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

Abstract

The present invention provides a control system for a power generation system, comprising a generator coupled to a turbine via a shaft. The control system includes a memory storing 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) bus voltage from an automatic voltage regulator (AVR), wherein the AVR is configured to control the voltage characteristics of the generator and determine the speed of the generator based on the DC bus voltage.

Description

Background Technology

[0001] The subject matter disclosed herein relates to gas turbine generators, and more specifically, to systems and methods for detecting low speeds in gas turbine generators.

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

[0003] Occasionally, the generator may need to be shut down, and the speed of the generator and / or turbine needs to be monitored to determine when the generator has stopped. Additional hardware is required to monitor the generator's low speed. For example, a zero-speed switch or a speed-actuated sensing switch could be used. However, utilizing such additional hardware may not be cost-effective. Summary of the Invention

[0004] The following outlines some embodiments that are comparable to the scope of the originally claimed subject matter. These embodiments are not intended to limit the scope of the claimed subject matter, but are merely intended to provide a brief overview of the possible forms of this subject matter. In reality, this subject matter can encompass a variety of forms that may be similar to or different from the embodiments set forth below.

[0005] In a first embodiment, a control system for a power generation system includes a generator coupled to a turbine via a shaft. The control system includes a memory storing 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) bus voltage from an automatic voltage regulator (AVR), wherein the AVR is configured to control the voltage characteristics of the generator and determine the speed of the generator based on the DC bus voltage.

[0006] In a second embodiment, a non-transitory computer-readable medium includes instructions configured to be executed by a processor for a control system of a power generation system, the control system including a generator coupled via a turbine. The instructions include instructions configured to cause the processor to receive a direct current (DC) bus voltage from an automatic voltage regulator (AVR), wherein the AVR is configured to control the voltage characteristics of the generator and determine the speed of the generator based on the DC bus voltage.

[0007] In a third embodiment, a 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 voltage from the AVR and determine the speed of the generator based on the voltage. Attached Figure Description

[0008] These and other features, aspects, and advantages of the subject matter of the invention will be better understood when the following detailed description is read with reference to the accompanying drawings, in which the same characters denote the same parts, wherein:

[0009] Figure 1 This is a block diagram of an implementation scheme for a power generation system (e.g., an AC power generation system) according to this embodiment;

[0010] Figure 2 This is a schematic diagram of an embodiment of a power generation system (e.g., an AC power generation system) coupled to an automatic voltage regulator (AVR) and a controller, according to this embodiment; and

[0011] Figure 3 It is used for monitoring according to this implementation plan. Figure 1 and Figure 2 A flowchart of an implementation scheme for a method to improve the speed of a turbine generator system. Detailed Implementation

[0012] One or more specific embodiments will be described below. To provide a concise description of these embodiments, not all features of the actual implementation may be described in the specification. It should be understood that in the development of any such actual implementation, as in any engineering or design project, many implementation-specific decisions must be made to achieve the developer's specific objectives, such as complying with system-related and business-related constraints, which may vary from implementation to implementation. Furthermore, it should be understood that such development work may be complex and time-consuming, but remains a routine task of design, fabrication, and manufacturing for those skilled in the art who benefit from this disclosure.

[0013] When describing elements of various embodiments of this disclosure, the articles “a,” “an,” “the,” and “the” are intended to mean one or more elements present in the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that additional elements may be present in addition to the listed elements.

[0014] Embodiments of this disclosure provide a system and method for monitoring the speed of a generator and / or shaft that couples the generator to a prime mover (e.g., a turbine) in a power generation system. Embodiments include a control system that receives voltage (e.g., direct current (DC) bus 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 (e.g., directly from) the DC bus voltage. In certain embodiments, the control system may utilize model algorithms and / or lookup tables to determine the speed of the generator and / or shaft. Utilizing the measurement of the DC bus voltage provides a cost-effective way to monitor low speeds (e.g., 50 revolutions per minute (RPM) or less) by eliminating the need for additional hardware for monitoring low speeds of the generator.

[0015] Considering the foregoing, describe the implementation scheme of the power generation system (such as...) Figure 1 The exemplary power generation system 10 shown may be useful. Power generation system 10 may include various subsystems such as turbine 12, generator 14 (e.g., synchronous generator), and exciter 16. Turbine 12 (e.g., gas turbine, steam turbine, water turbine, etc.) may be coupled to generator 14 via shaft 13. Generator 14 may in turn be communicatively coupled to generator exciter 16. Exciter 16 may provide direct current (DC) to the field winding 22 of generator 14. In particular, exciter 16 may provide DC field current (e.g., current used by the field winding 22 of generator 14 and / or other synchronous machines to establish a magnetic field for operation) to excite the magnetic field of generator 14. For example, exciter 16 may be a static (e.g., power electronic) or rotating (e.g., brush and / or brushless) exciter. In other embodiments, exciter 16 may be bypassed, and power output may directly power the field winding 22 of generator 14. Also as shown, the output terminals of generator 14 may be coupled to a large-scale utility power grid 26 via alternating current (AC) line 28. Alternatively, the output terminals of generator 14 can be coupled to a small industrial power plant.

[0016] 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, for example, based on measurement parameters and / or indications of measurement parameters received at one or more inputs to the excitation system 24. As described in more detail below, one of these inputs may be a voltage generated by a brushless permanent magnet generator (PMG) coupled to shaft 13. In a particular embodiment, the excitation system 24 may be used as excitation control for the generator 14 and the exciter 16. The excitation system 24 may include one or more controllers 32 and one or more power converters 34. The power converter 34 may include a subsystem of integrated power electronic switching devices, such as silicon controlled rectifiers (SCRs), semiconductor thyristors, insulated gate bipolar transistors (IGBTs), etc., which receive alternating current (AC), DC, or a combination thereof from a source such as, for example, the power grid 26. As described in more detail below, the power converter 34 may include an automatic voltage regulator (AVR). The excitation system 24 can receive this power via bus 29 and can provide power supply, control, and monitoring of the field winding 30 of the exciter 16 based on it. Therefore, the excitation system 24 and the exciter 16 can work together to drive the generator 14 according to desired outputs (e.g., gate voltage, power factor, load frequency, torque, speed, acceleration, etc.). For example, in one embodiment, the excitation system 24 can be an excitation controller system, such as the EX2100e purchased from General Electric Co., Schenectady, New York. TM Voltage regulator. As described in more detail below, the DC bus voltage measured from the AVR can be used to monitor and determine the low speed (e.g., 50 RPM or less) of generator 14 and / or shaft 13.

[0017] Turn now Figure 2 The diagram illustrates another power generation system 40 (e.g., a power synchronization system). Typically, power generation system 40 is as follows: Figure 1 As described herein. Turbine 12 includes a gas turbine 42 having a compressor 44, a burner 46, and a turbine 48. The gas turbine 42 can receive air to be compressed by the compressor 44. The compressed air is mixed with fuel, and the air-fuel mixture is burned in the burner 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 can be coupled to a shaft 13 to provide rotational energy to a generator 14.

[0018] Additionally, the power generation system 40 also includes a brushless PMG 50 coupled to shaft 13. The PMG 50 functions as a power source for the actuator field of the power generation system 40. Furthermore, the power generation system 40 includes an AVR 52 (e.g., Figure 1(Example of power converter 34 in excitation system 24). AVR 52 controls the voltage characteristics of generator 14. Specifically, AVR 52 changes the generator excitation voltage (e.g., by controlling the magnetic field of generator 14 via the voltage applied to the coils of the exciter field). AVR 52 includes a diode rectifier 54 coupled to inverter 56 via DC bus 58. DC bus 58 includes a capacitor 60 for reducing and smoothing the voltage applied to inverter 56. AVR 52 receives output 62 (e.g., voltage) from PMG 50. AVR 52 rectifies the voltage from PMG 50 (i.e., converts it from AC to DC) and outputs voltage 64 to control the exciter field of exciter 16, and then controls the voltage in the generator stator.

[0019] As generally shown in the figure, controller 32 may include one or more processors 66 and memory 68, which may collectively support operating systems, software applications, and systems that can be used to implement the techniques described herein. Specifically, controller 32 may include code or instructions stored in a non-transitory 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 controller 32. Processor 66 may receive a voltage 70 (e.g., DC bus voltage) measured from DC bus 58. Processor 66 may also utilize the DC bus voltage to determine the speed of shaft 13 and / or generator 14. The voltage 62 from PMG 50 varies according to the operating frequency of generator 14, and therefore varies according to the speed of shaft 13. Based on this relationship, the speed of generator 14 can be determined. For example, in a particular embodiment, processor 66 may derive the operating speed of shaft 13 and / or generator 14 from DC bus voltage 70 using an algorithmic model or lookup table (e.g., stored in memory 68). In a particular embodiment, processor 66 may determine when generator 14 has stopped based on DC bus voltage 70.

[0020] Figure 3 It is used for monitoring Figure 1 and Figure 2A flowchart of an implementation of a method 72 for determining the generator speed of a turbine-generator system. Method 72 can be performed by the aforementioned controller 32. One or more steps of method 72 can be performed simultaneously and / or in different orders. Method 72 includes receiving a voltage (e.g., DC bus voltage) measured directly from the DC bus of the AVR (box 74), wherein this voltage is a rectified voltage received by the AVR from the PMG. Method 72 also includes determining the speed of the shaft and / or generator of the turbine-generator system based on the DC bus voltage (box 76). Speeds of 50 RPM or less can be detected. For example, the speed of the shaft and / or generator can be determined using a model 78 that considers the relationship between the DC bus voltage and the generator's operating frequency or a lookup table 80. Method 72 also includes determining whether the speed of the shaft and / or generator (e.g., RPM) is zero (box 82). If the speed is zero, method 72 includes determining that the generator has stopped (box 84). If the speed is not zero, method 72 includes continuing to receive the measured DC bus voltage (box 74) and determining the speed of the shaft and / or generator (box 76).

[0021] The technical effects of the disclosed embodiments include providing systems and methods 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 using the DC bus voltage measured directly from the AVR without the need for additional hardware.

[0022] This written description uses examples to disclose the disclosed subject matter, including best practices, and also enables any person skilled in the art to practice the disclosed subject matter, including making and using any apparatus or system and performing any combination of methods. The patentable scope of the disclosed subject matter is defined by the claims and may include other examples that would occur to a person skilled in the art. Such other examples are contemplated within the scope of the claims if they have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims.

Claims

1. A control system for a power generation system, the power generation system comprising a generator coupled to a turbine via a shaft, the control system comprising: a memory storing instructions; and a processor coupled to the memory and configured to execute the instructions, wherein when the instructions are executed, the processor is caused to: receive a direct current (DC) link voltage from an automatic voltage regulator (AVR), wherein the automatic voltage regulator (AVR) is configured to control a voltage characteristic of the generator; and determine a speed of the generator based on the direct current (DC) link voltage, wherein the processor is configured to determine, when the instructions are executed, whether the generator has stopped, wherein the processor is configured to determine, when the instructions are executed, the speed of the generator based on the direct current (DC) link voltage using a mathematical model or a lookup table, wherein the mathematical model or the lookup table is configured to determine the speed of the generator using a relationship between the direct current (DC) link voltage and an operating frequency of the generator.

2. The control system of claim 1, wherein determining the speed of the generator based on the direct current (DC) link voltage comprises determining a speed of the shaft.

3. The control system of claim 1, wherein the turbine comprises a gas turbine.

4. The control system of claim 1, wherein the direct current (DC) link voltage comprises a rectified voltage of a voltage received by the automatic voltage regulator (AVR) from a permanent magnet generator coupled to the shaft.

5. A non-transitory computer readable medium comprising instructions configured to be executed by a processor of a control system for a power generation system, the power generation system comprising a generator coupled to a turbine via a shaft, wherein the instructions comprise instructions configured to cause the processor to: receive a direct current (DC) link voltage from an automatic voltage regulator (AVR), wherein the automatic voltage regulator (AVR) is configured to control a voltage characteristic of the generator; and determine a speed of the generator based on the direct current (DC) link voltage using a mathematical model or a lookup table, wherein the mathematical model or the lookup table is configured to determine the speed of the generator using a relationship between the direct current (DC) link voltage and an operating frequency of the generator.

6. The non-transitory computer readable medium of claim 5, comprising instructions configured to cause the processor to determine whether the generator has stopped.

7. The non-transitory computer readable medium of claim 5, wherein the turbine comprises a gas turbine.

8. The non-transitory computer readable medium of claim 5, wherein the direct current (DC) link voltage comprises a rectified voltage of a voltage received by the automatic voltage regulator (AVR) from a permanent magnet generator coupled to the shaft.

9. A power generation system, the power generation system comprising: a turbine; a generator coupled to the turbine via a shaft; an automatic voltage regulator (AVR), wherein the automatic voltage regulator (AVR) is configured to control a voltage characteristic of the generator; and a controller configured to receive a voltage from the automatic voltage regulator (AVR) and determine a speed of the generator based on the direct current (DC) link voltage using a mathematical model or a lookup table, wherein the mathematical model or the lookup table is configured to determine the speed of the generator using a relationship between the direct current (DC) link voltage and an operating frequency of the generator.

10. The power generation system of claim 9, wherein the automatic voltage regulator (AVR) includes a diode rectifier coupled to an inverter via a direct current (DC) link, and a capacitor located in the direct current (DC) link.

11. The power generation system of claim 10, including a permanent magnet generator coupled to the shaft, and the direct current (DC) link voltage includes a rectified voltage of a voltage received by the automatic voltage regulator (AVR) from the permanent magnet generator.

12. The power generation system of claim 9, wherein the turbine includes a gas turbine, and the generator includes a synchronous generator.

13. The power generation system of claim 9, wherein the controller is configured to determine whether the generator has stopped.

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