增强变流器对感性电网适应能力的虚拟阻抗控制

Virtual Impedance Control for Improving the Inductive Grid Adaptability of the Converter

弱电网条件下的感性电网阻抗会严重威胁到并网变流器的稳定运行。首先建立了弱电网下并网变流器的数学模型,采用根轨迹和小增益定理对电网阻抗中感性和阻性成分对系统稳定性的影响进行了分析。进一步,针对变流器对感性电网阻抗适应能力较低的问题,为了增大感性电网条件下系统的阻尼,引入了虚拟电网电阻控制策略。理论和仿真结果表明,虚拟电网电阻控制策略可显著提高变流器对感性电网的适应能力。

In the weak grid,the inductive grid impedance will seriously threaten the stable operation of the grid-connected converter.First,the mathematical model of grid-connected converter in the weak grid was built,and the influence of the inductive and the resistive component in the grid impedance on the system stability was analyzed using the root locus and the small gain theorem.Further,for the low inductive grid impedance adaptability of the converter,the virtual grid equivalent resistance control strategy was introduced to improve the damping of the system in inductive grid impedance.Theoretical analysis and simulation results show that the virtual grid equivalent resistance control strategy can significantly enhance the inductive grid impedance adaptability of the converter.