A method in a filter circuit of a power conversion system, the method comprising, in a first CALIBRATE mode during which a rectifier is off and an inverter is off and a multiphase AC power is provided to the filter circuit, the steps of: measuring filter voltages (v rn, v sn, v tn) associated with the filter circuit; using a first amplifier circuit, amplifying current sensor signals representing filter currents (i r, i s, i t) associated with the filter circuit to generate amplified current signals; using a second amplifier circuit, amplifying voltage sensor signals representing the measured filter voltages (v rn, v sn, v tn) associated with the filter circuit to generate amplified voltage signals; converting the amplified current signals using a first analog to digital converter circuit (108-1, 108-2); converting the amplified voltage signals using a second analog to digital converter circuit (108-3, 108-4); using a processor, automatically adjusting an amplifier gain, Gl, of the first amplifier circuit according to a conversion range of the first analog to digital converter circuit (108-1, 108-2) based at least partially on the amplified current signals; using the processor, automatically adjusting an amplifier gain, Gl, of the second amplifier circuit according to a conversion range of the second analog to digital converter circuit (108-3, 108-4) based at least partially on the amplified voltage signals; calculating (210, 212) capacitance values of filter capacitors of the filter circuit based at least partially on the amplified current signals and the amplified voltage signals; determining (214, 216) whether the calculated capacitance values are within an acceptable tolerance range; if the calculated capacitance values are not within the acceptable tolerance range, selectively identifying (218, 220, 222, 224) a filter capacitor fault in the power conversion system; and if the calculated capacitance values are within the acceptable tolerance range: storing the calculated capacitance values as base values in an electronic memory of the power conversion system, and changing to a second NORMAL mode with the rectifier on and the inverter on. measuring filter voltages (v rn, v sn, v tn) associated with the filter circuit; using a first amplifier circuit, amplifying current sensor signals representing filter currents (i r, i s, i t) associated with the filter circuit to generate amplified current signals; using a second amplifier circuit, amplifying voltage sensor signals representing the measured filter voltages (v rn, v sn, v tn) associated with the filter circuit to generate amplified voltage signals; converting the amplified current signals using a first analog to digital converter circuit (108-1, 108-2); converting the amplified voltage signals using a second analog to digital converter circuit (108-3, 108-4); using a processor, automatically adjusting an amplifier gain, Gl, of the first amplifier circuit according to a conversion range of the first analog to digital converter circuit (108-1, 108-2) based at least partially on the amplified current signals; using the processor, automatically adjusting an amplifier gain, Gl, of the second amplifier circuit according to a conversion range of the second analog to digital converter circuit (108-3, 108-4) based at least partially on the amplified voltage signals; calculating (210, 212) capacitance values of filter capacitors of the filter circuit based at least partially on the amplified current signals and the amplified voltage signals; determining (214, 216) whether the calculated capacitance values are within an acceptable tolerance range; if the calculated capacitance values are not within the acceptable tolerance range, selectively identifying (218, 220, 222, 224) a filter capacitor fault in the power conversion system; and if the calculated capacitance values are within the acceptable tolerance range: storing the calculated capacitance values as base values in an electronic memory of the power conversion system, and changing to a second NORMAL mode with the rectifier on and the inverter on. storing the calculated capacitance values as base values in an electronic memory of the power conversion system, and changing to a second NORMAL mode with the rectifier on and the inverter on.