说明：  The Two-Quadrant DC/DC Converter block implements a two-quadrant DC/DC power converter. You can choose three model types : Switching devices — The converter is modeled with IGBT/diode pairs controlled by firing pulses produced by a PWM generator. This model provides the most accurate simulation results. Switching function — The converter is modeled by a switching-function model. The switches are replaced with two voltage sources and two diodes on the AC side and with two current sources on the DC side. The converter is controlled by firing pulses produced by a PWM generator (0/1 signals) or by firing pulses averaged over a specified period (PWM averaging: signals between 0 and 1). Both modes of operation produce harmonics normally generated by a PWM-controlled converter and also correctly simulate rectifying operation as well as blanking time. This model type is well-suited for real-time simulation.