Simulation Study On Power Oscillation Induced By Turbine Governing System

Low Frequency Oscillation is a problem of complex dynamic stability in power system.In recent years, the low frequency oscillation conducted extensive research and has mademany achievements, one of which is the resonance mechanism theory. According to theresonance mechanism, when the frequency of disturbances in governing system is identical orclose to the natural oscillations frequency of a power system, disturbances can lead to lowfrequency power system oscillations.With the progresses of science and technology, high speed electro-hydraulic controlsystem has been widely adopted as the governing systems in generating units. The first task ofgenerating system is to ensure the safe operation of the unit; the second task is to output stablepower, so as to ensure the stability of power grid frequency.If there is a periodic disturbance in the governing system, the frequency of which isidentical or close to the natural oscillations frequency, it may cause low frequency oscillationof generator output power or even the local power system. In other words, the faults of thespeed governing systems will not only adversely affect the safety of generating units, but alsothreaten the safe and stable operation of power system. In recent years, there are a spate ofPower System Low Frequency Oscillation accidents in China Southern Power Grid, many ofwhich are forced low-frequency oscillation accidents caused by failures of governing systems.While simulations according to the model of existing power flow calculation programs areoften unable to simulate the scene reappearance and achieve fault diagnosis analysis.So it is necessary to study the characteristics and the dynamic response process of theturbine and its governing system, and establish a more effective analytical model of unit sidedynamic stability. And then combining with the actual problems, it is possible to proposemeasures to suppress or eliminate power oscillation caused by turbine governing systemfailures.This paper focus on power oscillations induced by the speed control system of generatingunit. The key links of the speed control system that strongly relevant to power oscillation aresorted out, and a suitable simulation model on dynamic stability analysis of power system isestablished. Then combining with an example of power oscillation, the causes of poweroscillation induced by the speed control system are studied, and the corresponding control andprevention measures are put forward.