Neutral-Point Voltage Balance Control of Three-Level Converter Based on Selection Method of Dynamical Adjustment for Small Voltage Vector

The balance control of neutral-point voltage (NPV) is important in the three-level converter. In this paper, problem studied by taking VIENNA circuit as an example. deviation NPV essentially caused mismatch between charging and discharging time two series capacitors current flowing into or out DC side. unbalanced will lead to stress power switches may cause overvoltage damage both also increase total harmonic distortion (THD) components AC current. analyzing role effect a small-voltage vector on NPV, strategy based selection method dynamical adjustment for small proposed. By judging fluctuation different vectors are dynamically selected act adjust NPV. For verification, proposed compared with traditional zero-sequence injection (ZSV-J) through simulation experiment. Compared ZSV-J, THD decreased about 27.2%, efficiency increased 1.66%, speed 50%. Therefore, feasibility advantages verified.