Flexible National Grid Operation...•> 1300 nos. 400 kV lines, •> 3200 nos. 220 kV lines Nepal...
Transcript of Flexible National Grid Operation...•> 1300 nos. 400 kV lines, •> 3200 nos. 220 kV lines Nepal...
Flexible National Grid Operation
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N. Nallarasan
Senior General Manager – System Operation
National Load Despatch Centre, New Delhi
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Indian Grid…Large Footprint
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NR
WR
SR
ERNER
Ennore
KudankulamKayamkulam
Partabpur
Talcher/Ib Valley
Vindhyachal
Korba
LEGEND
Coal
Hydro
Lignite
Coastal
Nuclear
VizagSimhadri
Kaiga
Tarapur
Mangalore
Krishnapatnam
RAPP
SIKKIM
MYANM
MAR
CHICKEN NECK
Cuddalore
SRI LANKACOLOMBO
NEPALBHUTAN
DESHBANGLA
South Madras
Pipavav
Generation Load-Centre
Kolkata
Bhubaneswar
PatnaLucknow
Delhi
Mumbai
ChennaiBangalore
Bhopal
Guwahati
Jammu
Ludhiana
Jaipur
Gandhinagar
Indore
Raipur
Thiruvananthapuram
Kozhikode
Hyderabad
Coal
Hydro
Wind and Solar Courtesy: NASA
Indian Power System
• Generating Stations > 900 Nos.
• Generating Units > 2200 Nos.
• > 7000 Sub-stations,
• > 3100 transformers
• 11 Nos. HVDC Bi-pole/BtB
• > 150 nos. 765 kV lines
• > 1300 nos. 400 kV lines,
• > 3200 nos. 220 kV lines
Nepal Bhutan
Bangladesh
Myanmar
• Demand met – 182610 MW on 30th May 2019
• Energy met – 4145 MU on 30th May 2019
• Hydro Generation – 816 MU on 9th Sep 2019
• Solar Generation – 147 MU on 6th May 2019
High growth International Interconnections
Diversity of Demand and Generation
Demand variability ~ 3-5 GW/block of 15 minutesTypical Ramp Rate ~ 250 MW/min
Special Days (Festivals…) ~ 500 MW/min
Thermal
Solar
Wind
Hydro
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Ramping in All India Demand
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All India Thermal Generation
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MW
All India Hydro Generation
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MW
Solar Generation
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Pumped Storage
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MW +gen
MW -Pump
Kadamparai
Pumped Storage Plants in India
Source: “ Large scale integration of Renewable Energy Sources-Way forward” Report by CEA
Frequency Profile over the years…
Slow Tertiary implemented from April, 2016
Maximum and Minimum Frequency patterns
Frequency Variation Index
Frequency Control Continuum in India
Pilot
Signs of Inflexibility
• Difficulty in balancing demand and supply
– Frequency excursions
• Renewable curtailment
– Inability to balance
• Area Balance Violations (Deviations)
• Electricity Markets
– Price volatility
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Source: Cochran, J. et al. (2012), “Flexibility in 21st Century Power Systems, A 21st Century Power Partnership Report”. Golden, CO: National Renewable Energy Laboratory. http://www.nrel.gov/docs/fy14osti/61721.pdf
Future Ready AGC for 175 GW of RE by 2022
• Forecasting of Load & RE• Use of Pumped Storage Plants• Automatic controls
EASTERN
REGION
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Region considered as an Area for secondary control
Ia = Actual net interchange, negative for NR meaning import by NR
Is= Scheduled net interchange, negative for NR meaning import by NR
Bf = Frequency Bias Coefficient in MW/0.1 Hz, positive value
Fa = Actual System Frequency
ACE positive means NR is surplus and NR internal generation has to back down
ACE negative means NR is deficit and NR internal generation has to increase
SOUTHERN
REGION
WESTERN
REGION
Eastern
REGION
NORTHERN
REGION
NORTH-EASTERN REGION
ACE = (Ia - Is) + 10 * Bf * (Fa - 50)
• Tie line bias mode and Frequency bias only mode both possible
New
Existing New
Architecture of the Project
Solar Plant AGC signal hierarchy
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Blog on zero inertia Power system by Prof. Vijay Vittalhttps://www.esig.energy/zero-inertia-power-systems/
RFA for Solar AGC Pilot project issued:https://www.gtg-india.com/work-with-us/
Tertiary ControlCues for System Operator
• Weather Forecast
• Load Forecast
• Availability of Reserves
• Monitoring of Renewables
• Outages of Transmission Lines / Generating units
• Anticipated Congestion
• Monitoring of Area Control Error (ACE)
• SCADA Visualization in Real Time
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• CERC order in Petition No. 07/SM/2018 (Suo-Motu) dtd. 16 Jul’18
– Pilot on 05-Minute Scheduling, Metering, Accounting and Settlement for Thermal/Hydro
– 26th Nov’18- Pilot on Hydro as Fast Response Ancillary Services (FRAS)
– In house Software
Fast Response Ancillary Services (FRAS)
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Sample Hydro Station Data
Security Constrained Economic Despatch (SCED)
• Objective: to minimize production cost of
Inter-State Generating Stations (ISGS)
• Pilot project on w.e.f. 1 Apr 2019
• 134 units with ~ 57 GW capacity covered
• All constraints including ramp rates, technical
minimum, transfer capability honoured
• Integration of scheduling applications at
National level with in-house developed
software
• 1-2 % saving in production cost being
observed 22
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Provisions Regarding Ramping (1)Provisions in the Indian Electricity Grid Code (IEGC):
Operating Code (Section 5.2):
System Security Aspects - Ramping of
All thermal units greater than 200 MW.
All Hydro units greater than 10 MW
Sudden change in generation / load by the utilities of more than 100 MW without prior intimation to and consent of the RLDC.
Scheduling and Despatch Code (Section 6.4)
Generators to declare rate of ramping up / ramping down in a 15 minute block.
Acceptable ramping rate – 200 MW/Hour (in NER 50 MW/Hour)
CEA Standard Technical Features of Super-Critical Units
Ramp rate: + 3% per minute (above 30% loading)
Technical minimum load of super critical units – 40%
Two shift operation mandated
Provisions regarding Ramping (2)
CERC Terms and Conditions of Tariff, 2019
Minimum ramp rate: 1% per minute for thermal ISGS
Reduction in rate of return of equity (RoE) by 0.25% for failure to provide minimum ramp rate
For providing ramp rate over 1%/min, additional rate of RoE of 0.25% allowed for every additional 1%/min
NLDC 24
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Increasing granularity of Despatch Interval
Quarter-hour vs Hourly Schedules Typical Hourly & 15-Minute Schedules
5-minute scheduling:Reduced the steep ramps
Eliminates sharp discreet changes
Reduced frequency fluctuations
Facilitates better load management
Facilitates integration of renewables
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Sch
edu
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Hour
15-Minute Schedule
Hourly Schedule
Flexibility - Ramping Requirement and Provision over the years
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Thermal Flexibility – lower turn down levels
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Simhadri Unit –1 500 MW
Grid Code 4th Amendment - 55% Technical Minimum for Central Generating Stations; effective from 15.05.17
Change in Technical Minimum from 70% to 55%
Thermal Flexibilization during Summer High Demand/Solar: May’19
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Thermal Flexibilization during High Hydro: 2014, 2016 & 2018
Dadri Thermal at High end of Merit order Stack !
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Analysis of Ramping Capability of Thermal Power Plants
Steeper net demand ramps expected in future with increasing RE
More flexibility needed from conventional generation
Attempt to quantify historical ramp rates of thermal generating units
Exhaustive report based on analysis of 7 years’ generation data of 438 units
Report released on 15th May 2019
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Hydro Flexibilization during Lean Hydro Season
2011: Flatter Hydro Curve between the peaks
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Gas Flexibilization during Summer High Demand/Solar: May’19
The gas availability is a subjective issue !
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Flexible Generation
• Hydro– Plan and implement more pumped storage
– High head stations; Pelton vs Francis turbine
– Operational norms to incentivize flexibility
• Thermal– Grid Code clauses on flexibility (ramp rate, minimum)
– Incentives for flexible generation
– Two-shift operation of thermal plants
– Primary, Secondary and Tertiary Controls
• Renewables– Low Voltage Ride Through (LVRT)
– Draft CEA standards notified33
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• HVDCs in India – 5 back to back HVDCs
– 6 bipole HVDC links
– 1 MTDC
– 1 more planned
• CEA Transmission Planning Criterion (Section 18)
– More than 2000 MW over long distance more than 700 km.
– Corridors of AC lines carrying heavy power flows (total more than 5000 MW)
Flexible Transmission
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Way Forward
Power systems are already flexible, designed to accommodate variable and uncertain load.
New actors RE, distributed generation, storage etc. to be accommodated
Need for ‘Flexible’ Systems
Flexible Generation
Flexible Transmission – FACTs, HVDC
Flexible Distribution – Price responsive demand
Flexible Markets -
More Frequent market operation, Ancillary services, Demand response
Policy / Regulatory Framework for Flexibility
Measuring Flexibility
Metrics for performance
Incentivizing and paying for flexibility
Policy support to anticipate flexibility needs and support system flexibility
Flexibility considerations can be integrated into the design of procurement policies
POSOCO 36
Thank You