Adaptive backstepping control in speed regulation systems of variable speed pumped storage units
[Objective]The expansion of the scale of renewable energy has highlighted power fluctuations and frequency control issues in the power grid.Variable-speed pumped storage units have become an effective means to absorb renewable energy owing to their fast power response,effective control of grid load frequency,and ability to balance frequency fluctuations caused by renewable energy.However,the mainstream control method for these units under power-generation conditions has the problem of reverse speed overshoot caused by rapid power changes.This problem places high demands on the control performance of the speed controller.Traditional speed controllers often struggle to maintain optimal control,which affects power regulation efficiency and unit operation.Therefore,this paper investigates the speed control system of variable-speed pumped storage units during active power regulation under power-generation conditions.[Methods]First,a mathematical model of the speed control system for variable-speed pumped storage units was established.This model includes the model of a water turbine and water diversion system,the model of an electro-hydraulic follow-up system,the load model of a generator,and an optimal speed module.The established model allows for further research into the speed controller's control capabilities.Second,an adaptive backstepping controller was designed for the adaptive estimation of electromagnetic power.To overcome the computational inflation problem in backstepping control,instruction filtering was introduced and verified.The control effect of backstepping control under different load conditions was confirmed through simulation experiments.[Results]The designed adaptive backstepping controller was simulated using MATLAB/Simulink to verify its control effect.By keeping all system and controller parameters unchanged,experiments were conducted at a water head of 0.788 p.u.under low and high initial loads.In Experiment ①,the power instruction was changed at 10 s,and the given power increased from 0.143 to 0.286 p.u.Moreover,the optimal speed was determined to be 0.528 p.u.through the optimal speed module,and the actual speed tracked this optimal reference speed for approximately 2 s.In Experiment ②,the given power increased from 0.643 to 0.714 p.u.As per the optimal speed module,the optimal speed changed from 0.586 to 0.607 p.u.after active power changes.The actual speed tracked the optimal reference speed within 1 s.In both experiments,the system displayed almost no overshoot,successfully tracking the optimal speed in a short time frame.[Conclusions]The simulation experiments demonstrated that the adaptive backstepping controller with instruction filtering,designed in this paper,can effectively track the desired optimal speed of the system under different load conditions.These results prove the efficacy of the designed speed controller and its good control effect.
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