Electrical Machines Virtual Laboratory: Grid Connection of a Synchronous Generator Claudia S. Mar is, Horia C. Hede iu, Loránd Szabó, Bogdan T t ranu, Florin Jurc , Claudiu Oprea Department of Electrical Machines, Technical University of Cluj, Romania Abstract—Virtual laboratories can become important components of the teaching process, because using them several experiment-oriented problems can be solved easily and also from the distance. Graduates using virtual laboratories will be better trained when they enter the job market. In the paper a laboratory work will be presented having two components: a simulation and an experimental module. Both can be used for the preparation of a real lab and for accessing the real-world experiments. The virtual lab modules can also allow multiple students to remote access the experiments, the multicast data transfer mechanisms and arbitration mechanisms. I. INTRODUCTION "Promotion of the necessary European dimension in higher education, particularly with regards to curricular development, inter-institutional cooperation, mobility schemes and integrated programmes of study, training and research" was set as an objective in the Bologna Declaration. In the frame of the common education and training activities possibly it could be necessary for students to study at different universities. In this context, student mobility could be seen as a means of acquiring knowledge and skills not available at the home institution, and of complementing and integrating the activities carried out at the home institution. The need to create equal studying opportunities for all the students implies additional funds that should be provided to cover the higher cost of joint degree programmes. In order to reduce or eliminate these needs, and the overhead incurred when achieving and maintaining a well-equipped laboratory, the new computer technologies and the Internet access can sustain the development of virtual laboratories. As an important component of the teaching process, these could offer experiment-oriented problems to be solved and could give graduates an added value when they enter the European/International job market. The objective of a virtual laboratory is to introduce students to experimentation, problem solving, data gathering and scientific interpretation. Educators and researchers, crunched between demand for an effective education and budget constrains, can use virtual instrumentation to automate routine tasks, accomplish new objectives, replace outdated and expensive equipment, and/or to demonstrate students the potential of high technology. For the implementation of the virtual laboratory LabVIEW, a product of National Instruments Inc., will be used. It is a flexible, general-purpose graphical programming tool intended for a broad spectrum of applications. LabVIEW has also controls to access a web page as an interactive interface to an own application, which implements, for example, a data acquisition task on a server. NI-DAQ, also a product of this company, includes a feature called Remote Device Access (RDA), which allows remote, network access to data acquisition systems using the company's wide-spread hardware. The Electrical Machines Virtual Laboratory integrates computers and industrial hardware expanding the range of instrumentation and control to virtually unlimited capabilities, offering for the students a pre-practice, a replacement or a post-analysis of the real laboratories. The methodology used in the Electrical Machines Virtual Laboratory is structured in a same manner as in the case of the real lab. It begins with an introduction containing a short discussion on the laboratory exercise to be performed (including details on data collection and data analysis), procedures (instructions on how to conduct the laboratory work), respectively a step-by-step guide through the virtual lab, analysis, report writing requirements and references. II. THE VIRTUAL LAB Connecting a generator to an ac power network is the synchronisation of the generator to the grid. Before this procedure the generator has to be accelerated to the correct speed and the rotor must be magnetized. The current I resulting at the moment of synchronization depends on how close the induced voltage (E q ) and the terminal voltage (V) are each to other. To avoid large circulating currents the phasor values of E q and V should be equal. This requires four conditions: same magnitude, phase and frequency of E q and V, respectively same phase order of both three-phase systems. A. The simulation module In the first part of the virtual laboratory work concerning the grid connection of a synchronous generator the simulation of the voltage waveforms of the two components of the system (the generator and the power grid) will be done. By varying all the parameters (amplitude, frequency, phase and phase order) of the two voltage systems different cases can be analysed from the worst situation, when neither of the four conditions are fulfilled, to the ideal case, when the connection to the grid could be done. In Fig. 1 the block diagram of the simulation program is given. The amplitudes (A n , A g ) and the frequencies (f n , f g ) of the two sources corresponding to the network, respectively to the synchronous generator can be set independently. The two waveforms are synchronised by imposing in both cases the same step number i. 1-4244-0121-6/06/$20.00 ©2006 IEEE EPE-PEMC 2006, Portorož, Slovenia 1709