S-shaped characteristics on the performance curves of pump-turbines in turbine mode – A review

Ren

IOP Conf. Ser.: Mater. Sci. Eng.

et al. 2018

Abstract. The switching between generating mode and pumping mode of pumped storage power station is significant for the grid control, for example, to compensate the power fluctuation caused by the renewable energy by using the pumped storage power station. In this paper, the simulation models of various states of pumped storage power station are summarized, and the control methods of each switching stage between the generating mode and pumping mode are proposed. The method to realize each switching stage is presented, and the simulation method of each switching stage of generating mode and pumping mode is established in MATLAB/Simulink, and the switching process is realized.

“…Simulation of start-up in generating mode. Start-up of VSPS in generating mode can be divided into three stages [11]. The first stage is the self-starting stage.…”

Section: Generating Mode Simulationmentioning

confidence: 99%

Simulation Method for Generating Mode and Pumping Mode Switching of Pumped Storage Hydropower Plant

Ren

IOP Conf. Ser.: Mater. Sci. Eng.

et al. 2018

“…Although various experimental studies including PIV (Particle Image Velocimetry) measurements [10], and bubble injections [11] were conducted for the purpose of studying the flow patterns in the pump-turbine, the descriptions of these flow patterns were still limited. Numerical simulation is thereby a major tool, which is less expensive, more flexible and leads to a more detailed database of the flow field.…”

Section: Introductionmentioning

confidence: 99%

Energy Balance and Local Unsteady Loss Analysis of Flows in a Low Specific Speed Model Pump-Turbine in the Positive Slope Region on the Pump Performance Curve

Zuo

Liu

et al. 2019

Energies

Self Cite

The positive slope on the pump performance curve of pump-turbines suggests potential operational instabilities in pump mode. Previous research has indicated that the increase of the hydraulic loss caused by sudden changes of flow patterns in pump-turbines is responsible for the positive slope, however its detailed flow mechanism is still unclear. A low specific speed model pump-turbine was numerically investigated against experiments in the present study, by applying unsteady RANS (Reynolds-Averaged Navier–Stokes equations) simulations with a v2-f turbulence model. The mechanism of occurrence of the positive slope on the pump performance curve was discussed regarding the energy balance, as this region appears when the value of ∂ P u ∂ Q is larger than the critical value P u Q . An unsteady local loss analysis, derived from the energy equation, was conducted to illustrate the contribution of local flow patterns to the loss in corresponding hydraulic components. The variation of the kinetic energy of the mean flow was taken into account for the first time so that this method can be applied to highly time dependent flow patterns, e.g., a rotating stall in the present study. The investigations on the flow patterns revealed that some guide vane channels stalled with a larger discharge coefficient than the positive slope region. Several guide vane channels near the stalled channels were stalling with minor decrease of the discharge coefficient, leading to sudden increases of the input power and the loss. When the discharge coefficient slightly decreased in further, the pump-turbine operated into the positive slope region, and the rotating stall with 3 stall cells appeared, proven by the FFT (Fast Fourier Transform) and cross-phase analysis on the pressure fluctuations.

Mathematical Problems in Engineering

“…Another feature is their flexibility to make up for the stochastic of solar and wind power, which is helpful for the multienergy complement [10]. e reversible pump turbine is an important component of the PSPS which experiences different transitional processes to achieve the function of regulation by switching between turbine and pump mode [11,12]. A conventional method to deal with the transient conditions of the pumped storage unit has been to optimize the GVCS.…”

Section: Introductionmentioning

confidence: 99%

Analysis on Guide Vane Closure Schemes of High‐Head Pumped Storage Unit during Pump Outage Condition

Zhang

Zheng

et al. 2019

When the pumping operation of pumped storage unit suffers from power outage, the hydraulic transient poses a serious threat to the safe operation of the unit and its pressure pipeline system. For high-head pumped storage power station (PSPS), the water hammer pressure (WHP) and rotational speed rise ratio (RSRR) of each hydraulic unit will be increased during the pump outage condition. In order to limit the fluctuation of rotational speed and WHP in power-off condition, optimizing and choosing a reasonable guide vane closure scheme (GVCS) is an economic and efficient means to improve the dynamic characteristics of pumped storage unit. On the basis of the calculation model of the transition process of single tube-double unit type of a high-head PSPS, an optimization model of GVCS balancing WHP and RSRR objectives is established. Furthermore, the two-stage broken line and three-stage delayed GVCSs are applied to the pump outage condition, and the nondominated sorting genetic algorithm-II (NSGA-II) is introduced to calculate the optimal solution set under different water heads and different closure schemes. For four typical water heads, the multiobjective optimization results of the closure law show that the two-stage broken line law has a better Pareto front under high water head, while the three-stage delayed law has a better performance under low water head. Furthermore, through the results of transition process of typical schemes, the adaptability of GVCS and water head is analyzed. The method proposed in this paper can make the RSRR not more than −0.89, and the three-stage delayed law can even make the RSRR only −0.01. Methods of this paper provide a theoretical basis for optimum guide vane closure mode setting of PSPS.