Modeling of a three-phase power conditioning system and improving its transient behavior following a heavy load drop

S.M. Miri, A. Keyhani
Dept. of Electr. Eng., North Carolina Univ., Charlotte, NC, USA;

This paper appears in: Electric Power Systems Research Journal
Volume: 25, No. 2
Publication Date: December 1992
On page(s): 137-147

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Abstract:
A power conditioning system is a device used to improve the quality of power in order to reduce equipment malfunctions. In a three-phase power conditioning system which utilizes ferroresonant circuits, the improved quality results from the synthesis of output voltages which remain constant over a wide range of input voltage variations caused by voltage sags, transients, noise, or harmonic distortions. This paper presents the development of, to our knowledge, the only existing model for three-phase power conditioning systems. It is shown, through extensive computer simulations and laboratory tests, that the developed model very closely mimics the behavior of the physical system under both transient and steady-state conditions. The validation of the model is verified in both time and frequency domains. The term ringing is used to describe the transient created in the output voltage following a sudden load drop. In a three-phase power conditioning system such transients may last up to one second. In this time period, the quality of power delivered to the consumers who remain connected to the system is poor. Two design modifications which would reduce the ringing time are presented in this paper. One of the proposed modifications has been successfully tested in the laboratory, while the success of the other has been demonstrated through computer simulations.