Measuring dc link capacitance in power conversion systems

A method comprising:

• suspending power flow between a direct current (“DC”) source and a DC link capacitor of a power converter and to suspend power flow between the DC link capacitor and a load of the power converter, a bleeding resistor is connected in parallel with the DC link capacitor and an auxiliary power supply draws power from the DC link capacitor, the auxiliary power supply providing control power for the power converter;
• measuring, using a voltage sensing circuit to measure voltage across the DC link capacitor, a first voltage at a first time, a second voltage at a second time, and a third voltage at a third time in response to suspending power from or to the DC source and power to or from the load;
• using a resistance of the bleeding resistor, the first, second and third voltages and the first, second and third times to determine a current capacitance of the DC link capacitor;
• comparing the current capacitance with an initial capacitance of the DC link capacitor;
• and
• sending an alert in response to determining that a difference between the current capacitance and the initial capacitance is above a capacitance degradation threshold.

A computer program product comprising a non-transitory computer readable storage medium having program code embodied therein, the program code executable by a processor to:

• suspend power flow between a direct current (“DC”) source and a DC link capacitor of a power converter and to suspend power flow between the DC link capacitor and a load of the power converter, the DC link capacitor comprising a bleeding resistor connected in parallel with the DC link capacitor, and an auxiliary power supply drawing power from the DC link capacitor, the auxiliary power supply providing control power for the power converter;
• measure, using a voltage sensing circuit to measure voltage across the DC link capacitor, a first voltage at a first time, a second voltage at a second time, and a third voltage at a third time in response to suspending power from or to the DC source and power to or from the load;
• use a resistance of the bleeding resistor, the first, second and third voltages and the first, second and third times to determine a current capacitance of the DC link capacitor;
• compare the current capacitance with an initial capacitance of the DC link capacitor;
• and
• send an alert in response to determining that a difference between the current capacitance and the initial capacitance is above a capacitance degradation threshold.