| Conventional Energy crisis and environmen tal pollution is a wake-up call for human existence,human urgently need to change the energy system structure,renewable energy in the future society will gradually replace the conventional energy sourcein the future society.In recent decades,wind power' s installed capacity has increased rapidly,wind power become a mature technology,because of its easily commercialization and industrialization,the wind energy has the most development prospects among all the renewable energy at present.With the rising of the capacity connected to the grid of wind power,the most stringent requirements of wind power grid technology is proposed,the control and design technology of converter is one of the key technologies of wind turbines.This article selected D-PMSG grid side converter as of D-PMSG as the research object,studied on the strategy of VF-DPC,deeply analyzed the dynamic performance of hysteresis,PI and sliding mode control strategy,which has important reference value and academic significance.First of all,this article selected three-phase voltage source PWM rectifier as the topology of the grid side converter,starting from the control principle of single phase converter,pointed out that as long as you can control the conduction time and state of the switch tube that you can achieve the purpose of th e power factor is adjustable,in order to make the controller design easily implementation,deduced the mathematical model in two phase rotating coordinate of grid si de converter and dc bus voltage,this paper also expounded the method to generate sine wave pulse by space voltage stratege,this part prepared a plenty of theory to buliding the model of the grid side converter for the article.Secondly,this paper introduced the instantaneous power theory an d the principle of virtual flux oriented,points out the VF-DPC superiority compared to the VOC,because of the power fluctuations in traditional switch table and the lack of reactive power regulation,this paper designed a new switch table that changing t he voltage space vector that improved the switch table's border jitter in a certain extent.Due to the hysteresis control system's frequency was no t fixed,this paper designed a PI controller based on VF-DPC that had a fixed frequency,deduced t he relationship between the d-q axis' s voltage in the ac part,the act ive power and reactive power,By introducing a feedforward decoupling part in control system this thesis im plemented that q axis' s voltage control the active power separately and d axis' s voltage co ntrol the reactive power separately,on the basis of this control theory,this article made a MATLAB/SIMULINK simulation model,and verified the feasibility of this two kinds of control strategies.Finally,By the understanding of the sliding mode variable structure control,this article analyzed the design steps of the sliding mode control,and put forward several measures to eliminate the chattering problem.according to its strong robustness and the advantages of easily realization,this article selecte d voltage control circle as the sliding mode surface design and the power control circle as the sliding mode control rate design.in order to eliminate the chattering problem,this article used saturation function instead of switching function to design the sliding mode direct power controller forthe grid side converter.this controller was applied to the direct drive wind power system,and the machine side converter was connected,this article build a simulation model of the wind power system in MATLAB/SIMU LINK,and compared to the PI direct power control strategy,the simulation results showed that the sliding mode direct power control strategy can get better dynamic response in the system. |
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