Effect of DC link capacitance on the transient response of a PWM AC-DC converter

A linearised, small-signal perturbation model of a PWM AC-DC voltage source power converter under phase and amplitude control is used to investigate the effect of DC link capacitance on the transient response of the power converter. The model uses classical s-plane techniques and significantly simplifies power converter analysis. The responses to step changes in the control inputs are investigated for a variety of capacitance values. For large values of capacitance, it is possible to model the power converter as a first order system. The results obtained from the small-signal model are compared with simulation results and show excellent agreement. The small-signal model analysis is potentially a very useful tool in power converter design.