System and method for detecting low speed in a gas turbine generator

Abstract

A control system for a power generation system includes a generator coupled to a turbine via a shaft. The control system includes a memory that stores instructions. The control system also includes a processor coupled to the memory and configured to execute the instructions. When the instructions are executed, the processor receives a direct current (DC) link voltage from an automatic voltage regulator (AVR), and the AVR is configured to control a voltage characteristic of the generator and determine a speed of the generator based on the DC link voltage.

Description

Background Art

[0004] , , , , , ,

[0001] The subject matter disclosed herein relates to a gas turbine generator, and more particularly, to a system and method for detecting low speed in a gas turbine generator.

[0002] Generators are frequently used to supply electricity to a power grid to provide power to one or more loads. A generator can operate at a specific voltage amplitude, phase, and frequency based on the operation of a turbine such as a gas turbine, a steam turbine, or another prime mover. For example, a turbine can supply rotational energy to a shaft that rotates within the generator. The shaft can rotate based on various settings of the turbine, such as the amount of air and fuel entering the turbine. To export power to the power grid, the power generated by the generator is controlled to be synchronized with the power on the power grid, and a circuit breaker is closed to electrically couple the generator to the power grid. That is, the parameters of the power generated by the generator, such as the voltage amplitude, phase, and frequency supplied by the generator, may be controlled to fall within the respective parameter ranges of the power grid, such as voltage amplitude, phase, and frequency, before closing the circuit breaker.

[0003] In some cases, the generator may stop operating, and it is necessary to monitor the speed of the generator and / or the turbine to determine when the generator stopped. Additional hardware is required to monitor the low speed of the generator. For example, a zero speed switch or a speed-operated sensing switch can be utilized. However, the use of this additional hardware may not be cost-effective.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The following is a summary of specific embodiments that correspond to the scope of the subject matter initially claimed. These embodiments are not intended to limit the scope of the claimed subject matter, but rather to provide an overview of feasible forms of the subject matter. In fact, the subject matter can encompass a variety of forms that may be similar to or different from the embodiments described below.

[0006] In the first embodiment, the control system of the power generation system includes a generator coupled to a turbine via a shaft. The control system includes a memory for storing instructions. The control system also includes a processor coupled to the memory and configured to execute instructions. When an instruction is executed, the processor receives a direct current (DC) link voltage from an automatic voltage regulator (AVR), which is configured to control the voltage characteristics of the generator and determine the generator speed based on the DC link voltage.

[0007] In a second embodiment, a non-transient computer-readable medium includes instructions configured to be executed by a processor in a control system for a power generation system, which includes a generator coupled to a turbine via a shaft. The instructions include instructions configured to cause the processor to receive a direct current (DC) link voltage from an automatic voltage regulator (AVR) configured to control the voltage characteristics of the generator, and to determine the speed of the generator based on the DC link voltage.

[0008] In a third embodiment, the power generation system includes a turbine, a generator coupled to the turbine via a shaft, and an automatic voltage regulator (AVR). The AVR is configured to control the voltage characteristics of the generator. The power generation system is configured to receive a voltage from the AVR and determine the speed of the generator based on the voltage.

[0009] These, as well as other, features, aspects, and advantages of this subject matter will be better understood by reading the following detailed description in conjunction with the attached drawings. In the attached drawings, similar reference numerals represent similar parts throughout the drawings. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram of one embodiment of the power generation system (for example, an AC power generation system) according to this embodiment. [Figure 2] This is a schematic diagram of one embodiment of a power generation system (e.g., an AC power generation system) coupled with an automatic voltage regulator (AVR) and a controller according to this embodiment. [Figure 3] This is a flowchart of one embodiment of a method for monitoring the generator speed of the turbine-generator system shown in Figures 1 and 2, according to this embodiment. [Modes for carrying out the invention]

[0011] One or more specific embodiments are described below. Not all features of actual implementations are described herein in order to provide a concise description of these embodiments. In developing such actual embodiments, it should be understood that, as with any engineering or design project, a number of decisions specific to each embodiment must be made to achieve the developer's particular goals, including compliance with system-related and business-related constraints, which may differ from embodiment to embodiment. Furthermore, it should be understood that while such development work may be complex and time-consuming, it is still routine work of design, fabrication, and manufacturing for those skilled in the art who benefit from this disclosure.

[0012] When describing elements of various embodiments of this disclosure, the articles “a, an,” “the,” and “said” are intended to indicate that there is one or more of those elements. The terms “comprising,” “including,” and “having” are comprehensive and mean that there may be additional elements other than those listed.

[0013] Embodiments of this disclosure provide a system and method for monitoring the speed of a generator and / or a shaft coupling the generator to a prime mover (e.g., a turbine) in a power generation system. Embodiments include a control system that receives a voltage (e.g., a direct current (DC) link voltage) from an automatic voltage regulator (AVR) that controls the voltage characteristics of the generator. The control system determines the speed of the generator and / or shaft from the DC link voltage (e.g., directly from the DC link voltage). In certain embodiments, the control system may utilize a model algorithm and / or a lookup table to determine the speed of the generator and / or shaft. By utilizing a measured value of the DC link voltage, a cost-effective method for monitoring low generator speeds (e.g., 50 revolutions per minute (RPM) or less) is provided, by eliminating the need for additional hardware to monitor these low speeds.

[0014] With the above in mind, it may be useful to describe an embodiment of a power generation system, such as the exemplary power generation system 10 shown in Figure 1. The power generation system 10 may include various subsystems such as a turbine 12, a generator 14 (e.g., a synchronous generator), and an exciter 16. The turbine 12 (e.g., a gas turbine, steam turbine, hydraulic turbine, etc.) may be coupled to the generator 14 via a shaft 13. The generator 14 may then be communicatively coupled to a generator exciter 16. The exciter 16 can supply direct current (DC) to the field winding 22 of the generator 14. In particular, the exciter 16 can supply a DC magnetic field current to excite the magnetic field of the generator 14 (e.g., a current used by the field winding 22 and / or other synchronous machinery of the generator 14 to establish a magnetic field for operation). For example, the exciter 16 may be a static (e.g., power electronics) exciter or a rotary (e.g., brushed and / or brushless) exciter. In other embodiments, the exciter 16 may be bypassed, and the power output may directly excite the field winding 22 of the generator 14. Also, as shown in the figure, the output terminals of the generator 14 may be coupled to a large commercial power grid 26 via an AC line 28. Alternatively, the output terminals of the generator 14 may be coupled to a small industrial power plant.

[0015] The power generation system 10 may also include an excitation system 24, which may provide various control parameters to each of the generator 14 and / or exciter 16 based on, for example, measurement parameters received at one or more inputs to the excitation system 24 and / or indications of measurement parameters. As will be described in more detail below, one of these inputs may be a voltage generated by a brushless permanent magnet generator (PMG) coupled to the shaft 13. In certain embodiments, the excitation system 24 may function as an excitation control unit for the generator 14 and exciter 16. The excitation system 24 may include one or more controllers 32 and one or more power converters 34. The power converters 34 may include subsystems of integrated power electronics switching devices such as silicon-controlled rectifiers (SCRs), thyristors, and insulated-gate bipolar transistors (IGBTs) that receive alternating current (AC) power, DC power, or a combination thereof from a power source such as a power grid 26. As will be described in more detail below, the power converters 34 may include an automatic voltage regulator (AVR). The excitation system 24 can receive this power via the bus 29 and, based on this, can provide power, control, and monitoring to the field winding 30 of the exciter 16. Thus, the excitation system 24 and the exciter 16 may operate collectively to drive the generator 14 according to a desired output (e.g., grid voltage, power factor, load frequency, torque, speed, acceleration, etc.). As an example, in one embodiment, the excitation system 24 may be an excitation controller system such as the EX2100e® regulator available from General Electric Company, Schenectady, New York. As will be described in more detail below, the DC link voltage measured from the AVR can be used to monitor and determine the low speed (e.g., 50 RPM or less) of the generator 14 and / or shaft 13.

[0016] Referring now to Figure 2, the figure shows another power generation system 40 (for example, a power synchronization system). Overall, the power generation system 40 is as described in Figure 1. The turbine 12 includes a gas turbine 42 having a compressor 44, a combustor 46, and a turbine 48. The gas turbine 42 can receive air compressed by the compressor 44. The compressed air is mixed with fuel, and the mixture is burned in the combustor 46. The combustion mixture of air and fuel can be used to rotate one or more blades of the turbine 48. The rotor of the turbine 48 may be coupled to a shaft 13 to supply rotational energy to the generator 14.

[0017] Furthermore, the power generation system 40 also includes a brushless PMG 50 coupled to the shaft 13. The PMG 50 serves as the power source for the exciter magnetic field of the power generation system 40. In addition, the power generation system 40 includes an AVR 52 (for example, an example of the power converter 34 of the excitation system 24 in Figure 1). The AVR 52 controls the voltage characteristics of the generator 14. Specifically, the AVR 52 modifies the generator excitation voltage (for example, by controlling the magnetic field of the generator 14 via the voltage applied to the coils of the exciter magnetic field). The AVR 52 includes a diode rectifier 54 coupled to the inverter 56 via a DC link 58. The DC link 58 includes a capacitor 60 for reducing and smoothing the voltage applied to the inverter 56. The AVR 52 receives an output 62 (for example, a voltage) from the PMG 50. The AVR 52 rectifies the voltage from the PMG 50 (i.e., converts it from AC to DC) and outputs a voltage 64 to control the exciter magnetic field of the exciter 16, and then controls the voltage in the generator stator.

[0018] As illustrated in the overall diagram, the controller 32 may include one or more processors 66 and memory 68 that can be used collectively to support operating systems, software applications, and systems, etc., useful for implementing the techniques described herein. In particular, the controller 32 may include code or instructions stored in a non-temporary machine-readable medium (e.g., memory 68 and / or other storage devices) and executed, for example, by one or more processors 66 that may be included in the controller 32. The processor 66 can receive a voltage 70 (e.g., DC link voltage) measured from the DC link 58. The processor 66 can also use the DC link voltage to determine the speed of the shaft 13 and / or the generator 14. The voltage 62 coming from the PMG 50 changes depending on the operating frequency of the generator 14, and therefore the speed of the shaft 13. From this relationship, the speed of the generator 14 can be determined. For example, in certain embodiments, the processor 66 can use an algorithmic model or a lookup table (e.g., one stored in memory 68) to derive the operating speed of the shaft 13 and / or the generator 14 from the DC link voltage 70. In a particular embodiment, the processor 66 can determine when the generator 14 stopped based on the DC link voltage 70.

[0019] Figure 3 is a flowchart of one embodiment of Method 72 for monitoring the generator speed of the turbine-generator system of Figures 1 and 2. Method 72 may be performed by the controller 32 described above. One or more steps of Method 72 may be performed simultaneously and / or in different orders. Method 72 includes the step (block 74) of receiving a voltage (e.g., DC link voltage) measured directly from the DC link of the AVR, where the voltage is the rectified voltage of the voltage received by the AVR from the PMG. Method 72 also includes the step (block 76) of determining the speed of the shaft and / or generator of the turbine-generator system based on the DC link voltage. Speeds of 50 RPM or less can be detected. For example, the shaft and / or generator speed can be determined using Model 78 or a lookup table 80 that considers the relationship between the DC link voltage and the operating frequency of the generator. Method 72 further includes the step (block 82) of determining whether the speed (e.g., RPM) of the shaft and / or generator is zero. If the speed is zero, Method 72 includes the step (block 84) of determining that the generator has stopped. If the speed is not zero, method 72 includes the steps of continuing to receive the measured DC link voltage (block 74) and determining the speed of the shaft and / or generator (block 76).

[0020] The technical effect of the disclosed embodiments includes providing a system and method for detecting and monitoring low speeds (e.g., 50 RPM or less) of the shaft and / or generator in a turbine generator system. In particular, the speed of the shaft and / or generator can be determined without requiring additional hardware by utilizing the DC link voltage measured directly from the AVR.

[0021] This specification discloses the disclosed subject matter, including the best mode, and uses examples to enable those skilled in the art to practice the disclosed subject matter, which includes the making and using of any device or system and the carrying out of any related methods. The patentable scope of the disclosed subject matter is defined by the claims and can include other examples that occur to those skilled in the art. Such other examples are to be within the scope of the claims if they have structural elements that do not differ from the language of the claims or if they include equivalent structural elements that do not substantially differ from the language of the claims.

Explanation of Reference Signs

[0022] 10 Power generation system 12 Turbine 13 Shaft 14 Generator 16 Generator exciter 22 Field winding 24 Excitation system 26 Large-scale commercial power transmission network 29 Bus 30 Field winding 32 Controller 34 Power converter​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​

Claims

1. A control system for a power generation system (10, 40) comprising a generator (14) coupled to a turbine (12, 48) via a shaft (13), An automatic voltage regulator (AVR) including a diode rectifier coupled to an inverter via a DC link, wherein the inverter is included in the automatic voltage regulator (AVR), A memory (68) for storing instructions, A processor (66) coupled to the memory (68) and configured to execute the instruction, wherein when the instruction is executed, the processor (66) receives The AVR receives a DC link voltage (70) from the AVR (52), which is configured to control the voltage characteristics of the generator (14) by changing the generator excitation voltage, and The speed of the generator (14) is determined based on the DC link voltage (70). Processor (66) and Equipped with, The DC link voltage (70) includes the rectified voltage of the voltage received by the AVR (52) from the permanent magnet generator (50) coupled to the shaft (13). A control system wherein the processor is configured to determine the speed of the generator (14) based on the DC link voltage using a mathematical model (78) or a lookup table (80), and the mathematical model (78) or the lookup table (80) is configured to determine the speed of the generator (14) using the relationship between the DC link voltage (70) and the operating frequency of the generator.

2. The control system according to claim 1, wherein the processor (66) is configured to determine whether the generator (14) has stopped when the instruction is executed.

3. The control system according to claim 1, wherein determining the speed of the generator (14) based on the DC link voltage (70) includes determining the speed of the shaft (13).

4. The control system according to claim 1, wherein the processor (66) is configured to determine the speed of the generator (14) based on the DC link voltage (70) using a mathematical model (78) or a lookup table (80) when the instruction is executed.

5. The control system according to claim 1, wherein the turbine (48) includes a gas turbine (42).

6. Turbine (12, 48) and A generator (14) is coupled to the turbine (12, 48) via a shaft (13), A permanent magnet generator (50) is coupled to the shaft (13), An automatic voltage regulator (AVR) including a DC link, wherein the AVR is configured to control the voltage characteristics of the generator (14) by changing the generator excitation voltage, A controller (32) is configured to receive a DC link voltage from the AVR (52) and determine the speed of the generator (14) based on the DC link voltage. Equipped with, The DC link voltage (70) includes the rectified voltage of the voltage received by the AVR (52) from the permanent magnet generator (50). The power generation system (10) is configured such that the controller (32) determines the speed of the generator (14) based on the DC link voltage using a mathematical model (78) or a lookup table (80), and the mathematical model (78) or the lookup table (80) determines the speed of the generator (14) using the relationship between the DC link voltage (70) and the operating frequency of the generator.

7. The power generation system (10, 40) according to claim 6, wherein the AVR (52) comprises a diode rectifier (54) coupled to an inverter (56) via a DC link (58) and a capacitor (60) located in the DC link (58).

8. The power generation system (40) according to claim 6, wherein the turbine (48) includes a gas turbine (42) and the generator (14) includes a synchronous generator.

9. The power generation system (10, 40) according to claim 6, wherein the controller (32) is configured to determine whether the generator (14) has stopped.

10. The power generation system (10, 40) according to claim 9, wherein the controller (32) is configured to determine the speed of the shaft (13) based on the DC link voltage.

11. The power generation system (10, 40) according to claim 6, wherein the controller (32) is configured to determine the speed of the generator (14) based on the DC link voltage using a mathematical model (78) or a lookup table (80).

12. The control system according to claim 1, wherein the processor (66) is configured to determine whether the generator (14) has stopped based on the speed of the generator when the instruction is executed.

13. The control system according to claim 12, wherein determining the speed of the generator (14) based on the DC link voltage (70) includes determining the speed of the shaft based on the DC link voltage.

14. The automatic voltage regulator (AVR) includes a diode rectifier coupled to an inverter via a DC link. The inverter is included in the automatic voltage regulator (AVR), The power generation system according to claim 6, wherein the controller (32) is configured to receive a direct current (DC) link voltage (70) from the AVR (52), determine the speed of the generator (14) based on the DC link voltage (70), and determine the speed of the shaft based on the DC link voltage (70).

15. The power generation system according to claim 14, wherein the controller (32) is configured to determine whether the generator (14) has stopped based on the speed of the generator.

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