Four Quadrant Converter

A four quadrant converter is shown in Figure 2 . The circuit is operated as a two quadrant converter to obtain:

1. a) Sequence 1: First and second quadrant operation

b) Sequence 2: Third and fourth quadrant operation

Figure 2: Four quadrant converter

 

Sequence 1 Operation

In this mode S₄ is kept permanently on . The switches S₁ and S₂ are controlled as per the following four steps:

• • Mode 1: If S₁ and S₄ are turned on , the input voltage V_in is applied across the load and current flows in the positve direction from a to b Figure 3a . The instantaneous output voltage across the load is .

• Mode 2: When S₁ is turned off at time , the current due to the stored energy of the inductor L drives through D₂ and S₄ as shown in Figure 3b . The switch S₂ is turned on at but it doesnot conduct because it is shorted by D₂.

• Mode 3: The switch S₂ conducts when the cureent reverses its direction (Figure 3c).

• Mode 4: Finally when S₂ is turned off at t = T , current flows in the negative direction (Figure 3d). The converter operates in the fourth quadrant and the power flows from load to source.

The wavforms for sequence 1 are shown in Figure 4 .