A Nonlinear Approach for Assessing Stability in Line-Commutated Converters With an Integrating Controller

Closed-loop stability analysis of line-commutated converters (LCCs) has been mainly based on linear, small-signal plant transfer modeling for the power stage. The inaccuracies derived from the use of these simple models in the frequency domain have led to conservative compensation strategies with reduced loop bandwidths. This paper presents a nonlinear time-domain approach for modeling LCCs under integrating control. The proposed technique was found useful to assess the onset of loop instability under different operating conditions. Bifurcations and possible routes to chaos in the parameter domain are also explored. The method is validated by simulation and stability boundary conditions leading to period-doubling behavior are demonstrated by means of experimental results.