Influence of Filter Inductances and Number of Paralleled Grid-Connected Converters on the System’s Stable Region Under Weak Grid Condition

It has been found that both the number of paralleled grid-connected converters and the filter inductance value will affect the system’s stability in weak grid condition. However, a quantitative study on this effect is missing in the current literature. The main contribution of this paper is to quantitatively evaluates the influence of the number of paralleled grid-connected converters as well as the inductance value of the L filters on the system’s stable region. It is first revealed that, when the same controller design principles are applied for L -type grid-connected converters, the stable region of the paralleled grid-connected converter system is dependent on the ratio between the filter inductances and the number of paralleled converters. Specifically, the stable region is proportional to the ratio. Compared to the qualitative analysis in previous work, this finding can provide quantitative guidelines on the filter inductors or control system design for grid-connected converter applications in weak grid. Finally, experimental tests are carried out using two paralleled grid-connected converters to confirm the findings.