Suppressing Effect of Synchronous Condenser on Transient Overvoltage of UHVDC System under Hierarchical Connection Mode
At present, hierarchical connection mode has been adopted in UHVDC projects, and with the increasing proportion of new energy generation, the power grid at the sending end is facing the problem of transient overvoltage (TOV), which can be restrained by installing synchronous condensers, so it is nec...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | zho |
| Published: |
State Grid Energy Research Institute
2020-03-01
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| Series: | Zhongguo dianli |
| Subjects: | |
| Online Access: | https://www.electricpower.com.cn/CN/10.11930/j.issn.1004-9649.201910021 |
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| Summary: | At present, hierarchical connection mode has been adopted in UHVDC projects, and with the increasing proportion of new energy generation, the power grid at the sending end is facing the problem of transient overvoltage (TOV), which can be restrained by installing synchronous condensers, so it is necessary to study the suppressing effect of synchronous condensers on the TOV of UHVDC system under hierarchical connection mode. A model is established for the UHVDC system under hierarchical connection mode with synchronous condensers, and the suppression mechanism of synchronous condensers for TOV is analyzed theoretically. The effect of different number of synchronous condensers on TOV is studied under four different working conditions, including power-down operation, bipolar blocking fault, unipolar blocking fault and simultaneous commutation failure of both high-end and low-end inverters. Finally, the TOV-based short circuit ratio increment (SCRI) is proposed, and the suppressing effect of synchronous condenser on TOV is quantitatively evaluated. The results show that the proposed index can be used for quantitative evaluation of the suppressing effect of synchronous condensers on TOV. When the short circuit ratio of AC system on the rectifier side of UHVDC system under hierarchical connection mode varies from 3 to 8, the TOV-based SCRI at the rectifier side AC system is between 0.106 and 0.396 after one synchronous condenser is put into operation, and between 0.251 and 0.788 after two synchronous condensers are put into operation. Therefore, the implementation of synchronous condensers can effectively enhance the short circuit ratio of AC system and effectively restrain the TOV at the sending side. |
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| ISSN: | 1004-9649 |