Hydraulic Coupling Characteristics Of Pipelines And Operation Control Of Turbine Units For Hydropower Station With Super-Long Headrace Tunnel

The hydropower station with super long headrace tunnel（SLHT）has the characteristics of pipelines arrangement,various coupling relations and complex transient process.Brings huge challenges to modeling and simulation of hydropower station,decoupling analysis of system and operation control of unit.and restricts the development and construction of hydropower station with super long headrace tunnel and the promotion of operation and maintenance.For this reason,this paper focuses on the complicated and unique transition process and control problem of hydropower station with super long headrace tunnel,study on hydraulic coupling characteristics of pipelines and operation control of turbine units for hydropower station with super long headrace tunnel.Based on the characteristics of pipelines arrangement and the physical nature of transient process of hydropower station with super long headrace tunnel.To meet the important needs of safety,stability and high efficiency in power station design and operation.The following four aspects has been studied:Coupling transient behavior of primary frequency regulation of hydropower plant with super long headrace tunnel.Robust H_∞control for hydro-turbine governing system（HTGS）of hydropower station with super long headrace tunnel.Stability of hydropower station with two turbine units sharing a super long headrace tunnel.Parameter optimization of hydro-turbine governing system of hydropower station with two turbine units sharing a super long headrace tunnel.The main research work and innovation achievements of the paper as follows:（1）Firstly,the mathematical model of hydropower plant with SLHT under primary frequency regulation is established.Then,the stability of primary frequency regulation is analyzed based on stable domain.The dynamic response of primary frequency regulation is analyzed based on dynamic response process and indexes.The effects of system characteristics on stability and dynamic response are revealed.Finally,the coupling effect of the nonlinearity of head loss of SLHT and elasticity of water hammer of penstock on the transient behavior of primary frequency regulation is studied.The results indicate that the stability of primary frequency regulation can be quantificationally described and evaluated by stable domain.The coupling effect of the nonlinearity of head loss of SLHT and elasticity of water hammer of penstock on the transient behavior of primary frequency regulation is influenced by the sectional area of surge tank.With the decrease of the sectional area of surge tank,the effect of the elasticity of water hammer of penstock is gradually weakened,while the effect of the nonlinearity of head loss of SLHT is gradually strengthened.When the sectional area of surge tank is greater than the critical stable value,the effect of the elasticity of water hammer of penstock plays a dominant role.The elasticity of water hammer of penstock is unfavorable for the stability and dynamic response of primary frequency regulation.（2）Firstly,the state equation of HTGS with SLHT is derived to describe the nonlinear performance of HTGS without control.Then,the robust H∞control strategy for HTGS with SLHT is designed based on the exact linearization of HTGS with SLHT and construction of nominal output function.Finally,the regulation quality of HTGS with SLHT under robust H∞control strategy is investigated.The applicability and robustness of robust H∞control strategy for HTGS with SLHT are studied.The results indicate that the optimal robust H∞control strategy for HTGS with SLHT is composed of the optimal gain variable,nominal output function and Lie derivative of nominal output function.The nominal output function is the linear combination of the four state variables of HTGS.Under robust H∞control strategy,the dynamic response of HTGS with SLHT is rapid and sensitive.The regulation quality of HTGS with SLHT under robust H∞control strategy is much better than that under Proportional-Integral-Derivative（PID）control strategy.The water level oscillation in surge tank can be effectively regulated and restrained by the robust H∞control strategy.The robust H∞control strategy has an excellent applicability for HTGS with SLHT.The robustness of robust H∞control strategy for HTGS with SLHT is much better than that of PID control strategy for HTGS with SLHT.（3）Firstly,the model of hydropower station with two turbine units sharing a super long headrace tunnel is established.Then,the method for the description and evaluation of stability of hydropower station is proposed.The stable domain of hydropower station is obtained.The dynamic response characteristics of hydropower station are analyzed.Finally,the stability of hydropower station under asymmetric turbine units is studied based on stable domain and dynamic response.The effects of asymmetric factors on the stability of hydropower station are revealed.The results indicate that there are two bifurcation lines for the hydropower station with two turbine units sharing a super long headrace tunnel.The stable domain is the left domain of the two bifurcation lines.The stable domain provides an effective method for the description and evaluation of stability.The stability under asymmetric turbine units depends on the total value of asymmetric parameters.Under the effect of asymmetric factors,the dynamic response processes of turbine frequencies show asymmetric characteristics.The asymmetric governor parameters and load adjustments have an obvious effect on the stability of hydropower station and dynamic response processes of turbine frequencies.（4）Firstly,the model of hydropower station with two turbine units sharing a super long headrace tunnel is established.Then,combined with the basic principle of genetic algorithm,study on the optimization of governor parameters of hydraulic turbine governing system.According to the important parameters affecting the design and operation of hydropower stations,further analysis of their influence on the study of system governor parameter optimization under different values,and the control quality of the optimized system is simulated,qualitative and quantitative analysis of the turbine governing system performance.The results indicate that the performance of parameter optimization based on genetic algorithm of hydro-turbine governing system of hydropower station with two turbine units sharing a super long headrace tunnel is better than that of the Stanning empirical formula.The iterative optimization process of hydro-turbine governing system of hydropower station with two turbine units sharing a super long headrace tunnel under symmetrical arrangement does not show symmetrical changes.the parameter combination of the optimized unit governor is not symmetric when the system reaches the optimal state.Parameters affecting design and operation of hydropower station and load disturbance have great influence on the study of parameter optimization of governor and system performance.The increase of T_{w P2}、h_P20 or m_g2 is not conducive to the performance of the turbine governing system.The increase of parameter T_a2 is beneficial to the performance of the turbine governing system.