Two-fold Simulated Annealing Approach to Unit Commitment Scheduling

Abstract

This article presents a new approach to generator scheduling using two-fold simulated annealing (two-fold-SA) method that consists of decomposed-SA and coupling-SA. An initial solution is generated by priority list method. Firstly, the solution is decomposed into hourly schedules and each hourly schedule is modified by decomposed-SA using single bit flipping. If the generated new hourly schedule is better, by convention, it is accepted deterministically. A worse hourly schedule is accepted with temperature dependent SA probability. A new solution consists of these accepted hourly schedules of entire scheduling period after repair as unit-wise constraints may not be fulfilled at the time of individual hourly schedule modification. This helps to detect and modify schedules of appropriate hours. Secondly, in coupling-SA, this new solution is accepted for the next iteration if its cost is less than that of current solution. A higher cost new solution is accepted with another temperature dependent SA probability. Besides, excess units with system dependent probability distribution handle constraints efficiently, and economic load dispatch (ELD) calculations are modified to save the execution time. The proposed method is tested using the reported problem data sets. Simulation results on two cases are compared to previous reported results. Numerical results show an improvement in solution cost and time compared to the results obtained from the powerful algorithms.

Keywords:

• best heat rate
• decomposition
• probability distribution
• simulated annealing
• unit commitment

Notes

^a Base window size = 8(5), coefficient of variable window = 8(8), and no. of strategies saved at each stage = 35(30).

^b Multiplier increasing factor = 0.01(0.01) and decreasing factor = 0.99(0.97).

^c Initial temperature = 6000(5000), cooling factor = 0.98(0.95), and equilibrium no. for each temperature = 1000(1000).

^a Indicates the best parameter value.