| Title |
A Small Signal Modeling of Three-level Neutral-Point-Clamped Inverter and Neutral-Point Voltage Oscillation Reduction |
| Authors |
Ja-Hwi Cho ; Nam-Joon Ku ; Seok-Eon Joung ; Dong-Seok Hyun |
| DOI |
10.6113/TKPE/2014.19.5.407 |
| Keywords |
Grid connected inverter system; Small signal modeling; Neutral point current; Neutral point voltage |
| Abstract |
This study proposes a control design for the grid output current and for reducing the neutral-point voltage oscillation through the small-signal modeling of the three-phase grid connected with a three-level neutral-point-clamped (NPC) inverter with LCL filter. The three-level NPC inverter presents an inherent problem: the neutral-point voltage fluctuation caused by the neutral-point current flowing in or out from the neutral point. The small signal modeling consists of averaging, dq0 transformation, perturbing, and linearizing steps performed on a three-phase grid connected to a three-level NPC inverter with LCL filter. The proposed method controls both the grid output and neutral-point currents at every switching period and reduces the neutral-point voltage oscillation. The validity of the proposed method is verified through simulation and experiment. |