ANTI-ISLANDING PROTECTION SYSTEMS FOR SYNCHRONOUS MACHINE BASED DISTRIBUTED GENERATORS

• US 20070126428A1
• Filed: 02/01/2007
• Published: 06/07/2007
• Est. Priority Date: 10/15/2004
• Status: Active Grant

• Current Assignee: John Nelson, Nicholas Miller, Pengwei Du, Reigh Walling, Zhihong Ye
• Original Assignee: John Nelson, Nicholas Miller, Pengwei Du, Reigh Walling, Zhihong Ye
• Inventors: Nelson, John, Ye, Zhihong, Du, Pengwei, Miller, Nicholas, Walling, Reigh
• Granted Patent: US 7,271,571 B2
• Time in Patent Office: Days
• US Class Current: 324/522
• 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

A system for providing anti-islanding protection of a synchronous machine based distributed generator includes a frequency sensor configured to generate a generator frequency signal, a bandpass filter configured for filtering the generator frequency signal, a governor controller configured for using the filtered frequency signal to generate a power feedback signal, and a governor summation element configured for summing the filtered frequency signal, the power feedback signal, and a reference power to provide an electrical torque signal. Another system includes a voltage sensor configured to generate a generator terminal voltage signal, a feedback power calculator configured for generating a reactive feedback power signal, a bandpass filter configured for filtering the terminal voltage signal, and a PI controller summation element configured for summing the filtered terminal voltage signal, the reactive power feedback signal, and a reference reactive power to provide an error signal.

Claims

1-6. -6. (canceled)

7. A system for providing anti-islanding protection of a distributed generator with respect to a feeder connected to an electrical grid, the system comprising:

a voltage sensor configured to generate a terminal voltage signal representative of a terminal voltage of the generator;

a feedback power calculator configured for generating a reactive feedback power signal;

a bandpass filter configured for filtering the terminal voltage signal;

a proportional-integral controller summation element configured for summing the filtered terminal voltage signal, the reactive power feedback signal, and a reference reactive power to provide an error signal for use by a proportional integral controller in generating a voltage reference signal for the generator.

8. The system of claim 7 further comprising a grid controller configured for receiving the terminal voltage signal and generating a grid disconnection signal upon the terminal voltage signal becoming out of a nominal terminal voltage range.

9. The system of claim 8 wherein the bandpass filter comprises a filter gain comprising a value that is greater than or equal to a gain required to result in a disconnected grid loop gain of greater than unity.

10. The system of claim 9 wherein a range of the bandpass filter extends from about 0.1 Hz to about 100 Hz.

11. The system of claim 8 wherein the bandpass filter is configured to increase the speed of detecting a change of the terminal voltage signal upon a disruption to the electrical grid.

12. The system of claim 8 wherein the grid controller is further configured for receiving a generator frequency signal representative of the rotational speed of the generator and generating a grid disconnection signal upon the generator frequency signal becoming out of a nominal frequency range.

13. The system of claim 7 further comprising a grid controller configured for receiving a generator frequency signal representative of the rotating frequency of the generator and generating a grid disconnection signal upon the generator frequency signal becoming out of a nominal frequency range.

14. A system for providing anti-islanding protection of a distributed generator with respect to a feeder connected to an electrical grid, the system comprising:

a frequency sensor configured to generate a generator frequency signal representative of a rotational speed of the generator;

an active loop bandpass filter configured for filtering the generator frequency signal;

a governor controller configured for using the filtered frequency signal to generate a power feedback signal;

a governor summation element configured for summing the filtered frequency signal, the power feedback signal, and a reference power to provide an electrical torque signal for use by a prime mover coupled to the generator;

a voltage sensor configured to generate a terminal voltage signal representative of a terminal voltage of the generator;

a feedback power calculator configured for generating a reactive feedback power signal;

a reactive loop bandpass filter configured for filtering the terminal voltage signal;

a proportional-integral controller summation element configured for summing the filtered terminal voltage signal, the reactive power feedback signal, and a reference reactive power to provide an error signal for use by a proportional integral controller in generating a voltage reference signal for the generator.

15. The system of claim 14 further comprising a grid controller configured for receiving the generator frequency signal and generating a grid disconnection signal upon the generator frequency signal becoming out of a nominal frequency range, the grid controller being further configured for receiving the terminal voltage signal and generating a grid disconnection signal upon the terminal voltage signal becoming out of a nominal terminal voltage range.

16. The system of claim 15 further comprising a frequency difference element configured for obtaining a difference between a reference frequency signal and the generator frequency signal, wherein the governor controller configured for using the difference in addition to the filtered frequency signal to generate the power feedback signal.

17. The system of claim 15 wherein the active loop bandpass filter comprises a filter gain comprising a value that is greater than or equal to a gain required to result in a disconnected grid loop gain of greater than unity.

18. The system of claim 17 wherein a range of the active loop bandpass filter extends from about 0.1 Hz to about 100 Hz.

19. The system of claim 15 wherein the active loop bandpass filter is configured to increase the speed of detecting a change of the generator frequency signal upon a disruption to the electrical grid.

20. The system of claim 15 wherein the reactive loop bandpass filter comprises a filter gain comprising a value that is greater than or equal to a gain required to result in a disconnected grid loop gain of greater than unity.

21. The system of claim 20 wherein a range of the reactive loop bandpass filter extends from about 0.1 Hz to about 100 Hz.

22. The system of claim 15 wherein the reactive loop bandpass filter is configured to increase the speed of detecting a change of the terminal voltage signal upon a disruption to the electrical grid.

23. The system of claim 15 wherein a range of the active loop bandpass filter extends from about 1 Hz to about 10 Hz and wherein a range of the reactive loop bandpass filter extends from about 1 Hz to about 10 Hz.