A method for detecting capacitor degradation in a filter circuit including three capacitor circuit branches (22r, 22s,22t), the filter circuit being coupled between a power converter input and a rectifier, and the filter circuit comprising first, second, and third series circuits individually including at least one filter inductor (Lu, Lv, Lw) coupled between a corresponding phase of the power converter input and a corresponding phase of the three phase AC input of the rectifier, the first, the second, and the third capacitor circuit branches (22r, 22s, 22t) respectively connected to the first, second and third series circuits, and three filter capacitors (C RS, C ST, C TR; C R, C S, C T) with each filter capacitor being connected to at least one of the capacitor circuit branches, the method comprising: measuring with a measurement circuit a plurality of filter circuit branch currents (i r, i s, i t) flowing in each of the capacitor circuit branches (22r,22s,22t) included in the filter circuit; measuring with the measurement circuit a plurality of filter circuit voltages (v rn, V sn, v tn) associated with the filter circuit; and, in a processor programmed thereto: computing a plurality of individual nominal filter circuit power values (P Rc, P Sc, P Tc) using the measured filter circuit voltages (v rn, V sn, V tn), a filter operating frequency (w), and at least one nominal capacitance value; computing a plurality of individual measured filter circuit power values (P Rm, P Sm, P Tm) using the measured filter circuit voltages (v rn, V sn, v tn) and the measured filter circuit branch currents (i r, i s, i t); computing a plurality of individual power change values (ΔP R, ΔP S, ΔP T) representing deviations of the individual measured filter circuit power values (P Rm, P Sm, P Tm) from the corresponding individual nominal filter circuit power values (P Rc, P Sc, P Tc) as a difference between a corresponding nominal filter circuit power value (P Rc, P Sc, P Tc) and a corresponding measured filter circuit power value (P Rm, P Sm, P Tm); and selectively identifying a capacitor degradation condition in the filter circuit according to the individual power change values (ΔP R, ΔP S, ΔP T) which comprises determining whether the individual power change values (ΔP R, ΔP S, ΔP T) are greater than or equal to a threshold value. measuring with a measurement circuit a plurality of filter circuit branch currents (i r, i s, i t) flowing in each of the capacitor circuit branches (22r,22s,22t) included in the filter circuit; measuring with the measurement circuit a plurality of filter circuit voltages (v rn, V sn, v tn) associated with the filter circuit; and, in a processor programmed thereto: computing a plurality of individual nominal filter circuit power values (P Rc, P Sc, P Tc) using the measured filter circuit voltages (v rn, V sn, V tn), a filter operating frequency (w), and at least one nominal capacitance value; computing a plurality of individual measured filter circuit power values (P Rm, P Sm, P Tm) using the measured filter circuit voltages (v rn, V sn, v tn) and the measured filter circuit branch currents (i r, i s, i t); computing a plurality of individual power change values (ΔP R, ΔP S, ΔP T) representing deviations of the individual measured filter circuit power values (P Rm, P Sm, P Tm) from the corresponding individual nominal filter circuit power values (P Rc, P Sc, P Tc) as a difference between a corresponding nominal filter circuit power value (P Rc, P Sc, P Tc) and a corresponding measured filter circuit power value (P Rm, P Sm, P Tm); and selectively identifying a capacitor degradation condition in the filter circuit according to the individual power change values (ΔP R, ΔP S, ΔP T) which comprises determining whether the individual power change values (ΔP R, ΔP S, ΔP T) are greater than or equal to a threshold value. computing a plurality of individual nominal filter circuit power values (P Rc, P Sc, P Tc) using the measured filter circuit voltages (v rn, V sn, V tn), a filter operating frequency (w), and at least one nominal capacitance value; computing a plurality of individual measured filter circuit power values (P Rm, P Sm, P Tm) using the measured filter circuit voltages (v rn, V sn, v tn) and the measured filter circuit branch currents (i r, i s, i t); computing a plurality of individual power change values (ΔP R, ΔP S, ΔP T) representing deviations of the individual measured filter circuit power values (P Rm, P Sm, P Tm) from the corresponding individual nominal filter circuit power values (P Rc, P Sc, P Tc) as a difference between a corresponding nominal filter circuit power value (P Rc, P Sc, P Tc) and a corresponding measured filter circuit power value (P Rm, P Sm, P Tm); and selectively identifying a capacitor degradation condition in the filter circuit according to the individual power change values (ΔP R, ΔP S, ΔP T) which comprises determining whether the individual power change values (ΔP R, ΔP S, ΔP T) are greater than or equal to a threshold value.