Case study: Simultaneous optimization of electrical grid stability and steam production

Abstract

Steam production and electric power system stability are often competing interests in an industrial refinery. Optimal control of steam production is required to meet plant process operating requirements, and electrical grid stability is required to prevent power system blackouts. For many industrial plants connected to a utility grid, both operating criteria cannot be met simultaneously, placing the power system in serious jeopardy of a blackout.Steam turbines, which are controlled to produce a desired tonnage per hour of steam, can hinder the ability of a power system to avoid blackouts. This issue occurs at any facility in which electric power is derived from steam turbines running in extraction flow or pressure control modes.The issue is explained using modeling and in-field results from a refinery with several three-stage extraction turbines, a large refinery load, and several utility grid interconnections. The implications of running these turbine governors in pure extraction priority, pure power priority, or mixed extraction and power priorities are explored in this paper.A comprehensive electric dispatch control strategy used at the facility is shared. This control system optimizes electrical grid stability throughout the facility while simultaneously interfacing with a steam optimization system.