一种提高变流器弱电网适应能力的虚拟阻抗控制策略

Virtual Impedance Control Strategy for Improving the Adaptability of Converter to Weak Grid

弱电网下较大的电网等值电感可能引起并网变流器失稳,为此,首先,建立了并网变流器的阻抗模型,根据阻抗比判据分析了电网等值电感对并网变流器稳定性的影响;其次,针对并网变流器对感性电网阻抗适应能力较低的问题,提出了一种基于带通滤波的虚拟阻抗控制策略,并研究了虚拟电阻值对变流器弱电网适应能力的影响,给出了虚拟电阻的选取原则;最后,搭建了系统仿真模型,仿真结果验证了文中理论分析的正确性和控制策略的有效性。

The large grid inductance in weak grid may cause a grid-connected converter to be unstable.Therefore,an impedance model of grid-connected converter is built at first,and the influence of grid inductance on the stability of grid-connected converter is analyzed according to the impedance ratio criterion.Then,aimed at the problem of low adaptability of the grid-connected converter to inductive grid impedance,a virtual impedance control strategy based on band-pass filter is proposed,and the influence of virtual resistance value on the adaptability of grid-connected converter to weak grid is studied.Furthermore,a selection principle for the virtual resistance value is also given.Finally,a system simulation model is built,and simulation results verify the correctness of theoretical analysis and the effectiveness of the proposed control strategy.