Interconnection power converter and power generation apparatus using the same

• US 6,320,769 B2
• Filed: 11/30/2000
• Issued: 11/20/2001
• Est. Priority Date: 12/01/1999
• 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): HAN, YOUNGHUIE JESSICA
• Application Number:
  US09/725,819
• Publication Number:
  US 20010004322A1
• Time in Patent Office: 355 Days
• Field of Search: 363/55, 363/56.01, 363/56.02, 363/56.03, 363/56.04, 363/56.05, 363/98, 363/132, 323/225, 323/299, 323/235, 323/906, 361/42, 361/45, 361/49
• US Class Current: 363/56.03
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 3/381 Dispersed generators
• 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 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 7/53873 with digital control
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y10S 323/906 Solar cell systems

Abstract

In a solar power generation apparatus using a solar battery having a relatively large ground capacitor and a power conditioner having a non-insulated input and output, a customer'"'"'s ground fault interrupter may perform unwanted interruption due to a ground fault outside the customer'"'"'s premises. To prevent this, when a ground fault is detected by a detector capable of detecting a ground fault within a shorter time than the customer'"'"'s ground fault interrupter, the gate of inverter of the power conditioner is blocked, a switch is changed to an open state, and the input voltage of inverter is held at a voltage value higher than the peak value of the alternate current voltage of a power system until at least the switch changes to the open state.

Claims

1. A power converter for converting direct current power to alternate current power and supplying the alternate current power to a power system, said power converter comprising:

a converter for boosting a voltage of direct current power supplied from a direct current power supply having a ground capacitor;

an inverter for converting the direct current power supplied from said converter into alternate current power, wherein an input and output of said inverter are not insulated;

a switch which is connected to an output terminal of said inverter and opens/closes an output of said power converter by a mechanical contact;

a detector for detecting a ground fault within a shorter time than an operation time of a customer'"'"'s ground fault interrupter interposed between said power converter and a power system having one grounded line; and

a controller for controlling operations of said converter, said inverter, and said switch, wherein when said detector detects a ground fault, said controller changes said switch to an open state, blocks a gate of said inverter, and holds an output voltage of said converter to be higher than a peak value of an alternate current voltage of the power system until at least said switch changes to the open state.

2. The power converter according to claim 1, wherein when a predetermined time elapses after said switch changes to the open state, said controller cancels the gate block, changes said switch to a closed state, and resumes running of said power converter.

3. The power converter according to claim 1, wherein when a predetermined time elapses after said switch changes to the open state, said controller changes said switch to a closed state while holding the output voltage of said converter to be higher than the peak value of the alternate current voltage of the power system, and then gradually increases an output from said inverter from substantially zero.

4. The power converter according to claim 1, wherein said controller outputs a warning when said detector detects a ground fault and/or when said detector successively detects ground faults.

5. The power converter according to claim 1, wherein said controller has a setting unit for setting a ground fault detection condition of said detector.

6. The power converter according to claim 1, wherein said controller sets in said detector a ground fault detection condition corresponding to output power of said inverter.

7. The power converter according to claim 1, wherein said controller sets a ground fault detection condition of said detector on the basis of a current value detected by said detector when said power converter runs.

8. The power converter according to claim 7, wherein said controller has a display for displaying the ground fault detection condition.

9. The power converter according to claim 1, wherein said controller has a memory for recording a ground fault detection result by said detector.

10. The power converter according to claim 1, wherein said detector detects a ground fault by the same method as the customer'"'"'s ground fault interrupter.

11. The power converter according to claim 1, wherein said detector detects a zero-phase current and a phase difference between the zero-phase current and a ground voltage of each line of the power system, and detects a ground fault on the basis of detected values.

12. The power converter according to claim 1, wherein said detector detects variations in ground voltage of each line of the power system, and detects a ground fault on the basis of a detected value.

13. The power converter according to claim 1, wherein said inverter has switching elements having a full-bridge arrangement.

14. The power converter according to claim 1, wherein the direct current power supply includes a solar battery.

15. A controlling method of a power converter which converts direct current power to alternate current power, supplies the alternate current power to a power system, and comprises a converter for boosting a voltage of direct current power supplied from a direct current power supply having a ground capacitor, an inverter for converting the direct current power supplied from said converter into alternate current power, wherein an input and output of said inverter are not insulated, a switch which is connected to an output terminal of said inverter and opens/closes an output of said power converter by a mechanical contact, and a detector for detecting a ground fault within a shorter time than an operation time of a customer'"'"'s ground fault interrupter interposed between said power converter and a power system having one grounded line, said method comprising the steps of:

changing said switch to an open state when said detector detects a ground fault;

blocking a gate of said inverter; and

holding an output voltage of said converter to be higher than a peak value of an alternate current voltage of the power system until at least said switch changes to the open state.

16. The method according to claim 15, further comprising the step of, when a predetermined time elapses after said switch changes to the open state, canceling the gate block, changing said switch to a closed state, and resuming running of said power converter.

17. The method according to claim 15, further comprising the step of, when a predetermined time elapses after said switch changes to the open state, changing said switch to a closed state while holding the output voltage of said converter to be higher than the peak value of the alternate current voltage of the power system, and then gradually increasing an output from said inverter from substantially zero.

18. The method according to claim 15, further comprising the step of outputting a warning when said detector detects a ground fault and/or when said detector successively detects ground faults.

19. A power generation apparatus for supplying alternate current power to a power system and comprising a direct current power supply having a ground capacitor, and a power converter for converting direct current power into alternate current power,

wherein said power converter comprises:

a converter for boosting a voltage of direct current power supplied from the direct current power supply;

an inverter for converting the direct current power supplied from said converter into alternate current power, wherein an input and output of said inverter are not insulated;

a switch which is connected to an output terminal of said inverter and opens/closes an output of said power converter by a mechanical contact;

a detector for detecting a ground fault within a shorter time than an operation time of a customer'"'"'s ground fault interrupter interposed between said power converter and a power system having one grounded line; and

a controller for controlling operations of said converter, said inverter, and said switch, wherein when said detector detects a ground fault, said controller changes said switch to an open state, blocks a gate of said inverter, and holds an output voltage of said converter to be higher than a peak value of an alternate current voltage of the power system until at least said switch changes to the open state.

20. The apparatus according to claim 19, wherein the direct current power supply includes a solar battery.