Based On The Dual Controllable DFIG System Control And Optimization Research

Doubly-fed induction generator(DFIG)is one of the two major models in the wind power market,and it has been widely used in AC wind farms.However,compared with AC wind power technology,DC wind power technology has a lot of advantages,such as convenient control,low price,no AC power quality index,and more suitable for long-distance transmission.Therefore,in order to make DFIG more effectively applicable to DC power grid,this paper carries out the research by centering on the DC-based doubly-fed induction generator(DFIG)converter system control and system optimization.The specific work is as follows:1)Study on the control strategy of DC-based DFIG systemDC-based DFIG system mostly adopts double-loop cascade control structure.Aiming at the complex parameter design and control delay caused by the structure,a single-loop MPC control strategy was proposed in this paper.The control scheme was improved from three aspects: 1.the system control structure was simplified,the difficulty of parameter design was reduced,and the system dynamic response capability was enhanced;2.The integral discretization method was adopted to solve the prediction problem of the second-order model,which reduced the prediction complexity;3.To protect DFIG system and prevent the phenomenon of over current,the current limit function on the stator and rotor side was taken as the nonlinear additional term of the cost function.Finally,the feasibility and effectiveness of the control strategy were verified by simulation and experiment.2)Study on the optimization design of DC-based DFIG systemIn order to reduce the gearbox ratio and improve the economic benefit of DFIG system,a two-level optimum strategy based on DC-based DFIG system was proposed in this paper.In view of the high system cost and loss caused by the gearbox system in DFIG system,based on the system cost model and taking system cost reduction as the target,this paper proposed a two-level optimization scheme adjusting system current and generator pole pairs.In order to reduce gearbox ratio and system cost,the pole pairs of the power generator and the current of generator system could be adjusted through the primary optimization.Finally,in this paper,the effectiveness of the two-level optimization strategy was verified by using Ansys software to design and simulate the motor model before and after optimization.