Effect of Rotational Speed on Pressure Pulsation Characteristics of Variable-Speed Pump Turbine Unit in Turbine Mode

Pressure balance pipe is an important technical solution for the internal pressure balance of pump turbine and is widely used in pumped storage power units. This article systematically explains the application of pressure balance pipes in pump turbines, and sorts out three typical pressure balance application methods: the external pressure balance pipe structure balances the external side of the upper wearing ring and the lower wearing ring, the internal pressure balance pipe structure balances the internal side of the upper wearing ring and the draft tube, which improves the axial water thrust distribution of the unit and avoid uneven distribution of the axial water thrust on the runner. The spiral case pressure balance pipe realizes the control of water ring flow in the vaneless area under the synchronous condenser mode and pressure water by balancing the pressure of the spiral case and draft tube. For the above three structures, the current research progress, main problems and future development directions are elaborated.

Section: Brief Description Of Internal and External Pressure Pipe Str...mentioning

confidence: 99%

State of the art of technical background and practicality of pressure balance pipes for pumped storage turbine

Wang,

Zhao,

Wei

et al. 2024

“…He Wang et al [8] proposed an optimization step in variable-speed operation based on the model of a VSPSU. In terms of operational stability, Linmin Shang et al [9] revealed that the stability of VSPSUs decreases with the increase of speed in turbine mode. Giovanna Cavazzini et al [10] illustrated the effect of the S-Shape zone in turbine mode and the hump zone in pump mode on power regulation.…”

Section: Introductionmentioning

confidence: 99%

Preliminary study on power regulation rapidity in pump mode of variable-speed pumped storage unit with DFIM

Liu,

Yang,

Yang

et al. 2024

Variable-speed pumped storage unit (VSPSU) has a wider power regulation range than fixed-speed pumped storage unit (FSPSU) in pump mode. When conducting large-amplitude power regulation, the operating point changes greatly, and the influence of various parameters on the power response in this transient process is not yet clear. In order to study the power regulation rapidity of VSPSU in pump mode, the factors affecting the response rapidity and overshoot of power under fast speed control strategy are explored through numerical simulation of a variable-speed pumped storage plant (VSPSP) model, in which doubly fed induction machine (DFIM) is adopted. The factors include power command, controller parameters of governor (Kp-g , Ki-g ), and controller parameters of converter (Kp-c , Ki-c , Kp-c2 , Ki-c2 ). Accordingly, preliminary study is conducted on the parameter matching law for obtaining the fastest power response, and suggestions on the settings of the parameters are provided. The results show that the fastest power response can be obtained when adopting a step power command and the VSPSU has the fastest response rate of 12.5%/s when adjusting 30% power using the parameters recommended in this paper. This study could provide technical support to the practical operation of VSPSU.

“…However, most PSH plants are only capable of regulating their power production output in turbine mode [4], while pumps are only able to run at full capacity. Furthermore, the conventional fixed speed pumped storage units (FSU) cannot meet the requirements of fast and accurate regulation when frequency fluctuation occurs [5,6], especially in the grids with high proportion of intermittent renewable energy [7]. With variable speed drives, (1) the operation efficiency and stability of the turbine can be improved, (2) the pump input power can be regulated, and (3) the unit can respond to the power fluctuation of the power grid in milliseconds by flywheel effect [8].…”

Section: Introductionmentioning

confidence: 99%

The method for identifying the potential of the fast response capability of a variable-speed pumped storage turbine in pump mode

Meng,

Zheng,

Wang

et al. 2024

Variable-speed pumped storage technology was being increasingly adopted by new power system to improve the operating and regulating characteristics of the hydropower unit and to stabilize the grid fluctuations. By connecting to a frequency converter, the variable-speed pumped storage unit can respond to grid fluctuations at a speed of hundreds of milliseconds. The fast response capability of a variable-speed pumped storage turbine should be considered in the design stage, be identified during the model test and be used as prerequisite during the commissioning stage of the unit. This article described the method for identifying the fast response capability and methods for improving the power regulation potential of a variable-speed pumped turbine in pump mode. The pipeline hydraulic loss, the guide vanes opening, the energy, cavitation and hump characteristics of the pump are the key parameters and should be carefully considered during the selection of the variable-speed operating zone.