A power conversion system, comprising: a power converter input operative to receive multiphase AC input power; an active front end rectifier, comprising a multiphase AC input, and a plurality of switching devices (S1-S6) operative according to a plurality of rectifier switching control signals to convert power received at the input to provide DC output power; an input filter circuit coupled between the power converter input and the AFE rectifier, the input filter circuit comprising a plurality of filter inductors (LR1, LR2, LS1, LS2, LT1, LT2) coupled between a corresponding phase of the power converter input and a corresponding phase of the AC input of the AFE rectifier, and a capacitor circuit including a plurality of filter capacitors (CR, CS, CT) individually connected to at least one of the filter inductors (LR1, LR2, LS1, LS2, LT1, LT2); a sensing circuit operative to determine a plurality of measured currents (i R, i S, i T) and measured voltages (v RS, v ST) associated with the input filter circuit; and a degradation detection system operatively coupled with the input filter circuit, characterized by the degradation detection system comprising at least one processor configured to: compute fundamental frequency current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST) based on the measured currents (i R, i S, i T) and voltages (v RS, v ST), compute positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n) based on the computed fundamental frequency filter circuit current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST), compute at least one off-diagonal term (Y np, Y pn) of a filter circuit admittance matrix based on at least one of the computed positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n), compare the at least one off-diagonal term (Y np, Y pn) to at least one threshold, and selectively detect degradation of one or more of the filter capacitors (CR, CS, CT) if the at least one off-diagonal term (Y np, Y pn) exceeds the at least one threshold. a power converter input operative to receive multiphase AC input power; an active front end rectifier, comprising a multiphase AC input, and a plurality of switching devices (S1-S6) operative according to a plurality of rectifier switching control signals to convert power received at the input to provide DC output power; an input filter circuit coupled between the power converter input and the AFE rectifier, the input filter circuit comprising a plurality of filter inductors (LR1, LR2, LS1, LS2, LT1, LT2) coupled between a corresponding phase of the power converter input and a corresponding phase of the AC input of the AFE rectifier, and a capacitor circuit including a plurality of filter capacitors (CR, CS, CT) individually connected to at least one of the filter inductors (LR1, LR2, LS1, LS2, LT1, LT2); a sensing circuit operative to determine a plurality of measured currents (i R, i S, i T) and measured voltages (v RS, v ST) associated with the input filter circuit; and a degradation detection system operatively coupled with the input filter circuit, characterized by the degradation detection system comprising at least one processor configured to: compute fundamental frequency current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST) based on the measured currents (i R, i S, i T) and voltages (v RS, v ST), compute positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n) based on the computed fundamental frequency filter circuit current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST), compute at least one off-diagonal term (Y np, Y pn) of a filter circuit admittance matrix based on at least one of the computed positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n), compare the at least one off-diagonal term (Y np, Y pn) to at least one threshold, and selectively detect degradation of one or more of the filter capacitors (CR, CS, CT) if the at least one off-diagonal term (Y np, Y pn) exceeds the at least one threshold. compute fundamental frequency current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST) based on the measured currents (i R, i S, i T) and voltages (v RS, v ST), compute positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n) based on the computed fundamental frequency filter circuit current and voltage phasors (Ĩ R, Ĩ S, Ĩ T, Ṽ RS, Ṽ ST), compute at least one off-diagonal term (Y np, Y pn) of a filter circuit admittance matrix based on at least one of the computed positive and negative sequence current and voltage component phasors (Ĩ p, Ĩ n, Ṽ p, Ṽ n), compare the at least one off-diagonal term (Y np, Y pn) to at least one threshold, and selectively detect degradation of one or more of the filter capacitors (CR, CS, CT) if the at least one off-diagonal term (Y np, Y pn) exceeds the at least one threshold.