Internal-Stability-Considered Performance Analysis and Parameter Co-Design for Grid-Tied Inverters with Passivity-Oriented Phase-Corrected Resonant Controller and Voltage Feedforward

The passivity-based approach is effective to tackle the instability of grid-tied inverters under weak grid, with which both the internal-stability and external-stability should be examined. The control scheme based on the proportional resonant (PR) controller and the proportional voltage feedforward (PVF) is commonly applied to ensure the harmonic suppression ability and dynamic performance, while the passivity-oriented phase correction (POPC) of the PR controller has been developed to specifically address the well-known external-stability issue. However, the effects of POPC on internal-stability, harmonic suppression ability, and dynamic performance were totally overlooked, which would cause improper parameter selection and consequently degraded performance or even internal instability. In this paper, the previously undocumented internal instability mechanism due to POPC and the associated stability boundaries of the key parameters are revealed. Furthermore, considering this stability boundaries, the relationships among key parameters, harmonic suppression, and dynamic performance are rebuilt, providing valuable insights for parameter design. Accordingly, an improved parameter co-design procedure is proposed, which configures the key parameters collaboratively rather than independently, avoiding the risk of internal instability and achieving the superior balance between harmonic suppression and transient dynamics. Experimental results from a 20-kHz prototype with rated power of 4-kVA validate the theoretical analysis.