Analysis And Control Of Wind Power Grid Integration Based On A Permanent Magnet Synchronous Generator

Nowadays,with the rapid development of economy and technology,demand for electric power increases sharply.In addition,energy shortage and environmental problems become the focus of attention today.All this has prompted wind power,photovoltaic and other renewable energy generation to play an increasingly important role in the development of society.Wind power generation has attracted much attention because of its efficient application in renewable energy.The direct-drive permanent magnet synchronous generator(PMSG)adopts direct drive motor and full capacity grid-connected power generation.Compared with the double-fed induction generator(DFIG)system,the efficiency and operating reliability of the power generation system are greatly improved,and it is widely used in the field of large-scale wind power generation.In order to meet the power quality requirements of the new smart grid,it is required that the wind power unit can maintain grid-connected operation under a certain range of grid-voltage fluctuation and side-power fluctuation.This must exert control over the grid-side inverter of the wind power system.Therefore,it is of great practical significance to further study the control strategy of the wind power system based on direct-drive PMSG and improve its fault ride-through ability.In this thesis,the mathematical model of the PMSG wind power system was established in the three-phase stationary coordinate system and the two-phase synchronous rotating coordinate system.It mainly included the basic structure of the PMSG,the voltage directional vector control strategy of the grid-connected inverter of the wind power system during normal operation,and the two-level space vector pulse width modulation(SVPWM).In addition,based on the law of energy conservation,the transient characteristics of DC bus voltage in a wind power system based on directdrive PMSG was analyzed under the power balance and unbalance conditions.In view of the shortcomings of traditional PI control,such as slow response speed,poor disturbance rejection,prone to overshoot,and complex crossover decoupling design,the current loop and voltage loop were respectively improved in this thesis.In the current loop,the traditional PI controller was replaced by linear active disturbance rejection control with correction link(LADRC-C),and its stability,convergence and disturbance rejection were analyzed in the frequency domain.In the voltage loop,a fuzzy adaptive controller was introduced to make the controller adaptively adjust the coefficients in the linear feedback rate link during the operation of the system,improved the transient process of the system,and realized automatic optimization of parameters in complex working conditions.Furthermore,the integration link in the fuzzy adaptive controller causes the system to produce sluggish response,easy to shock and control quantity saturation,the differential link cannot be used because of noise signal,and the input cost of the fuzzy adaptive controller is too high.In this thesis,the linear extended state observer(LESO)was introduced into the fuzzy adaptive PI controller,and some model information of wind power system was integrated into LESO.On the one hand,the negative effect of integration link was avoided and differential link can be applied to practical system.On the other hand,it reduced the requirement of sampling accuracy of fuzzy adaptive controller and the operation burden of the arithmetic unit.Finally,the fault ride-through capability of the wind power system with LADRC-C and the fuzzy control strategy with linear extended state observer(FLS-LESO)was studied on the MATLAB/Simulink digital simulation test platform under the conditions of grid voltage balance sag,unbalanced sag,sudden loading on the side of the machine and load shedding.The effectiveness and feasibility of the proposed control strategy were verified by the 3.6MW power unit full wind field simulation experiment platform.