Design Of Current Controller Of Grid-connected Voltage Source Inverter Based On Neutral-point-clamped Three-level VSI

The traditional energy and air pollution are more urgent in our life, improving the structure of renewable energy and enhancing the power quality have been the Strategic measures of our state. Recent years, multilevel inverter has been widely used in power electronics, there is more and more study on its control strategies and the topology of its power circuit. In comparison to two-level inverter, it has some advantages as following: Mutillevel inverter reduce the di/dt and the dv/dt on switches; At a same frequency, a multilevel inverter's output has a better waveform than that of a two-level one; Mutillevel inverter can have higher voltage with the increasing of the number of its levels. Because of the advantages of three-level inerter, people want to change the traditional Grid-Connected VSI into three-level, to improve the efficiency, capability and characteristic of grid-connection of Grid-Connected VSI.Based the intrinsic relationship between SVPWMs for two-level inverters and three-level inverters, a novel SVPWM control algorithm is proposed for three-level in this paper. The dwell time of voltage vector for three-level inverter can be acquired from dwell time of voltage vector for two-level inverter by using a linear transition. This paper discussed oscillation of neutral point (NP) voltage of NPC three-level inverters under space vector pulse width modulation (SVPWM) control, bring out a new SVPWM strategy to control neutral point (NP) voltage.At last, the proposed algorithm is verified on prototype in laboratory based three-level Grid-Connected VSI with DSP and MOSFET. The simulation and experimental results show that the algorithm is verified and it can be extended more level inverter easily.