Method of reducing leakage current in power supply systems

A non-insulated type inverter for converting DC power to AC power and outputting the AC power to a single-phase three-wire AC power system having a grounded neutral point, comprising:

• a converter circuit for boosting voltage of entered DC power;
• an inverter circuit for converting DC voltage, which has been boosted by said converter circuit, to alternating current;
• an intermediate smoothing capacitor provided between said converter circuit and said inverter circuit;
• a first detector for detecting an AC component of DC voltage that is input to said converter circuit;
• a second detector for detecting an AC component of voltage at both ends of said intermediate smoothing capacitor;
• and
• a controller for controlling the DC voltage input to said converter circuit in such a manner that the two AC components detected by said first and second detectors will be synchronized.

A non-insulated type inverter for converting DC power to AC power and outputting the AC power to a single-phase three-wire AC power system having a grounded neutral point, comprising:

• a converter circuit for boosting voltage of DC power that has entered from two terminals;
• an inverter circuit for converting DC voltage, which has been boosted by said converter circuit, to alternating current;
• and
• an input-voltage controller for controller for changing the value of voltage, which is input to said converter circuit, in such a manner that AC components of the voltages to ground produced at the two terminals will take on phases that are the opposite of each other.

A power supply system comprising:

• a DC power supply having an earth capacitance;
• and
• a non-insulated type inverter for converting DC power to AC power and outputting the AC power to a single-phase three-wire AC power system having a grounded neutral point, including,
• a converter circuit for boosting voltage of entered DC power,
• an inverter circuit for converting DC voltage, which has been boosted by said converter circuit, to alternating current,
• a detector for detecting AC components of voltages to ground produced at respective ones of the two terminals, and
• a controller for reducing the AC components of the DC voltage, which is input to said inverter circuit, based upon outputs of said detector.

A power supply system comprising:

• a DC power supply having an earth capacitance;
• and
• a non-insulated type inverter for converting DC power to AC power and outputting the AC power to a single-phase three-wire AC power system having a grounded neutral point, including,
• a converter circuit for boosting voltage of entered DC power,
• an inverter circuit for converting DC voltage, which has been boosted by said converter circuit, to alternating current,
• an intermediate smoothing capacitor provided between said converter circuit and said inverter circuit,
• a first detector for detecting an AC component of DC voltage that is input to said converter circuit,
• a second detector for detecting an AC component of voltage at both ends of said intermediate smoothing capacitor, and
• a controller for controlling the DC voltage input to said converter circuit in such a manner that the two AC components detected by said first and second detectors will be synchronized.

A power supply system comprising:

• a DC power supply having an earth capacitance;
• and
• a non-insulated type inverter for converting DC power to AC power and outputting the AC power to a single-phase three-wire AC power system having a grounded neutral point, including
• a converter circuit for boosting voltage of DC power that has entered from two terminals,
• an inverter circuit for converting DC voltage, which has been boosted by said converter circuit, to alternating current, and
• an input-voltage controller for changing the value of voltage, which is input to said converter circuit, in such a manner that AC components of the voltages to ground produced at the two terminals will take on phases that are the opposite of each other.