Virtual Synchronous Generator Control And Harmonic Suppression Of Wind Farm Grid-connected Converter

With the rapid development of new energy distributed power generation represented by wind power,the proportion of grid-connected converters with power electronic devices as grid-connected interfaces in the grid has gradually increased,replacing some of the synchronous generators in the grid,which will impact on the stability of frequency and voltage.Moreover,a large number of non-linear loads and power electronic devices are connected to the power grid,causing serious harmonic pollution problems.In this paper,the power control,regulation frequency and voltage,harmonic suppression strategies of grid-connected converters in wind farms are studied,a multi-functional control strategy for grid-connected converters is analyzed.The completed work is as follows:Firstly,the basic principles of wind power generation are briefly analyzed,and the basic power control block diagram of the wind power grid-connected converter is given.then the factors affecting the frequency and voltage amplitude of the power grid are analyzed.By changing the power setting value of the wind power grid-connected converter,that is,adding inertia and damping active power to adjust the frequency,the voltage regulation is achieved by controlling the output reactive power,which can effectively allow the wind power grid-connected converter to participate in the voltage and frequency adjustment process.For the harmonic suppression part,compared with some harmonic extraction methods,a method based on recursive discrete Fourier transform(RDFT)for harmonic current suppression is selected in this paper.Then,designing the corresponding control parameters for each part in the control block diagram.Among them,the current inner loop adopts PI plus repeated control strategy to achieve no static error tracking of the current,and the phase-locked loop part adopts a dual second order generalized integrator-frequency locked loop(DSOGI-FLL)to obtain frequency information quickly and accurately.The outer power loop part is designed by combining droop control and corresponding grid code and criteria.The principle of RDFT is analyzed,which is chosen to extract the specified harmonics.Finally,the correctness of theoretical analysis and the effectiveness of control strategy are verified by MATLAB/Simulink and the 66 k VA experimental prototype.