A simple zero-sequence voltage injection method to balance the neutral-point potential for three-level NPC inverters

The neutral-point (NP) potential balance should be maintained during the three-level neural-point-clamped (NPC) inverter operating. Zero-sequence voltage injection methods based on carrier-based pulse width modulation (PWM) have been proven to be effective in controlling the NP potential. This paper proposes a simple algorithm of calculating the zero-sequence voltage. Compared with conventional methods, the proposed algorithm simplifies the computational process of the zero-sequence voltage and saves more digital signal processor (DSP) computing resource without sacrificing accuracy. Discrete simulation results are shown in MATLAB/SIMULINK environment. A 3 kW three-level grid-tied inerter has been built to validate the effectiveness of the proposed algorithm experimentally.