Method of reducing leakage current in power supply systems

• US 6,611,441 B2
• Filed: 02/20/2002
• Issued: 08/26/2003
• Est. Priority Date: 02/26/2001
• Status: Expired due to Fees

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Takehara, Nobuyoshi, Manabe, Naoki, Kurokami, Seiji
• Primary Examiner(s): Sterrett, Jeffrey
• Application Number:
  US10/077,816
• Publication Number:
  US 20020118559A1
• Time in Patent Office: 552 Days
• Field of Search: 363/40, 363/41, 363/53, 363/56.01, 363/56.02, 363/95, 363/97, 363/98, 363/131, 363/132
• US Class Current: 363/56.02
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/123 Suppression of common mode voltage or current
• CPC Class Codes: H02M 1/15 using active elements
• CPC Class Codes: H02M 7/48 using discharge tubes with control electrode or semiconductor devices with control electrode

Abstract

In a power supply system for converting the output of a DC power supply having an earth capacitance to AC power, an input voltage from an input-voltage detector and an intermediate voltage from an intermediate-voltage detector are input to an input-ripple controller. The latter calculates the difference between ripple voltages of the two voltages. The input-ripple controller adjusts the size of a ripple command value, which indicates the ripple current that is to be input to a converter circuit, so as to null the difference between the ripple voltages. Furthermore, using a ripple reference waveform having a DC level, the input-ripple controller generates a ripple current waveform so as to null the average value of a full-wave rectified waveform synchronized to the output of an inverter circuit, and outputs the generated ripple current waveform to an output calculator. The output calculator adds the DC current command from the input-voltage controller and the ripple current waveform from the input ripple controller to thereby generate an output current waveform, which is output to a converter circuit driver.

Claims

1. 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;

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.

2. The inverter according to claim 1, wherein said controller includes an input-voltage controller for changing the value of voltage, which is input to said converter circuit, based upon outputs from said detector 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.

3. The inverter according to claim 1, wherein said controller includes an electrostatic-capacity adjuster for applying electrostatic capacity to the terminal which has smaller AC component of voltage to ground than that of the other, based upon outputs from said detector.

4. 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.

5. The inverter according to claim 4, wherein said converter circuit is of non-inverting type, and said controller controls the DC voltage that is input to said converter circuit in such a manner that the AC component of the DC voltage that is input to said converter circuit will take on a phase identical with that of the AC component of the voltage at both ends of said intermediate smoothing capacitor.

6. The inverter according to claim 4, wherein said converter circuit is of non-inverting type, and said controller controls the DC voltage that is input to said converter circuit in such a manner that the AC component of the DC voltage that is input to said converter circuit will take on a phase opposite that of the AC component of the voltage at both ends of said intermediate smoothing capacitor.

7. The inverter according to claim 4, wherein said controller controls the DC voltage that is input to said converter in such a manner that the size of the AC component of the DC voltage that is input to said converter circuit will become substantially equal to that of the AC component of the voltage at both ends of said intermediate smoothing capacitor.

8. The inverter according to claim 4, wherein said controller controls the DC voltage that is input to said converter in such a manner that the size of the AC component of the DC voltage that is input to said converter circuit will become half that of the AC component of the voltage at both ends of said intermediate smoothing capacitor.

9. The inverter according to claim 8, further comprising an electrostatic-capacity adjuster for applying electrostatic capacity to the terminal of two input terminals of said converter circuit which has the smaller AC component of voltage to ground.

10. The inverter according to claim 4, further comprising a voltage-to-ground detector for detecting voltage to ground of an input to said converter circuit, wherein said controller controls the AC component of the DC voltage that is input to said converter circuit based upon an output from said voltage-to-ground detector.

11. The inverter according to claim 4, further comprising a zero-phase current detector for detecting zero-phase current of said inverter, wherein said controller controls the AC component of the DC voltage that is input to said converter circuit based upon an output from said zero-phase current detector.

12. 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.

13. The inverter according to claim 12, further includes an electrostatic-capacity adjuster for applying electrostatic capacity to the terminal which has smaller AC components of voltage to ground than that of the other.

14. 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.

15. The system according to claim 14, wherein said DC power supply is a solar battery.

16. The system according to claim 15, wherein said solar battery has a reinforcing member on a back side thereof.

17. The system according to claim 15, wherein said solar battery is formed as an integral part of a building material and is installed on the roof of a building.

18. 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.

19. The system according to claim 18, wherein said DC power supply is a solar battery.

20. The system according to claim 19, wherein said solar battery has a reinforcing member on a back side thereof.

21. The system according to claim 19, wherein said solar battery is formed as an integral part of a building material and is installed on the roof of a building.

22. 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.

23. The system according to claim 22, wherein said DC power supply is a solar battery.

24. The system according to claim 23, wherein said solar battery has a reinforcing member on a back side thereof.

25. The system according to claim 23, wherein said solar battery is formed as an integral part of a building material and is installed on the roof of a building.

26. A method of reducing leakage current of a power supply system having a non-insulated type inverter which includes a converter circuit for boosting voltage of DC power that has entered from two terminals, and an inverter circuit for converting the DC voltage, which has been boosted by said converter circuit, to alternating current, said inverter converting DC powder to AC power and outputting the AC power to a single-phase, three-wire AC power system having a neutral point that is connected to ground, said method comprising the steps of:

detecting AC components of voltages to ground produced at respective ones of the two terminals; and

reducing the AC components of the DC voltage, which is input to said inverter circuit, based upon results of detection.

27. A method of reducing leakage current of a power supply system having a non-insulated type inverter which includes 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, and an intermediate smoothing capacitor provided between said converter circuit and said inverter circuit, said inverter converting DC powder to AC power and outputting the AC power to a single-phase, three-wire AC power system having a neutral point that is connected to ground, said method comprising the steps of:

detecting an AC component of DC voltage that is input to said converter circuit and an AC component of voltage at both ends of said intermediate smoothing capacitor; and

controlling the DC voltage input to said converter circuit in such a manner that the two AC components will be synchronized.