Research On Power And Signal Synchronous Transmission Strategy For Three-Phase Four-Leg Inverter

Under the call of the era of striving to achieve the "carbon peaking and carbon neutrality goals",the research on distributed generation and micro grid has far-reaching practical significance.The three-phase four leg inverter is an important type of interface converter for constructing DC microgrids,which has the ability to carry unbalanced loads.In addition to energy exchange,the DC microgrid also needs to achieve information transmission between different nodes.This thesis focuses on the threephase four leg inverter and studies power and signal synchronous transmission strategy.Firstly,a three-phase four leg topology is introduced,and mathematical models in the abc stationary coordinate system and dq synchronous rotating coordinate system are derived,providing a theoretical basis for subsequent control strategies;We studied the three-dimensional SVPWM modulation in the abc coordinate system,with the aim of synthesizing a space vector.We analyzed the selection,action time,and action sequence of the switch vector,and provided an example waveform.Then,the sequence circuit of the three-phase four leg inverter was analyzed and a sequential control strategy was designed;By coordinate transformation,the positive and negative zero sequence components are transformed into three sets of direct flow,and PI control is carried out separately in the rotating coordinate system.In the control of a single sequence,in order to achieve separate control of the dq axis,a feedforward decoupling control strategy is proposed;After completing the device and controller parameter design,simulation and experiments were conducted to prove that the control strategy designed in this thesis can ensure the symmetry of output voltage under unbalanced loads.Finally,for the three-phase four leg inverter,it is proposed to superimpose a 2FSK(Binary Frequency Shift Keying)signal on the DC given by sequence voltage control.Determine the frequency range and injection point of the 2FSK signal through analysis of signal gain and loop stability at different injection points.Two signal demodulation methods based on digital filters and short time Fourier analysis were designed.By utilizing chaotic sequences for symbol modulation and frequency hopping communication,signal encryption transmission is achieved.BP neural network was trained,feature values were selected,and signal symbol classification was achieved in this thesis.The simulation and experimental results indicate that the designed energy and signal synchronous transmission strategy is feasible.There are 87 figures,9 tables and 91 references in this thesis.