Minimum time delay filtering method for automatic voltage regulators

• US 5,315,229 A
• Filed: 09/30/1991
• Issued: 05/24/1994
• Est. Priority Date: 09/30/1991
• Status: Expired due to Fees

• Current Assignee: Eaton Corp. (Wisconsin) (Eaton Corporation PLC.)
• Original Assignee: Westinghouse Electric Company LLC (Brookfield Asset Management Incorporated)
• Inventors: Markus, David R.
• Primary Examiner(s): HICKEY, ROBERT
• Application Number:
  US07/769,065
• Time in Patent Office: 967 Days
• Field of Search: 322/25, 322/28
• US Class Current: 322/28
• CPC Class Codes: H02P 2101/10 for water-driven turbines
• CPC Class Codes: H02P 9/305 controlling voltage H02P9/302 takes precedence

Abstract

An automatic voltage regulator senses and controls the terminal voltage of a separately excited generator by controlling the field current applied to the field winding. In order to improve the response time of the circuit, the circuitry relies on the phasor relationships between the generator phase voltages to obviate the need for a rectification and filtering circuit, used in known AVR'"'"'s. More specifically, each of the sinusoidal phase voltages is sampled and squared. The squared phase voltages are then summed together. The square root of the sum is used to provide a DC voltage signal, proportional to the terminal phase voltages V_A, V_B and V_C. The DC voltage signal may then be compared with a reference signal to generate an error signal for use in regulating the generator terminal voltage by controlling the field current applied to the generator field winding.

Claims

1. An automatic voltage regulator for controlling the terminal voltage of a polyphase electrical generator defining a plurality of phase voltages, comprising:

receiving means for receiving a signal representative of one of said phase voltages;

responsive means responsive to said receiving means for squaring said phase voltage signal;

generating means, responsive to said receiving means for generating a DC signal equal to √

3/2A representative of said phase voltages, where A is the amplitude of said phase voltage;

reference signal means for providing a reference signal;

error signal generating means, responsive to said generating means and said reference signal means for comparing said DC signal with said reference signal and generating an error signal representative of the difference and;

controlling means, responsive to said error signal generating means, for controlling said terminal voltage.

2. An automatic voltage regulator as recited in claim 1, wherein said receiving means includes sampling means for sampling said phase voltage amplitude at predetermined time intervals.

3. An automatic voltage regulator as recited in claim 2, wherein said sampling means includes storing means for storing the sampled phase voltage amplitude.

4. An automatic voltage regulator as recited in claim 3, further includes converting means for converting said sampled phase voltage amplitude to a digital signal.

5. An automatic voltage regulator as recited in claim 2, wherein said predetermined time interval is selected to be at a frequency that is at least twice the frequency of said phase voltage representative signal.

6. An automatic voltage regulator for controlling the terminal voltage of a polyphase electrical generator defining a plurality of phase voltages, comprising:

receiving means for receiving an analog signals signal representative of one of said phase voltages;

converting means for converting said analog signal to a digital signal related to √

3/2A, where A is the amplitude of said phase voltage;

reference signal means for providing a reference signal; and

error signal generating means, responsive to said converting means and said reference signal means, for comparing said digital signal with said reference signal and generating an error signal representative of the difference;

controlling means responsive to said error signal generating means, for controlling said terminal voltage.

7. An automatic voltage regulation as recited in claim 6, wherein said converting means includes sampling means for sampling said analog signal at predetermined intervals and converting the sampled analog signals to digital signal.

8. An automatic voltage regulator as recited in claim 7, further including digital processing means for processing said digital signal.

9. An automatic voltage regulator as recited in claim 8, wherein said processing means includes a microprocessor.

10. An automatic voltage regulator for controlling the terminal voltage of a polyphase electrical generator defining a plurality of phase voltages comprising:

receiving means for receiving an analog signal representative of one of said phase voltages;

sampling means, responsive to said receiving means, for sampling said analog signal at predetermined intervals;

converting means, responsive to said sampling means, for converting the sampled analog signal to a digital signal;

processing means, responsive to said sampling means, for processing said digital signal in accordance with the function √

3/2A, where A is the amplitude of said phase voltage and generating a digital signal representative of the generator terminal voltage;

reference signal means for providing a reference signal;

error signal generating means responsive to said processing means and said reference signal means for comparing said digital signal and said reference signal and generating an error signal representative of the difference; and

controlling means responsive to said error signal generating means, for controlling said terminal voltage.

11. A process for automatically controlling the terminal voltage of a polyphase electrical generator defining a plurality of phase voltages comprising the steps:

(a) providing a source of signals representative of the phase voltages;

(b) sampling said phase voltage representative signals for a predetermined time period;

(c) perform the following function √

3/2A where A is the amplitude of said phase voltage to provide a signal representative of the generator terminal voltage signal;

(d) providing a reference signal;

(e) comparing said terminal voltage representative signal with said reference signal;

(f) generating an error signal representative of the difference between said terminal voltage representative signal and said reference signal; and

(g) utilizing said error signal to control said generator terminal voltage.

12. A process for automatically controlling the terminal voltage of a polyphase electrical generator defining a plurality of phase voltages comprising the steps:

(a) providing a source of analog signals representative of said phase voltages;

(b) sampling said analog signals at predetermined time intervals;

(c) converting the sampled analog signals to digital signals;

(d) processing said digital signals in accordance with the function √

3/2A where A is the amplitude of said phase voltage to provide a signal representative of the generator terminal voltage;

(e) providing a reference signal;

(f) comparing said reference signal with said generator terminal voltage representative signal;

(g) generating an error signal representative of the difference between said terminal voltage representative signal and said reference signal; and

(h) utilizing said error signal to control the generator terminal voltage.

13. An automatic voltage regulator for controlling the terminal voltage of a balance polyphase electrical generator defining a plurality of phase voltages, comprising:

receiving means for receiving a source of analog signals representative of said phase voltages;

converting means including sampling means for sampling said analog signals at predetermined intervals and for converting said analog signals to digital signals; and

processing means for processing said digital signals according to a predetermined function given by the following relationship;

##EQU2## where V_a, V_b, and V_c represent the phase voltages;

reference signal means for providing a reference signal;

error signal generator means, responsive to said converting means and said reference signal means, for comparing said digital signals with said reference signal and generating an error signal representative of the difference; and

controlling means responsive to said error signal generating means, for controlling said terminal voltage.

14. An automatic voltage regulator for controlling the terminal voltage of a balance polyphase electrical generator defining a plurality of phase voltages, comprising:

receiving means for receiving a source of analog signals representative of said phase voltages;

sampling means, responsive to said receiving means, for sampling said analog signals at predetermined intervals;

converting means, responsive to said sampling means, for converting the sampled analog signals representative of the phase voltages to digital signals;

processing means, responsive to said sampling means, for processing said digital signals in accordance with the function ##EQU3## where V_a, V_b and V_c represent the phase voltages; and

generating a digital signal representative of the generator terminal voltage;

reference signal means for providing a reference signal;

error generating means responsive to said processing means and said reference signal means for comparing said digital signal representative of said generator terminal voltage and said reference signal and generating an error signal representative of the difference; and

controlling means responsive to said error signal generating means for controlling said generator terminal voltage.

15. A process for automatically controlling the terminal voltage of a balance polyphase electrical generator defining a plurality of phase voltages comprising the steps:

(a) providing a source of analog signals representative of said phase voltages;

(b) sampling said analog signals at predetermined time intervals;

(c) converting the sampled analog signals to digital signals;

processing said digital signals in accordance with the function ##EQU4## where V_A (t), V_B (t), and V_C (t) represent the phase voltages to provide a signal representative of the generator terminal voltage;

(d) providing a reference signal;

(f) comparing said reference signal with said generator terminal voltage representative signal;

(g) generating an error signal representative of the difference between said terminal voltage representative signal and said reference signal; and

(h) utilizing said error signal to control the generator terminal voltage.