HDR is by definition the extension of the dynamic range portrayed in the final image beyond what the camera can capture in one shot. The camera has a 11 stop range but your final image has detail from elements in the original scene that were 18 stops apart. One RAW from that camera will have 11 stops worth of data, no matter what you do to it. You are not God nor is your computer, you can't create new data from nothing. However, blending multiple conversions from a single RAW into what is called a "fake HDR" can be an excellent way to get the maximum milage out of the data you do have. Another way is to convert to a single 16 bit tif, to retain almost all the data, and work on it with something like PS's Highlight/Shadow tool. But the three conversion method does have a certain advantage in that you are pushing and pulling linear RAW data before it gets bent out of shape by the gamma correction of the conversion.
SOME SAMPLES OF HDR pic :