Study On Control Technology Of The Three-Phase Four-Leg Inverter

With the development of industry and technology, The user of electricity need the quality of the electricity better and better, they need the ability of higher and higher loading and more and more kinds of loading.As to three phase inverter, traditional three phase three legs inverter are widely used. But its three phase voltage outputs will be dissymmetrical when it supply to the three phase unbalanced loads.in allusion to this, a design which combines three phase four legs inverter, repetitive controller and PI double loop controller is proposed,in this article,.the scheme of control will be deeply studied.This article researches on the asheme of the voltage and currient closed-loop control for three-phase four-leg inverter,in order to meet the purpose of achiving three phase standard output voltage as well as the ability of adapting unbalanced loads.At the beginning,on the basis of studying closed loop control of voltage and current in the d,q and 0 aixs,adding negative sequence PI controller and repetitive controller into 0 axis in order to control negative sequence and zero sequence components of output voltages.realizing the control with no steady errors. Subsequently,In order to predigest the scheme of control,trying to control based on the abc frame with the outer PI controller paralleled with repetitive controller and inner proportion controller,this asheme is simpler, which can achieve the same effect as the first one , further more this scheme has preferably abilities of adapting non-linear loads as well as restraining the effect of dead time.Secondly, the simulation of system control and switch strategy validated consistency with theory analysis using MATLAB. The result match with the analyse. Finally, the experiments are completed under TMS320F2812 DSP made in TI company,programming with C language, the results is verified. Thedesign which combines repetitive controller and PI controller is proposed in this article can achieve symmetrical outputs of three phase voltage, which has the ability of adapting non-linear loads.