Hidden danger and Optimization for the DEH Logic of STC-Siemens Ultra Supercritical Unit

Abstract

With the wide application of STC-Siemens ultra supercritical unit technology, the structure design and control logic of the turbine electro-hydraulic control system (DEH) are also popularized. However, due to the defects of Siemens DEH logic design and the unavoidable mistakes of STC auto control center in the process of translating Siemens DEH logic, some hidden dangers of this type of unit are gradually exposed, which affects the reliability and safety of the unit. It is mentioned in this paper that due to the hidden trouble of ATT test logic, during the process of ATT test, 12% command signal of regulating valve setting is sent out, and the unit abnormal shutdown; When the unit is put into the AGC mode to track the AGC command, the logic hidden danger causes triggering of the quick closing condition C20 of the regulating valve (the deviation between the flow instruction converted by the valve feedback and the actual flow instruction is greater than 40%), and the unit abnormal shutdown. In order to solve these problems, the optimization suggestions of DEH logic are put forward, in order to improve the reliability of unit operation. It provides a reference for this type of unit.