| Power electronic technology is used to control the power by controlling power electronic devices. Modulation technology, as the pore of the control, deeply influences the quality of electric energy control. With the development of new energy, renewable energy grid generation has attracted more and more attention. Good PWM modulation technology play an important role to improve the quality of power grid inverter because the grid inverter control are realized by controlling the power electronic switching devices. Scholars still hope to develop new modulation strategy to further improve the working efficiency of inverters although there are more then ten kinds of modulation technology, which play an important role in industrial development. Wavelet modulation is a novel technology. Compared with other modulation technology, WM performances well in the quality of the output of inverter,for example good capability of anti-interference, lower switching power loss, lower harmonic distortion rate, higher fundamental voltage amplitude and simple to control.This paper first studied the WM inverter output voltage waveform, aimmed at getting the WM inverter voltage quality. Firstly, this paper analyzes the working principle of WM inverter briefly. Establishes the mathematical model of WM inverter and use fourier analysis to get the voltage harmonic spectrum and fundamental content. And then this study compares with the experimental results of WM,SPWM and SVPWM through Matlab simulation. And then a novel technology based on tracking duty ratio is proposed for WM inverter to reduce the low harmonic distortion because WM bring more total harmonic. The simulation results show that, compared with traditional modulation technology, this WM output less harmonic,improve the the frequency spectrum and reduce the harmonic near the switch frequency.This paper further studies the application of WM inverter in grid generation system.Firstly this paper analyzes the traditional current closed-loop control based on PI controller and direct power control system based on power hysteresis comparator. The 3-phase WM inverter mathematical model is put forward in d-q coordinate when the frequency is 50 Hz.Introducing the mathematical model in d-q coordinate to the grid inverter, this paper get the current closed-loop control system in grid WM inverter using PI controller. Then this paper analyzes the SVPWM switch table of direct power control system based on power hysteresis comparator and then raises the direct power control system based on WM.At last sets up the Matlab simulation platform and the experimental prototype based on TMS320F2812 to prove current closed-loop control and direct power control system through power hysteresis comparator based WM correctness. The results show that the grid inflows current harmonic has been significantly reduced including the harmonic near the switch frequency, which can reduce the electromagnetic interference of the system. The direct power control system show more stable power waveform and lower harmonic near the switch frequency compared with traditional control strategy. |
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