Modeling of a three-phase power conditioning system and improving its transient behavior following a heavy load drop

The components of a three-phase power conditioning system were modeled using the time-domain signals obtained by 'looking into' the system terminals while they are operating as components of the overall system. The overall system model was obtained by interconnecting the component models. It is shown that the model obtained adequately represents the power conditioning system for its entire loading range. The adequacy of the computer model is shown through graphical (time-domain) and spectral (frequency-domain) comparisons of the actual and simulated system responses to the same inputs. Transients of up to 1 s in three-phase power conditioning systems result in the delivery of low-quality power at their outputs. Design modifications for improving their transient behavior are presented. Laboratory tests have shown that by lowering the impedance of the second harmonic filter to 60 Hz signals, the output voltage ringing time following a sudden load drop can be reduced significantly. Computer simulation has shown that the ringing time can also be reduced by redesign of the nonlinear line chokes, which in addition will minimize the harmonics generated as the result of their operation.<
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