The objective of this paper is to present a new paradigm in control strategy for unsupported paraplegic standing, based on closed-loop control of paraplegics' lower extremities. The main advantage of our approach is taking into account voluntary motions of the upper-part of the body by controlling Center of Mass (CoM) position. The validity of our approach is tested, in computer simulations, using human CoM trajectories estimated from experimental data and by applying perturbations in simulation during quiet standing in order to simulated voluntary upper body movements. From the results presented in this study it can be seen that controller is able to track desired CoM position with satisfied precision and to maintain stability even in the presence of movements in upper part of the model.