基于虚拟阻抗参数优化的并联逆变器控制研究

Parameter Optimization of Virtual Impedance for Parallel Inverter

无互联线的并联逆变器以其冗余度高、灵活性好等优点备受关注。但是由于无信息的交流,逆变器本身参数、线路阻抗、参考电压等因素的差异可能引起逆变器间的环流流动。基于虚拟阻抗的并联逆变器控制方式可降低系统对上述差异的敏感度,减小逆变器间的环流。但是传统虚拟阻抗的参数通过经验和逆变器等效阻抗的波特图选取,参数往往非最优化,均流效果的动态性能也不理想。通过分析逆变器等效阻抗的零极点位置变化对系统稳态及暂态性能的影响,提出了一种优化虚拟阻抗系数的方法,有效地改善了逆变器的动态及稳态性能,提高了多逆变器并联运行的稳定性。建立两个逆变器并联的拓扑结构,通过仿真结果的分析验证了所提方法的可行性和正确性。

Wireless control strategy for parallel inverter attracts much attention for its high redundancy and flexibility. However, without communications among parallel modules, circulating current may emerge due to the differences of their parameters, line impedance, reference voltage and so on. Parallel inverter based on virtual impedance may solve the problems caused by differences and decrease circulating current. Conventional design methods determine the parameters of virtual impedance by observing the changes of Bode curves of their equivalent impedance, which leads to poor dynamic performance, The fact that position change of zeroes and poles of equivalent impedance effects steady and transient performance is proposed. A novel method to optimize the coefficients of virtual impedance is put forward. Steady and transient performance of parallel inverter is improved, as well as operational stability. The topology of two inverters in parallel is established and simulation results verify the feasibility and correctness of the proposed method.