Research On Harmonic Suppression Method For 12 Pulse Rectifier

With the wide application of high-power rectifiers in electrochemical machining,renewable energy conversion and aerospace,the nonlinearity and time-varying of power electronic devices also bring serious harmonic pollution to the power grid.The multi-pulse rectification system can solve the above problems well,but the harmonic content in the grid is still high.In order to achieve better harmonic suppression,a 12-pulse rectifier with cascaded Buck-Boost converter is studied to suppress the grid-side current harmonics.This article starts from the conventional 12-pulse rectification system.According to the conversion relationship between the DC side and the AC side variable of the system,the Fourier expression of the grid side current and the DC side voltage of the system is derived.Based on the principle of DC side harmonic suppression,this paper discusses two DC side harmonic suppression techniques for DC side unified modulation and DC side voltage adjustable.In order to suppress the current harmonics on the DC side,the harmonic suppression mechanism of the DC side of the rectifier under ideal conditions is studied.At the same time,the influence of ESR on the current harmonic suppression of the rectifier circuit is analyzed,and the effectiveness of the optimal ESR for harmonic suppression is demonstrated.On the basis of the conventional 12-pulse rectification,a cascaded Buck-Boost converter is added to compensate the output current of the rectifier bridge,so that the output current waveform of the rectifier bridge is approximated to a standard triangular wave,which achieves the purpose of suppressing the harmonics on the grid side.At the same time,several working states of the cascaded Buck-Boost converter are analyzed to ensure that the system can still operate normally when the rectifier bridge output current is not continuous.Compared with other DC side harmonic suppression technologies,this system has the advantages of less floor space,low switching loss and high conversion efficiency.Compared with APF,the control strategy of this system is simpler.The simulation model was built in MATLAB/Simulink to simulate the system.The currents on the AC side of the cascaded Buck-Boost converter are compared to prove the effectiveness of the system on the AC side harmonic suppression.Finally,the hardware and software of the 12-pulse rectifier are designed.