Aiming at the issue of zero-sequence current (ZSC) in the dual-inverter fed open-end winding transformer (OEWT-DI) based photovoltaic (PV) grid-tied system with common DC bus, a carrier-based pulse width modulation (CBPWM) strategy with steerable zero-sequence is proposed. The modulation wave of the dual-inverter is decomposed into two modulation waves with same amplitude and 120 • phase difference, and each of the modulation waves is modified through adding steerable zero-sequence component.

more »

... e zero-sequence component is regulated by the ZSC control loop based on a quasi-proportional resonant regulator, which is designed to suppress the ZSC caused by the dead-time effect and other nonlinear factors. Meanwhile, the effective modulation range is also analyzed. The proposed strategy is an alternative approach to the conventional zero-sequence steerable phase shift based space vector pulse width modulation (SVPWM) strategy, but has the advantage of easy implementing and low computation cost. With the proposed strategy, both the high-frequency and low-frequency ZSC in the system can be effectively suppressed. Effectiveness of the proposed strategy is validated by experimental results on a 30-kW OEWT-DI experimental platform. INDEX TERMS Dual-inverter, open-end winding transformer, zero-sequence current, carrier-based pulse width modulation (CBPWM). This work is licensed under a Creative Commons Attribution 4.0 License. For more information, see https://creativecommons.org/licenses/by/4.0/ VOLUME 8, 2020