Active Power Smoothing Control Of A Doubly-fed Wind Power System Including Super Capacitors

Doubly-fed induction generators are the main models in the field of wind power.The grid-connected operation of a large number of wind turbines has increased the penetration rate of new energy generation and brought about considerable economic benefits.However,due to the fluctuation of wind energy,when a large number of grid-connected doubly-fed induction generators are connected,the output power fluctuations will bring many problems to the power quality and operation stability of the power grid.Therefore,the research on the active power smoothing control of doubly-fed induction generators appears to be significant.Particularly important.At the same time,due to the use of a super capacitor energy storage system,the maximum power point tracking and output power smoothing of doubly-fed induction generator are balanced to a certain extent.This paper focuses on the control problem of output active power of wind turbines and the application of super capacitors in them.In order to analyze the wind energy capture problem of wind turbines,this paper establishes a combined model that reflects various wind speed changes and further analyzes the aerodynamic model and transmission mechanism model of wind turbines.A set of small-capacity aerodynamic and mechanical parameters of the unit corresponding to the actual wind turbine system was obtained through the reduction,and a wind turbine simulation method was established.The correctness of the contraction ratio method and the wind turbine simulation method was verified through simulation.In order to obtain the best wind energy tracking control strategy of the doubly-fed wind power generation system,this paper establishes the mathematical model and vector control strategy of the doubly-fed induction generator.According to the maximum power point tracking control strategy of the power signal feedback method,the wind speed is estimated and the power command is modified to improve the maximum power point tracking control strategy.The simulation results show that the maximum power point tracking control strategy with wind speed estimation and power command correction is applicable to the control of doubly-fed generators with low wind speed fluctuation frequency in wind field,and the frequency of wind speed fluctuations.The effect is related to the mechanical time constant of the wind turbine.In order to realize the power smoothing control of the doubly-fed induction generator system,the mathematical model and control strategy of the grid-side converter were established.According to the operation mode of the interleaving triple bi-directional Buck-Boost converter,the current ripple is analyzed;and a power-current double closed-loop control strategy is proposed,so that the super capacitor passes the interleaved parallel triple bi-directional Buck-Boost converter and the network side conversion The device exchanges energy with the grid to achieve a smooth power control of the power generation system during the maximum power point tracking control stage.Simulation proved that the method can smoothly control the power of the power generation system running in the maximum power point tracking phase.Finally,a physical simulation experimental platform for the power control of a doubly-fed wind power generation system is built.The platform verifies that the maximum power point tracking control strategy with wind speed estimation and power command correction can realize the maximum power point tracking faster,and the power smoothing control strategy can realize the power smoothing control of the system when the maximum power point tracking is tracked.