Impact of Wind Farms Aggregation on Large System Scheduling Cost Under Frequency Linked Deviation Settlement Mechanism Presented by Anoop Singh Authored by Parul Mathuria, Anoop Singh Department of Industrial and Management Engineering, Indian Institute of Technology Kanpur, U.P., India.

All India Electricity Generation Capacity (As on 31 Dec 2016 )

Growing role of RE in Grid Thermal dominated and large wind penetrated system of India. (~70%) RE capacity share ~ 15% India targets 175 GW of renewable power capacity (75 GW Wind) by 2022. Growing share of RE impinges on grid stability Need for flexible generation Storage Forecasting load and RE generation Demand response

Managing Grid stability in the Indian power system - ABT Demand supply mismatch causes system frequency to deviate Frequency linked pricing for Availability Based Tariff (ABT) Three components of ABT, (i) Capacity Charge – for the plant availability (ii) Energy Charge – for scheduled energy exchange and (iii) Unscheduled Interchange Charge – for deviating from the schedule, linked top prevailing frequency.

Research Questions What is the cost of intermittent wind to the system? What should be the optimal scheduling (commitment and dispatch) of generators connected into the grid? How geographically diversified wind sites supports system operation?

Description This work Determine the production levels of thermal units to deal with the uncertain wind power production. Quantum of wind curtailment and load shedding Considers operational characteristics unique to the Indian power system such as frequency linked pricing (UI mechanism) Wind uncertainty is modelled by Monte Carlo Simulations (MCS) using Choleskey decomposition Correlation between generation outputs of geographically diversified wind sites Objective: Minimizing cost => Total system operation cost (Cost of thermal generation + UI cost + Load shedding cost)

24 hour scheduling problem considering hourly load profiles and inter-temporal constraints that bind each of the 24 hourly solutions. Net interchange between considered area and rest of the grid is responsible for frequency deviations Case Study of real utility system of the Indian state of Tamil Nadu.

Mathematical Modeling Scheduling (advanced planning with forecasted wind) and Rescheduling (real time dispatch with uncertain wind realization) Cost of Thermal Generation Operational Constraints Start-up, shutdown costs Minimum, maximum capacity Ramp up, Ramp down Minimum Up time, down time Cost due to Unscheduled Interchange Frequency Linked Price curve Cost of Load Shedding Network Constraints Rescheduling does not desynchronize previously committed units, though real time commitments of additional generators are allowed

Case Study – Tamil Nadu Tamil Nadu 62-bus transmission test network 16 thermal generators (3190 MW total), 3 wind farms at buses 2, 25, 58 (30% penetration in terms of energy in 24 hours) Forecasted load profiles (max 3219 MW total)

Case Study - system

Wind Generation Profile Wind generation output (at bus 2, 25, 58) for 24 hours for two different sets of locations Case 1 Distinct Located wind farms Case 1I Closely Located wind farms W1 W2 W3 1 0.996014 0.967072 0.973758 W1 W2 W3 1 0.379876 0.2973 0.880002

Results Total system operation cost (Cost of thermal generation + UI cost + Load shedding cost) Significantly high cost in Case 2 with correlated wind sites

Results (3 components of total cost) High cost of thermal generation with correlated wind (Case 2) Earning from UI in Case 2 due to bulk wind generation during certain hours. Load shedding is affected by network constraints

Results (Frequency Deviations and NI) Large frequency deviations with Case 2 when system needs to manage bulk wind with area interchange

Results (Wind Curtailments) High wind curtailments in Case 2 due to bulk availability of wind at same time instant

Conclusions & further work…. Geographically diversified wind sites may contribute to lower operation cost by offering better grid management. Imbalances can be managed, perhaps, in a better way for a large integrated system.  more transmission capacity; better regional inter-connection Higher thermal cost and system operation cost due to high stress on thermal generation in case of correlated wind generation output. Wear of machines not accounted for. Wind+ solar variability…….need to be studied

www.iitk.ac.in/ime/anoops anoops@iitk.ac.in Thank You www.iitk.ac.in/ime/anoops anoops@iitk.ac.in