Optimizing hydrothermal coordination scheduling for large scale power

The Tenaga Nasional Berhad (TNB) system comprises 53 thermal units and 10 hydro plants of 37 generators (80 units). Lagrangian relaxation (LR) technique, Datzig-Wolf linear programming, sub-gradient method (SGM) and branch and bound (B&B) have been used to relax the LR multipliers for demand and reserve requirements, and decompose the problem into unit-wise initially and thermal and hydro sub-problems finally. The multipliers are then updated at the lower bound level by SGM. B&B along with some heuristics to get a feasible schedule in the hydro-thermal coordination system. The heuristics used are based on programming with C language code that simplifies on/off statuses of units for commitment (UC) and scheduling and economic load dispatch (ELD). The TNB costs have been reduced as shown in the results.