Islanding-operation prevention apparatus, and dispersed power generation apparatus and power generation system using the same

• US 5,686,766 A
• Filed: 04/12/1995
• Issued: 11/11/1997
• Est. Priority Date: 04/12/1994
• Status: Expired due to Term

• Current Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Original Assignee: Canon Kabushiki Kaisha (Canon Inc.)
• Inventors: Tamechika, Masanari
• Primary Examiner(s): Shoop, Jr., William M.
• Assistant Examiner(s): PALADINI, ALBERT WILLIAM
• Application Number:
  US08/420,803
• Time in Patent Office: 944 Days
• Field of Search: 307/43, 307/32, 307/53, 307/87, 307/31, 307/52, 307/38, 323/906, 323/205, 363/2, 363/13, 361/186, 361/187
• US Class Current: 307/43
• CPC Class Codes: F03D 9/11 storing electrical energy
• CPC Class Codes: F03D 9/255 connected to electrical distribution networks; Arrangements therefor
• CPC Class Codes: F05B 2210/16 Air or water being indistinctly used as working fluid, i.e. the machine can work equally with air or water without any modification
• CPC Class Codes: F05B 2270/337 Electrical grid status parameters, e.g. voltage, frequency or power demand
• CPC Class Codes: H02J 2300/24 of photovoltaic origin
• CPC Class Codes: H02J 2300/28 The renewable source being wind energy wind motors F03D
• CPC Class Codes: H02J 2300/40 wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
• 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: H02J 5/00 Circuit arrangements for transfer of electric power between ac networks and dc networks H02J3/36 takes precedence
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers
• CPC Class Codes: Y02E 10/72 Wind turbines with rotation axis in wind direction
• CPC Class Codes: Y02E 10/76 Power conversion electric or electronic aspects
• CPC Class Codes: Y02E 70/30 Systems combining energy storage with energy generation of non-fossil origin
• CPC Class Codes: Y02P 90/50 Energy storage in industry with an added climate change mitigation effect

Abstract

Even when a plurality of dispersed power generation systems are connected to a utility gride, an islanding-operation prevention apparatus can easily and assuredly prevent an islanding operation of each dispersed power supply constituting the corresponding dispersed power generation system. The apparatus includes a breaker provided between the utility gride and a dispersed power supply, an electric-power-value detector for detecting a value of electric power from a power line connected to the utility gride, a switch for electrically connecting or disconnecting an electric-power changing device for changing the value of electric power to the power line in accordance with an output from a pulse circuit, and a controller for controlling the breaker in accordance with the width of fluctuations of the value of electric power during the connection or the disconnection. A dispersed power generation apparatus and a dispersed power generation system uses such an apparatus. By further providing a synchronous circuit for synchronizing the output of the pulse circuit with a signal output from a reference-signal source, even if the amount of the generated power and the amount of a load are in a complete equilibrium state during an islanding operation, the islanding operation can be assuredly prevented with a short time period until the stop of the islanding operation and without using large-scale equipment.

Claims

1. A utility linking system comprising:

a utility grid; and

a plurality of distribution systems each including;

a dispersed power supply being connected in parallel to the utility grid,

a first distribution line for connecting the utility grid to the dispersed power supply,

detection means, provided on the first distribution line, for detecting a voltage outputted to the first distribution line or an electrical current flowing in the first distribution line,

breaking means, provided on the first distribution line and situated closer to the dispersed power supply than the detection means, which is capable of setting both a connecting state and a disconnecting state between the utility grid and the dispersed power supply and generally sets the connecting state,

a second distribution line provided between the dispersed power supply and the breaking means,

a pulse circuit for emitting a pulse, and

switching means, connected to the second distribution line, for performing a switching operation in response to the pulse emitted from the pulse circuit,

wherein said utility linking system further comprises;

a plurality of control means, each provided to each of the plurality of distribution systems, for comparing each of output values respectively outputted from each of the plurality of detection means with each of output voltage values respectively outputted to each of the plurality of second distribution lines through the intermediary of each of the plurality of switching means, and commutating, in the case where at least one of the comparison results shows a fluctuation which is greater than the predetermined amount, the breaking means provided in the corresponding distribution system from the connecting state to the disconnecting state; and

a plurality of synchronization circuits for setting each number of the pulses respectively emitted from the plurality of pulse circuits each provided in the plurality of distribution systems to a predetermined number.

2. A utility linking system according to claim 1, wherein said plurality of synchronization circuits respectively respond to the frequency of the utility grid.

3. A utility linking system according to claim 1, wherein said plurality of synchronization circuits respectively respond to the frequency of a broadcasting electric wave.

4. A utility linking system according to claim 1, wherein each of said plurality of dispersed power supplies is a generator having a solar cell.

5. A utility linking system according to claim 1, wherein each of said plurality of distribution systems further comprises a battery.

6. A utility linking system according to claim 1, wherein said battery is a lithium secondary battery or a nickel-hydrogen secondary battery.