Series and parallel transformer resonant DC-DC converter using optimal digital servo and repetitive learning control schemes

A digitally processed repetitive learning control approach is presented ill combination with a type-1 optimal digital servo control scheme of the reso nant DC-DC converter using IGBT modules for a medical X-ray power generator , This scheme is considered for achieving a rapid transient response withou t any overshoot in addition to high-voltage characteristics with low ripple in its steady-state within a wide setting range of output voltage. To impr ove nonlinear voltage regulation performance of the series capacitor compen sated transformer parallel resonant inverter-type fixed frequency, phase-sh ifted PWM DC-DC converter with a high-voltage transformer link, the repetit ive learning control method is introduced into medical X-ray power generato r systems using a series and parallel resonant DC-DC converter with high vo ltage transformer matching. This makes use of transformer parasitic paralle l resonance with a series-compensated resonant capacitor connected to a tra nsformer parasitic leakage inductor. The effectiveness of the repetitive le arning control for this converter is discussed. A digital servo control sch eme with error compensation loops is implemented to eliminate periodic volt age ripple fluctuations and abrupt voltage changes in the rectified DC inpu t of this converter. This scheme also aims to realise good reproducibility, which is an important requirement in an X-ray power generator. The practic al effectiveness of the repetitive learning control method and the type-1 o ptimal digital servo control scheme are confirmed by simulation analysis an d experiments.