Detection and mitigation of instability of synchronous machines

Patent metadata

Field	Value
Publication number	US-9960600-B1
Application number	US-201615339597-A
Country	US
Kind code	B1
Filing date	Oct 31, 2016
Priority date	Oct 31, 2016
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

Methods and systems for stabilizing a power system include receiving a set point for a power system that includes the compensation circuitry controlled by the control system. A firing angle for the power system is set based at least in part on the set point. An angle between a generator terminal of a generator of the power system and a bus of the power system is calculated. A determination is made whether the angle is within a threshold value of the firing angle. When the angle is not within the threshold value of the firing angle, compensation circuitry is engaged to stabilize the power system.

First claim

The invention claimed is:

1. A compensation system, comprising:
compensation circuitry; and
a control system comprising:
memory storing instructions; and
one or more processors configured to execute the instructions that are configured to cause the one or more processors to:
receive a set point for a power system that includes the compensation circuitry controlled by the control system;
set a firing angle for the power system based at least in part on the set point;
calculate an angle between a generator terminal of a generator of the power system and a bus of the power system;
determine whether the angle is within a threshold value of the firing angle; and
when the angle is not within the threshold value of the firing angle, engage the compensation circuitry.

2. The compensation system of claim 1 , wherein the compensation circuitry comprises circuitry that is in series with a line transmitting power from the generator to a load of the power system.

3. The compensation system of claim 2 , wherein the compensation circuitry comprises an adjustable capacitive reactance circuit.

4. The compensation system of claim 3 , wherein the compensation circuitry comprises thyristor-controlled series compensation circuitry.

5. The compensation system of claim 4 , wherein engaging the compensation circuitry comprises asserting or deasserting a signal to a gate of one or more thryristors of the compensation circuitry.

6. The compensation system of claim 1 , wherein the control system comprises a human-to-machine interface configured to receive the set point.

7. The compensation system of claim 1 , wherein calculating the angle comprises using the following equation:

δ
=

sin

-
1

⁡

(

P
*

X
L

V
R

*

V
S

)

,

where P is real power transferred from the generator to a load of the power system, X L is an inductive reactance of a line between the generator and load used to transfer the real power, V R is a voltage difference at the load, and V S is the voltage difference at the generator.

8. The compensation system of claim 1 , wherein the threshold value is a relative threshold indicating a relative relationship between the firing angle and the angle.

9. The compensation system of claim 8 , wherein threshold value comprises a value of 5 percent.

10. The compensation system of claim 1 , wherein the instructions are configured to cause the one or more processors to disengage the compensation circuitry while continuing to periodically calculate the angle and determine whether a periodically calculated angle is within a threshold value of the firing angle.

11. The compensation system of claim 10 , wherein the instructions are configured to cause the one or more processors to re-engage the compensation circuitry after disengaging the compensation circuitry when the periodically calculated angle is not within a threshold value of the firing angle.

12. The compensation system of claim 10 , wherein the control system comprises a human-to-machine interface, and the instructions are configured to cause the one or more processors to disengage the compensation circuitry in response to a disengage command received via the human-to-machine interface.

13. The compensation system of claim 10 , wherein the instructions are configured to cause the one or more processors to, during engagement of the compensation circuitry:
periodically calculate a periodic angle between the generator terminal of the generator and the bus of the power system; and
determine whether the periodic angle is within the threshold value of the firing angle, wherein the one or more processors cause disengagement of the compensation circuitry when the periodic angle is within the threshold value.

14. A non-transitory computer-readable medium comprising instructions configured to be executed by one or more processors of a control system, wherein the instructions comprise instructions configured to cause the one or more processors to:
monitor for indications of a transient event in a power system including a generator configured to generate power that is transferred over a line to a load;
when indications of transient event are detected, engage compensation circuitry of power system to stabilize the power system during the transient event;
monitor one or more parameters of the supplied power;
determine whether the one or more monitored parameters surpass respective thresholds; and
when the one or more monitored parameters surpass the respective thresholds indicative of passage of the transient event, disengage the compensation circuitry.

15. The non-transitory computer readable medium of claim 14 , wherein engaging the compensation circuitry comprises asserting or deasserting a signal at a gate of a thyristor of a thyristor-controlled series compensation circuitry of the compensation circuitry.

16. The non-transitory computer readable medium of claim 14 , wherein the indications comprise a current of the generator exceeds a threshold rate of change, mechanical power of the power system is greater than electrical power transferred, or shaft speed of a shaft of the power system exceeds a shaft speed threshold.

17. The non-transitory computer readable medium of claim 14 , wherein the instructions are configured to cause the one or more processors to deem the indications as detected when the indications includes the current of the generator exceeding the threshold rate of change, the mechanical power of the power system is greater than the electrical power transferred, and the shaft speed of the shaft exceeds the shaft speed threshold.

18. The non-transitory computer readable medium of claim 14 , wherein the one or more parameters of supplied power comprises a voltage level of the supplied power and the respective threshold for the voltage level is a source voltage from the generator.

19. The non-transitory computer readable medium of claim 11 , wherein the one or more parameters of supplied power comprises a current level of the supplied power and the respective threshold for the current level is when the current level is less than or equal to a target current.

20. A method for increasing voltage stability of a power system that includes a generator and compensation circuitry, comprising:
detect a change in voltage demand by a load of the power system;
enabling the compensation circuitry to reduce reactive power demand from the generator by engaging the compensation circuitry comprises asserting or deasserting a signal at a gate of a thyristor of a thyristor-controlled series com

Assignees

• Gen Electric

Inventors

• Shakeel Tabrez
• Rahim Muhammed

Classifications

• H02J3/24

  Electricity · mapped topic

• H02J3/16

  by adjustment of reactive power · CPC title

• H02J3/1864 Primary

  using reactive elements connected in series with semiconductor switches, e.g. static VAR compensators [SVC], thyristor-controlled reactors [TCR] or thyristor-switched capacitors [TSC] · CPC title

• Y02E40/10

  Flexible AC transmission systems [FACTS] · CPC title

• Y02E40/30

  Reactive power compensation · CPC title