A nonlinear hierarchical general predictive governing control scheme for pumped storage units

Abstract

The speed governor system is known as the key part of the pumped storage unit (PSU) and plays an important role in ensuring its stable operation. To improve the control performance of the pumped storage governing system (PSGS), this paper introduces a hierarchical control strategy improved generalized predictive control-proportional-integral-derivative (IGPC-PID) for PSU. Firstly, we establish a precise state-space differential equation model of PSGS. Secondly, we propose a parameter approximation strategy based on the F-test, which is used to approximate the higher-order transfer function model of the PSGS. Besides, the model parameters are estimated online by the least square method (LSM) to reduce the model error. Combined with the model parameter approximation method and hierarchical control strategy proposed in this paper, numerical experiments are conducted on the simulation platform established in the study. The results indicate that the proposed model can accurately describe the hydraulic dynamic characteristics of the piping system, and the IGPC-PID can effectively inhibit the rotational speed oscillations of the PSGS under perturbation. Simulation results show that under 5 % frequency perturbation, the IGPC-PID controller can make the system reach a stable state in about 4 s with almost no overshooting. Compared with the traditional proportional-integral-derivative (PID), generalized predictive control (GPC) controller reduces about 9 s, 5 s, the overshooting amount reduces 0.0026. The stabilization time of the IGPC-PID controller is also the shortest is 3.5 s under 10 % load perturbation. So IGPC-PID has a better control performance and robustness than that of the PID and GPC.