| A technological alternative for the interconnection of two electrical networks had recently been developed by GE Energy: the variable frequency transformer. This system is a new way of using well known components in electrical engineering, which are the direct current machine and the asynchronous machine with wounded rotor.Results from both of the software used don't enable us to conclude that these models simulate efficiently the asynchronous machine when it is connected to two three-phase sources. Thus, at the end of this document we'll give advice for future work on this system.The point of this work is to study this system's working and more particularly the behavior of the asynchronous machine when it interconnects two electrical networks (one on the stator side and the other on rotor side). For this kind of machine, it's a new way of running which is worth paying more attention. Frequencies of the networks interconnected can be identical or different and we will consider these two cases at each step of this work. We'll confine ourselves to the study of steady state. First, by using magnetic fields, a theoretical analyze of the asynchronous machine's behavior in these conditions will be presented. This part will permit detail why it is possible to regulate the active power flow by applying a torque on the shaft with the direct current machine. Then, we'll present the experimental results obtained for a variable frequency transformer made with a group of machine of 15 hp. The behavior of the asynchronous machine observed while interconnecting two electrical networks will allow us to confirm the theoretical study. Finally, after having identified parameters of the asynchronous machine thanks to a series of experimental tests, we'll try to simulate the variable frequency transformer. With the help of existing mathematical models of asynchronous machine wounded rotor from two different software (Matlab and EMTP), the objective is to check if we can meet up with the experimental measures by using these models in these particular conditions. |
