Analysis And Suppression Of Input And Output Harmonics Of Two-stage Matrix Converter

As a new type of "green" power converter,the two-stage matrix converter not only has the advantages of traditional direct matrix converters with bidirectional energy flow,good input-output waveform characteristics,controllable input power factor,etc.,but also due to its special structure It also has the advantages of simple clamping circuit,zero-current commutation of the rectification stage,and one rectification stage connected to multiple inverter stages through a DC bus at the same time.However,due to factors such as the switching characteristics of power electronic devices,it will bring large harmonics to the input and output waveforms,which will cause adverse effects such as electromagnetic interference and noise.Therefore,this thesis analyzes the harmonics of the input current and output voltage of the two-stage matrix converter,and proposes measures to suppress the harmonics.Because there is no large-capacity energy storage element in the DC bus of the two-stage matrix converter,the current on the load side directly affects the input current on the grid side.When the DC bus is connected to two inverters at the same time,the harmonic analysis of the input current waveform will be It will be more complicated.Based on the concept of pulse center of gravity and Fourier integral transform,the formula of the input current harmonic content of the dual-stage matrix converter dual-inverter-stage system is derived through mathematical derivation.And by analyzing the influence of the different overlapping degree of the two inverter-level zero vectors in a control period on the input current harmonic content,the law of the low-order harmonic content of the input current with the distribution position of the pulse in a control period is obtained,and An improved modulation strategy is proposed to suppress the input current harmonics.Because there is no energy storage element in the DC link of the two-stage matrix converter,the DC bus voltage fluctuates greatly,which easily affects the output voltage waveform.The traditional space vector pulse width modulation strategy uses the average value of the DC bus voltage in the inverter stage modulation.This will cause an error when calculating the modulation degree of the inverter stage,which will cause a deviation between the output voltage and the reference voltage.In view of the above problems,a single-cycle segmented space vector pulse-width modulation strategy for the inverter stage is proposed.According to the instantaneous value of the DC bus voltage at different times,the inverter stage output voltage is segmentally modulated in a control cycle to make the output The voltage is closer to the reference value.In this dissertation,the proposed improved modulation strategy is reproduced in simulation software,and a two-stage matrix converter dual inverter stage system is built,and the proposed improved modulation strategy is experimentally verified.Simulation and experimental results show that the proposed improved modulation strategy can suppress the harmonics of input current and output voltage respectively.