Three Phase Four Legs Inverter Base On Repetitive Control And PI Double Close Loop Control

With the development of the society, the need for high power and highperformance inverter is increased widely. Traditional three phase three legsinverter can provide relative good performance. However it will be ineffectivewhen it is connected to non-linear unbalanced loads which are often used invital occasion such as military, bank, hospital and so on. In order to solve theproblem mentioned above, a novel design which combines three phase fourlegs inverter, repetitive controller and PI double loop controller is proposed inthis paper.Based on comparison of three phase four legs inverter control strategies,this paper introduces repetitive controller in three phase four legs inverter,which not only improves inverter performance under unbalance loads, but alsoenhances the periodical non-linear load disturbance rejective capability. PIdouble loop regulator based on synchronous frame is applied. The mathematicmodel of three phase four legs inverter is established in different coordinates.Paper accomplishes the decoupling of the three phase four legs inverter. Themechanism how it suppresses the unbalanced load disturbance is analyzed intwo views. The analysis, design and simulation of repetitive control and PIdouble loop regulator are discussed. The simulation results verified veracity oftheory analysis.The main circuit is composed of three phase four legs inverter. The controlcircuit consists of DSP TMSLF2407 and CPLD, which are programmed in Clanguage and assemble language. Experimental results proved the theoreticaland simulation analysis that repetitive control can lead to three phase four legsinverter to achieve better performance than conventional control.