Integrating Intermittent Renewable
Energy Resources:
TSO Operational Challenges and
Solutions
Cihangir Gençoğlu
08.03.2011,
Joint Transmission System Operator – Utility Regulator
Renewable Energy Workshop,
Istanbul
Outline
1) The present Turkish Electricity Transmission System
1) ENTSO-E CESA trial parallel operation and frequency
control performance indices
1) The possible effects of rapid growing intermittent
generation on Turkish Electricity Transmission System
a) Geographical distribution of renewable generation
b) The expected challenges
1) Conclusions
Part 1
The Present Turkish Electricity
Transmission System
(Before Synchronization)
Some Facts about Turkish Grid
• ~50 GW installed capacity
• More than 32 GW of peak demand (summer)
• Annual increase in demand 7–8 %
• Hydro, coal and combined cycle power plants
• Deregulated generation sector
• Privatized distribution sector
• TEIAS is natural monopoly in transmission
business (regulated by EMRA)
CESA System
Organization Chart of the Project
Rehabilitation of the Frequency
Control Performance of TPS for
Synchronous Operation with UCTE
Survey of Power Plants
Site Tests & Studies
Design of Governor Control and
Parameter Optimization
Secondary Control
Design and Optimization of
AVR/PSS
Special Protection Scheme
Restoration Plan
Training
Preliminary Studies
• Site Survey
– Power Plant Dynamical Data
•Generator Parameters
•AVR, PSS, Speed Governor Models and Parameters
•Reliability of the data is very important!!!
• Identification of the Problems
– Very Low Frequency Periodical Frequency Oscillations
(b/w 20-30 sec, depending on the state of the system)
•Governor Rehabilitation and Retuning Studies (mostly
concentrated on HPPs)
– Poor Quality of Frequency Control
•Coordination with PPs, Balancing & Settlement Market
– Expected Low Frequency Inter Area Oscillations (caused by
static excitation systems and longitidunal structure of the system)
•PSS Rehabilitation and Retuning Studies
•Innovative Measures
Periodical Frequency Oscillations
• Major HPPs out of Service
Periodical Frequency Oscillations
• Major HPPs in Service
Basic Problem (Challenging !!!)
• Periodical frequency oscillations have been resolved by
rehabilitation of Ataturk & Karakaya HPPs.
• According to the simulation studies, the expected inter
area mode after interconnection of Turkey is ~0.15Hz.
• ~0.15Hz oscillations are inside the control bandwidth of:
– PSSs
– Governors
• Conclusion: The speed governing structures of power
plants (Governors and Turbines) should not contribute to
inter area power swings of ~0.15Hz.
Primary Frequency Control – TPPs & NGCCPPs
• TPPs
– Site specific problems
•Quality of coal
•Old power plants (rehabilitation !!!)
– Boiler follows turbine !!!
– Pressure control !!!
• NGCCPPs
– No problems as far as there is sufficient reserve for all conditions
•Base load ~ f(temperature, pressure, humidity)
– Temperature control !!!
• HPPs
– Designed according to the site specific geographic conditions
– High nonlinearity
– Every HPP is a small kingdom having its own rules 
Part 2
ENTSO-E CESA Trial Parallel
Operation and Frequency Control
Performance Indices
(After Synchronization)
Inter Area Oscillations – After Interconnection
• Expected mode shape after interconnection of
Turkish Power System to ENTSO-E CESA system.
Simulation Studies - Time Domain Analysis
Frequency of Turkey and Spain in Case of an Accident
50.01
Frequency of Turkey
Frequency of Spain
50
Frequency (Hz)
49.99
49.98
49.97
49.96
49.95
49.94
0
20
40
60
80
100
Time (Sec)
120
140
160
180
200
Stability Related Issues
• Low frequency modes (~0.15 Hz) are
present in the system!!!
Dynamic Stability - Solution Methodology
• Road map for enhancing the steady state stability of the
interconnected system
Interconnected System Frequency
• δf ~ 25 mHz
• faverage ~ 50.001 Hz
• Total 30 sec reserve (i.e., primary reserve) of the CESA
system including Turkey is ~3000 MW
• Turkey as a control area provides ~300 MW of this
reserve
Daily Frequency
50.1
50.05
Frequency (Hz)
50
49.95
49.9
49.85
0
5
10
15
Time (hr)
20
Performance Indices
1) The hourly integral of ACE should not exceed ±60
MWhrs
– To limit unintended energy exchanges
2) Number of cases with ACE > ±175 MW (measured per
2 seconds, evaluated per 4 seconds) over an hour
should not exceed 10% of the cases in normal
operation
– To prevent overloads in the electricity transmission systems of
the neighboring Balkan countries
3) The amount of sum of tie line flows due to inter area
oscillations should not exceed 30 MWs in normal
operation
– To prevent overloads due to inter area power oscillations in the
CESA countries
Frequency Control Problems
• High standard deviation of ACE due to
– Intermittent loads
– Hourly load variations up to 2500 MW/hr (annual peak
load is ~32000 MW)
– Balancing and settlement market problems (mostly
related to market regulations)
– IT infrastructure of TEIAS
• Solution
– Effective management of tertiary reserve (long term,
not possible with the current market regulations)
– Increased amount of secondary reserve under the
influence of the AGC system (short term) for certain
periods of the day.
Frequency Control Problems
Frequency Control Problems
Frequency Control Problems
Present State
• Frequency Stability (1&2)
• Rotor Angle Stability (3)
• Operational Issues
– On progress
Part 3
The Possible Effects of Rapid
Growing Intermittent Generation
on Turkish Electricity Transmission
System
Current Situation in Turkey
Incentive mechanism for renewable generation
Technology
First 10 years of operation Second 10 years of operation
(€cent/kWh)
(€cent/kWh)
Hydro
7
Wind
8
Wind (offshore)
12
Geotermal
9
Solar – PV
25
20
Solar – SMES
20
18
Biomass (incl. LFG)
13.3
Wave, tidal
16
-
–
–
–
–
–
–
90 % discount in system usage tariff & 99% discount in license fees
Extra incentives in the case of usage of domestic equipment
Technical previleges (ancillary services & market regulations)
Priority in system interconnection
Land usage incentives
For further details see Turkish Law #5346
Characteristics of Wind Generation
Characteristics of Wind Generation
Characteristics of Wind Generation
Geographical Distribution of Renewable Generation
Geographical Distribution of Renewable Generation
Geographical Distribution of Renewable Generation
Geographical Distribution of Renewable Generation
The Expected Challenges
• Increased standard deviation of ACE due to
– Intermittent generation in short term (turbulent peaks/dips)
– Balancing and settlement market problems due to bad
prediction of wind capacity in long term
– IT infrastructure of TEIAS
•Special monitoring/control system requirement
especially for wind power
• Solution
– Effective management of tertiary reserve (current market
regulations do not encourage generation curtailment)
– Increased amount of secondary reserve under the
influence of the AGC system (short term) for the entire
day.
Part 4
Conclusions
Conclusions
• The frequency stability of TETS has been drastically
enhanced with the ENTSO-E CESA Interconnection
• Intermittent generation characteristics in short term,
together with balancing and settlement market problems
due to the stochastic nature of renewable resources will
definitely have adverse effects on this issue.
• Possible solution:
– Effective management of tertiary reserve (current market
regulations do not encourage generation curtailment)
– Increased amount of secondary reserve under the influence of
the AGC system (short term) for the entire day.
– Monitoring and control infrastructure investments (both hardware
and software)