| Along with the rapid growth of industry and power electronic technology, power system has increasingly become an essential part in people’s lives. However, many power electronic devices in the power grid which are also the main source of harmonics, will cause severe harmonic pollution to the power system. Power harmonic interference results in the abnormal conditions of the electric equipment, the aging of running transmission line damaging, the misoperation of the relay protection and the poor power supply quality. Therefore, we must take action to solve such problems as the inhibition and disabused of the harmonic. High-quality elimination of harmonic pollution is imminent; the key to suppress the harmonic power grid is to detect what are the components of harmonic in the power grid. To remove the harmonics, we can use the method of removing specific harmonic, typical of PWM technology, which is characterized by removing a certain number of harmonics.Based on the control of a variety of PWM Inverter output voltage harmonic analysis, the essay has furthered and discussed the specific method of harmonic elimination. In SHEPWM, we can know the switching angles through nonlinear SHEPWM FFT conversion. However, without the transforming time and frequency localization effect of FM, the SHEPWM nonlinear solution of the model is not the only one. Since wavelet transform can realize both time and frequency orientation in signal processing, wavelet analysis has to do with every aspect of our life, including signal processing, numerical analysis, seismic survey and etc. Meanwhile, it also adopts wavelet technology in the Inverter modulation.In this paper, the major contents are listed below:(1) Using the nonlinear model of known three-phase unipolar and bipolar SHEPWM Inverter and taking Wu method, to calculate the switching angles of three-phase unipolar and bipolar Inverter in SHEPWM for K=3 and K=4, to prove that SHEPWM is not the unique.(2) Through the research of harmonic detection methods for establishing the harmonic signal model in the power system, taking the MATLAB software to make the simulation experiment. The results of the simulation experiment show that only taking the harmonic current Uni-wavelet detection mode, there will be intermittent and uneven defects.(3) In order to avoid the disadvantages of Uni-wavelet in harmonic detection, harmonic detection method of multiplicative is continually studied; as well first setting up the system of harmonic signal model in power system, using the MATLAB software to do the simulation experiment, the results at last show that the accuracy of the harmonic detection of power system harmonic detection of Multi-wavelet and the removal effect are much better than that of Uni-wavelet. The filtering effect is also better than that of Uni-wavelet. But the both still can’t clearly detect a harmonic material, and also can’t achieve the required effects. For the sake of the task requirements, we go on studying the FFT transform method, and finally combine the method of Multi-wavelet with FFT transform named Multi-wavelet and FFT method of harmonic detection, and then apply the MATLAB software simulation, finding that this way can effectively show a harmonic material and can meet the subject of requirements.(4) Selecting wavelet modulation PWM Inverter technology to do experiments, applying MATLAB software simulation, showing it has a relatively little harmonic distortion rate.(5) Compared with the harmonic distortion of single-phase and three-phase Inverter output voltage waveform and wavelet modulation of single-phase and three-phase unipolar SHEPWM rate, we may draw conclusions that the characteristics of Inverter wavelet modulation are not complicated and easy to implement algorithm; harmonic content is relatively little and the shape of the wave is the unique.
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