弱电网下双向并网变流器虚拟正阻尼重塑控制

Virtual Positive-damping Reshaped Control for Bidirectional Grid-connected Converter in Weak Grid

针对弱电网下恒功率控制模式中双向并网变流器系统稳定性会因功率传输方向的不同而产生差异进而引发系统振荡甚至失稳的问题,提出了一种虚拟正阻尼重塑控制策略,将负阻抗重塑为正阻抗,增强系统阻尼进而提升稳定性。首先,详细地建立了双向并网变流器交流侧端口阻抗在d-q坐标系下的小信号模型,分析了不同功率方向下阻抗特性的差异。其次,结合系统最小环路比表达式和电网等值阻抗表达式,基于奈奎斯特稳定判据,分析了电网等值阻抗大小和功率传输方向两个因素对系统稳定性的影响。然后,分析了弱电网下双向逆变器虚拟正阻尼重塑控制策略,并对其进行建模与分析。结果表明:虚拟正阻尼重塑控制可以实现将负阻抗重塑为正阻抗,并增强系统阻尼。并且,即使在电网等值阻抗较大的弱电网下,系统也能保持较好的双向功率稳定性。最后,基于MATLAB/Simulink和小功率实验平台验证所提策略的有效性。

Aiming at the problem that the system stability of bidirectional grid connected converter in constant power control mode under weak current network will vary due to different power transmission directions,resulting in system os-cillation and even instability,this paper proposes a virtual positive damping remodeling control strategy,which reshapes the negative impedance into positive impedance,enhances the system damping,and improves the stability.Firstly,the small signal model of AC side port impedance of bidirectional grid connected converter in d-q coordinate system is estab-lished in detail,and the differences of impedance characteristics in different power directions are analyzed.Secondly,combined with the expression of system minimum loop ratio and grid equivalent impedance,based on the Nyquist stabil-ity criterion,the effects of grid equivalent impedance and power transmission direction on system stability are analyzed.Then,the virtual positive damping remodeling control strategy of bidirectional inverter under weak current network is an-alyzed,modeled and analyzed.The results show that the virtual positive damping reshaping control can reshape the negative impedance into positive impedance and enhance the system damping.Moreover,even in the weak current net-work with large equivalent impedance,the system can maintain good bidirectional power stability.Finally,the effectiveness of the proposed strategy is verified by using the MATLAB/Simulink and low-power experimental platform.