Research On Frequency And Voltage Control Strategy Of Doubly Fed Wind Power Grid-connected Units Considering Source-load Fluctuation

With the development of new energy sources,the proportion of wind power generation in the power system has increased,but it also poses challenges to the operation of the power system.Due to the instability and variability of wind energy in wind power generation,a series of adverse effects such as frequency instability and voltage fluctuation.The main research contents of this thesis are as follows:Firstly,the voltage and frequency control strategies based on synchronous generators are studied.As a theoretical support for the control of doubly-fed wind turbines,the voltage and frequency control models suitable for doubly-fed wind turbines are discussed.Secondly,due to the current maximum power tracking control strategy commonly used by doubly-fed fans and traditional pitch,overspeed load shedding and DC bus parallel supercapacitors for short-term frequency adjustment,each has its own shortcomings,and proposed based on variable power point tracking and supercapacitor energy storage.The coordinated frequency control strategy of the doubly-fed wind turbines is fully combined with the advantages of the above control strategies to make up for its shortcomings,to achieve the effect of one frequency adjustment of the system without losing the power generation efficiency of the wind turbine.Capacity and power generation benefits,economic advantages are significant,which provides a new application idea for the energy storage device in the context of increasing penetration rate of new energy units,and provides a theoretical basis for the new method of wind turbine participation in frequency modulation.Finally,considering that the doubly-fed wind turbine can achieve active and reactive decoupling control,it provides a corresponding technical basis for the voltage control of the wind turbine.Moreover,although the doubly-fed wind turbine is operating in the maximum power tracking mode,the wind speed does not reach the rated wind speed,so the active power does not reach the rated value,so that the fan can leave a part of the reactive spare capacity for participating in the system.Voltage regulation,therefore,an active frequency and reactive voltage coordinated control strategy suitable for doubly-fed wind turbines in the source-slave random fluctuation scenario is proposed.Under the voltage and frequency coordinated control,the fan output active reactive power can follow the system.Frequency and voltage fluctuations produce responses,and voltage-frequency coordinated control strategies can adequately suppress voltage and frequency fluctuations under random fluctuations in source and load.