This paper presents a model of a bidirectional MV/LV solid-state transformer (SST) for distribution system studies. A modular multilevel converter configuration is used in the MV side of the STT. The LV side uses a three-phase four-wire configuration that can be connected to both load and generation. The model developed for this work has been implemented in MATLAB/Simulink, and its behavior has been tested by carrying out several case studies under different operating conditions. The simulation results support the feasibility of the SST and its advantages in comparison to the conventional transformer. The paper also includes a discussion of the main model limitations and the future work.
The inductance of single- and multi-conductors intended for electronic devices, power transmission and distribution, or grounding, lightning, and bonding systems greatly depends on the specific geometry and the supply frequency. It is also influenced by skin and proximity effects. The inductance is an important design parameter, since it significantly influences the voltage drop in the conductor, thus raising reactive power consumption and limiting the conductors’ current-carrying capacity. Although there exist some internationally accepted approximated and exact formulas to calculate the AC inductance of conductors in free air, its accuracy and applicability has been seldom analyzed in detail in the technical literature, which is done in this paper. Since such formulas can be used for a wide diversity of conductors’ configurations and under different operating conditions, it is highly desirable to evaluate their applicability. This evaluation is carried out by comparing the results provided by the formulas with data provided by finite-element method simulation.
This work analyzes the behavior of surface-mounted permanent magnet synchronous motors (SPMSMs) operating under stator faults. The studied faults are resistive unbalance and winding inter-turn short circuits, which may lead to unbalanced conditions of the motor. Both faults may reduce motor efficiency and performance and produce premature ageing. This work develops an analytical model of the motor when operating under stator faults. By this way, the theoretical basis to understand the effects of resistive unbalance and stator winding inter-turn faults in SPMSMs is settied. This work also compares two methods for detecting and discriminating both faults. For this purpose, a method based on the analysis of the zero-sequence voltage component is presented, which is compared to the traditional method, i.e. the analysis of the stator currents harmonics. Both simulation and experimental results presented in this work show the potential of the zero-sequence voltage component method to provide helpful and reliable data to carry out a simultaneous diagnosis of resistive unbalance and stator winding inter-turn faults.
La publicación final está disponible en Springer a través de 10.1007/s00202-014-0316-z
The global trends nowadays in the power generation industry are to supplement the electricity production using distributed generation (DG) technologies based on renewable energy resources such as photovoltaic, wind power, etc. However, failure to properly control the operation of distributed energy resources as they connect to the exiting power grid could provoke many power quality problems on the grid side. For this reason, due considerations must be given to power generation and safe running before DG units is actually integrated into the power grid. The main aim of this paper is to address the grid interconnection issues that usually arise as DG units connect to the electric grid. The proposed strategy, implemented in Matlab/Simulink environment in different operating scenarios, provides compensation for active, reactive, unbalanced, and harmonic current components of grid-connected nonlinear unbalanced loads. The simulation results obtained in this study demonstrate the level of accuracy of the proposed technique, which ensure a balance in the overall grid phase currents, injection of maximum available power from DG resources to the grid, improvement of the utility grid power factor, and a reduction in the total harmonic distortion of grid currents.
Gomis-Bellmunt, O.; Montesinos-Miracle, D.; Galceran-Arellano, S.; Joan Rull-Duran; J. Rull; J. Rull-Duran Electrical engineering Vol. 90, num. 2, p. 115-125 DOI: 10.1007/s00202-007-0067-1 Data de publicació: 2007-05 Article en revista