Study On Ternary Operation Mode In Ternary Pumped Storage Hydro Plant

In recent years,with the development of new energy power generation technology,power systems integrated with large-scale new energy power generation put forward higher requirements for the dynamic regulation capacity of pumped storage hydro(PSH)plants.However,due to the operating characteristics of conventional reversible PSH unit,the power of unit cannot be regulated in pumping mode.To a large extent,it limits the regulation capabilities to wind power fluctuation of conventional reversible PSH units after power systems integrated with large-scale wind power generation.Ternary pumped storage hydro(TPSH)plant has many advantages because of its ternary operation that TPSH plant can simultaneously operate both pump and turbine as same as motor-generator.Ternary operation can realize the full power regulation of the active power in pumping mode.In addition,during the transition process of pump off and shutdown of pump,the rapid changes in water pressure and flow rate as well as rotational speed will cause pressure fluctuations in hydraulic system,and ultimately endanger the safety of the entire system.If ternary operation is adopted during the transition process of pump off and shutdown of pump,it can mitigate impacts of rapid change of parameters in the hydraulic system and units and eventually improve the transition process in the water diversion and power generation system of plant.Therefore,the research on ternary operation in TPSH plant will enrich operation theory of TPSH plant and facilitate application of joint operation of TPSH plant and wind farm,which has important theoretical research value and broad application prospect in engineering.Because of the study of mathematical model of main components of water diversion and power generation system in TPSH plant,the whole simulation model has been established.Based on whole simulation model,the study on ternary operation in TPSH plant will be systematically implemented.The main contents include three parts.In the first part,according to the characteristics of ternary operation,the whole system was divided into three main parts:hydraulic system,mechanical system and electrical system.These parts were separately analyzed and modeled.And then the whole simulation model of water diversion and power generation system in TPSH plant was established by adopting MATLAB/Simulink platform.Steady flow assignment was used in the model and the modeling process followed the route from mathematical equations to the mathematical model to the general module.These two features made the simulation model visualization and portability and optimization and enhance the flexibility and versatility of the model.Finally,the calculation results both on generating mode and pumping mode of model were compared with two pieces of practical software and this will verify the correctness of the model,which provided a reliable tool for the research of this paper.In the second part,aiming at the valve higher pressure in transition process of pump off and shutdown of pump,this paper researched on improvement through ternary operation of transition process of pump off and shutdown of pump in TPSH plant,and analyzed the influencing factors.The results reveals that the governor speed setting value and the governor parameters have a significant impact on transition process of pump off while the turbine valve opening speed of needle valve of turbine and governor speed setting value as well as the governor parameters have a significant impact on transition process of shutdown of pump.Through the optimization of the above parameters,the transition process of pump off and shutdown of pump by ternary operation was improved.In the third part,by adopting the numerical simulation model of TPSH plant,the deficiency that power of pump cannot be regulated was verified.Then,it researched on the steady and dynamic characteristic of power regulation in pump mode by ternary operation.Moreover,it demonstrated the dynamic process of power regulation of TPSH unit in pump mode by using the grid load data.These results reveal that the power of unit in TPSH plant can trace the grid load fluctuation in pump mode,and regulation time and wave amplitude of power depend on amplitude of load disturbance and rate of change,which reflects the good capability of dynamic regulation of TPSH unit.At the end of this part,the influence to TPSH plant after unit accidentally off the grid in ternary mode was researched on and its result reveals this accident is not the most unfavorable condition of transition process of TPSH plant.The results of this paper demonstrate ternary operation mode of is safe mode of in TPSH plant and further reveal its two advantages.They are the improvement of the transition process of pump off and shutdown of pump by ternary operation,and the implementation of power regulation in a full scope of unit in pumping mode by ternary operation.These results can enrich the theory of operation of TPSH plant and provide a theoretical basis for the application of combined operation of TPSH plant and wind farm,which have significant theoretical value and broad application prospect.