OFDM DA conversion problem
Imaginary part of a complex number is real. For example

$$z = 1 - 2j$$
$$\mathsf{Re}(z) = 1$$
$$\mathsf{Im}(z) = -2$$

The same will happen with the imaginary part of your FFT. In the end, you get two real signals. Then you modulate them by two sinusoids which are 90 degrees out of phase, and add the modulated signals at the output stage.