The aim of this study is to present system reconfiguration for a doubly fed induction machine (DFIM) after an open-switch fault is detected in its back-to-back converters. The open-switch fault and its detection for the scheme are discussed first. System reconfiguration is applied to operate the DFIM after the fault is detected. A four-switch converter topology with dc-link midpoint connection is selected to reconfigure the system. An existing pulse-width modulation method is investigated and applied to reconfigure the system, but uncontrollable capacitor voltage drift occurs. This study proposes a technique to solve the drift problem and also improve the quality of the dc-link voltage. Its effectiveness is substantiated by both simulation and experiment
An open circuit fault diagnostic method in IGBTs for the ac to dc converters used in microgrid applications is developed in this paper. An ac to dc converter is a key technology for microgrids in order to interface both distributed generation (DG) and renewable energy resources (RES). Also, highly reliable ac to dc converters are necessary to keep converters in continuous operation as long as possible during power switch fault conditions. Therefore, the proposed fault diagnostic method is developed to reduce the fault detection time and to avoid any other fault alarms because continuous operation is desired. The proposed diagnostic method is a combination of the absolute normalized dc current technique and the false alarm suppression algorithm to overcome the long fault detection time and fault alarm problems. The simulation and experimental results show that the developed fault diagnostic method can perform fault detection within about one cycle. The results illustrate that the reliability of an ac to dc converter interfaced with a microgrid can be improved by using the proposed fault diagnostic method.
This paper aims at the realization of the acceleration method for the small three-phase integral horsepower induction motors as referred to IEEE standard 112-1996 [l]. Testing on the small induction motors with an increasing moment of inertia technique is proposed. The characteristic results, the current-speed and torque-speed characteristics, are presented. In addition, verification of the results, limitation, and problems of this method are also interpreted. The limitation of this method is illustrated by loss calculation performed by comparing with current data from the locked-rotor test at rated voltage. This paper presents the method to find the appropriate time for the acceleration test. Finally, the problem which presents during the test is also discussed.
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