A hierarchical fuzzy control strategy for suppressing low-frequency oscillations on prime mover side of thermal power units
With the large-scale development and grid integration of new energy sources,the fundamental control and operational mechanisms of power system have undergone significant changes to power balance and safety stability control.Low-frequency oscillation events in power systems have typically been simulated and analyzed using standard speed control system models.However,these standard models fail to reflect the regulation characteristics of the units and cannot accurately reproduce the low-frequency oscillation process.Based on the nonlinear characteristics of steam turbine valves and combined with the actual frequency control logic,a small frequency deviation compensation module and a valve flow module are introduced into the typical speed control system model to establish low-frequency oscillation model.The accuracy and effectiveness of the model are verified using actual operational data.Moreover,low-frequency oscillation evaluation indicators are established,by employing the analytic hierarchy process(AHP)and fuzzy evaluation methods,online identification and grading evaluation of low-frequency oscillations are achieved.On this basis,a phased suppression strategy for low-frequency oscillations on the prime mover side of thermal power units is proposed.The corresponding suppression measures are executed based on low-frequency oscillation evaluation results,and the low frequency oscillation model is used to carry out simulation verification.The results demonstrate the suppression strategy can effectively eliminate low-frequency oscillations on the prime mover side and improve operation safety of thermal power units.
low frequency oscillationoscillation suppression controlgoverning systemprimary frequency regulationfuzzy control
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