Study On The Hybrid Modulation Method Based On The SPWM Inverter

Due to the widely use of transducer, the power grid and the motor are harmed from its harmonic. The rectifier feeds back harmonic to the grid and the inverter outputs harmonic to motor at the same time. Consequently, restraining harmonic is concerned by inverters' manufacturer and user.The hybrid modulation method in the SPWM inverter is studied particularly in this paper. On the basis of the presentation of SPWM control technique and characteristic of the output harmonic from the inverter, the limited factors are summarized and the evaluating function is conceived to evaluate the output quality of inverter synthetically. In order to improve the effect of high frequency of SPWM, the characteristic of harmonic and how to calculate switch angles on SHE is analyzed, calculating formula of the switch angle is presented. The SHE characteristic on the over modulating and the switch frequency is concluded. Three optimize scheme on the high frequency of the SPWM is analyzed. The hybrid method is presented as SPWM for low frequency and SHE for high frequency, its model is set up. The program to calculate the switch angle and analyze the harmonic is designed. The effect of the hybrid method is verified by contrasting the SPWM and the SHE respectively. MATLAB is used to simulate variable frequency system which applies the hybrid method .The result verifies that the method is doable and valid. The hybrid method is value to the development of the inverter in this paper.