Design Of Three-level T-type Grid-connected Inverter System

With the energy and environment issues increasingly restricting the development of human society, and the regenerable energy developping, grid-connected inverter efficiency and its power quality becomes more important. Pulse width modulation has direct impact on these two indices.Based on the three level T-Type grid-connected inverter, this paper analysed and compared mainly two different PWM scheme of the device loss and inverter bridge efficiency. Discontinuous pulse width modulation includes DPWMO, DPWM1, DPWM2and DPWM3. Considering the operation condition of the power factor is1, DPWM1can reduce swithcing loss most and achieve the highest efficiency.Based on three-Phase three-wire topology, the grid-connect current THD was calculated. DPWM1scheme was choosed for calculating the grid-connected current THD to be compared with SVM. It found out that SVM makes the lower THD than DPWM1, but after considering dead-time effect, DPWM1makes the lower THD than SVM.Results were validated by experiment on10kW T-type three-level Inverter.