Stability Region Exploring of Shunt Active Power Filters Based on Output Admittance Modeling

Shunt Active Power Filter (SAPF) is coupled with load admittance in weak grid conditions, which poses a challenge to stability analysis. In this paper, the admittance model of the SAPF is developed, which reveals the coupling mechanism between SAPF and load concisely and accurately. On top of that, the stability region of the system is investigated. The passivity region of the load admittance to guarantee the system stability is firstly explored. However, the passivity region has a very narrow band at a specific frequency, which makes it difficult to achieve. The stability region is then studied and it turns out to be an extension of the passivity region, and especially the narrow band is expanded. Therefore the stability region is much easier to meet. The stability-oriented design is then summarized in a flow chart. In the end, the effectiveness of the newly defined stability region is verified by experimental results.