Numerical detection of the current instability phenomena due to the balance of the electric machines

The instabilities arising in the power delivery network may cause serious problems for the whole system security. The most difficult detectable event is the energy balance phenomena. This has specific evolution characteristics, which are not so easy to be observed. The paper presents a real type situation, studied on a physically realized model, on a reduced scale. It is based on a permanent magnet synchronous motor. This is susceptible to give similar balance phenomena as conventional loaded equipment. The supply source is tuned as to obtain quasi-stable motion. The current and voltage evolution is represented in the phasespsila plane. To result a smooth enough wave, regression methods are used. In order to obtain useful information about the instability characteristics, special indicator functions are used. They emphasize, on one hand, the relative balance parameters and, on the other hand, the most unstable moment of evolution. This gives a discontinuous evolution for the derivativespsila variation for the current wave. The paper presents, as well, the mathematical background and the methods used for the processing of the measured parameters.