Comparing Active and Passive Small-Signal Stability Improvement Methods for Power Converters in Weak Grids, Considering Practical Switching Frequencies Achievable by SiC MOSFETs Versus Si IGBTs

Abstract

With advancements in semiconductor technology, switching frequencies of 10–20 kHz, enabled by SiC MOSFETs, are becoming viable for megawatt-scale converters, significantly reducing switching losses and filter size. This highlights SiC MOSFETs' potential in future power conversion. However, careful system design is crucial for stable operation. This paper examines active and passive methods to improve small-signal stability in weak grids across practical switching frequencies achievable by SiC MOSFETs and Si IGBTs. Multi-parallel inverters and various grid scenarios emulate real-world conditions. The findings reveal that while both damping methods enhance stability margins, they exhibit distinct trade-offs. Passive damping, requiring a lower quality factor at lower switching frequencies, results in higher damping losses, while active damping achieves similar stability with minimal losses. Both improve resonance stability but have limited impact on low frequencies. Additionally, results show that combining a phase compensator with active damping improves stability for both low and high-frequency ranges. A summary table presenting the analysis of component costs, power losses and system stability margins for different converter designs was provided, which can assist designers in identifying trade-offs to achieve the optimal design with Si IGBTs and SiC MOSFETs for the targeted application.