Question

For a single-phase dual converter, with converters C1 and C2 connected in anti-parallel, which relation among the following is true to keep the average voltages from C1 and C2 equal?  C1 and C2 have firing angles α1 and α2 respectively.

(a) α1 = α2

(b) α1 + α2 = 360°

(c) α1 + α2 = 180°

(d) none of the mentioned

I got this question in an international level competition.

Question is from Dual Converters-1 in division Converters of Power Electronics

Answer 1

The correct choice is (c) α1 + α2 = 180°

To explain: By maintaining α1 + α2 = 180°, one converter can operate as converter and another as an inverter hence, the average output voltages are equal . This can be proved as follows

Vom cos α1 = Vom cos α2

Vom = 2Vm/π . . (Vm for both the converters is same)

cos α1 = cos α2

cos α1 = cos (180 – α2)

α1 + α2 = 180°.