Improved dynamic average modeling and impedance analysis of multi-pulse diode rectifiers

Detailed switching models of power-electronic rectifiers accurately represent diode commutation and waveform discontinuities, but they require long simulation times and may introduce numerical difficulties in system-level studies. Conventional static average-value models reduce computational burden but may not adequately capture transient load-dependent dynamics and impedance characteristics. This study presents improved dynamic average-value models (AVMs) for 6-pulse and 18-pulse uncontrolled diode rectifiers using a first-order Taylor-series representation of the load-current variation. The proposed models preserve the dominant low- and medium-frequency dynamics while eliminating high-frequency switching events. DC output impedance and AC-side dq-domain impedance components are extracted using network-analyzer-based measurement and line-to-line small-signal current injection. The proposed AVMs are validated against detailed switching models and laboratory prototypes using waveform comparison, RMSE, MAPE, and simulation-time reduction. The results show close agreement with detailed models and experimental measurements while reducing simulation time by approximately 100-110 times. These findings demonstrate that the proposed dynamic AVMs provide an efficient and experimentally supported modeling framework for impedance-based analysis of multi-pulse diode rectifiers.