On-line monitoring of the transformer winding using electromagnetic waves has recently been proposed for the detection of mechanical defects of transformer winding. In this paper, a new method, which uses the UWB radar measurement results and is based on locus of objects in the space, is proposed for the three-dimensional positioning of transformer winding radial deformation location. The proposed experimental set-up for this method named "Hyperboloid method" is modeled using CST (Computer Simulation Technology) software. In this paper, Vivaldi antennas suitable for measurements in environments with multi-path, are used and the analysis is performed in the time domain. The simulation results show that the exact threedimensional location of the radial deformation can be detected with a good accuracy.

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This paper presents an active-reactive power control strategy for voltage source converters (VSCs) based on derivation of the direct and quadrature components of the VSC output current. The proposed method utilizes a multivariable proportional-integral controller and provides almost completely decoupled control capability of the active and reactive power with almost full disturbance rejection due to step changes in the power exchanged between the VSC and the grid. It also imposes fast transient response and zero steady-state error as compared to the conventional power control approaches. The applicability of the proposed power control strategy for providing the robust stability of the system against the uncertainties of the load parameters is also investigated. The superiority of the proposed control strategy over conventional approaches in the new condition of supplying the load is demonstrated. The theoretical aspects of the proposed multivariable-based power control strategy and the conventional approaches are reviewed and simulation results are presented in two separate sections. MATLAB/Simulink 2009a is used to simulate different scenarios of the simulation.