Method and system for rapid load support for grid frequency transients - Patents.com

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 particularly to providing rapid load support in response to grid frequency transients. [Background technology]

[0002] A power plant, or power generation 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 and provides electrical power to a power grid. The power grid then distributes the electricity to various power consumers. To ensure that a power generation system operates effectively, the turbine shaft speed and the resulting grid frequency must be synchronized with each other within their operating range. If a transient event causes the grid frequency to change suddenly, power may be lost.

[0003] The adverse effects of transient events, such as sudden changes in grid frequency, are amplified on 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. Therefore, small grids tend to experience more frequent frequency changes than larger grids. This lack of stability can result in power outages and / or loss of power to the grid. Therefore, 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 exists 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 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 exists 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 fuel demand dynamics to a turbine fuel valve governor 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 exists 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 fuel demand dynamics 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 skilled in the art from a review of the following detailed description, taken in conjunction with the several drawings and the appended claims. [Brief explanation of the drawings]

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

[0009] Referring now to the drawings, wherein 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 electrical 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 an electrical generator to provide electrical 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, which supplies power to 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] Gas turbine engine 150 may use natural gas, various types of syngas, liquid fuels, and / or other types of fuels and blends thereof. 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, which is controlled by the exciter controller 110. The exciter 120 may be configured to automatically regulate voltage and provide a direct current (DC) output. For example, the exciter 120 may include an electrical circuit that provides DC current and 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 generator shaft has rotated 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 drop in electrical grid 140 is detected, a speed drop can be detected because speed moves with grid frequency. Fuel intake by the prime mover is increased based on the sensed speed drop, and active power output is increased to compensate for the frequency drop.

[0015] The turbine 150 may rotate a shaft within the generator 130, causing the generator 130 to output a voltage. The voltage output of the generator 130 may then be synchronized with the voltage of the electrical grid 140. In certain embodiments, the exciter controller 110 may monitor electrical characteristics of the electrical grid 140. In this manner, the exciter controller 110 may monitor the electrical grid 140 for transient events, such as an increase or decrease in grid frequency, an increase or decrease in the active or reactive power of the generator 130, etc. The transient events may include changes in electrical characteristics, such as voltage, current, power, power factor, etc.

[0016] In some embodiments, 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 a transient event, exciter controller 110 may send a command or notification to turbine controller 160 to adjust prime mover operation and compensate for changes in generator frequency. That is, exciter controller 110 may monitor electrical parameters, such as the power output and electrical frequency of generator 130, and detect a 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 transients through a combination of one or all of the following: (i) early electrical detection of the grid event, (ii) the use of MW modeled values ​​instead of measured wattmeter values ​​(e.g., avoiding wattmeter readings that contribute to changes in the generator's kinetic energy in response to frequency transients), and / or (iii) the use of flexible dynamics for the fuel value control loop. As a result, turbine response acceleration can be achieved without turbine frequency oscillations. Furthermore, in response to grid frequency reductions, immediate 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 small grids, or electrical grids that may be unstable. Some embodiments may use aeroderivative gas turbines with fuel sources 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 drop 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, voltage, current, power, or 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 occurring on the electrical grid. For example, if one or more of the frequency, voltage, current, power, or power factor associated with the electrical grid increase or decrease 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, 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 is one of the electrical characteristics monitored by AVR / exciter controller 200) to determine if a transient is occurring. If a transient is detected, AVR / exciter controller 200 may send a notification 220 of the transient to turbine controller 210. Because AVR / exciter controller 200 may be coupled to the generator and exciter, 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 a first operating parameter 240 of the turbine by replacing a conventional dynamics 232 of fuel demand to the turbine's fuel valve governor with an improved dynamics 230 of fuel demand to the turbine's fuel valve governor. The dynamics replacement can adjust the first operating parameter 240 to increase or decrease fuel in response to the detected event. The first operating parameter 240 can be modified as a result of the notification 220. The dynamics replacement can be temporary to account for 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 can adjust a second operating parameter 284 in response to the notification 220. The second operating parameter 284 is a measurement of the generator's electrical power. Due to the rotational inertia of the rotating machinery coupled to the generator, the rotating machinery 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 generator's electrical power output that is generated by the turbine's working fluid (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 power feedback, thereby causing a large negative error in the fuel governor, causing the fuel governor to erroneously reduce fuel when the desired response for a frequency reduction is to increase fuel and increase power to restore system frequency. Thus, a turbine controller regulating fuel flow to governor 270 as a function of the error between power demand 250 and power feedback 290 has improved response through electrical transient events by detecting event 220 using a switch feedback mechanism 284 that can select either measured electrical power 282 or modeled power output 280, which may not include inertial response, if event 220 is known and detected to result in an undesirable fuel governor response. In this manner, turbine controller 210 can replace MW value 282 measured by a power meter with MW modeled value 280. The value substitution can adjust second operating parameter 284 to increase or decrease fuel in response to the detected event. The value substitution can be temporary to account for the event and may return to normal operation after the event has passed.

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

[0025] The first operating parameters 240 may be provided to a MW demand module 250 in 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 in the turbine controller 210, which may also be used to control the operation of the valve 260. The valve 260 may be used to provide 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, where the modeled value is a megawatt modeled value 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 on the turbine's power meter. Additionally, the turbine controller 210 may be configured to adjust fuel demand dynamics to the turbine's fuel valve governor, where the fuel demand dynamics may be flexible dynamics, and the fuel demand dynamics may be adjusted by temporarily replacing first dynamics with second dynamics. The second dynamics may cause controlled acceleration of the turbine. In some embodiments, the turbine controller 210 may be further configured to determine a grid frequency boundary and increase the valve response time to avoid oscillations in the turbine frequency response. Some embodiments may configure the turbine's fuel actuator to reach 95% of its travel between the initial and final positions in approximately 4 seconds (49 Hz), a nadir frequency relative to a nominal frequency of 50 Hz.

[0027] The described control system therefore ensures reliable 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 notifications 220 through flexible dynamics of fuel valve control without affecting stability. Embodiments of the present disclosure 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 a different order 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 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, have suddenly increased or decreased by more than 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] In 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 at 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 the risk of power loss due to sudden 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 a different order 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 transient events.

[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 fuel demand at block 440. For example, the turbine controller may adjust the dynamics of 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 may enable the gas turbine to operate on multiple types of fuel, provide fast response during grid events, and provide improved control over fuel supply valves when controlled acceleration of the turbine is required.

[0041] It should be apparent that the foregoing relates only to certain embodiments of this 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 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 Electrical 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 Conventional Dynamics 240 First operating parameter 250 Power Demand, MW (Megawatt) Demand Module 260 valves 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 blocks 450 blocks

Claims

1. A method for controlling a power generation system, the power generation system comprising: a generator configured to supply power to an electrical grid; a first gas turbine coupled to the generator, the first gas turbine including a first controller and a compressor, the first controller configured to generate a modeled value of electrical power generated by the generator, the modeled value of electrical power based on a compressor discharge pressure of the compressor, the modeled value of electrical power representing an estimated electrical power output of the generator; and an exciter for the generator, the exciter including a second controller; Including, The method comprises: monitoring, by the second controller, a first set of characteristics of the electrical grid, the characteristics including a frequency of the electrical grid; the second controller detecting a frequency drop in the electrical grid based on the monitoring; the second controller determining that the frequency drop exceeds a threshold; the second controller determining that a transient event exists in the electrical grid based on a determination that the frequency dip exceeds the threshold; and the second controller sending a notification of the transient event to the first controller; the first controller determining an updated fuel demand based on the modeled value of the electric power; the first controller, in response to the notification, temporarily replacing a default fuel demand to a fuel valve governor of the first gas turbine with the updated fuel demand; and the first controller returning to the default fuel demand after the transient event is no longer present on the grid. A method comprising:

2. The method comprises:

2. The method of claim 1, further comprising: after receiving the notification, the first controller replacing a measured electrical power reading of the generator with a modeled value of electrical power in a fuel demand calculation used to determine the updated fuel demand.

3. The method comprises: The method of claim 1 , further comprising the first controller using the updated fuel demand to control acceleration of the first gas turbine before returning to the default fuel demand.

4. The method comprises:

2. The method of claim 1, further comprising: the second controller determining, based on the monitoring, whether a voltage, current, power, or power factor associated with the electrical grid has increased or decreased below a threshold value.

5. The method comprises: The method of claim 1 , further comprising the first controller determining boundaries for the grid frequency to avoid turbine frequency oscillations of the first turbine.

6. A method for controlling a power generation system, the power generation system comprising: a generator configured to supply power to an electrical grid; a first aeroderivative gas turbine coupled to the generator, the first aeroderivative gas turbine including a first controller and a compressor, the first controller configured to generate a modeled value of electrical power generated by the generator, the modeled value of electrical power based on a compressor discharge pressure of the compressor, the modeled value of electrical power representing an estimated electrical power output of the generator; and an exciter for the generator, the exciter including a second controller; Including, The method comprises: monitoring, by the second controller, a first set of electrical characteristics associated with the electrical grid, the characteristics including a frequency of the electrical grid; the second controller detecting a frequency drop in the electrical grid based on the monitoring; the second controller determining that the frequency drop exceeds a threshold; the second controller determining that a transient event exists in the electrical grid based on a determination that the frequency dip exceeds the threshold; and the second controller sending a notification of the transient event to the first controller; the first controller determining an updated fuel demand based on the modeled value of the electric power; the first controller, in response to the notification, temporarily replacing a default fuel demand to a fuel valve governor of the first aeroderivative gas turbine with the updated fuel demand; and the first controller returning to the default fuel demand after the transient event is no longer present on the grid. A method comprising:

7. The method comprises:

7. The method of claim 6, further comprising the second controller determining, based on the monitoring, whether a voltage, current, power, or power factor associated with the electrical grid has increased or decreased below a threshold value.

8. The method comprises:

7. The method of claim 6, wherein the first controller uses the updated fuel demand to control acceleration of the first aeroderivative gas turbine before returning to the default fuel demand supplied to the fuel valve governor.

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