Methods and systems for rapid load support for grid frequency transient events

Abstract

To provide methods and systems for rapid load support for grid frequency transient events.SOLUTION: Example systems may include: a turbine having a first controller; a generator coupled to the turbine, where the generator is configured to provide power to an electrical grid; and an exciter configured to provide a direct current (DC) voltage and a DC current to a rotor of the generator. The exciter may include a second controller configured to monitor a first set of electrical properties associated with the electrical grid, determine that a transient event is present on the electrical grid based on the first set of electrical properties, and send a notification of the transient event to the first controller.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] TECHNICAL FIELD This application and the resulting patent relate generally to gas turbine systems, and more specifically to providing rapid load support in response to grid frequency transients. [Background technology]

[0002] A power plant or generating system can generate electrical power from other primary energy sources. For example, a prime mover, such as a gas turbine, is a rotating mechanical device with a gas turbine shaft that drives a generator to provide electrical power to a power grid. The power grid then distributes the electricity to various power consumers. To ensure that the generating system operates effectively, the turbine shaft speed and the resulting grid frequency need to be synchronized with each other within the operating range. If a transient event causes the grid frequency to change suddenly, power may be interrupted.

[0003] The adverse effects of transient events, such as sudden changes in grid frequency, are amplified in small grids, such as grids providing approximately 500 megawatts (MW) of load capacity. Small grids are often less stable than larger grids because the same magnitude of load change results in a larger frequency change. Thus, small grids tend to experience more frequent frequency changes than larger grids. The lack of stability can result in power outages and / or loss of power to the grid. Thus, systems and methods that provide rapid load support for grid frequency transients are desired to increase the stability of power to the grid. Summary of the Invention

[0004] The present application and resulting patent provide a system for providing rapid load support using a gas turbine. The system may include a turbine having a first controller, a generator coupled to the turbine, the generator configured to provide electrical power to an electrical grid, and an exciter configured to provide a direct current (DC) voltage and a DC current to a rotor of the generator. The exciter may include a second controller configured to monitor a first set of electrical characteristics associated with the electrical grid, determine that a transient event is present on the electrical grid based on the first set of electrical characteristics, and send a notification of the transient event to the first controller. The first controller may be configured to adjust operation of the turbine based on the notification.

[0005] The present application and the resultant patent further provide a method for providing improved load support for grid frequency transient events. The method may include monitoring, by a first controller, a first set of electrical characteristics associated with an electrical grid, determining, by the first controller, that a transient event is present on the electrical grid based on the first set of electrical characteristics, and sending a notification of the transient event to a second controller. The second controller may be configured to adjust operation of the turbine based on the notification by (i) adjusting dynamics of fuel demand to a fuel valve governor of the turbine, and (ii) adjusting a primary frequency algorithm.

[0006] The present application and the resulting patent further provide a system for providing rapid load support. The system may include a prime mover, such as an aeroderivative gas turbine having a first controller, a generator coupled to the aeroderivative gas turbine, the generator configured to provide electrical power to an electric grid, and an exciter configured to provide a direct current (DC) voltage and a DC current to a rotor of the generator. The exciter may include a second controller configured to monitor a first set of electrical characteristics associated with the electric grid, determine that a transient event is present on the electric grid based on the first set of electrical characteristics, and send a notification of the transient event to the first controller. The first controller may be configured to adjust operation of the aeroderivative gas turbine based on the notification by (i) adjusting dynamics of fuel demand to a fuel valve governor of the aeroderivative gas turbine, and (ii) adjusting a primary frequency algorithm.

[0007] These and other features and improvements of the present application and the resulting patent will become apparent to those of ordinary skill in the art from a review of the following detailed description, taken in conjunction with the several drawings and the appended claims. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a power generation system. [Diagram 2] FIG. 2 is a schematic diagram of a control system for an exciter and gas turbine as may be described herein. [Diagram 3] 1 is an example process flow for rapid load support for grid frequency transients that may be described herein. [Figure 4] 1 is an example process flow for rapid load support for grid frequency transients that may be described herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Referring now to the drawings, where like numerals refer to like elements throughout the several views, FIG. 1 is a schematic diagram of a power generation system 100. The power generation system 100 may include a prime mover that generates electric power from other primary energy sources. An exemplary prime mover may be a gas turbine 150, such as an aeroderivative gas turbine, which may be a rotating mechanical device with a gas turbine shaft that drives a generator to provide electric power to a power grid, which in turn provides the power to users. Other embodiments may include different types of turbines, such as steam turbines. For fault-free operation, the turbine shaft speed and resulting grid frequency must be maintained within an operating range.

[0010] The gas turbine 150 may be coupled to a generator 130 that powers the electrical grid 140. The gas turbine engine 150 may include a compressor. The compressor compresses an incoming flow of air. The compressor delivers the compressed flow of air to a combustor. The combustor mixes the compressed flow of air with a pressurized flow of fuel and ignites the mixture to generate a flow of combustion gases. The flow of combustion gases is then delivered to a turbine. The flow of combustion gases drives the turbine to generate mechanical work. The mechanical work generated in the turbine drives the compressor via a shaft and an external load, such as the generator 130.

[0011] The gas turbine engine 150 may use natural gas, various types of synthetic gas, liquid fuels, and / or other types of fuels and blends thereof. The gas turbine engine 150 may have different configurations and may use other types of components. Other types of gas turbine engines may also be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment may also be used together herein.

[0012] The gas turbine 150 may also be coupled to a turbine controller 160. The turbine controller 160 may control the operation of one or more aspects of the gas turbine 150. The generator 130 may be coupled to an exciter 120 controlled by the exciter controller 110. The exciter 120 may be configured to automatically regulate the voltage and provide a direct current (DC) output. For example, the exciter 120 may include an electrical circuit that provides a DC current and a DC voltage to a field winding of a rotor of the generator 130, thereby inducing a magnetic field within the generator 130. The magnetic field may then cause the rotor to spin within the generator, causing the shaft of the generator 130 to rotate. In addition to generating a magnetic field within the generator 130, the exciter 120 may be used to control the frequency, amplitude, and phase characteristics of the voltage output by the generator 130. In this manner, the exciter 120 may be used to synchronize the voltage output by the generator 130 with the voltage of the electrical grid 140 after the shaft of the generator rotates at its rated speed.

[0013] Exciter controller 110 may be a computing system that optionally includes one or more of input interface 112, output interface 118, one or more processors 114, and / or one or more memory devices 116. Exciter controller 110 facilitates recognition of transient grid events in the control of power generation system 100, as described in more detail below. In alternative embodiments, a controller separate from exciter controller 110 may be used in place of or in addition to exciter controller 110.

[0014] Power generation system 100 can use turbine controller 160 to rebalance the system after a transient event on electrical grid 140 that causes a frequency deviation. As an example, when a frequency sag in electrical grid 140 is detected, a speed sag can be detected because speed moves with grid frequency. Fuel intake by the prime mover is increased based on the sensing of the speed sag, and active power output is increased to compensate for the frequency sag.

[0015] The turbine 150 can rotate a shaft in the generator 130 such that the generator 130 outputs a voltage. The voltage output of the generator 130 can then be synchronized with the voltage of the electrical grid 140. In certain embodiments, the exciter controller 110 can monitor electrical characteristics of the electrical grid 140. In this manner, the exciter controller 110 can monitor the electrical grid 140 for transient events such as a rise or fall in grid frequency, a rise or fall in active or reactive power of the generator 130, etc. Transient events can include changes in electrical characteristics such as voltage, current, power, power factor, etc.

[0016] In some embodiments, the exciter controller 110 may be configured to detect or recognize a transient grid event in the early stages of the grid transient leading up to its occurrence. Upon detecting the transient event, the exciter controller 110 may send a command or notification to the turbine controller 160 to adjust the operation of the prime mover and compensate for changes in the generator frequency. That is, the exciter controller 110 may monitor electrical parameters, such as the power output and electrical frequency of the generator 130, and detect the transient event based on the electrical parameters.

[0017] The power generation system 100 described herein can provide rapid load support in response to grid frequency transient events through a combination of one or all of the following: (i) early electrical detection of grid events, (ii) use of MW modeled values ​​instead of measured power meter values ​​(e.g., avoiding power meter readings of components of power contributed by changes in generator kinetic energy in response to frequency transients), and / or (iii) use of flexible dynamics for the fuel value control loop. As a result, turbine response acceleration can be performed without oscillations in turbine frequency. Furthermore, in response to grid frequency reductions, instantaneous electrical power can be provided using, for example, an aeroderivative gas turbine.

[0018] 2 is a schematic diagram of a control system for an exciter and gas turbine as may be described herein. Other embodiments may have additional, fewer, and / or different components or configurations than those described with respect to the example shown in FIG.

[0019] The control system shown in Figure 2 can be used to provide high speed power in response to frequency events in a small grid, or an electrical grid that may be unstable. Some embodiments may use an aeroderivative gas turbine with a fuel source such as diesel or ethanol.

[0020] In FIG. 2, an automatic voltage regulator (AVR) / exciter controller 200 may be configured to control the operation of an exciter that provides a DC voltage and / or a DC current to a rotor of a generator. The AVR / exciter controller 200 may include one or more early electrical detection modules 202. The early electrical detection module 202 may be configured to detect a frequency sag in the electrical grid as a potential disturbance. For example, the early electrical detection module 202 may be configured to monitor one or more features or electrical characteristics of the electrical grid, such as a frequency, a voltage, a current, a power, or a power factor associated with the electrical grid. Based on changes in the features or electrical characteristics of the electrical grid, the early electrical detection module 202 may determine whether a transient event is present on the electrical grid. For example, if one or more of the frequency, voltage, current, power, or power factor associated with the electrical grid increases or decreases beyond a threshold, the early electrical detection module 202 may determine that a transient event is occurring or is about to occur. In one example, the AVR / exciter controller 200 may sense the rate of change of electrical frequency at the terminals of the generator and determine the rate of change of shaft line acceleration (rate of change being one of the electrical characteristics monitored by the AVR / exciter controller 200) to determine if a transient is occurring. If a transient is detected, the AVR / exciter controller 200 may send a notification 220 of the transient to the turbine controller 210. Because the AVR / exciter controller 200 may be coupled to the generator and the exciter, the AVR / exciter controller 200 may detect grid events faster and more reliably than speed measurement techniques.

[0021] The AVR / exciter controller 200 may be in communication with a turbine controller 210. The turbine controller 210 may be configured to control the operation of a turbine, such as an aeroderivative gas turbine. The turbine controller 210 may receive a notification 220 of a transient event from the AVR / exciter controller 200. The turbine controller 210 may adjust the operation of the turbine based on the notification 220. For example, the turbine controller 210 may adjust the operation of the turbine based on a modeled value of electrical power and / or based on the dynamics of fuel demand to a fuel valve governor of the turbine.

[0022] After receiving the notification 220 from the AVR / exciter controller 200, the turbine controller 210 can modify the first operating parameters 240 of the turbine by replacing the conventional dynamics 232 of the fuel demand to the fuel valve governor of the turbine with the improved dynamics 230 of the fuel demand to the fuel valve governor of the turbine. The replacement of the dynamics can adjust the first operating parameters 240 to increase or decrease the fuel in response to the detected event. The first operating parameters 240 can be modified as a result of the notification 220. The replacement of the dynamics can be temporary to take into account the event and can be restored to normal operation after the event has passed. The flexible dynamics of the fuel valve control loop can also ensure a fast response without compromising stability.

[0023] In some embodiments, in addition to or instead of modifying the fuel dynamics, the turbine controller 210 may adjust the second operating parameter 284 in response to the notification 220. The second operating parameter 284 is a measurement of the electrical power of the generator. Due to the rotational inertia of the rotating machine coupled to the generator, the rotating machine gains kinetic energy as its rotational speed increases. When a grid transient occurs that results in a change in rotational speed, the kinetic energy also changes. The rate of change of kinetic energy induces a component of the electrical power output (and / or input) known as the inertial response, which is superimposed on the component of the electrical power output of the generator that is generated by the working fluid of the turbine (e.g., an increase in observed power but not due to an increase in fuel in the combustor). For example, a negative grid frequency transient on a high inertia machine operating at a constant power demand results in a large positive inertial response that increases the power feedback, thereby causing a large negative error in the fuel governor, causing the fuel governor to erroneously reduce fuel when the desired response of the frequency reduction is to increase fuel and increase power to restore the system frequency. Thus, the turbine controller, which is regulating the flow of fuel to the governor 270 as a function of the error between the power demand 250 and the power feedback 290, has an improved response through electrical transient events by detecting the event 220 using a switch feedback mechanism 284 that can select either the measured electrical power 282 or the modeled power output 280, which may not include the inertial response, if the event 220 is known and detected to result in an undesirable fuel governor response. In this manner, the turbine controller 210 can replace the MW value 282 measured by the power meter with the MW modeled value 280. The value replacement can adjust the second operating parameter 284 to increase or decrease the fuel in response to the detected event. The value replacement can be temporary to account for the event and may be restored to normal operation after the event has passed.

[0024] In some embodiments, the turbine controller 210 may generate or determine the MW modeled value 280. For example, the turbine controller 210 may determine the MW modeled value 280 based on a high pressure compressor discharge pressure of the gas turbine. By using the MW modeled value 280, the turbine controller 210 may avoid reading an inertial response on a power meter at the moment of a grid event. In some cases, the MW modeled value 280 may be calculated internally by the turbine controller 210 based on variable geometry positions and fuel demand.

[0025] The first operating parameters 240 may be provided to a MW demand module 250 at the turbine controller 210, which may be used to control the operation of a valve 260. Similarly, the second operating parameters 284 may be provided to a MW feedback module 290 at the turbine controller 210, which may also be used to control the operation of the valve 260. The valve 260 may be used to supply fuel to a fuel governor 270 for operation of the turbine.

[0026] Thus, the turbine controller 210 may be configured to generate a modeled value of electrical power, the modeled value being a modeled value in megawatts generated based on the compressor discharge pressure of the compressor at the turbine. The modeled value may temporarily replace an actual generator electrical power reading at the turbine's power meter. Additionally, the turbine controller 210 may be configured to adjust a fuel demand dynamic to the turbine's fuel valve governor, the fuel demand dynamic being a flexible dynamic, the fuel demand dynamic being adjusted by temporarily replacing a first dynamic with a second dynamic. The second dynamic may cause a controlled acceleration of the turbine. In some embodiments, the turbine controller 210 may be further configured to determine a grid frequency boundary and increase a valve response time to avoid oscillations in the turbine frequency response. Some embodiments may be configured such that the turbine's fuel actuator reaches 95% of the movement between the initial and final positions in about 4 seconds (49 Hz), a nadir frequency for a nominal frequency of 50 Hz.

[0027] Thus, the described control system ensures reliability of turbine response to frequency events in harsh grid conditions and does not use traditional speed control. The turbine controller 210 can activate controlled acceleration of the turbine in response to notification 220 through flexible dynamics of fuel valve control without affecting stability. The disclosed embodiments can adjust one or more operations of the turbine based on modeled values ​​of electrical power, including a primary frequency algorithm, and dynamics of fuel demand to the valve governor. As a result, immediate electrical power can be provided upon detection of a major grid frequency drop.

[0028] 3 is an example process flow 300 for rapid load support for grid frequency transient events as may be described herein. One or more of the operations described in FIG. 3 may be performed in different orders and / or by the same or different computer systems across a distributed computing environment. In one example, the operations of FIG. 3 may be performed by the AVR / exciter controller 200 of FIG. 2.

[0029] In block 310, a first controller (such as the AVR / exciter controller 200) may monitor a first set of electrical characteristics associated with the electrical grid. For example, the first controller may monitor frequency, voltage, current, power, power factor, and / or other electrical characteristics associated with the electrical grid.

[0030] At decision block 320, a determination may be made by the first controller as to whether there has been a sudden change in grid frequency. For example, the first controller 210 may determine whether one or more characteristics of the electrical grid, such as grid frequency, has suddenly increased or decreased beyond a threshold amount. If at decision block 320, it is determined that there has not been a sudden change in grid frequency, the process flow 300 may return to block 310 and monitoring may continue using the first controller. If at decision block 320, it is determined that there has been a sudden change in grid frequency, the process flow 300 may proceed to block 330.

[0031] At block 330, the first controller may determine that a transient event is present on the electrical grid based on the first set of electrical characteristics. For example, based on a grid frequency changing by more than a threshold amount over a particular length of time, the first controller may determine that a transient event is present on the electrical grid.

[0032] The first controller may send a notification of the transient event to a second controller in block 340. For example, the first controller may send a notification of the transient event to a turbine controller.

[0033] In block 350, the first controller may actuate a controlled acceleration of the turbine. In some embodiments, the first controller may cause the actuation of the controlled acceleration of the turbine by having the second controller actuate the controlled acceleration of the turbine. The controlled acceleration may reduce a risk of power loss due to abrupt changes in grid frequency.

[0034] 4 is an example process flow 400 for rapid load support for grid frequency transient events as may be described herein. One or more of the operations described in FIG. 4 may be performed in different orders and / or by the same or different computer systems across a distributed computing environment. In one example, the operations of FIG. 4 may be performed by turbine controller 210 of FIG. 2.

[0035] A turbine controller of the turbine may receive notification of the transient event at block 410. For example, the AVR / exciter controller may detect a transient event in the generator and / or the electrical grid, and the turbine controller may receive notification of the transient event from the AVR / exciter controller.

[0036] At block 420, the turbine controller may determine a MW modeling value to replace the measured power meter value based on the compressor discharge pressure of the compressor at the turbine. For example, the turbine controller may at least temporarily replace the measured power meter value with the MW modeling value. The MW modeling value may be determined based on the compressor discharge pressure of the compressor at the turbine and may reflect a transient event.

[0037] At block 430, the turbine controller may determine an improved dynamic fuel value for the fuel demand. The improved dynamic fuel value may be used, at least temporarily, in place of the conventional dynamic fuel value.

[0038] The turbine controller may use the improved dynamics values ​​to adjust the fuel demand in block 440. For example, the turbine controller may adjust the dynamics of the fuel demand to a fuel valve governor of the turbine.

[0039] In optional block 450, the turbine controller may adjust a primary frequency algorithm for operation of the turbine.

[0040] As a result, the turbine controller can enable the gas turbine to operate on multiple types of fuel, provide fast response during grid events, and provide improved control over the fuel supply valves when controlled acceleration of the turbine is required.

[0041] It is apparent that the above relates only to certain embodiments of the present application and the resulting patent. Numerous changes and modifications may be made herein by those skilled in the art without departing from the general spirit and scope of the present invention as defined by the following claims and their equivalents. [Explanation of symbols]

[0042] 100 Power Generation System 110 Exciter Controller 112 Input Interface 114 processors 116 Memory Device 118 Output Interface 120 Exciter 130 Generator 140 Electricity Grid 150 Gas turbine engines, gas turbines 160 Turbine Controller 200 Automatic Voltage Regulator (AVR), Exciter Controller 202 Early Electrical Detection Module 210 Turbine controller, first controller 220 Transient Event Notification, Event 230 Improved Dynamics 232 Traditional Dynamics 240 First Operating Parameter 250 Power Demand, MW (Megawatt) Demand Module 260 Valve 270 Fuel Governor 280 Modeled Power Output, MW modeled value 282 Measured electrical power, measured in MW by a wattmeter 284 Second operating parameter, switch feedback mechanism 290 Power Feedback, MW Feedback Module 300 Process Flow 310 Block 320 Decision Block 330 Block 340 blocks 350 blocks 400 Process Flow 410 Block 420 Block 430 Block 440 Block 450 Block

Claims

1. A system (100) for providing rapid load support using a gas turbine (150), comprising: a turbine (150) having a first controller (210); a generator (130) coupled to the turbine (150), the generator (130) configured to provide electrical power to an electrical grid (140); An exciter (120) configured to provide a direct current (DC) voltage and a DC current to a rotor of the generator (130), the exciter (120) comprising: monitoring a first set of electrical characteristics associated with the electrical grid (140); determining that a transient event is present on the electrical grid (140) based on the first set of electrical characteristics; Sending a notification (220) of the transient event to the first controller (210). an exciter (120) having a second controller (200) configured as follows: Equipped with The first controller (210) is configured to adjust operation of the turbine (150) based on the notification (220). System (100).

2. The system (100) of any preceding claim, wherein the first controller (210) is configured to adjust operation of the turbine (150) based on a modeled value of electrical power (280).

3. The system (100) of claim 1, wherein the first controller (210) is configured to generate a modeled value (280) of electrical power.

4. The system (100) of any of claims 3 to 6, wherein the modeled value (280) is a modeled value in megawatts generated based on a compressor discharge pressure of a compressor at the turbine (150).

5. The system (100) of claim 3, wherein the modeled value (280) temporarily replaces an actual kinetic energy reading on a power meter of the turbine (150).

6. The system (100) of any of the preceding claims, wherein the first controller (210) is configured to regulate dynamics of fuel demand to a fuel valve governor (270) of the turbine (150).

7. The system (100) of claim 6, wherein the fuel demand dynamics are flexible dynamics.

8. The system (100) of claim 6, wherein the fuel demand dynamics are adjusted by temporarily replacing a first dynamics with a second dynamics.

9. The system (100) of claim 8, wherein the second dynamics causes a controlled acceleration of the turbine (150).

10. 2. The system of claim 1, wherein the second controller determines that the transient event is present on the electrical grid when a frequency, voltage, current, power, or power factor associated with the electrical grid increases or decreases beyond a threshold value.

11. The second controller (200) Sensing the rate of change of electrical frequency at the terminals of the generator (130); Determine the rate of change of shaft line acceleration The method further comprises: the rate of change being one of the electrical properties in the first set of electrical properties. The system (100) of claim 1.

12. The system of claim 1 , wherein the first controller is configured to adjust a primary frequency algorithm.

13. The system of claim 1 , wherein the first controller is configured to determine grid frequency boundaries and increase valve response times to avoid oscillations.

14. The system (100) of claim 1, wherein the turbine (150) is an aeroderivative gas turbine.

15. A method (300, 400) for providing improved load support for grid frequency transients, comprising: monitoring (310) a first set of electrical characteristics associated with the electrical grid (140) by a first controller (210); determining (330), by the first controller (210), that a transient event is present on the electrical grid (140) based on the first set of electrical characteristics; Sending (340) a notification of the transient event (220) to a second controller (200); Including, the second controller (200) is configured to adjust operation of the turbine (150) based on the notification (220) by (i) adjusting (440) a dynamics of fuel demand to a fuel valve governor (270) of the turbine (150), and (ii) adjusting (450) a primary frequency algorithm; Method (300, 400).

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