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| Influence of AC system voltage on the current of the arm of the converter during an MMC-HVDC grounding fault before converter latching |
| DOI：10.19783/j.cnki.pspc.190986 |
| Key Words:MMC-HVDC single pole ground fault influence mechanism AC system bridge arm current |
| Author Name | Affiliation | | WANG Zhenhao | College of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China | | JI Qing | College of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China | | SUN Yinfeng | College of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China | | CHENG Long | College of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China | | LI Guoqing | College of Electrical Engineering, Northeast Electric Power University, Jilin 132012, China |
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| Abstract:DC line ground faults are the primary fault type of Modular Multilevel Converters (MMC). In the event of a fault, in order to meet the cut-off current requirement of DC circuit breaker, the fault should be cut off before the MMC latching, and the time latching of the MMC depends on the ability of the Insulated Gate Bipolar Transistor (IGBT) to withstand the bridge arm fault current. Therefore, more detailed and specific requirements are put forward for the analysis of the characteristics of the single-bridge arm current in the event of a fault. First, the topology and working principle of the true bipolar MMC are introduced, and the flow path of the different components of the fault current on the MMC bridge arm before the converter latching during the DC line grounding fault is analyzed. Then, using the calculation method of the complex frequency domain, a mathematical model of the bridge arm current at fault is constructed, and the influence mechanism of the AC system voltage on the short-circuit current of the bridge arm before MMC latching is derived. Studies have shown that the voltage phase angle of the AC system has a significant effect on the amplitude of the bridge arm current at fault. Finally, based on the PSCAD simulation experiment platform, 31-level single-ended and 51-level double-ended true bipolar MMC-HVDC models are built. The simulation results under different voltage amplitudes and phase angles verify the correctness of the mechanism. This work is supported by National Key Research and Development Program of China (No. 2018YFB0904600). |
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