Research Of Three-phase Current-source PWM Grid-Connected Inverters

In recent years,many concerns have been raised over the fossil fuel-electricity generation,since it pollutes our environment and depletes the energy supply.On the other hand,alternative energy sources,such as solar energy and fuel cells,gain a lot of attention because they are friendly to the environment and flexible for installation..However,these types of sources supply dc power while the present power grid accepts ac power;therefore grid-connected inverters are necessary for dc-ac conversion.In order to utilize the current infrastructure of the grid for power transmission and distribution,grid-connected dc-to-ac inverters are needed. Direct-current side voltage of the commonl voltage inverters must be higher than the network voltage peak value,and maintains the permanent value is invariable,among needs to use the voltage -rise link,but the current mode inverters has the voltage-rise characteristic itself,can realize the voltage to start from zero to adjust.In this paper, Three-Phase current-source PWM Grid-Connected inverters have been deeply studied in theory and practice.In the beginning,the mathematical model of three-phase current-source PWM Grid-Connected inverters has been founded in three-phase stationary coordinate from low frequency and high frequency.They establish theoretical foundation for the deeper research on three-phase current-source PWM Grid-Connected inverters.The dissertation analyzes SPWM modulation strategy of three-phase current-source PWM Grid-Connected inverters;it introduces tri-logical switch function of current-source PWM Grid-Connected inverters that comes from bi-logical signal of voltage-source PWM inverters.It researches the tri-logical signal's generation and the switches' operating mode of three-phase current-source PWM Grid-Connected inverters,and it decides the zero-state selection from switching combination according to the minimum switch rule.This paper also researches the control strategy;it introduces particularly the direct current control method of three-phase current-source PWM Grid-Connected inverters.Deduced the formula of inductance in DC sideIn theoretical analysis's foundation,carried on the simulation to the three-phase current-source PWM Grid-Connected inverters,the simulation obtained the very good expectation effect,had the very good guiding sense to the experimental verification. This article has also built a set of test installation,and has carded on the open-loop and the closed loop experiment,the simulation and the experimental result indicated identically the three-phase current-source PWM Grid-Connected inverters can not only make output current are sinusoidal but also achieve unity power factor.The research of the paper is supported by National Science Foundation.(No. 50707030)...