SYSTEM AND METHOD FOR SYNCHRONIZING AN AUXILIARY ELECTRICAL GENERATOR TO AN ELECTRICAL SYSTEM

• US 20110115302A1
• Filed: 01/25/2011
• Published: 05/19/2011
• Est. Priority Date: 08/21/2007
• Status: Active Grant

• Current Assignee: EI Electronics LLC (Hubbell, Inc.)
• Original Assignee: Electro Industries/Gaugetech
• Inventors: Chen, Henry (Ying Hong), Slota, Frederick B.
• Granted Patent: US 8,407,016 B2
• Time in Patent Office: Days
• US Class Current: 307/87
• 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, said meter comprising:

a meter module comprising;

a plurality of sensors for sensing electrical parameters of lines of an electrical power distribution system;

a plurality of analog-to-digital (ND) converters for receiving the sensed electrical parameters output from the plurality of sensors, the analog-to-digital 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 A/D converters to perform calculations required to determine power usage of a load and for controlling the overall operations of the 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 the 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 electrical distribution system are within a defined tolerance; and

control means for outputting a second control signal to synchronize said auxiliary generator with said three-phase power electrical 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 said auxiliary generator voltage 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 a phase-angle difference between said three-phase auxiliary generator and said three-phase electrical system.

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

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

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

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

10. An energy meter of claim 1, further comprising an Ethernet connection for coupling said 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 AC generator, having a voltage phase which corresponds to said selected phase of the three-phase power electrical system and further configured to output a zero-crossing time of said auxiliary AC generator voltage;

a frequency computation module for computing an 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 a selected phase of the three-phase power electrical system and for receiving, as a second input, said zero-crossing time of said voltage of said auxiliary AC generator and computing a phase-angle difference value therefrom.

12. An energy meter of claim 1, further comprising a counter for calculating generator frequency and power 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 a defined tolerance.