Research On Optimal Control Of Hydroelectric Generating Units Based On Generalized Smith Predictor And Minimum Time Control

With the accelerated transformation of energy structure,the proportion of new energy generation capacity with intermittent,random,and volatile has rapidly increased,bringing great challenges to the safe and stable operation of power grids.Hydroelectric generating unit,due to their excellent regulation performance,undertake important tasks such as regulating power balance an d stabilizing power grid frequency in the power grid.When hydroelectric generating units are deeply involved in power grid regulation,the hydraulic turbine and water diversion system show obvious time-varying,nonlinear,and non minimum phase characteristics,resulting in exceptionally complex system characteristics.At present,PID governors are mostly used as controllers for hydroelectric generating unit.The PID control principle is simple and the technology is mature,but there is little consideration for the deep participation of units in power grid regulation.As a result,the regulation quality could decline and or even regulation process could be unstable when the units deviate from the design operating conditions,making it difficult to meet the requirements of rapid response and high-precision operation of units in the new power grid.Therefore,optimizing the traditional PID control strategy and proposing new control strategies are of great significance for improving the regulation quality of the hydro-turbine regulation system,promoting th e consumption of n ew energy in the power grid,and accelerating the construction of a new type of power system with the new energy as the core.This dissertation proposes a new regulation strategy for hydraulic turbines based on the generalized Smith predictor and minimum time control to improve the control performance of hydroelectric generating unit.Firstly,the generalized Smith predictor is introduced to predict hydraulic turbine model characteristics are introduced into the prediction model of the controller to improve the adaptability of the controller to the nonlinear characteristics of the system,so as to ensure the stability of the unit under a wide range of operating conditions.In addition,the minimum time controller is designed for the minimum phase link.In the minimum time controller,the system state equation and controller output constraint equation are established based on the load model of the water turbine and generator.On this basis,the system Hamiltonian function and adjoint equation are established.The optimal control method is used to establish the functional of the time required for system frequency stability,so that the system output function can be established based on the analysis of the system phase trajectory family line to realize rapid adjustment of unit operating conditions to ensure the rapid response of unit regulation.Finally,the new control strategy proposed in this dissertation is applied to the speed regulation system of fixed speed hydroelectric generating unit and variable speed hydroelectric generating unit,and the control effects of the new control strategy and traditional PID control are compared by using PSCAD simulation tools to verify the effectiveness of the proposed control strategy.The results show that the proposed control strategy is significantly superior to the PID control after parameter tuning and optimization,which shortens the speed adjustment time,greatly improves the dynamic quality of the system,enhances the speed and stability of the unit,and provides reference for optimizing the control of the hydro-turbine regulating system.