The evolved capacitor commutated converter (ECCC), embedded with anti-parallel thyristors based dual-di-rectional full-bridge modules (APT-DFBMs), can effectively reduce commutation failure (CF) risks of line-commutated con-verter-based high voltage direct current (HVDC) and improve the dynamic responses of capacitor-commutated converter-based HVDC. This paper proposes an improved coordinated control strategy for ECCC with the following improvements: ① under normal operation state, series-connected capacitors can accelerate the commutation process, thereby reducing the overlap angle and increasing the successful commutation margin; ② under AC fault conditions, the ability of ECCC to mitigate the CF issue no longer relies on the fast fault detection, since the capacitors inside the APT-DFBMs can consistently contribute to the commutation process and further reduce the CF probability; ③ the inserted capacitors can output certain amount of reactive power, increase the power factor, and reduce the required reactive power compensation capacity. Firstly, the proposed coordinated control approach is presented in detail, and the extra commutation voltage to mitigate the CFs provided by the proposed control approach and an existing approach is compared. Secondly, the mechanism of the improved control approach to accelerate commutation process and improve the power factor is analyzed theoretically. Finally, the detailed electromagnetic transient (EMT) simulation in PSCAD/EMTDC is conducted to validate the effectiveness of the proposed coordinated control. The results show that the proposed approach can present a further substantial improvement for ECCC, especially enhancing the CF mitigation effect.

中文翻译：

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改进的CCC-HVDC系统协调控制方法，提高换相失败的缓解效果

演进的电容器换向转换器（ECCC）嵌入了基于反并联晶闸管的双方向全桥模块（APT-DFBM），可以有效降低基于线路换向转换器的高电压换向失败（CF）的风险直流电压（HVDC）并改善基于电容器换向的基于转换器的HVDC的动态响应。本文提出了一种改进的ECCC协调控制策略，并进行了以下改进：①在正常工作状态下，串联电容器可以加速换向过程，从而减小重叠角，增加成功的换向裕度；②在AC故障情况下，ECCC缓解CF问题的能力不再依赖于快速故障检测，因为APT-DFBM内部的电容器可以始终为换向过程做出贡献，并进一步降低CF概率；③插入的电容器可以输出一定量的无功功率，增加功率因数，降低所需的无功补偿能力。首先，详细介绍了所提出的协调控制方法，并比较了所提出的控制方法和现有方法所提供的减轻CFs的额外换向电压。其次，从理论上分析了改进控制方法加速换向过程，提高功率因数的机理。最后，在PSCAD / EMTDC中进行了详细的电磁瞬变（EMT）仿真，以验证所提出的协调控制的有效性。