Research On The Application Of Controllably Inductive Filtering Technology In Wind Power Grid Connection

A large number of power electronic devices such as converters are used in wind farms,which cause serious harmonic pollution and power quality problems such as low-power factors in the wind power system due to their nonlinearity.Therefore,it is of great significance to study new filtering schemes for harmonic control and reactive power compensation of wind power.Therefore,this paper proposes a new type of wind power grid connected system based on inductive regulation and filtering technology and real-time tracking compensation of harmonic and reactive power demand by using control.The related research is carried out on the basic theory of the new type of wind power system,impedance matching of grid connected transformer,design of inductive regulation and filtering branch and comprehensive control strategy.The research work of this paper is mainly reflected in the following aspects:1)The harmonic damping performance and reactive power compensation principle of a new type of wind power system with inductive control filter are revealed.First,the simplified three-phase equivalent circuit model of the system is established,and the basic mathematical model with the grid connected transformer as the core is obtained.Then,the mathematical expression of the three-phase harmonic current coupling network side current of the system is derived.By comparing the filtering characteristics of different harmonic suppression schemes,the necessary conditions for the system to carry out the inductive control filtering and its unique advantages in harmonic damping are revealed.Secondly,the structure of transformer winding and the calculation method of filter parameters are introduced,and the zero impedance control strategy is designed to coordinate the control between the tuning device and the inverter,so as to improve the frequency selection characteristics of the tuning branch while meeting the requirements of system impedance matching;finally,the reactive power compensation control principle under the inverter steady-state model is introduced to improve the power factor of the system network side.2)The resonance damping and filtering characteristics of the new scheme are analyzed.The harmonic amplification principle of the system is analyzed,the harmonic damping control based on the frequency division detection algorithm is proposed,the single-phase harmonic equivalent model of the system is established,the equation reflecting the harmonic power of the grid side under the premise of three-phase symmetry of the system is derived,and the ability of the wind power system to suppress the harmonic series parallel resonance is analyzed.In order to analyze the effectiveness of the inductive control filtering scheme in improving the current distortion of the grid side of the wind power system,an evaluation system based on the filtering rate and damping rate is established to evaluate the harmonic damping capacity of the system.The simulation results show that the new filtering scheme can effectively prevent harmonic amplification and meet the requirements of the system for filtering effect.3)The wind power system with inductive regulation and filtering scheme is simulated and verified.In order to verify the effect of the theory proposed in this paper,a simulation model is built in Matlab / Simulink.The influence of the harmonic damping control and reactive power control algorithm on the system performance is discussed.The harmonic suppression effect of the wind power system under different working conditions is compared and analyzed.The simulation results show that the scheme has a high level in harmonic damping,resonance prevention and reactive power tracking compensation.In this paper,the main circuit topology,harmonic mathematical model,harmonic two-way suppression characteristics and supporting multi-objective integrated virtual impedance control strategy of the new wind power grid connected system are studied,and a set of basic theoretical system of wind power grid connected system,which is characterized by virtual impedance control to improve power quality,is preliminarily constructed,which lays a foundation for further research and application in other fields.