| National energy shortages and environmental degradation affect people's lives and hinder social development.Wind energy,as one of clean energy,has developed rapidly in the world's new renewable energy sequence.Various high-efficiency and R&D institutions' research on control technologies for wind turbines and grid-connected inverters has promoted the development and utilization of wind energy in China.Under this background,this paper focuses on the maximum wind energy tracking of variable-speed constant-frequency doubly-fed wind power generation systems.The main research of VSCF and energy two-way flow technology and inverter grid-connected control technology is as follows:Briefly analyze the development direction and basic concepts of wind power generation technology and the theoretical basis of doubly-fed wind power generation system.Based on the results of current scientific research,a mathematical model of a doubly-fed machine in a two-phase synchronous rotating coordinate system was established.Based on this model,two conventional vector control techniques under constant voltage conditions of the grid were analyzed.Based on the control objectives of the rotor-side and grid-side converters,a mathematical model of the converter was established.According to the operating status of the VSCF wind power system in four different regions,the accurate calculation of the reference value of the active power is given,which is combined with the system block diagram.Finally,the rotor-side converter control system was verified by simulation.Doubly-fed generators can respond well to changes in wind speed,adjust the speed of the generator in time,and make it work at optimal speed.When the doubly-fed generator is switched in different states,it can be seen from the current waveform output from the rotor side that the rotor-side converter well realizes bidirectional flow of energy and ensures frequency stability.According to the working principle and mathematical model of the grid-side converter,a feed-forward decoupled PQ control and grid-connected year inverter based on dq transformation is proposed.When the wind power is connected to the grid,the phase and frequency information is obtained from the power grid through the software phase lock technology(PLL)and passed to the PQ controller.The power P and Q of the inverter output are obtained through the PQ controller and calculated through the power calculation.Reference values of the current inner loop,active and reactive reference values are set according to the output power of the doubly fed motor.At this moment,the output current of the inverter is decomposed in the above-mentioned rotating coordinate system to obtain two current components,and then the instantaneous expressions of active and reactive power are obtained,so that the output power of the grid-connected inverter meets the power grid demand.Finally,a simulation model for doubly-fed wind generators and grid-connected inverters was established in MATLAB/Simulink environment.The simulation results proved that the control technology adopted for wind turbines can meet the operational requirements of doubly-fed machines,and the grid voltage The static and dynamic performance of the system is good under constant conditions.The control technology used for the grid-connected inverter can be constant power output,and the voltage and current waveforms output by the inverter meet the grid connection requirements.It verifies the correctness and scientificity of the control technology used,and it has a certain role in promoting the development of wind power in China. |
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