| The surge tank with lateral pipe is an important pressure reduction facility in high head hydropower station.Not only can it guarantee the structural safety of pipeline but also lessen the size of surge tank,thus being higher practicability and economical.The flow inertia and head loss in lateral pipe have obvious influences on the reflection ability of water hammer wave and the transient characteristics of surge wave in surge tank,which affects the regulating quality and safety of hydropower station during transient process.From the aspects of scientific research and engineering application,it is urgent to pay attention to the three aspects,including the nonlinear mathematical model of hydropower station with surge tank of lateral pipe,the stability and control of regulating system during small oscillation transient process,the superposition characteristics of surge wave under combined conditions and control optimization during large oscillation transient process.Therefore,this paper is carried out from four researches on the nonlinear stability of regulating system in the oneturbine-one-tunnel hydropower station with surge tank of lateral pipe,the synergetic control strategy of regulating system in the one-turbine-one-tunnel hydropower station with surge tank of lateral pipe,the control of surge wave superposition in the multiple-turbine-onetunnel hydropower station with surge tank of lateral pipe,the optimization of the shape for surge tank with lateral pipe in multiple-turbine-one-tunnel hydropower station based on surge wave superposition.The innovative achievements are as follows:(1)Aiming at the nonlinear stability of regulating system in the one-turbine-one-tunnel hydropower station with surge tank of lateral pipe during small oscillation transient process,it is established that the mathematical model considering the high-order head loss in pipeline,the flow inertia and head loss in lateral pipe.The stable domain and dynamic respones of regulating system are studied based on Hopf bifurcation theory.Moreover,the effect mechanism of lateral pipe on the stability and dynamic characteristics are explored.In addition,the couple effect between the hydropower station and power grid are analyzed.The results indicate that: a)The stable domain of regulating system is reduced under considering the flow inertia and head loss of lateral pipe.b)The length and area of lateral pipe affect the stability and dynamic characteristics from changing the flow inertia.With the increase of its length and the decrease of its area,the system stable domain shrinks,the fluctuation amplitude of the unit speed increases,the fluctuation amplitude of the water level in the surge tank decreases,and the period becomes longer.The head loss coefficient of the lateral pipe affects the dynamic characteristics of the regulating system by changing the energy consumption during transient process.The larger the loss coefficient,the smaller the fluctuation amplitude and the faster the convergence for the dynamic response of the unit speed and the water level in surge tank.c)The stability and dynamic characteristics of the system are worsened by coupling of small-scale power grids.d)During the design stage of hydropower station,the parameters of lateral pipe should be determined by adjusting the system stability,the dynamic characteristics of the unit speed and the water level in surge tank comprehensively.Meanwhile,the governor parameters far away from the bifurcation line in the stable domain should be selected to ensure the stability and dynamic characteristics of regulating system.(2)Based on the mathematical model considering the characteristics of lateral pipe,it is derived that the synergetic control strategy for the water hammer wave and mass wave of the regulating system in one-turbine-one-tunnel hydropower station with surge tank of lateral pipe adopting to the synergetic control theory,which is in the form of unit speed and water level in surge tank.It is investigated that the dynamic characteristics of regulating system to various disturbances under synergetic control strategy.The robustness of regulating system under synergetic control strategy and the application of it in hydropower station are analyzed.The results indicate that: a)Under synergetic control strategy,the dynamic responses of regulating system have the advantages of fast response,small fluctuation amplitude,fast convergence rate and no static error to various disturbances.It shows good performance in the control for the amplitude of high frequency water hammer wave and the attenuation of low frequency mass wave.b)The synergetic control strategy has wide applicability in the hydropower station with surge tank of lateral pipe,and the regulating system has good robustness under it.3)The research on surge wave superposition in surge tank with lateral pipe is investigated in complex layout hydropower station with multiple turbine one tunnel during large oscillation transient process.The analytical formula is derived,which is for the extremum value and occurrence time of surge wave during simple operation condition.The solution equation for the most adverse superposition time of surge tank with lateral pipe is given during the combined operation condition.On this basis,an analytical model for the superimposed extremum value of surge wave is proposed during combination operation conditions.It is analyzed that the influence of lateral pipe on the index of regulation guarantee calculation during combination operation condition.The results indicate that: a)It is within 0.5% that the calculation error of the analytical formula for surge wave extremum and occurrence time in surge tank with lateral pipe during simple operation condition.The analytical model of surge wave in surge tank with lateral pipe is suitable for solving surge wave extremum and occurrence time of the combination operation condition in any multiturbine-one-tunnel hydropower station,of which the calculation error is less than 2%,with high accuracy.b)Load increase before load rejection,and load rejection before load increase are the control conditions of the highest and lowest surge wave in the surge tank.The unit should be controlled to avoid operating condition conversion at the most adverse superposition time.c)The lateral pipe increases the hydraulic damping during water flowing in and out of the surge tank,which reduces the fluctuation amplitude of surge wave,weakens the reflection ability of water hammer wave,and increases the fluctuation amplitude in pipeline.(4)An optimization model is presented for the shape of surge tank with lateral pipe in multiple-turbine-one-tunnel hydropower station based on surge wave superposition.A multi-objective optimization-decision making framework combining the improved gravity search algorithm with the improved entropy weight and relative target proximity method is established,which is applied to determine the best scheme for the shape of surge tank.Considering the universal valve on the lateral pipe,the optimization result of surge tank is analyzed.Furtherly,the control strategy of universal valve is optimized under the combined operation condition.The results indicate that: a)The multi-objective optimization-decision making framework combining the improved gravity search algorithm with the improved entropy weight and relative target proximity method can solve the optimization model for the shape of surge tank with lateral pipe in multiple-turbine-one-tunnel hydropower station effectively.b)The optimized shape of surge tank reduces the maximum surge wave in the surge tank,the maximum water pressure at the end of the volute and the maximum water pressure in the diversion tunnel to a certain extent under combination operation condition.It is noteworthy that the size of the surge tank is reduced.c)The universal valve installing in the lateral pipe reduces the fluctuation amplitude of surge wave.And the pressure tail wave at the key parts of water delivery system,which is caused by surge wave in the surge tank,enters the stable state faster. |
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