Reflexões metodológicas sobre a operação de sistemas hidrotérmicos de energia elétrica

Abstract

There are three forms of a hidroelectric system to self-protect by hydrological and load risks: the first one is the water storage; the second is the complementarities thermal; the third is the increase of the elasticity of the demand, with strong signal of generation price. Historically, the use of reservoirs was the way of protecting of the uncertainties. In this phase the concepts of firm energy and critical period had appeared, and the economic criterion had minor value than the technical criteria. With the entrance of some thermal generation, it was transferred to operate the reservoir, according to criterion of the rule curve. The great advantage of the rule curve is the transparency. Moreover, it has a certain isonomy between the reservoirs, not allowing that one if finds emptied total, while the other meets full or almost full. All the reservoirs have that to be in the same band. With the evolution of the computational models, Brazil abandoned the previously criterion, evolving for one with strong economic bias, that if based on the costs of the thermal generation and the deficit, beyond the expansion of the generating park. The sophistication of the models demanded a simplification of the physical reality. Thus, this second phase of the electro-energy operation in the country if did not worry about the aspects to maximize the hydroelectric generation (that it is the same that to minimize the thermal generation). The 2001 crisis presented the fragility of the sector, imposing the creation of the aversion risk curve, that is a rule curve; when the storage in the reservoirs is less than established level, determines the forwarding of all the thermal capacity. Today, the sector indicates the necessity of other curves of aversion that determines the forwarding of parts of thermal the generating grid, before if transgressing to the current aversion curve. This nothing more is that the rescue of the rule curve, only that still applied to the reservoir equivalent. The objective of this paper is to develop a strength and plain method for the hydroelectric plants reservoirs operation. It is understood that strength way is the capacity for the operation without major economic losses under unexpected conditions. The plain way means the capacity of for reproducing or projecting the operation results with no major differences, is that to say, forecasting and repeatability.