Integrating Intermittent Renewable Energy Resources TSO Operational Challenges

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. 15 Hz. • ~0. 15 Hz 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. 15 Hz.

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

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 m. Hz • 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

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

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/k. Wh) 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

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)