Optimization and Mechanism of the Wicket Gate Closing Law for High-Head Pumped Storage Power Stations

Chang Liu,Jianzhong Zhou,Tianyu Zhang,Xinjie Lai

doi:10.1109/access.2021.3049914

Abstract

The high-head pumped storage power station (PSPS) has complex working conditions and severe transient processes. Under load rejection conditions, the turbine speed and the flow channel pressure will threaten the unit. By adjusting the wicket gate closing law (WGCL), we can effectively alleviate the adverse effects of the transient process. In this study, a full flow channel refined model of a high-head PSPS was constructed, and the influence mechanism of load rejection conditions on key parameters was analyzed by tracking the operating trajectory on the S characteristic curves and simulating the transient flow field inside the pumped turbine by three-dimensional computational fluid dynamics (3D-CFD). Given the contradiction between different parameters in the wicket gate closing process, a third-generation non-dominated genetic algorithm based on reference point selection (NSGA-III) was introduced, and a high-dimensional multi-objective WGCL optimization model was constructed. We compared parameter changes in the two-phase and three-phase WGCL optimized elite solutions and explained the rationality of adopting the three-phase WGCL in high-head PSPSs. By proposing an improved three-phase WGCL, a new scheme—the most suitable WGCL under load rejection—was obtained through precise optimization. The research embodied the excellent effect of the heuristic multi-objective (MO) optimization algorithm based on the Pareto strategy in solving the operation problem of the large fluctuation transient process of hydraulic machinery. It revealed the theoretical basis of engineering adjustment for the safe production and operation of hydropower.

Highlights

Pumped storage power stations (PSPSs) have unique operation modes of peak-valley filling, frequency and phase modulation, and rapid response functions such as spinning reserve, which have become a critical method of green energy production
MODEL VERIFICATION CALCULATION The single-tube and single-unit of the PSPS were calculated under 100% and 75% load rejection conditions, and the processes were based on the designed one-stage wicket gate closing law (WGCL)
INTERNAL FLOW FIELD ANALYSIS We further demonstrate the change characteristics of the load rejection conditions of the pumped turbine using 3D computational fluid dynamics (3D-CFD) and dynamic mesh technology to analyze the internal transient flow field

Summary

INTRODUCTION

Pumped storage power stations (PSPSs) have unique operation modes of peak-valley filling, frequency and phase modulation, and rapid response functions such as spinning reserve, which have become a critical method of green energy production. For addressing the adverse effects of the pumped turbine during the load rejection transient process, the water hammer pressure at the spiral case inlet, the rate increase of the runner speed, and the vacuum at the draft tube outlet were selected as key indicators. 3 and 4, respectively, illustrate the operation trajectory in the S-region and the key indicator change curves of the pumped turbine under load rejection conditions. The resultant torque is positive, causing the runner to suddenly increase in speed after load rejection and the wicket gates to start closing At this time, n11 gradually rises and reaches a maximum value at Point 2, and the rotation speed n of the. Choosing the turning point time and the opening is challenging

OPTIMIZATION OF WGCL

RESULT

Findings

CONCLUSION