Sharif Digital Repository

The Brushless Doubly-Fed Machine (BDFM) is a new kind of doubly-fed machines which incorporates the robustness of the squirrel cage induction machine and the speed and power factor control of a synchronous machine. All of these advantages are obtained from a relatively low rating power electronic converter. The stator of a BDFM is furnished with two balanced three phase windings of conventional design. At this thesis the effects of an unbalanced grid on the operation of a BDFM has been studied. A balanced grid contains three phases with the same amplitude and the phase angle of 120 degrees between each two phases. The unbalanced grid is defined by any turbulent grid. There are some kinds of... 

Recently, the primal-dual interior point methods for nonlinear programming has attracted considerable attention. Here, we consider an optimal zero-forcing beamformer design problem in multi-user multiple-input multiple-output broadcast channel. The minimum user rate is maximized subject to zero-forcing constraints and power constraint on each base station antenna array element. This is a convex optimization problem which is equivalent to a nonlinear convex optimization problem having linear equality and inequality and quadratic inequality constraints. This problem is reduced to a convex optimization problem of lower dimension with only inequality constraints. Finally, the problem is solved...