Study On STATCOM Control Method Of Wind Farm Intermediate H Bridge

As the country attaches great importance to the development of new energy,domestic wind farms are also vigorously promoted.However,wind power has instability and randomness,so once the stable power grid merges with the power grid,it will become unstable.Therefore,in order to stabilize the voltage and frequency of the power system,it is necessary to install the null compensation device.Through data analysis and comparison,it is concluded that STATCOM has the highest priority among the current invalid compensation devices.The compensation device has high compensation level,easy to expand,suitable for different voltage levels,anti-interference ability and strong tracking ability,etc.It points out the direction for a new generation of ineffective compensation device.However,since the DC capacitors of the single bridge module of H bridge are independent of each other,the DC voltage of the whole device is unstable,which affects the quality of the output waveform and endangers the operation of the entire power system.Therefore,the balance control of DC side capacitance voltage is the key of the whole process.In this paper,the cascade H-bridge STATCOM device of wind power station is taken as the research object,and the following works are mainly implemented.First of all,the structure and principle of the whole device should be analyzed,based on the establishment of mathematical model and the current modulation strategy used to analyze the model.In this paper,we choose positive semi-loose mobile anatomy and unipolar mobile anatomy.Through the analysis of these two decryption structures and the comparison of their working principles,it is finally verified that under the same conditions,the single-pole wave mobile decryption has more obvious advantages.Secondly,the feedforward decoupling control strategy is analyzed according to the mathematical model of the device,and the advantage of the strategy is verified by the simulation model in Matlab.At the same time,the reasons for the DC side voltage imbalance were analyzed.Through theoretical analysis and the establishment of Fourier mathematical model,the factors affecting the DC side voltage imbalance were verified by building simulation in MATLAB from six aspects.At last,through the power equation of each bridge module list out what are the factors to influence various modules capacitor voltage,is controlled by three layers of control strategy for STATCOM dc voltage cascaded H bridge for stability control,create device power model,rely on the influence on the flow and P to study the cause of injecting zero sequence voltage and negative sequence current injection strategy,The correctness of the whole theory is proved by mathematical model and simulation.For the in-phase aspect,the use of single-pole frequency doubling will cause a time difference on the DC side of the single bridge of the whole device,which will affect the voltage difference on the DC side of each module.Therefore,this paper uses the carrier rotation method to solve this problem,but it cannot solve the energy consumption problem caused by different parameters.Therefore,this paper adjusts the control strategy of the modulated wave to solve this problem.Finally,the above theory is confirmed by simulation.At the same time,for the whole model to generate voltage twofold fluctuation,the control strategy of injecting threefold zero-sequence voltage is adopted to suppress it.Combined with the actual engineering background,the engineering parameters obtained by setting up the model in Matlab confirm that the correct control strategy of the whole model can greatly change the operation of the power system in the wind farm.