Cihangir Gençoğlu08.03.2011,

Joint Transmission System Operator – Utility Regulator Renewable Energy Workshop,

Istanbul

Integrating Intermittent Renewable Integrating Intermittent Renewable Energy Resources:  Energy Resources: 

TSO Operational Challenges and TSO Operational Challenges and SolutionsSolutions

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 generationb) 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 ControlDesign and Optimization of

AVR/PSS

Special Protection SchemeRestoration 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

0 20 40 60 80 100 120 140 160 180 20049.94

49.95

49.96

49.97

49.98

49.99

50

50.01

Time (Sec)

Fre

qu

en

cy

(H

z)

Frequency of Turkey and Spain in Case of an Accident

Frequency of TurkeyFrequency of Spain

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

0 5 10 15 2049.85

49.9

49.95

50

50.05

50.1

Time (hr)

Fre

qu

ency

(H

z)

Daily Frequency

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 operationSecond 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)