This paper investigates the hybrid HVDC with cascaded multi‐infeed MMCs' basic control characteristic and designs the coordinates control strategy considering the DC voltage control and commutation failures of the LCC inverters. The complete basic UI curves of the hybrid HVDC are obtained, and the interaction mechanism of each converter is also clarified, which is in master‐slave control mode. Through the obtained basic characteristic, to reduce the commutation failures of the LCC inverter, the coordinated DC voltage control strategy with dynamic limiter is designed to enhance the AC voltage stability. And the coordinated DC voltage control method coped with the dynamic limiters is also designed. Based on the proposed method, the DC voltage can be stable and unbalanced active power can also be distributed reasonably by the DC voltage control strategy, while much more reactive power can simultaneously be released from VSC to support the stable operation of the LCC inverter. Such that the DC side operation and AC side voltage stability of the hybrid HVDC can both be improved. Finally, the simulations verify the theoretical analysis done in the paper.

中文翻译：

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考虑换向失败的混合直流HVDC与多馈MMC逆变器的协调DC电压控制策略

本文研究了具有级联多馈MMC的基本控制特性的混合HVDC，并考虑了LCC逆变器的直流电压控制和换相故障，设计了坐标控制策略。获得了混合高压直流输电的完整基本UI曲线，并且还阐明了每个转换器的交互机制，这是在主从控制模式下进行的。通过获得的基本特性，为减少LCC逆变器的换向故障，设计了带有动态限幅器的协调直流电压控制策略，以提高交流电压的稳定性。并设计了与动态限幅器相适应的协调直流电压控制方法。根据提出的方法，直流电压可以保持稳定，并且可以通过直流电压控制策略合理分配不平衡有功功率，同时可以从VSC释放更多无功功率以支持LCC逆变器的稳定运行。这样可以同时提高混合HVDC的DC侧操作和AC侧电压稳定性。最后，仿真验证了本文所做的理论分析。