The Vienna rectifier can produce three voltage levels, however only the connection to the neutral-point is fully controllable using the bidirectional switches. When the neutral-point voltage is not imposed in a phase-leg, the polarity of the pulses generated depends on the diode that is conducting in that phase-leg, which is defined by the current direction. As a result, the voltage pulses generated can go in the opposite direction to what is demanded by the controller, and the current becomes distorted. This can be mitigated by injecting a particular zero sequence so that the reference voltage is clamped to the neutral-point during the intervals, where the current of a phase-leg has the opposite sign than its reference voltage. However, the converter is at risk of entering into overmodulation when operating with high modulation indices. In this article, a hybrid modulation strategy is introduced where a calculated minimal amount of reactive current depending on the operating conditions is injected to avoid overmodulation. The reduction of reactive current required compared to the state-of-the-art solutions is up to 100% in certain operating conditions. With the proposed method, the Vienna rectifier can operate in a wide range of power factors without compromising the quality of the source currents. The concept is verified by simulation and in a 1-kW Vienna rectifier experimental setup.

中文翻译：

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维也纳整流器的混合调制策略


维也纳整流器可以产生三个电压电平，但是只有与中性点的连接可以使用双向开关完全控制。当相脚中未施加中性点电压时，生成的脉冲的极性取决于该相脚中导通的二极管，这由电流方向定义。结果，产生的电压脉冲可能与控制器要求的方向相反，并且电流变得失真。这可以通过注入特定的零序列来缓解，使得参考电压在间隔期间被钳位到中性点，其中相脚的电流具有与其参考电压相反的符号。然而，转换器在高调制指数下工作时存在进入过调制的风险。在本文中，介绍了一种混合调制策略，其中根据操作条件注入计算出的最小无功电流量，以避免过调制。与最先进的解决方案相比，在某些操作条件下，所需的无功电流减少高达 100%。通过所提出的方法，维也纳整流器可以在很宽的功率因数范围内运行，而不会影响源电流的质量。该概念通过仿真和 1 kW Vienna 整流器实验装置得到验证。