International Review of Automatic Control (I.RE.A.CO.), Vol. 3, n. 2 March 2010 Manuscript received and revised February 2010, accepted March 2010 Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved A Novel Optimization Methodology for Multi-Constraint Unit Commitment of Thermal Generating Units with Considerations for Hydro Pumped Energy Storage M. E. Nazari, M. M. Ardehali (Corresponding Author: ardehali@aut.ac.ir) , S. Jafari Abstract – Utilization of hydro pumped-storage (PS) units in conjunction with thermal generating units (TGU) could serve not only as an effective means for providing ancillary services and levelizing demand curve but also as a mechanism for lowering costs for TGUs operation. The objective of this study is to develop a multi-constraint (leveling demand curve, providing spinning reserve, and decreasing fuel and start-up costs (TC)) solution of the unit commitment (UC) problem with TGUs and considerations for PS units (PSUC). After determining the output power of PS units, a new optimization methodology (NOM) is examined to solve the UC problem for TGUs. The NOM benefits from a newly developed fitness function. The application of proposed methodologies is examined for power systems, used in other studies, for a 24 hour operation period. For the UC, the results show improvements between 0.01 and 4.16% in TC, as compared with the best results reported in the literature. The PSUC results show that the savings in TC for this study, when PS units are dispatched for leveling demand curve and providing spinning reserve, are 2.62 and 2.65%, respectively. Also, as a result of utilizing PS units, the demand curve is leveled and all of spinning reserve requirement is met. Copyright © 2010 Praise Worthy Prize S.r.l. - All rights reserved Keywords: Optimization, Pumped Energy storage, Unit commitment Nomenclature , , i i i a b c Cost function coefficients ($/(MWh) 2 , $/MWh, $) ( ( )) i C Pi TGU () i fuel cost ($) () CSC i TGU () i cold start cost ($) () CST i TGU () i cold start hours (h) ,1 ,6 ,..., l l c c Coefficients of power function of PS units (,) start C it Function (in NOM) that determines the value of TGU () i start-up cost at hour t ($) ave D Average demand (MW) DCPR(j,t), ICPR(j,t) Decreasing, increasing cost to power ratio of TGU () j at hour t ($/MW) i FF TGU () i fitness function ((MW) 2 /$) * i FF Fitness function using * (,) P it ((MW) 2 /$) () HSC i TGU () i hot start cost ($) 1,..., i N = TGU index () IS i TGU () i initial status (h) (,) Iit TGU () i commitment state at hour t j Committed TGU index 1,..., l L = PS unit index () MDT i TGU () i min down time (h) () MUT i TGU () i min up time (h) () D P t Total power system demand at hour t (MW) , () D Th P t Demand met by TGUs at hour t (MW) (,) Pit TGU () i output power at hour t (MW) * (,) P it TGU () i optimal output power maximizing i FF (MW) ** (,) P jt Changed output power of committed TGU ( j) (MW) min max ( ), () P i P i TGU () i min, max output power (MW) g P , p P Generating, pumping power function of PS units (MW) (,) Plt PS unit () l output power at hour t (MW)