Mihai Octavian Popescu

Transient analysis of DG interfaced low voltage dc system

The paper deals with the analysis of a low voltage dc distribution system. This dc system efficiently uses the opportunities that distribution generators (DG) offers for the power quality improvement, considering the more easily interconnection of the energy storage devices. The analysis of the energy management system and the behavior of the dc system during faults in the ac grid and dc grid are conducted.

An object oriented data structure for field analysis

A structure of classes suitable for a general electromagnetic field analysis program is presented. This class structure is highly decoupled in order to be implemented in a distributed environment. The data structure was tested on a simple case, being implemented in both C++ and JAVA languages.

Stand-alone hybrid wind-photovoltaic power generation systems optimal sizing

Wind and photovoltaic energy resources have attracted energy sectors to generate power on a large scale. A drawback, common to these options, is their unpredictable nature and dependence on day time and meteorological conditions. Fortunately, the problems caused by the variable nature of these resources can be partially overcome by integrating the two resources in proper combination, using the strengths of one source to overcome the weakness of the other. The hybrid systems that combine wind and solar generating units with battery backup can attenuate their individual fluctuations and can match with the power requirements of the beneficiaries. In order to efficiently and economically utilize the hybrid energy system, one optimum match design sizing method is necessary. In this way, literature offers a variety of methods for multi-objective optimal designing of hybrid wind/photovoltaic (WG/PV) generating systems, one of the last being genetic algorithms (GA) and particle swarm optimization (PSO). In this p...

Grid connected and stand alone DC power system prototype

Nowadays, the delivery of electrical energy with high power quality to the supplied customers is required. Voltage quality and continuity of supply represents an important aspect of future smart grids. The present paper proposes a dc power system standalone or grid connected, applying advanced power control techniques, supplied by distributed generators: wind turbine, photovoltaic panel, storage battery, and fuel cell. The proposed system is implemented in a laboratory facility. The laboratory experiments and simulation results revealed the correct operation of the implemented control techniques. The system has the advantage of modularity. Various power sources can be connected to the dc power system determining a flexible expansion.

Coupled multiphysics-RF reduced models for MEMS

This paper proposes a fast and accurate order reduction algorithm for the extraction of compact macromodels for electrostatic actuated micro-electro-mechanical (MEMS) switches used in radio-frequency (RF) applications. The algorithm uses as input the information obtained from field simulations, in which coupled equations of electrostatic, structural-dynamic, air flow and full wave electromagnetic fields are used. The reduced macromodel is described as a circuit netlist which includes both the electro-structural-fluid flow multiphysics and the RF behavior of the switch. For the benchmark considered, the reduction is impressive, from more than 400000 degrees of freedom of the field models, to a macromodel of order 2 both for the multiphysics part and the RF part. The accuracy is checked by comparing relevant quantities (e.g. pull-in voltage for the multiphysics part and S parameters for the RF part) of the original field model with the same quantities obtained from the reduced macro-model. Relative errors less than 2% are obtained.

Comparison of Hill-Climbing and Artificial Neural Network Maximum Power Point Tracking Techniques for Photovoltaic Modules

In this paper, two maximum power point tracking (MPPT) algorithms in a photovoltaic electrical energy generation system are analyzed and compared. The Matlab/Simulink is used to establish the model of a photovoltaic system with MPPT function. This system is developed by combining the models of established solar module and DC-DC boost converter with the algorithms of hill climbing (HC) and artificial neural network (ANC), respectively. The system is simulated under different atmospheric conditions and MPPT algorithms. According to the comparisons among the simulation results, it can be concluded that the photovoltaic system with ANN MPPT algorithm is simpler: it does not require knowledge of internal system parameters, needs less calculation, is faster and provides a compact solution for multi-variable problems.

System used for Power Quality monitoring in a distribution grid

In this article I have presented the composition and functioning of a power quality monitoring system used in distribution grids. I presented an analyzer for power quality monitoring, the ways of transmitting data, a global positioning system clock and a general schema of a power quality monitoring system.

System monitoring of energy quality for wind power generators

The interconnection of wind sources characterized by a significant variability of generated power and the continuous growth of installed power in wind farms raises a number of specific problems both to the utilities and to the power system operator. One of these issues is the injection of current and voltage harmonics into the electrical networks, affecting the quality of energy delivered to customers. Due to the output power variations of the wind turbines, electrical flicker is produced. Thus, on-line monitoring systems are required to obtain information about the influence of these generators over the electrical network.

Building integration of 30 kWp photovoltaic system at University Politehnica of Bucharest, Romania

A Building Integrated Photovoltaic Power System of 30 kWp was recently installed at University Politehnica of Bucharest, Romania. It is the first grid-connected and largest PV system of the country. With this opportunity, an innovative non-penetrating system that uses the modules and mounting hardware as ballast was designed and implemented. Personnel with no previous experience with the roof PV systems, putting an innovative mounting system and documentation to the test, performed array installation. In the paper, the PV power system and its installation process are described, special attention being accorded to the complex mounting system. The provided information can be useful to anyone implementing a PV system.

Trends in evolution of electrical engineering curriculum

Society evolution toward the information and knowledge-based economy made necessary a new and more specific definition of electrical engineering. The paper discusses about new approach of electrical energy systems as power systems microprocessor controlled. From this point of view computer use was integrated in electrical engineering. Some tendency in electrical engineering curricula reform are presented and commented.