交直流混合系统的序网络及其在CDSM-MMC直流侧短路对交流侧影响分析中的应用

Sequence Component Networks in Hybrid AC/DC Power Systems and Its Application in Analysis on Influence of CDSM-MMC DC-Side Short Fault on AC Side

在交直流混联电网中,直流（交流）侧故障会对交流（直流）侧电气量产生影响,但目前还缺乏一种具备较强普适性的能定量分析这种影响的方法。为此,首先在分析交、直流电气量之间映射关系的基础上,提出了交直流混合系统序分量网络模型及各序网存在的条件。其中,混合系统的＂正序网络＂反映了交流电气量正序分量与直流系统中直流分量的映射关系;＂负序网络＂反映了交流电气量负序分量与直流系统中二次谐波分量的映射关系;＂零序网络＂反映了交流电气量零序分量与直流系统中工频分量的映射关系。其次,以光伏直流接入系统为例,利用其序分量网络模型分析了直流短路后交流侧的电气特征。最后,在光伏直流接入系统的PSCAD/EMTDC模型中,验证了混合系统序分量网络模型的正确性以及直流故障后的交流电气特征,并分析了换流站接地方式对序分量网络及故障特征的影响。

In hybrid AC/DC power networks, DC-side（AC-side） faults may affect AC-side（DC-side） electrical quantities. Nevertheless, there are still few quantitative analytical approaches with adaptability to reflect the influence. Therefore, based on analysis of mapping relation between AC and DC quantities, the concept and existing conditions of sequence component network of hybrid AC/DC systems were proposed. Among them, positive-sequence network showed mapping relation between conventional positive-sequence component in AC-side and DC component in DC-side; negative-sequence network reflected mapping relation between conventional negative-sequence component in AC-side and the 2 nd harmonics in DC-side. Based on mapping relation between conventional zero-sequence component in AC-side and power-frequency component in DC-side, zero-sequence network was established. Subsequently, taking a DC-type grid-connection system of photovoltaics（PVs） as an example, AC-side electrical features after DC fault were discussed employing the proposed approach. Finally, a model of PV integration system was established in PSCAD/EMTDC to verify the sequence component network model and the AC-side features after DC fault. The impact of grounding modes of the converter station was also taken into account.