| 摘要: |
| 分析了模块化多电平电力电子变压器(MMC-PET)在配电网电压跌落故障下的几种工作模式，指出了可以利用中压母线电容和低压母线电容的储能来维持逆变输出电压稳定。为了延长维持时间，提出了变模块化多电平换流器(MMC)子模块结构的故障工作模式，使得MMC子模块电容也可用于拓展维持时间。阐述了各母线电容和子模块电容的设计方法，以及它们与维持时间的关系。针对变MMC子模块结构在故障运行过程中出现的输入侧低频电流振荡现象，提出了在配电网侧加入对地电阻和电感的策略，并推导了设计方法。对一个10 kV输入/380 V输出的配电网MMC-PET进行仿真测试，采用了所提的控制模式后，逆变输出电压在电网电压跌落后能够维持0.7 s，并且不产生输入侧低频振荡现象，证明了所提方法的有效性。 |
| 关键词: 配电网 电力电子变压器 模块化多电平换流器 电压跌落 维持时间 |
| DOI：10.16081/j.issn.1006-6047.2019.02.007 |
| 分类号:TM46;TM41 |
| 基金项目:国家自然科学基金资助项目(51467005)；江西省自然科学基金资助项目(20181BAB206033) |
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| Research on PET in smart distribution network under voltage sag |
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YUAN Yisheng, TANG Zhe
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School of Electric Engineering and Automation, East China Jiaotong University, Nanchang 330013, China
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| Abstract: |
| In the case of the voltage sag fault in a distribution network, a few operating modes of the MMC-PET(Modular Multilevel Converter Power Electronic Transformer) are analyzed. Energy storage of the medium-voltage bus capacitance and the low-voltage bus capacitance can be utilized to maintain the output voltage stability of the inverter. To extend the maintenance time, variable MMC sub-module structure in the failure operating mode is proposed. As a result, the MMC sub-module capacitance can also be used to extend the maintenance time. The design approaches of each bus capacitance and sub-module capacitance are explained as well as their relationship with maintenance time. As for the input-side low-frequency current oscillations that occur during the fault operation of the variable MMC sub-module structure, the strategy that adds resistance and inductance to the ground at the distribution network side is proposed, and the design approach is deduced. The simulation test of a 10 kV input/380 V output distribution network MMC-PET is carried out. It shows that the proposed control mode ensures that the inverter output voltage can maintain 0.7 s after a voltage sag. At the same time, the low-frequency oscillation does not happen at the input side. These results validate the effectiveness of the proposed approach. |
| Key words: distribution network power electronic transformer MMC voltage sag maintenance time |
