For a single-phase dual converter, with converters C1 and C2 connected in antiparallel, 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.

The relation to keep the average voltages from converters C1 and C2 equal in a single-phase dual converter connected in antiparallel is given by:

α1 + α2 = π (or 180 degrees)

This means that if the firing angle of one converter increases, the firing angle of the other must decrease correspondingly to maintain equal average output voltages.