The Research Of Microgrid Modeling And Harmonic Analysis Methods By Using Wavelet Transform And HHT

Micro-grid is a new structure for power-grid in order to increasing electricity demand, it is composed of distributed power supply, control device, such as load, distributed power supply and distribution network together. In recent years, with the rapid development of power electronic technology,Micro-grid in the process of using large number of nonlinear loads and inverter, making power quality deterioration, affect the micro Micro-grid.Paper first analyzes the working principle of Micro-grid, to the micro power: photovoltaic cells and wind turbine as the main research object, carries on the modeling and simulation. Micro-grid method is adopted for the control of grid harmonic detection of PQ control.In view of the traditional Micro-grid harmonic detection methods:fast Fourier transform (FFT) and wavelet analysis, Hilbert-huang transform (HHT) is analyzed and simulated, founding that the harmonic detection method limitations exist in different extent.Because of the complexity of the Micro-grid signals and the stability of designed based on TMS320F2812 processor Micro-grid current harmonic acquisition system, and the current sensor and A/D conversion chip model selection, and design the current signal adjusting circuit and the software process.Finally the paper proposes a harmonic signal to make use of wavelet transform and HHT secondary decomposition method of improvement. This method firstly, the wavelet transform is used in mallat decomposition method to Micro-grid current signal signal decomposition,decomposing the signal after HHT the empirical mode decomposition (EMD), get a series of empirical mode function components (IMF); Then each IMF component was isolated in fundamental component and harmonic component; Using the Hilbert transform to get the weight of the amplitude and frequency. Micro-grid model is established, using the traditional detection method and the method of grid current harmonic detection. Comparing the simulation results, and verified the method reduced modal aliasing phenomenon, high precision and small errors are accordance with the requirements of the harmonic detection of Micro-grid.