Research On Predictive Direct Power Control Strategy Of Double Stator Brushless Doubly Fed Wind Generator

In recent years,the rapid development of global economy has led to the increasing demand for energy.The traditional fossil energy with limited reserves will eventually be exhausted due to excessive exploitation and low utilization rate.However,wind energy as a clean and renewable energy and huge storage,cause the attention of researchers all over the world.Accordingly,wind power technology has entered rapid development stage.At present,the permanent magnet synchronous generator and doubly fed induction generator in wind power system applications occupy the important position.However,the former requires a large converter capacity and high cost;the latter has a slip ring with poor reliability and requires regular maintenance.therefore,the new brushless doubly fed generator of low cost and high reliability is more suitable for wind power system.Therefore,the double stator brushless doubly fed wind generator(DS-BDFG)is taken as the research object,a direct power control method of DS-BDFG based on predictive control is proposed in this paper.The main research contents of this paper include the following aspects:Firstly,this paper expounds the research background and significance of the subject systematically.It analyzes the research history,latest research and future development trend of wind power generation comprehensively.Then,the research and development history of the double stator brushles doubly fed generator and its control strategy are analyzed in detail.And the research object of the brushless doubly fed wind generator is further studied and analyzed comprehensively.Secondly,the structure and working principle of the double stator brushless doubly fed wind generator are studied in depth,and its mathematical model under the stationary coordinate system and the rotating coordinate system are established,Whereafter,the power flow direction of the generator under different operation modes is deeply studied and analyzed.Again,direct power control strategy and the theory of instantaneous power are reseached in this paper to realize double stator brushless doubly fed wind generator power tracking control.Namely,direct power control method is applied to the double stator brushless doubly fed wind generator power tracking control.The sector division and the voltage vector selection table are determined and made respectively.Finally,the simulation model is built for simulation analysis.The simulation results show that this method can realize power tracking control and variable speed constant frequency power generation,but the power fluctuates greatly.To solve this problem,a control strategy of predictive direct power is proposed.The principle of predictive direct power control and the action time of each vector are systematically studied.By comparing the simulation results of the two methods,it can be seen that the latter has less power fluctuation and better tracking effect.Finally,a model predictive control method is proposed to solve the problem that the switching frequency is not fixed,which combines predictive control with Space Vector Pulse Width Modulation(SVPWM)technology.Switching Pulse is generated by SVPWM method,which can fix the switching frequency.Then a simulation model is built for simulation research.And the response speed,power fluctuation and other control effects of the two predictive control methods are compared and analyzed.