Apparatus and method of detecting ground fault in power conversion system

A ground fault detection method in a power conversion system having a DC power supply which has an almost fixed DC voltage to ground and a predetermined stray capacitance to ground and outputs a DC power, and a power converter which converts the DC power output from the DC power supply into an AC power by switching, comprising:

• the first phase detection step of detecting a phase of an AC voltage to ground generated in the DC power supply by switching;
• the second phase detection step of detecting a phase of an AC ground fault current that flows through the stray capacitance to ground and a ground fault resistance of the DC power supply;
• and
• the ground fault determination step of determining a DC ground fault in the DC power supply by comparing a difference between the phases detected in the first and second phase detection steps with a predetermined threshold value.

A computer program for causing a computer to execute a ground fault detection method in a power conversion system having a DC power supply which has an almost fixed DC voltage to ground and a predetermined stray capacitance to ground and outputs a DC power, and a power converter which converts the DC power output from the DC power supply into an AC power by switching, comprising:

• program codes corresponding to
• the first phase detection step of detecting a phase of an AC voltage to ground generated in the DC power supply by switching;
• the second phase detection step of detecting a phase of an AC ground fault current that flows through the stray capacitance to ground and a ground fault resistance of the DC power supply;
• and
• the ground fault determination step of determining a DC ground fault in the DC power supply by comparing a difference between the phases detected in the first and second phase detection steps with a predetermined threshold value.

A storage medium which stores a computer program for causing a computer to execute a ground fault detection method in a power conversion system having a DC power supply which has an almost fixed DC voltage to ground and a predetermined stray capacitance to ground and outputs a DC power, and a power converter which converts the DC power output from the DC power supply into an AC power by switching, the storage medium storing program codes corresponding to

• the first phase detection step of detecting a phase of an AC voltage to ground generated in the DC power supply by switching;
• the second phase detection step of detecting a phase of an AC ground fault current that flows through the stray capacitance to ground and a ground fault resistance of the DC power supply;
• and
• the ground fault determination step of determining a DC ground fault in the DC power supply by comparing a difference between the phases detected in the first and second phase detection steps with a predetermined threshold value.