Isolated operation detecting method, control apparatus for detecting isolated operation for distributed power supply

• US 20070179724A1
• Filed: 01/12/2007
• Published: 08/02/2007
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: Omron Corporation
• Original Assignee: Omron Corporation
• Inventors: Mabuchi, Masao, Tsubota, Yasuhiro, Kato, Masaya, Imamura, Kazuyoshi, Oka, Seiji, Hosomi, Shinichi, Toyoura, Nobuyuki
• Granted Patent: US 7,630,794 B2
• Time in Patent Office: Days
• US Class Current: 702/60
• CPC Class Codes: G01R 19/2513 Arrangements for monitoring electric power systems, e.g. power lines or loads; Logging
• CPC Class Codes: H02J 13/00 Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
• CPC Class Codes: H02J 2300/10 The dispersed energy generation being of fossil origin, e.g. diesel generators
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/30 The power source being a fuel cell
• CPC Class Codes: H02J 3/381 Dispersed generators
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 40/70 Smart grids as climate change mitigation technology in the energy generation sector
• CPC Class Codes: Y04S 10/12 Monitoring or controlling equipment for energy generation units, e.g. distributed energy generation [DER] or load-side generation
• CPC Class Codes: Y04S 10/123 the energy generation units being or involving renewable energy sources

Abstract

An isolated operation detecting method according to the present invention includes: a first step that injects a power fluctuation into the power system; a second step that measures a system cycle; a third step that adjusts the injection of the power fluctuation so that the system cycle increases when the system cycle is found increased than the previous system cycle as a result of the measuring, and decreases when the system cycle is found decreased than the previous system cycle; a fourth step that produces a change pattern of a latest system cycle on the basis of a deviation of the latest system cycle from a fixed number of cycle-passed previous system cycle; and a fifth step that determines an isolated operation on the basis of the change pattern.

Claims

1. An isolated operation detecting method for detecting whether a distributed power supply is cut off from a power system and isolatedly operated or not on the basis of a power fluctuation injected into the power system, comprising:

a first step that injects a power fluctuation into the power system;

a second step that measures a system cycle;

a third step that adjusts the injection of the power fluctuation so that the system cycle increases when the system cycle is found increased than the previous system cycle as a result of the measuring, and decreases when the system cycle is found decreased than the previous system cycle as a result of the measuring;

a fourth step that produces a change pattern of a latest system cycle on the basis of a deviation of the latest system cycle from a fixed number of cycle-passed previous system cycle; and

a fifth step that determines an isolated operation on the basis of the change pattern.

2. An isolated operation detecting method according to claim 1, wherein the fourth step calculates whether each of the deviations between each of plural latest system cycles and each of a fixed number of cycle-passed previous system cycles exceeds a corresponding one of plural threshold values set for every deviation, and forms the change pattern on the basis of the result of the calculation.

3. An isolated operation detecting method according to claim 2, wherein the interval between the latest system cycles and the previous system cycles is fixed.

4. An isolated operation detecting method according to claim 2, wherein the plural deviations are the deviations between each of the plural latest system cycles and an average value of a fixed number of cycle-passed previous system cycles.

5. An isolated operation detecting method according to claim 2, wherein the fourth step forms an isolated operation determination area from each of threshold values set corresponding to each of the plural latest system cycles, and wherein the fifth step determines the isolated operation by judging whether the change pattern formed from the plural deviations is within the isolated operation determination area or not.

6. An isolated operation detecting method according to claim 2, wherein the threshold value is set to be greater for the most latest system cycle.

7. An isolated operation detecting method according to claim 2, wherein in case increased threshold is set, the first threshold value is set to be negative.

8. An isolated operation detecting method according to claim 2, wherein in case decreased threshold is set, the first threshold value is set to be positive.

9. An isolated operation detecting method according to claim 2, wherein an average value of the plural latest system cycles is used as each of the latest system cycles.

10. An isolated operation detecting method according to claim 2, wherein the threshold values are set to slowly increase or decrease compared to system cycles.

11. An isolated operation detecting method according to claim 9, wherein each of the threshold values comprises a threshold value determined with a prolonged cycle of more than one latest system cycle.

12. An isolated operation detecting method according to claim 2, wherein the threshold values comprise a set of threshold values for determining a sharp system cycle change during a short cycle period and a set of threshold values for determining a gentle system cycle change during a long cycle period.

15. A control apparatus that controls an operation of an isolated operation detecting apparatus that detects whether a distributed power supply is cut off from a power system and isolatedly operated or not, comprising incorporated therein a microcomputer including software program executing the method according to claim 1.

13. A control apparatus that controls an operation of an isolated operation detecting apparatus that detects whether a distributed power supply is cut off from a power system and isolatedly operated or not, comprising:

a first unit that injects a power fluctuation into the power system;

a second unit that measures a system cycle;

a third unit that adjusts the injection of the power fluctuation so that the system cycle increases when the system cycle is found increased than the previous system cycle as a result of the measuring, and decreases when the system cycle is found decreased than the previous system cycle as a result of the measuring;

a fourth unit that producing a change pattern of a latest system cycle on the basis of a deviation of the latest system cycle from a fixed number of cycle-passed previous system cycle; and

a fifth unit that determines an isolated operation on the basis of the change pattern.

14. A control apparatus according to claim 13, wherein the first to the fifth units are distributedly mounted both in the distributed power supply and the isolated operation detecting apparatus.

16. An isolated operation detecting apparatus that detects whether a distributed power supply is cut off from a power system and isolatedly operated or not, comprising the control apparatus according to claim 13.

17. A distributed power supply that has incorporated therein an isolated operation detecting apparatus that detects whether a distributed power supply is cut off from a power system and isolatedly operated or not, wherein the isolated operation detecting apparatus comprises the control apparatus according to claim 13.