Haochen,
I went through the exercise of creating a phase-shifted full bridge converter with the parameters outlined in the document. I observed a clean sinusoidal waveform on the input current. Please see the attached model. Note the component parameters are defined in the Initialization tab of the Simulation + Simulation Parameters... drop-down menu.
In the future if you could post the PLECS model file (*.plecs) you are working with it would be helpful. There likely is a small error in a circuit parameter or in the implementation that would be very difficult to detect without the exact simulation model.
Regards,
Bryan