A General Analytical Calculation of DC-Link Current and Voltage Ripple for 3L-NPC-Voltage Source Inverter

Abstract

In this paper, a general analytical calculation of dc-link current and voltage ripple is presented for three-level three-phase neutral-point-clamped voltage source inverter (3L-NPC-VSI). Based on the analysis of average dc-link current of the upper and lower switches, the low-frequency oscillation of the neutral point (NP) voltage can be eliminated by injecting a zero sequence component. Moreover, the general expression of the root-mean-square (RMS) dc-link current is derived. In addition, the dc-link average current, rms current, and voltage ripple of the 3L-NPC-VSI are compared with those of the 2L-VSI, and it shows similar dc-link characteristics. Simulation results are shown to verify the theoretical analysis. The results can be extended to any PDPWM with NP voltage control strategy.