Research On State Feedback Control Strategy And PWM Modulation Method For The Three-phase Four-leg Inverter

The control strategy and PWM modulation method for the three-phase four-leg inverter operating in off-grid state as the interface circuit of distributed generation power system are studied aims to further improve its load adaptability in this paper.On the basis of the theory of the traditional voltage and current control loop and the three-dimensional space vector modulation(3DSVM),the existed problems is analyzed,and the feasibility that the state feedback control combining with the discontinuous 3DSVM(D3DSVM)strategy is discussed to optimize the control characteristic and transmission efficiency of the system.First of all,take the single-phase inverter as an example,the working principle of the state feedback control is discussed,the method of establishing state space model,the method of pole assignment and the basis of parameters selection are studied,and its adaptability and limitation of the load are analyzed.According to the adaptive problems of the nonlinear load,the state feedback control combines with the proportional resonant(PR)controller to increase the gain of system at the corresponding harmonic frequency point,and to improve the output power quality of the system under the nonlinear disturbance.By means of simulation and experiment,the feasibility and effectiveness of the compound control are discussed to extend to the three-phase four-leg inverter.Secondly,on the basis of no influence on the output power quality of the system and the state feedback control,a class of D3DSVM strategy is studied to reduce the energy transmission loss of system,and the specific implementation methods are discussed under the different expressions,such as the sector classification,the switch vector selection,the vector effect time calculation,the vector sequence model.Meanwhile,the total harmonic distortion of output voltage and the switching loss of the inverter have been carried on the theoretical and experimental analysis under different D3DSVM strategies.Finally,based on Matlab/Simulink simulation software and the above analysis,the system simulation and experimental platform of the infineon XE164 MCU are constructed,and each part is done by means of simulation and experiment.The results of simulation and experiment have been analyzed and compared with the theoretical analysis.Comparison and analysis of the simulation and experimental results are discussed,and it confirms that the theoretical analysis and experimental results are consistent.The output power quality of the three-phase four-leg inverter can satisfy the corresponding standard under the condition of linear,nonlinear,balanced and unbalanced loads respectively,which verifies that the state feedback control and D3DSVM strategy are right and feasibile.