Study On Multi-objective Optimization And Generalized Predictive Control Of Start-up Strategy For Pumped Storage Units

Pumped storage unit which undertakes important tasks in power system,such as peak regulation and frequency modulation,is an indispensable part to ensure the safe and stable operation of the power system.Pumped storage unit governing system has the characteristics of time-varying,non-minimum phase,and strong non-linearity.It cannot accurately describe its dynamic characteristics with analytical models.Compared with the conventional turbine,it has the characteristics of quick start and stop,various working conditions,frequent switching of working conditions,and easy access to the "S" area for low head operation,which brings great challenges to the safe and stable operation control of the unit.In order to improve the control quality of pumped storage unit governing system,the modeling of governing system,start-up control optimization and control algorithm design have always been the focus of domestic and foreign scholars.This paper studies a nonlinear fine model for pumped storage unit governing system,and establishes simulation platform,which lays the foundation for control strategy optimization and control algorithm design.The multi-objective optimization model and algorithm of start-up strategy for pumped storage unit are studied.For two typical layout forms of one tunnel one unit and one tunnel two units,the multi-objective optimization scheme of start-up strategy is designed respectively,which is dedicated to improving the performance indices of start-up transition process.Furthermore,the generalized predictive control algorithm is studied,and a nonlinear generalized predictive controller is designed to improve the adaptability and robustness of the controller.The research results have engineering application value for improving the control quality of pumped storage units and the safe and stable operation level of power system in China.The main research work and innovative achievements are summarized as follows:(1)In order to ensure the modeling accuracy of the pumped storage unit governing system,the improved Suter transformation method is adopted to deal with the original full characteristic curve of the unit,so as to solve the multi-value problem in interpolation caused by the characteristics of the original curve "S" area.The nonlinear characteristics such as dead zone of servo device,output limiting of main distributing valve and output limiting of main servomotor are considered.For two typical layout forms of one tunnel one unit and one tunnel two units,the nonlinear fine simulation platform of the governing system is established respectively.(2)For the pumped storage power station with one tunnel one unit,the objective function is speed overshoot and speed rise time.The decision variables,the number of oscillations and the limit of opening are considered as constraints.A multi-objective optimization model of start-up strategy for pumped storage unit is established.Multiobjective particle swarm optimization algorithm is adopted.Thus,the multi-objective optimization of start-up strategy of pumped storage unit can be realized.(3)For the pumped storage power station with one tunnel two units,the hydraulic interference between two units is analyzed.The influence of successive time interval on the start-up transition of two units is studied.Speed overshoot of 1# unit and speed rise time of 2# unit are selected as the objective function.The various constraints of the start-up transition process of the two units are fully considered.Thus,the multi-objective optimization scheme for two units’ successive start-up strategy is designed to improve the performance indices of start-up transition process of the pumped storage units.(4)Nonlinear generalized predictive control algorithm is studied for pumped storage unit.At each sampling time,the control system is linearized instantaneously,and the CARIMA model is identified by the forgetting factor recursive augmented least squares method.By introducing the improved generalized predictive control algorithm,an improved nonlinear generalized predictive control based on the instantaneous linearized CARIMA model of the governing system is designed to improve the adaptability and robustness of the pumped storage unit controller.