Cristian Vasar

Iosif Szeidert, Ioan Filip, Octavian Prostean et al.

The paper deals with the modelling and control of a double winded induction generator. The controlled process is an induction generator with distinct excitation winding. At the generator terminal is connected a load (electrical consumer). There are presented the results obtained by using a minimum variance adaptive control system. The main goal of the control structure is to keep the generator output (terminal voltage) constant by controlling the excitation voltage from the distinct winding. The study cases in the paper are for the validation of the reduced order model of induction generator (5th order model) used only to design the adaptive controller. There is also validated the control structure. There were considered variations of the mechanical torque.

Cristian Vasar, Octavian Prostean, Ioan Filip et al.

This paper presents some considerations regarding the prediction of the electrical energy consumption. It is well known that the central element of a microeconomic analysis is represented by the economical agents actions, actions that follow their own interest such as: the consumer maximization of his satisfaction, the producer maximization of his profit. The study case is focused on the prediction of the sold energy in Banat region. The goal of this study case is to optimize the electrical energy quantity purchased from the producer by the energy distributor in Banat region. The prediction is based on neural networks. There are used feed-forward and Elman type neural networks. In order to enhance the prediction accuracy there have been used both linear and nonlinear preprocessing units. The aspects considered in this paper can be extrapolated in any general case of prediction based application, not only in the already stated case of electrical energy.

Cristian Vasar, Octavian Prostean, Ioan Filip et al.

This paper presents a laboratory setup usable for the design and testing of a Wind Energy Conversion System respectively their control solutions. The stand can be used for research or in the engineering educational system offering the possibility of studying the behavior of wind energy conversion systems, including testing of some adequate control techniques, allowing the transition from simple simulations on the computer to practical functional tests, much closer to the reality of the site. The stand architecture is based on a hardware platform integrating electrical machines, control equipment, power devices, sensors, computing systems and appropriate software, all allowing one flexible configuration to test a multitude of scenarios specific to the wind energy domain. The wind turbine is emulated using an asynchronous motor with direct torque control based on rotating speed measurement. The controlled torque is applied to a synchronous generator and the output power is injected into the grid.

Ioan Filip, Octavian Prostean, Cristian Vasar et al.

This paper describes a PI fuzzy adaptive control structure. Based on classical PI fuzzy control structure (with integration on controller output) the authors have developed, implemented and validated an on-line self-tuning mechanism of regulator parameter. A study case for validation of proposed tuning mechanism is presented and analyzed with application to control of synchronous generator excitation system.

Octavian Prostean, Iosif Szeidert, Nicolae Budisan et al.

In the complex case of wind energy conversion systems (WECS) analysis and synthesis, the mathematical models of each component element are required. In the paper are presented some contributions to preset values establishing strategies and models of specific elements: rotation speed and voltage preset values establishing strategies, a simplified fixed blade wind turbine model, the induction generator squirrel rotor induction generator Park mathematical model, specific to current frequency converter supplier use, current frequency converter inverter model. The presented models are used for WECS analysis in its specific transient regimes as well for its controller design.

Cristian Vasar, Iosif Szeidert, Ioan Filip et al.

This paper presents issues regarding short term electric load forecasting using feedforward and Elman recurrent neural networks. The study cases were developed using measured data representing electrical energy consume from Banat area. There were considered 35 different types of structure for both feedforward and recurrent network cases. For each type of neural network structure were performed many trainings and best solution was selected. The issue of forecasting the load on short term is essential in the effective energetic consume management in an open market environment.

Ioan Filip, Iosif Szeidert, Cristian Vasar

The paper presents a flexible and efficient method to secure the access to a Web site implemented in PHP script language. The algorithm is based on the PHP session mechanism. The proposed method is a general one and offers the possibility to implement a PHP based secured access to a Web site, through a portal page and using an additional script included in any site page, which is required to be accessed only by registered users. This paper presents the design, implementation and integration of the algorithm on any generic WEB site.