A Multi-impedance Optimization Control for AC Microgrid DC Interconnected Converter System

doi:10.11930/j.issn.1004-9649.202203057

Abstract

Abstract: The two AC microgrids are DC interconnected through back-to-back structured VSC converters. Usually one side converter adopts DC voltage control, and the other side converter adopts constant active power control. Under bidirectional power flow, when the power-controlled converter mode is used as a power load, its DC or AC port impedance will show negative impedance characteristics, reducing system damping and stability. To solve this problem, a multi-impedance optimization control is proposed, which not only optimizes the negative impedance to positive impedance, but also reduces the phase difference on DC side, enhancing the stability of the system completely. First, the structure of the AC micro-grid DC interconnected converter system, the topology and control of the converter are briefly introduced. Secondly, small-signal modeling was modelled of the multiple ports of the converters on both sides before the optimization, and the impedance characteristics were analyzed. Then, the working mechanism of multi-impedance optimization control is analyzed, and the optimized port impedance is re-modeled. The results show that the proposed multi-impedance optimization control can optimize the impedance of multiple ports in the system. It can not only optimize the negative impedance of the original AC and DC sides to positive impedance, but also reduce the phase difference between the impedances of the DC side，maintaining a larger stability margin and greatly improving system stability.

Key words: AC microgrid, current converter, small signal modeling, stability analysis, coordinative control

LIU Zhenguo, JIN Ming, YU Hai, CHEN Wentao, YANG Dingqian. A Multi-impedance Optimization Control for AC Microgrid DC Interconnected Converter System[J]. Electric Power, 2023, 56(2): 93-101,156.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.202203057

https://www.electricpower.com.cn/EN/Y2023/V56/I2/93

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