| The hydroelectric capacity of a certain scale was required for China's coal-based energy structure to be responsible for power grid load regulation,while the traditional hydropower station is affected by the seasonal runoff,it needs a lot of abandoned water to participate in the peak-cutting and valley-filling of the power grid.The doubly-fed pump-turbine generator set is a new type of hydropower system,and the doubly-fed asynchronous generator in it can realize the functions such as variable speed constant frequency generation of generator sets and independently adjusting active and reactive power,thus,when the pump-turbine regulation system and the doubly-fed asynchronous generator are jointly controlled,the unit can work at the optimal operating point within a certain range of large head change,to ensure that the unit can participate in the peak cutting and valley filling of the power grid under the condition of reducing the abandoned water.The doubly-fed combined with pump-turbine is a complex nonlinear system with a strong coupling of water,machinery,and electricity.Not only is it difficult to use the conventional mathematical model to calculate the transition process,but the doubly-fed asynchronous generator is a system with strong coupling between variables.However,the fine modeling of the pump-turbine and the advanced control strategy applied to the doubly-fed asynchronous generator are rarely considered by the existing modeling and analysis of the doubly-fed pump-turbine unit.In this paper,a new analysis method of doubly-fed pump-turbine generators is proposed by combining the full characteristic curve model of the pump-turbine and the advanced control strategy applied to the doubly-fed asynchronous generator.It is as follows:(1)Firstly,the model of the doubly-fed hydro-generator is built.the full characteristic curve of the hydraulic pump-turbine obtained by the experiment has a multi-value phenomenon and "S"characteristic.if it is directly used in the calculation of the pump-turbine transition process,it will lead to the instability of the pump-turbine operation.in this paper,the Suter transformation method is used to treat the pump-turbine characteristic curve,and the full characteristic curve can be used to calculate the pump-turbine transition process is obtained.Secondly,the mathematical model of the dual-feed asynchronous generator in the three-phase stationary coordinate system under ideal(2)For the rotor-side inverter control of doubly-fed induction generator,the traditional PI controller has poor effect in frequency converter control of doubly-fed induction generator because of its long adjustment time and large overshoot,meanwhile,sliding mode control in the nonlinear controller has attracted more and more attention because of its strong robustness and easy physical realization.By using vector control based on stator flux orientation,the non-singular fast terminal sliding mode is used for control in this paper.Compared with other sliding mode controllers,non-singular fast terminal sliding mode not only avoids the disadvantage of uncertain convergence time of ordinary sliding mode controller but also avoids the singular phenomenon that the terminal sliding mode controller will produce.(3)A model of the doubly-fed pump-turbine generator set is built-in MATLAB platform,which includes a pump-turbine model based on a full characteristic curve,a speed regulation system model,a doubly-fed asynchronous generator model and so on.And the simulation verification is carried out under three working conditions:active power,reactive power reference value step,and parameter fluctuation.Compared with the traditional PI controller,the performance of the doubly-fed induction generator can be improved effectively because the output power buffeting is smaller,the number of buffeting is less and the adjustment time is shorter under the control of non-singular fast terminal sliding mode. |
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