Research on Vector Asymmetric Dead-time Compensation Modulation Strategy of Three-level Inverter Based on Narrow Pulse Elimination

For the problem of load current distortion caused by the dead time effect and narrow pulse in the Three Level Neutral Point Clamped Inverter, the asymmetry of the time distribution of the same vector action during a switching period after the dead time compensation was discussed. The processing method of vector sequence in the case of non-extremely narrow pulse and extremely narrow pulse was introduced in detail. The paper studied the contradiction of a switching cycle that simultaneously implements dead time compensation and narrow pulse elimination, and proposed a modulation strategy that performs asymmetric vector action time dead time compensation and narrow pulse elimination partition execution. If the resultant vector was within a specific area of the dead time compensation, the system performs dead time compensation of the asymmetric vector action time according to the direction of the AC side current. The vector area containing narrow pulses was processed by the judgment and elimination methods of non-extreme narrow pulses and extreme narrow pulses in this paper. The control system composed of DSP and FPGA was used to experiment the modulation method. The results show that the modulation method in this paper can effectively reduce the total harmonic distortion (THD) value of the system and solve the problem of narrow pulses. © 2021 Chin. Soc. for Elec. Eng.