Supervisory control method and equipment for smart grids

• US 8,880,234 B2
• Filed: 07/26/2011
• Issued: 11/04/2014
• Est. Priority Date: 07/29/2010
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Fukui, Chihiro, Yamada, Tetsuo, Sekoguchi, Masahiro
• Primary Examiner(s): PATEL, RAMESH B
• Application Number:
  US13/190,666
• Publication Number:
  US 20120029716A1
• Time in Patent Office: 1,197 Days
• Field of Search: 700286-287, 700291-298, 702 60- 62
• US Class Current: 700/296
• CPC Class Codes: H02J 3/38 Arrangements for parallely feeding a single network by two or more generators, converters or transformers
• CPC Class Codes: H02J 3/388 Islanding, i.e. disconnection of local power supply from the network

Abstract

Supervisory control equipment for smart grids provided with a plurality of generators and loads and operated in interconnection with a commercial power system through an interconnected circuit breaker, comprising a frequency control ability calculation part for calculating the frequency control ability of the interconnected system by using a total power demand and a bus bar frequency; and an islanding and interconnection detection part for calculating frequency control ability of the commercial power system according to the frequency control ability of the system of the frequency control ability calculation part to discriminate between the interconnected and islanding operations according to the magnitude of the frequency control ability.

Claims

1. A supervisory control method for smart grids which comprise a plurality of generators and loads and are operated in interconnection with a commercial power system, comprising:

calculating frequency control ability of the commercial power system; and

discriminating between an interconnection operation and an islanding operation according to the magnitude of the frequency control ability;

wherein the frequency control ability is calculated as a ratio between a time-series standard deviation of a system load short cyclic variation and a time-series standard deviation of a system frequency short cyclic variation.

2. The supervisory control method for smart grids according to claim 1, wherein when it is discriminated that the commercial power system is interconnected with the smart grids, a generator governor-free operation capacity in the smart grids is adjusted according to the frequency control ability of the commercial power system.

3. The supervisory control method for smart grids according to claim 2, wherein the commercial power system and the smart grid are compared for the frequency control ability, and the generator governor-free operation capacity in the smart grid is adjusted to conform the frequency control ability of the smart grid to the frequency control ability of the commercial power system.

4. The supervisory control method for smart grids according to claim 1, wherein when it is discriminated that the smart grid is in the islanding operation, the governor-free operation capacity is determined according to a permissible frequency variation of the smart grid.

5. The supervisory control method for smart grids according to claim 1, wherein when it is discriminated according to a change in the frequency control ability of the commercial power system that the smart grid is in the islanding operation, an open instruction is given to a circuit breaker interconnected between the commercial power system and the smart grid.

6. The supervisory control method for smart grids according to claim 5, wherein when it is discriminated according to the change in the frequency control ability of the commercial power system that the smart grid is in the islanding operation and the discriminated result of an active type islanding operation determination unit matches, the open instruction is given to the circuit breaker interconnected between the commercial power system and the smart grid.

7. The supervisory control method for smart grids according to claim 1, wherein the frequency control ability for discriminating between the interconnection and islanding operations according to the magnitude of the frequency control ability is determined to be frequency control ability of the system that the commercial power system and the smart grids are interconnected.

8. Supervisory control equipment for smart grids provided with a plurality of generators and loads and operated in interconnection with a commercial power system through an interconnected circuit breaker, comprising:

a frequency control ability calculation part for calculating the frequency control ability of the interconnected system by using a total power demand and a bus bar frequency; and

an islanding and interconnection detection part for calculating frequency control ability of the commercial power system according to the frequency control ability of the system of the frequency control ability calculation part to discriminate between the interconnected and islanding operations according to the magnitude of the frequency control ability;

wherein the frequency control ability calculation part calculates the frequency control ability as a ratio between a time-series standard deviation of a system load short cyclic variation and a time-series standard deviation of a system frequency short cyclic variation.

9. The supervisory control equipment for smart grids according to claim 8, further comprising a cooperated operation control part that adjusts the generator governor-free operation capacity in the smart grids according to the frequency control ability of the commercial power system when it is discriminated as an interconnected operation by the islanding and interconnection detection part.

10. The supervisory control equipment for smart grids according to claim 9, wherein the islanding and interconnection detection part calculates the frequency control ability of the commercial power system and the smart grids, and the cooperated operation control part adjusts the generator governor-free operation capacity in the smart grids to conform the frequency control ability of the smart grid to the frequency control ability of the commercial power system.

11. The supervisory control equipment for smart grids according to claim 8, further comprising an islanding operation control part that determines the governor-free operation capacity according to a permissible frequency variation of the smart grids when it is discriminated as an islanding operation by the islanding and interconnection detection part.

12. The supervisory control equipment for smart grids according to claim 8, further comprising a control part for interconnected circuit breaker that gives an open instruction to the interconnected circuit breaker between the commercial power system and the smart grids when it is discriminated as an islanding operation by the islanding and interconnection detection part.

13. The supervisory control equipment for smart grids according to claim 12, wherein the control part for interconnected circuit breaker gives an open instruction to the interconnected circuit breaker between the commercial power system and the smart grids when it is discriminated as the islanding operation by the islanding and interconnection detection part and the discriminated result of an active type islanding operation determination unit matches.