Cause analysis and preventive measures of low frequency oscillations in power system with medium-pressure regulating valves of steam turbine

Abstract

Low frequency oscillations in power system with medium-pressure regulating valve of steam turbine occur from time to time， threatening the safe operation of generating units and power system. Three typical low frequency oscillations of power system induced by medium-pressure regulating valve are given. Given the roles of medium-pressure regulating valves in different types of steam turbines， the ways they induce or participate in low frequency oscillations are introduced. It is pointed out that one of the major reasons for low frequency oscillations occurring in deep peaking-shaving units is the reduction of the turbine’s integrated valve position command， resulting in the frequent participation of medium-voltage regulating valves of poor linearity in the power regulation of the units. In view of the current operating environment of thermal power units in China， six specific measures to prevent the medium-pressure valves from participating in low frequency oscillations in power system are given for reference.

Keywords

• steam turbine
• power system
• low frequency oscillation
• medium-pressure regulating valve
• sliding pressure curve