Research On Harmonic Suppression Method In AC/DC Hybrid Micro Grid

Because of the nonlinear load and power electronic device produce a lot of harmonics in the AC/DC hybrid micro grid,it affects the safe,reliable and stable operation of the hybrid micro grid.Eliminating harmonics in AC/DC hybrid micro grid is one of the most important topics in the electric field.And how to seek effective and feasible harmonic suppression methods is the issue of research.Therefore,this thesis studies the harmonic suppression methods in hybrid micro grid,and it has theoretical and practical value to improve the quality of power in the micro grid.According to the functional characteristics of various components in AC/DC hybrid micro grid,the reason for harmonic generation and the number of harmonics generated by each component unit are given.Especially the harmonic problem in the process of energy exchange between DC bus and AC bus is analyzed.On this basis,the Bristol relative gain matrix is adopted to further analyze the harmonic interaction effect in hybrid micro grid,and the contents of all harmonics on AC bus are given.Then,the harmonic peak value on the AC bus in the micro grid is analyzed from the influence of the harmonic propagation process.In order to eliminate the harmonics caused by the interaction,this thesis proposes a coordinated control strategy of the filter and the inverter basing on the characteristics of hybrid micro grid.Comparing the dominant harmonics detected in AC bus with the dominant harmonic generation produced by each component.According to the comparison result,if the dominant harmonic’s frequency in AC bus is closed to some units’,the dominant harmonic in AC bus can be eliminated by controlling the corresponding inverter.If not,the APF control method is used to eliminate the harmonics in hybrid micro grid.In order to ensure the accuracy of dominant harmonics detection results,considering the harmonic characteristics of hybrid micro grid,the ip-iq detection method is adopted and simulation circuit is built,Through the FFT analysis of the output waveform,it is verified that the detection method can meet the requirements of the harmonic detection accuracy of the hybrid micro grid.In order to verify the rationality of control strategy proposed in this thesis,an APF model and inverter model with LCL are established,and then the proposed control strategy is simulated on the basis of the model.The simulation results show that the method proposed in this thesis can eliminate the harmonics effectively in the hybrid micro grid.