Connecting circuit and method for connecting a generator to the electricity grid making use thereof

• US 7,078,830 B2
• Filed: 03/12/2002
• Issued: 07/18/2006
• Est. Priority Date: 03/12/2001
• Status: Expired due to Fees

• Current Assignee: Enatec Micro-Cogen B.V.
• Original Assignee: Enatec Micro-Cogen B.V.
• Inventors: Van Kampen, Berend Jan, Beckers, Gerardus Jacobus Josephine, Van Kampen, Willem Antoon, Bekkering, Dirk Lucas, Ribberdink, Johannes Sjoerd, Zutt, Jacobus Gerardus Maria
• Primary Examiner(s): Feild, Lynn
• Assistant Examiner(s): RUTLAND WALLIS, MICHAEL
• Application Number:
  US10/471,708
• Publication Number:
  US 20040130216A1
• Time in Patent Office: 1,589 Days
• Field of Search: 307/66, 307/85, 307/80, 307/84, 307/78, 322/20
• US Class Current: 307/85
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved

Abstract

The present invention relates to a connecting circuit for connecting to an electricity grid an electric generator for generating electrical energy, comprising a measuring circuit for measuring the current through the connecting circuit; a storage element for storing charge supplied by the generator for at least some period of time; a second measuring circuit for measuring the amount of stored charge, which circuit is connected to a storage element; and a first controllable switch for connecting the generator to the electricity grid subject to the measured current intensity-and measured stored charge.

Claims

1. A connecting circuit for connecting to an electricity grid an electric generator generating electrical energy, comprising:

(a) a current measuring circuit for measuring the current through the connecting circuit;

(b) a storage element for storing charge supplied by the generator for at least some period of time;

(c) a charge measuring circuit for measuring the amount of stored charge, which circuit is connected to the storage element;

(d) a first controllable switch having an open position for disconnecting the electric generator from the electricity grid and a closed position for connecting the electric generator to the electricity grid in accordance with measured current intensity and measured stored charge;

(e) a dissipative element; and

(f) a second controllable switch connected in parallel with the storage element;

wherein;

(i) mutual synchronization of the phase of the current generated by the electric generator in the connecting circuit and the phase of the voltage of the electricity grid is created by;

(1) the storing of charge supplied by the electric generator in the storage element when the second switch is in the open position;

or

(2) dissipating charge from the storage element via the dissipative element when the second switch is in the closed position; and

(ii) mutual synchronization of the phase of the current generated by the electric generator in the connecting circuit and the phase of the voltage of the electricity grid causes the first switch to close and the second switch to open and exceptional operating conditions in the electricity grid cause the first switch to open and the second switch to close.

2. The connecting circuit claimed in claim 1, wherein the current measuring circuit comprises a transformer.

3. The connecting circuit claimed in claim 1 or 2, wherein the charge measuring circuit comprises a differential amplifier.

4. The connecting circuit claimed in claim 1, further comprising a circuit for generating a voltage of a predetermined value.

5. The connecting circuit claimed in claim 1, further comprising a phase circuit for determining and shifting the phase of the measured signals.

6. The connecting circuit claimed in claim 4, wherein the circuit for generating a voltage of a predetermined value comprises a microprocessor, an EPROM in which the signal of predetermined value is stored in digital form, and a DA-converter.

7. The connecting circuit claimed in claim 6, including a counter connected to the EPROM for phase-shifting of the output of the EPROM.

8. The connecting circuit claimed in claim 5, wherein the phase circuit comprises a phase comparator, a phase-locking and a return loop.

9. A connecting circuit for connecting an electric generator generating electrical energy to an electricity grid comprising:

(a) a current measuring circuit for measuring current flow through the connecting circuit;

(b) a storage element for storing charge supplied by the electric generator;

(c) a charge measuring circuit for measuring the charge stored by the storage element;

(d) a first controllable switch for connecting the electric generator to and disconnecting the electric generator from the electricity grid;

(e) a charge dissipative element;

(f) a second controllable switch for connecting the charge dissipative element in parallel with and disconnecting the charge dissipative element from the storage element; and

(g) a control system for receiving signals representing the current measured by current measuring circuit and the charge measured by the charge measuring circuit and controlling the first and second controllable switches such that mutual synchronization between the phase of the current generated by the electric generator in the connecting circuit and the phase of the voltage of the electricity grid is controlled by controlling the charge supplied to the storage element by the electric generator, mutual synchronization causing the first controllable switch to connect the electric generator to the electricity grid and the second controllable switch to disconnect the charge dissipative element from the storage element and exceptional operating conditions in the electricity grid causing the first controllable switch to disconnect the electric generator from the electricity grid and the second controllable switch to connect the charge dissipative element in parallel with the storage element.

10. The connecting circuit claimed in claim 9, wherein the current measuring circuit includes a transformer.

11. The connecting circuit claimed in claim 9 or 10, wherein the current measuring circuit includes a differential amplifier.

12. The connecting circuit claimed in claim 9, wherein the control system includes a circuit for generating a voltage of a predetermined value.

13. The connecting circuit claimed in claim 12, wherein the circuit for generating a voltage of a predetermined value includes a microprocessor, an EPROM in which the signal of predetermined value is stored in digital form, and a DA-converter.

14. The connecting circuit claimed in claim 13, including a counter connected to the EPROM for phase-shifting of the output of the EPROM.

15. The connecting circuit claimed in claim 9, wherein the control system includes a phase circuit for determining and shifting the phase of the measured signals.

16. The connecting circuit claimed in claim 15, wherein the phase circuit comprises a phase comparator, a phase-locking and a return loop.

17. A method of connecting an electric generator generating electrical energy to an electricity grid comprising:

(a) measuring the current flow through a connecting circuit connecting the electric generator to the electricity grid;

(b) storing a charge supplied by the electric generator;

(c) measuring the stored charge;

(d) controlling the connecting circuit and the stored charge such that mutual synchronization between the phase of the current generated by the electric generator in the connecting circuit and the phase of the voltage of the electricity grid is controlled by controlling the stored charge supplied by the electric generator, mutual synchronization causing the connecting circuit to connect the electric generator to the electricity grid and maintain the stored charge and exceptional operating conditions in the electrical grid causing the connecting circuit to disconnect the electric generator from the electric grid and dissipate the stored charge.

18. The method claimed in claim 17, wherein measuring current flow through a connecting circuit includes transforming the current flow.

19. The method claimed in claim 17, wherein controlling the connecting circuit and the stored charge includes generating a voltage of a predetermined value.

20. The method claimed in claim 17, wherein controlling the connecting circuit and the stored charge includes determining and shifting the phase of the measured signals.