虚拟阻抗对不同电压等级逆变器并联系统的稳定性影响分析

doi:10.11930/j.issn.1004-9649.202004204

摘要/Abstract

摘要： 利用虚拟阻抗技术对双闭环控制结构进行优化，可将逆变器的等效输出阻抗改善为强感性，提高传统感性下垂控制策略在低压微电网中的功率分配精度，有效抑制环流，但往往忽略了虚拟阻抗对系统稳定性的影响。鉴于此，推导包含虚拟阻抗、线路阻抗及公共点电压的三环控制传递函数，建立考虑虚拟复阻抗的不同电压等级逆变器并联模型，并利用戴维宁等效原理对模型进行简化，在多种工况下根据Nyquist稳定判据分析虚拟阻抗对系统稳定性的影响。结果表明：不同电压等级的逆变器并联系统在添加虚拟阻抗后仍可保持稳定运行。

关键词: 低压微电网, 虚拟阻抗, 戴维宁定理, Nyquist稳定判据, 稳定性

Abstract: Using virtual impedance technology to optimize the double closed-loop control structure can improve the equivalent output impedance of the inverter to be inductive and enhance the accuracy of power distribution by traditional inductive droop control strategies in low-voltage micro-grids, thus inhibiting circulating current. This approach, however, tends to overlook the impact of virtual impedance on system stability. In this regard, the transfer function of a three-loop control structure is derived, which includes virtual impedance, line impedance and common point voltage. A parallel model of inverters with different voltage levels is built, considering virtual complex impedance, and the model is simplified with the Thevenin’s equivalent. According to the Nyquist stability criterion, the effect of virtual impedance on system stability is analyzed under various operating conditions. The results show that the multi-inverter parallel system can maintain stable operation after the virtual impedance is added.

Key words: low-voltage micro-grid, virtual impedance, Thevenin's equivalent, Nyquist stability criterion, stability

马文涛, 王金梅, 王永奇. 虚拟阻抗对不同电压等级逆变器并联系统的稳定性影响分析[J]. 中国电力, 2021, 54(9): 135-142,175.

MA Wentao, WANG Jinmei, WANG Yongqi. Influence Analysis of Virtual Impedance on the Stability of Parallel System of Inverters with Different Voltage Levels[J]. Electric Power, 2021, 54(9): 135-142,175.

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https://www.electricpower.com.cn/CN/Y2021/V54/I9/135

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