System and method for synchronizing an auxiliary electrical generator to an electrical system

• US 8,407,016 B2
• Filed: 01/25/2011
• Issued: 03/26/2013
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: EI Electronics LLC (Hubbell, Inc.)
• Original Assignee: Electro Industries/Gaugetech
• Inventors: Slota, Frederick B., Chen, Henry (Ying Hong)
• Primary Examiner(s): Bahta, Kidest
• Application Number:
  US13/013,171
• Publication Number:
  US 20110115302A1
• Time in Patent Office: 791 Days
• Field of Search: 702/61, 702/57, 700/286
• US Class Current: 702/61
• CPC Class Codes: H02J 3/42 with automatic parallel connection when synchronisation is achieved

Abstract

There is provided herein methods and apparatus for apparatus for controlling the interconnection of an auxiliary AC generator with an electrical system, such as an electrical distribution system, e.g., a utility grid. A measuring circuit measures the frequency of an auxiliary AC generator and the phase angle between one voltage phase of the generator and the correspondent voltage phase of the electric utility'"'"'s electricity supply lines, i.e., the grid, each of which are averaged and filtered. The measured frequency of the auxiliary AC generator is matched to the frequency of the electrical system and the measured phase angle of the generator is matched to the electric utility'"'"'s electricity supply lines. Once matching is achieved to within a defined tolerance, interconnecting contactors are closed.

Claims

1. An energy meter for measuring the delivery of electrical energy from an energy supplier to a consumer through an electric circuit, the energy meter comprising:

a meter module comprising;

a plurality of sensors for sensing electrical parameters of lines of a multi-phase electrical power distribution system;

a plurality of analog-to-digital (A/D) converters for receiving the sensed electrical parameters output from the plurality of sensors, the analog-to-digital (A/D) converters being configured to convert the sensed electrical parameters to digital signals for processing by at least one digital signal processor;

the at least one digital signal processor configured for receiving the digital signals from the analog-to-digital (A/D) converters to perform calculations required to determine power usage of a load and for controlling the overall operations of the energy meter;

a communication device for interacting with a user and for communicating events, alarms and instructions to the user;

a display for providing visual indications to the user;

a synchronization module comprising control logic operative to output a first control signal to adjust a frequency of an auxiliary generator, said control logic being further operative to determine when a phase angle difference between a voltage phase of the auxiliary generator and a corresponding voltage phase of the multi-phase electrical power distribution system are within a defined tolerance; and

control means for outputting a second control signal to synchronize the auxiliary generator with the multi-phase electrical power distribution system upon determining that said phase angle difference is within said defined tolerance.

2. An energy meter of claim 1, further comprising a memory for storing audio and/or video files, and sensed and generated data for further processing and retrieval.

3. An energy meter of claim 1, further comprising a frequency computation module operative to compute a frequency of a voltage of the auxiliary generator using zero-crossing time values output from a zero-crossing detector module.

4. An energy meter of claim 3, further comprising a phase angle computation module operative to compute the phase- angle difference between the auxiliary generator and the multi-phase electrical power distribution system.

5. An energy meter of claim 4, wherein the display is further configured for providing a graphical display of said phase angles difference, said auxiliary generator frequency and an electrical power distibution system frequency.

6. An energy meter of claim 1, wherein said control means is further operative to output a control signal to interconnect interconnecting contactors to couple the auxiliary generator to the multi-phase electrical power distribution system.

7. An energy meter of claim 1, wherein said frequency is computed by averaging zero-crossing time difference values over a number of cycles to yield an average zero-crossing time difference value of the auxiliary generator and computing said frequency of the auxiliary generator as:

frequency (aux)=1/[filtered time difference value].

8. An energy meter of claim 1, wherein the determined phase angle difference is an analog value.

9. An energy meter of claim 1, wherein the determined phase angle difference is a digital value.

10. An energy meter of claim 1, further comprising an Ethernet connection for coupling the energy meter to an external module.

11. An energy meter of claim 1, wherein the synchronization module, further comprises:

a zero-crossing detector module configured to receive a voltage of said auxiliary generator, having a voltage phase which corresponds to a selected phase of the multi-phase electrical power distribution system and further configured to output a zero-crossing time of the auxiliary generator voltage;

a frequency computation module for computing the auxiliary AC generator frequency; and

a phase angle computation module for receiving, as a first input, said zero crossing time of a voltage associated with the selected phase of the multi-phase electrical power distribution system and for receiving, as a second input, said zero-crossing time of said voltage of the auxiliary generator and computing a phase-angle difference value therefrom.

12. An energy meter of claim 1, further comprising a counter for calculating said auxiliary generator frequency and an electrical power distribution system line frequency.

13. An energy meter of claim 1, wherein the display is further configured for displaying an instantaneous phase, frequency, phase angle difference values and a visual indication of when said phase angle difference value, is within said defined tolerance.

14. An energy meter for measuring the delivery of electrical energy from an energy supplier to a consumer through an electric circuit, the meter comprising:

a meter module comprising;

a plurality of sensors configured to sense electrical parameters of lines of a multi-phase electrical distribution system;

a plurality of analog-to-digital (A/D) converters configured to receive the sensed electrical parameters output from the plurality of sensors, the analog-to-digital (A/D) converters being configured to convert the sensed electrical parameters to digital signals for processing by at least one digital signal processor; and

the at least one digital signal processor configured to receive the digital signals from the analog-to-digital (A/D) converters, to perform calculations required to determine power usage of a load and to control the overall operations of the meter; and

a synchronization module comprising control logic configured to output a first control signal to adjust a frequency of an auxiliary generator, the control logic being further operative to determine when a phase angle difference between a voltage phase of the auxiliary generator and a corresponding voltage phase of the multi-phase electrical distribution system are within a defined tolerance and to output a second control signal to synchronize the auxiliary generator with the multi-phase electrical distribution system upon determining that the phase angle difference is within the defined tolerance.

15. An energy meter of claim 14, further comprising a frequency computation module configured to compute a frequency of a voltage of the auxiliary generator using zero-crossing time values output from a zero-crossing detector module.

16. An energy meter of claim 15, further comprising a phase angle computation module configured to compute the phase angle difference between the auxiliary generator and the multi-phase electrical distribution system.

17. An energy meter of claim 14, wherein the synchronization module is further configured to output a control signal to interconnect interconnecting contactors to couple the auxiliary generator to the multi-phase electrical distribution system.

18. An energy meter of claim 14, wherein the frequency is computed by averaging zero-crossing time difference values over a number of cycles to yield an average zero-crossing time difference value of the auxiliary generator and computing the frequency of the auxiliary generator as:

frequency (aux)=1/[filtered time difference value].

19. An energy meter of claim 14, wherein the synchronization module, further comprises:

a zero-crossing detector module configured to receive a voltage of the auxiliary generator having a voltage phase which corresponds to a selected phase of the multi-phase electrical distribution system and further configured to output a zero-crossing time of the auxiliary generator voltage;

a frequency computation module configured to compute an auxiliary generator frequency; and

a phase angle computation module configured to receive, as a first input, the zero crossing time of a voltage associated with the selected phase of the multi-phase electrical distribution system and to receive, as a second input, the zero-crossing time of the voltage of the auxiliary generator and to compute a phase angle difference value therefrom.

20. An energy meter of claim 14, further comprising a counter configured to calculate the auxiliary generator frequency and an electrical power distribution system line frequency.

21. An energy meter of claim 14, further comprising a display configured to display an instantaneous phase, frequency, phase angle difference values and a visual indication of when the phase angle difference value is within the defined tolerance.

22. An energy meter of claim 14, wherein the first and second control signals are transmitted over a communication medium.

23. An energy meter of claim 22, wherein the communication medium operates via Modbus.

24. An energy meter of claim 22, wherein the communication medium operates via DNP.

25. An energy meter of claim 22, wherein the communication medium operates via Ethernet.

26. An energy meter of claim 14, wherein the first and second control signals are communicated to an external module, the external module being configured to control the auxiliary generator.