Transient dynamic analysis of a pump-turbine with hysteresis effect

Abstract

Hysteresis effect, which has a significant impact on transient characteristics of a pump-turbine, attracts more and more researchers’ attention and shows great potential. Influences of hysteresis on dynamic characteristics of a pump-turbine are investigated during the transient process in this paper. Transient trajectories of pump-turbines actually do not match their static operation trajectories, especially in the condition of turbine braking. In order to establish a transient model of a pump-turbine in different moving directions of dynamic trajectories, time delays among the relative parameters are introduced in this paper. Furthermore, effects of hysteresis on the dynamic characteristics of the pump-turbine are analyzed in detail by using numerical simulation. Based on the established transient model, influences of unit head on the dynamic characteristics of the pump-turbine are studied during the bidirectional transient process. The simulation results show the transient characteristic of the pump-turbine can be improved with the enhancement of hysteresis effect. While it gradually loses stability with the increase of hysteresis. The conclusions provide us a new approach for regulating the transient performance and stability of pump-turbines by using hysteresis effect during transient process.

Stability analysis of hydro-turbine governing system based on machine learning

“…Impact: Too many nodes, the training time increases, and the network is easy to overfit. According to the optimal hidden layer node number selection formula, we determine the range of hidden layer node number selection interval (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15). The relationship between the number of hidden layer nodes and the stability prediction error rate of the BP neural network of the HTGS is shown in Fig.…”

“…Qu et al [7] presented the state equation of HTGS with SLHT to describe the nonlinear performance of HTGS without control and designed the robust H-infinity control strategy for HTGS. Guo et al [8] investigated the effect of hysteresis on the characteristics of a pump-turbine during transient process and the dynamic characteristics of the system were analyzed by simulations. Lai et al [9] studied the stability and dynamic characteristics of the nonlinear HTGS-PG coupling system based on the nonlinear mathematical model and Hopf bifurcation theory.…”

Numerical investigation on the transient gas–liquid flow in the rapid switching process of pump turbine

“…14 Under the pump mode, the fluid is pumped from the downstream reservoir to the upstream reservoir by using the electric energy at the low power load, while under the turbine mode, the fluid is discharged from upstream reservoir to downstream reservoir for power generation to relieve peak pressure of power load. 15 For the long-term development of pump turbine units, experts and scholars have focused on the following three aspects: (1) Hydraulic performance improvement of pump turbine units. Dai et al 16 studied the influence of the runner blades geometry on the energy performance of pump turbines, such as head and efficiency.…”

“…As a key component of the pumped storage system, the working principle of pump turbine units is contained in two working modes 14 . Under the pump mode, the fluid is pumped from the downstream reservoir to the upstream reservoir by using the electric energy at the low power load, while under the turbine mode, the fluid is discharged from upstream reservoir to downstream reservoir for power generation to relieve peak pressure of power load 15 . For the long‐term development of pump turbine units, experts and scholars have focused on the following three aspects: (1) Hydraulic performance improvement of pump turbine units.…”

“…Zeng et al 20 studied the rapid switching process of pump turbines through model experiments and improved the “S” characteristics by setting different guide vane opening schemes. Guo et al 15 analyzed the effects of hysteresis on the dynamic characteristics of the pump turbine in detail by using numerical simulation. Due to the complexity of transient flow and the coexistence of liquid and gas in the rapid switching process for pump turbine units, there are few existing research results on this process.…”