Condition Monitoring of Metallized Polypropylene Film Capacitors in Railway Power Trains

A novel technique for monitoring the condition of metallized polypropylene film (MPPF) capacitors installed in the dc link of railway power trains is proposed in this paper. The technique is based on the capacitance estimation of the two different capacitors used in the dc link (dc filtering and 2F filter capacitors), and it is done without adding any extra sensor or filter to the respective traction drive scheme. Therefore, the proposed method is implemented using software but not additional hardware for the different trains. Two other important passive component parameters of the traction drive are also monitored, all of them by means of curve fitting based on the least-mean-square (LMS) algorithm. The proposed technique is implemented and validated at simulation and experimental levels, using MATLAB/Simulink and a 1.2-MW traction drive test bench. Very accurate results are obtained, and the predictive maintenance of MPPF capacitors for different topologies of railway power trains can be set through the proposed technique.