Detection of faulty incremental encoder in a DFIM-based variable speed pump-turbine unit

This paper aims to show the effectiveness of a faulty detection method based on the parity space approach to detect an abrupt change in the measured position value using an incremental encoder, for a variable speed pump-turbine system, based on doubly fed induction machine. The operating principal of the incremental is detailed in order to analyze the origin of a fault and its impact on encoder output, and then on its propagation on the whole control of the system under study. The developed algorithm depends only on previous measures and does not require any parameter system knowledge. It is simple, so, it does not need a specific target device to be implemented. Simulation results are carried out to illustrate this analysis, and experimental results on a 4kW laboratory setup are provided to demonstrate the effectiveness of the method in cases of total loss and gain fault encoder output.