Spectrum Calculation Method Research Based On Double Fourier Series For PV Inverter With Multi-period SPWM And Chaotic SPWM

With the rapid development of the Photovoltaic power industry, harmonic and electromagnetic interference problem bring by PV inverter has also got more and more concern. Serious harmonic pollution and EMI not only affects the normal operation of the power equipment itself but also cause serious electromagnetic pollution to grid when the PV inverter operates in the grid-connecting mode. At present, shielding, filtering, well-grounded are the main measures to EMI suppression. Chaotic PWM has attracted lots of interests due to its effectiveness for EMI suppression in power converters, but the current researches focuses on the simulation and experimental verification, which lacks of theoretical analysis, especially spectrum quantitative analysis. Therefore, in this paper, chaotic SPWM is proposed to suppress EMI for PV inverter from the EMI produce source. What’s more, based on the research status of chaotic SPWM now, this paper proposed a spectrum calculation method for multi-period SPWM and chaotic SPWM based on double Fourier series.Firstly, this paper introduces the research background of PV inverter and its EMI problems, and gives the spectrum calculation for bipolar conventional SPWM by the traditional double Fourier series method, the further spectrum analysis shows that in switching frequency and its integer multiples have high harmonic peaks.Then the proof of the constant of total harmonics energy for conventional SPWM and multi-period SPWM is given. And on the basis of the mathematical modeling for multi-period SPWM output waveforms, a spectrum calculation method for multi-period SPWM is proposed, further, the contrast between spectrum calculation results and MATLAB simulation results for multi-period SPWM are given.On the basis of spectrum calculation and analysis for multi-period SPWM output waveforms, the calculation method is extended to the spectrum calculation for chaotic SPWM output waveforms. In order to research the spectrum effects of different chaotic mappings and different variation ranges of carrier periods, a spectrum comparison between the Tent and Chebyshev mappings is conducted, and form which results the effects is analyzed in the long term and the short term.Finally, on the basis of theoretical calculation and software simulation, a chaotic SPWM PV inverter experiment platform is designed in this paper. Then, the conventional SPWM and chaotic SPWM experiments are conducted, and, by the spectrum analysis of the output voltage and output current, the spectrum calculation method proposed in this paper is verified further.