Research On Tail Wave Suppression Strategy With Tail Wave Base Wave As Additional Signal

With the increase of hydropower stations in long distance transmission,the transient stability of hydropower stations with surge Chambers has been paid more and more attention.Although the setting of pressure regulating chamber meets the requirements of regulating guarantee to some extent,the slow attenuation of tail wave caused by the fluctuation of water level in the pressure regulating chamber is the main reason that worsens the regulating quality of the unit.In view of the above problems,most of the early studies were conducted from the aspects of governor parameters,water flow inertia time constant and section area of pressure regulating chamber,etc.,but still no effective method was found to suppress the tail wave.In this paper,the variation of water head caused by fluctuation of water level in surge chamber is regarded as fundamental wave as additional signal of tail wave suppression strategy.Firstly,the mathematical model of turbine regulating system with downstream pressure regulating chamber including water delivery system,water dispenser system and governor is established.Secondly,in the simulation model,the transition process of the unit after power grid load cut is simulated,which further verifies that the change of the unit’s working head caused by the fluctuation of the water level in the surge chamber is the main reason for generating the tail wave,the basic wave of water head can be used as an additional signal to suppress the tail wave.Without considering the influence of turbine speed change on unit output,Ewb between guide blade opening and basic wave signal of water head is deduced,and its output is added to the output of PID governor.Finally,the simulation experiment is carried out for the proposed tail wave suppression strategy,which is mainly conducted from two aspects:First,the stability experiment of the unit under the control of traditional PID governor was carried out,and the frequency change curve corresponding to the optimal PID parameter was used as the verification benchmark of the tail wave suppression strategy experiment.Second,on the basis of the PID parameters,the sensitivity analysis of Ewb of the feedback weight value is carried out,and the control effect of the wake wave after the introduction of the fundamental wave signal is verified.The results show that the tail wave suppression strategy with the basic wave of water head as the additional signal has an obvious suppression effect on the tail wave,and when Ewb is in the range of 0.5～3.0,the larger the value is,the smaller the amplitude of the wake wave oscillation and the faster the attenuation speed are,while beyond this range,the suppression effect on the wake wave becomes weaker.The proposed strategy alleviates the problem that the governor loses the correction function to the wake wave under the existing technology,and guarantees the adjustment quality of the unit transition process.