Implementation and Operation of Security Constrained Unit Commitment in Indian power system

Indian power system in April 2024 as part of regulatory reforms under the Indian Electricity

Grid Code (IEGC). SCUC aims to enhance grid security by ensuring sufficient spinning reserves through the day-ahead commitment of thermal generating units, primarily to maintain resource adequacy and load generation balance amid increasing variability from renewable energy sources. This paper summarizes more than one year of operational experience, key learnings and impact of SCUC on system reliability and decentralized generation scheduling in

India. The SCUC process optimizes the scheduling of thermal units to meet reserve requirements based on historical Area Control Error (ACE) data, minimum turndown levels

(MTL) and economic merit order, while respecting technical constraints. It dovetails into the existing Security Constrained Economic Dispatch (SCED) framework, focusing on committing units ahead of real-time dispatch to create up reserves necessary for reliable grid operation in the after solar hours.

Over the past year, SCUC has proven instrumental in maintaining generation availability during critical evening peak demand periods, particularly when renewable generation declines and conventional plants must ramp up rapidly. The implementation framework involves automated daily runs of the SCUC algorithm by the National Load Despatch Centre (NLDC) at 1500 hrs of D-1 (i.e., on a day ahead basis), generating a list of units to be committed to their MTL to sustain required reserves. The algorithms of day-ahead and real time SCUC are also discussed in the paper. Coordination with Ancillary Services has been vital in a strict timeline.

Several operational challenges have emerged, including frequent scenarios of down reserve shortfall, where all thermal plants operate near or at MTL, limiting the system’s ability to provide downward regulation and leading to high frequency episodes. These challenges underscored the need for enhanced flexibility in the system. Discussion in the paper will focus on coordinated scheduling practices within the current decentralized framework. The critical need for energy storage solutions and stakeholder participation have been examined. Paris Session 2026

August 23 to 28

Palais des Congrès, Paris, France