Patent ID: 9651603
Date: 2017-05-16
CPC Classifications: G01R,H02M

Claim:
1. A method of determining a capacitor degradation parameter associated with a degree of degradation of a cell capacitor in a converter cell of a power converter, the power converter comprising a plurality of identical converter cells, wherein one of the plurality of identical converter cells, prior to determining the capacitor degradation parameter, has been bypassed, wherein the capacitor degradation parameter is a capacitance of the cell capacitor, and wherein the method comprises: a) obtaining a measurement parameter value associated with discharging of the cell capacitor, forming a dc-link, from a measurement start voltage level at a measurement start time to a measurement end voltage level at a measurement end time, b) determining a value of the capacitor degradation parameter based on the time difference between the measurement start time and the measurement end time, wherein the determining of the value of the capacitor degradation parameter is further based on the measurement start voltage level, the measurement end voltage level, and a cell resistor value or a power consumption of an auxiliary power supply of the converter cell, wherein the capacitor degradation parameter is directly proportional to the time difference between the measurement start time and the measurement end time.