0

C. León 94 207 224 81 228 67

C. Mancha 88 142 148 49 231 73

TOTAL 243 451 471 164 565 165

The reduction was instructed due to the risk of losing the interconnection with France if certain faults occurred, which would cause a sudden wind generation loss even if the fault was correctly isolated by the protection equipment.

Set-points were recalculated each hour to adapt to changing conditions in the wind generation.

34



Facing the future (i) Current Challenges in 2011: 20 000 MW wind installed capacity:

Balance in off-peak hours → downward reserve management is an issue Voltage dip tripping should no longer be a problem due to compliance with

the grid code Active voltage control with set-points (instead of load factors keeping)

Challenges beyond 2011: Up to 38 000 MW wind installed capacity. Safe integration will depend on several factors: Need for wind generation to provide frequency control (primary reserve,

inertia emulation,…). Increase of storage capability: more hydro-pump units Need of more flexible and fast thermal plants (open cycle gas turbine) Interaction between wind and solar production will be an issue Improvement of wind forecast tools Demand side management More Flexible market mechanisms and regulatory measures



Facing the future (ii): more flexible market mechanisms and regulatory measures

Encourage flexible and fast conventional generation throughout capacity payment:

Open cycle gas turbines Household isolated operation of conventional units

Introduction of negative pricing (balancing markets/energy markets): Adequate for manage deep off-peaks and high wind production It will encourage more pump storage units and other storage facilities

Inter-TSO balancing actions: Need of compatibility of ancillary services to exchange Need of compatibility of gate closures associated Usage of ATC

Encourage RES to change from user towards providers of system services



Thanks for your attention!

Documents

March 2011 Spanish TSO Operational Challenges and Solutions Dirección de Operación