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This paper investigates the operation of the back-to-back neutral point clamped (BTBNPC) converters when the ac voltages on both ends are asynchronous. The zero-sequence injection (ZSI) technique has been used to extend the linear modulation range of the pulsewidth modulation operation. This paper investigates the ZSI of the BTBNPC to maximize the dc-bus voltage utilization while the ac voltages of both ends have different magnitudes and phases. This study further explores the reactive current injection to reduce the risk of overmodulation when grid voltages surge. The combination of these techniques can extend the operation range of the BTBNPC over varying ac voltages of both ends with the available dc-bus voltage. In addition, the issue of the neutral-point balance is also taken into consideration. Laboratory test results are provided to verify the proposed technique. [ABSTRACT FROM AUTHOR]

This article investigates the effect of the leakage current on the back-to-back neutral-point clamped (BTBNPC) converter. The analysis indicates the leakage current of the BTBNPC converter is closely associated with the difference of the common-mode voltage (CMV) between the rectifier and the inverter, so an equivalent model for the leakage current is derived to explore their relationship. Subsequently, an edge-aligned pulsewidth modulation (EAPWM) technique is presented to eliminate the CMV of the BTBNPC converter. This article also shows how to coordinate the rectifier and the inverter to develop the full potential of this circuit. Laboratory test results will verify the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]