Gas turbine unit protection anti-ac direct current into the input control method and system

Abstract

This invention belongs to the field of power system relay protection technology, and provides a method and system for controlling input quantities to prevent AC interference with DC intrusion in gas turbine unit protection. The method includes acquiring the output voltage value of the optocoupler in the input circuit of the gas turbine unit and comparing it with a voltage threshold matching the current input circuit voltage level. If the former is greater than the latter, the output state is set to "1"; otherwise, the output state is set to "0". A set observation period for the output state is selected, and the total number of output states of "1" within that observation period is continuously counted and compared with a set threshold. If the total number of output states of "1" is not less than the set threshold, the input state is determined to be valid, and the input state is set to "1"; otherwise, the input state is determined to be invalid, and the input state is set to "0". This method can improve the reliability of gas turbine unit relay protection.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection technology, and particularly relates to a method and system for controlling input quantities to prevent AC interference with DC intrusion in gas turbine units. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Relay protection devices for gas turbine units are essential facilities for the safe and reliable operation of gas turbine units and power systems. These devices need to distinguish between various faults and abnormal operating conditions of the gas turbine unit or the protected equipment. This includes real-time acquisition of analog values ​​such as system voltage and current, as well as the acquisition of input status as important judgment conditions for protection, and inputs for direct trip protection from external inputs, such as the closing position input of the gas turbine unit's static frequency converter (SFC) isolating switch (DSF), the trip position input of the turbine-end circuit breaker (GCB), and thermal protection inputs. Therefore, accurate identification of input status is particularly important.

[0004] Currently, the secondary power supply of gas-fired power plants consists of a DC power supply system and an AC power supply system. Under normal operation, the two power supply systems are not connected to each other. However, due to various reasons, when the AC power supply is connected in series with the DC power supply system, it is easy to cause the protection input status to change incorrectly, which may cause the non-electrical recirculation protection (such as thermal protection) to trip directly from the external input, or other protection (such as main transformer differential protection) to operate incorrectly.

[0005] Most existing gas turbine unit relay protection and automation devices use optocouplers for photoelectric isolation in their input circuits. For this type of input circuit, power system users generally require reliable operation of the optocouplers within 55% to 70% of the rated DC power supply voltage. However, this cannot prevent malfunctions caused by AC interference. Although existing input acquisition technologies have improved the DC grounding resistance by using intermediate relays with a series operating power of not less than 5W and software measures, they still cannot completely prevent malfunctions caused by AC interference. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method and system for controlling the input quantity of gas turbine unit protection against AC interference with DC, which can improve the reliability of gas turbine unit relay protection.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a method for controlling the input quantity of a gas turbine unit to prevent AC interference with DC.

[0008] In one or more embodiments, a method for controlling the input of a gas turbine unit protection device against AC-DC interference is provided. This method is executed within the microcontroller of the gas turbine unit protection device and specifically includes the following steps: Obtain the output voltage value of the optocoupler of the gas turbine unit's input circuit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, set the output status to "1"; otherwise, set the output status to "0". Select an observation period for the output status, continuously count the total number of times the output status is "1" within that observation period, and compare it with a set threshold. If the total number of times the output status is "1" is not less than the set threshold, the input status is determined to be valid and the input status is set to "1"; otherwise, the input status is determined to be invalid and the input status is set to "0".

[0009] As one implementation method, the observation period of the output state is set as N, and its value is the number of sampling points per cycle.

[0010] As one implementation method, the threshold is set to M, and its value is Na; where a is the number of points with a sample value of zero.

[0011] As one implementation method, the previous week of the current sampling point is selected as the observation period.

[0012] As one implementation method, the voltage threshold matching the current input circuit voltage level is: ; in, This represents the current input circuit voltage level, i.e., the rated DC power supply voltage of the input; Percent% is the voltage threshold percentage value.

[0013] As one implementation method, the percentage is 55% to 70%.

[0014] As one implementation method, different levels of input circuit voltage and their matching voltage thresholds are pre-stored in different buffer areas.

[0015] A second aspect of the present invention provides an input control system for protecting gas turbine units against AC interference with DC input.

[0016] In one or more embodiments, a gas turbine unit protection control system for AC-DC interference includes: The output status determination module is used to obtain the output voltage value of the optocoupler of the gas turbine unit's input circuit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, the output status is set to "1"; otherwise, the output status is set to "0". The input status judgment module is used to select an observation period for the output status, continuously count the total number of output statuses of "1" within the observation period and compare it with a set threshold. If the total number of output statuses of "1" is not less than the set threshold, the input status is judged to be valid and the input status is set to "1"; otherwise, the input status is judged to be invalid and the input status is set to "0". Here, N is the number of sampling points per cycle.

[0017] A third aspect of the present invention provides a computer-readable storage medium.

[0018] A computer-readable storage medium having a computer program stored thereon, which, when executed by a microcontroller, implements the steps of the above-described method for controlling the input quantity of a gas turbine unit against AC interference with DC.

[0019] A fourth aspect of the present invention provides a gas turbine unit protection device.

[0020] A gas turbine unit protection device includes a memory, a microcontroller, and a computer program stored in the memory and executable on the microcontroller. When the microcontroller executes the program, it implements the steps in the above-described gas turbine unit protection anti-AC DC input control method.

[0021] Compared with the prior art, the beneficial effects of the present invention are: This invention determines the output status by comparing the output voltage value of the optocoupler in the input circuit of the gas turbine unit with a voltage threshold that matches the current input circuit voltage level. Then, based on the comparison result of the total number of output statuses of "1" within one observation period and the set threshold, it determines whether the input status is valid. This solves the technical problem of protection maloperation caused by direct tripping of external inputs of the gas turbine unit protection when AC power is connected in series with DC power supply system, or incorrect operation of electrical protection related to inputs, and improves the reliability of gas turbine unit relay protection. Attached Figure Description

[0022] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0023] Figure 1 This is a flowchart of the input control method for protecting gas turbine units against AC-DC interference according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the main protection configuration scheme for a gas turbine unit according to an embodiment of the present invention; Figure 3 This is a schematic diagram of AC input to the positive DC terminal according to an embodiment of the present invention; Figure 4This is a schematic diagram of the voltage waveform and input displacement of the AC-to-DC positive terminal open-ended optocoupler according to an embodiment of the present invention. Figure 5 This is a schematic diagram of the relay protection input acquisition circuit according to an embodiment of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] Terminology Explanation: Gas turbine units: Gas turbine units are core power equipment that converts the chemical energy of fuel (usually natural gas or liquid fuel) into mechanical energy to drive generators or other equipment. When starting a gas turbine from a standstill, a static frequency converter (SFC) is typically used as the primary starting method, and it is widely used in scenarios such as grid peak shaving and combined cooling, heating and power (CCHP).

[0028] AC interference: AC interference with DC refers to the accidental introduction of AC components into a circuit or system that should originally be pure DC.

[0029] Input signal: also known as switch input or digital input, refers to a signal from the outside that has only two definite states: on or off.

[0030] Existing input acquisition technologies, while employing intermediate relays with a series operating power of not less than 5W and software measures to improve the input's resistance to DC grounding, still cannot completely prevent malfunctions caused by AC interference. This invention provides an input control method and system for gas turbine unit protection against AC interference with DC. The specific implementation of this method is illustrated using a gas turbine unit's main protection system as an example.

[0031] The main electrical wiring diagram and the wiring diagram of the main protection system of the gas turbine unit are attached. Figure 2As shown. The protection device is connected to the SFC switch DSF closed position contact, the turbine terminal circuit breaker (GCB) open position contact, and thermal protection inputs of the gas turbine unit.

[0032] The SFC start-up circuit of a gas turbine unit is generally located within the main transformer differential protection zone, as shown in the attached... Figure 2 As shown. The main transformer differential protection (87MT) is designed to take into account the possibility of abnormal operation of the main transformer differential protection when the generator is started but not connected to the grid. Therefore, when it is determined that the generator SFC switch DSF is in the closed position and GCB is in the open position, the main transformer differential protection is switched from the three-sided differential protection composed of CT2, CT4 and CT5 to the two-sided differential protection composed of CT4 and CT5. The main transformer differential protection sets the generator terminal current to 0 and no longer includes the generator terminal current in the differential current calculation of the main transformer differential protection.

[0033] When AC is introduced into DC in the gas turbine protection device, it may cause the DSF closing position contact and the turbine terminal circuit breaker (GCB) opening position contact to change incorrectly, thereby causing the main transformer differential protection to malfunction.

[0034] Common causes of AC interference with DC circuits include: shared AC / DC cables, condensation on terminal blocks, rainwater intrusion, damaged AC / DC cables, accidental contact, and incorrect wiring. The analysis of input error shifts caused by AC interference with DC is as follows: like Figure 3 As shown, when an AC power supply is connected in series with the DC positive power supply side ( Figure 3 At point A, the AC voltage can be connected to the input circuit, the DC battery insulation monitoring circuit, the cable, and the distributed capacitance to form a circuit.

[0035] The impedance of the entire input circuit is: The voltage applied across the optocoupler is: .

[0036] This is the AC voltage inserted in series, typically 220V. To control the distributed capacitance of the cable, R is the resistance of the input circuit. The larger the value, the larger the voltage applied to the input optocoupler. The voltage waveform across the input optocoupler is as follows: Figure 3 As shown.

[0037] If the voltage applied to the input optocoupler During the change process, the time when the optocoupler operating voltage Uset is greater than the operating voltage Uset is t0. If t0 is long enough, exceeding the operating power of the input circuit, the operating time of the series intermediate relay, or the software delay time, it will cause the external input direct trip protection to malfunction or the electrical protection related to the input quantity to malfunction.

[0038] The following is combined with Figure 1 This invention provides a method for controlling the input of a gas turbine unit protection device against AC-DC interference, which is executed within the microcontroller of the gas turbine unit protection device. Specifically, it includes the following steps: Step S101: Obtain the output voltage value of the optocoupler of the gas turbine unit's input circuit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, set the output status to "1"; otherwise, set the output status to "0".

[0039] Schematic diagram of the input acquisition circuit for the gas turbine unit protection device, as follows: Figure 5 As shown. The input circuit mainly includes: an optocoupler, a series resistor on the primary side of the optocoupler, a parallel capacitor on the primary side of the optocoupler, a grounding resistor on the secondary side of the optocoupler, a grounding capacitor on the secondary side of the optocoupler, and a microcontroller (MCU) for acquiring the analog signal from the optocoupler.

[0040] In this embodiment of the invention, the voltage threshold matching the current input circuit voltage level is: ;in, This refers to the current input circuit voltage level, i.e., the rated DC power supply voltage of the input, typically 220V or 110V DC; Percent% is the voltage threshold percentage value. For example, Percent% is 55%~70%.

[0041] In practical implementation, different voltage levels of the input circuit and their corresponding voltage thresholds are pre-stored in different buffer areas. For example, different voltage levels of the input result in different optocoupler output voltage values ​​U. The MCU stores the voltages of different voltage levels... The voltage threshold percentage (Percent%) is stored in different areas of the EEPROM, automatically adapting to different voltage levels of input. With a Percent% value of 60%, the voltage threshold Uset is 132V when the DC rated voltage is 220V, and 66V when the DC rated voltage is 110V.

[0042] The microcontroller (MCU) acquires the output voltage value U of the optocoupler in the input circuit. At the current sampling point, the optocoupler output voltage value is... Comparison with voltage threshold Uset: (1) If the above expression is true, then output the state. ;otherwise .

[0043] Step S102: Select an observation period for the output state, continuously count the total number of output states that are "1" within the observation period and compare it with a set threshold. If the total number of output states that are "1" is not less than the set threshold, then the input state is determined to be valid and the input state is set to "1"; otherwise, the input state is determined to be invalid and the input state is set to "0".

[0044] The observation period is selected as the previous cycle before the current sampling point. The observation period shifts as the sampling points move to ensure that the observation period always contains the latest sampling data. The observation period for the output state is set as N, and its value is the number of sampling points per cycle. If the number of sampling points per cycle is 24, then... Let the threshold be M, and its value be Na; where a is the number of points with a sample value of zero, for example... Figure 4 The number of points with a sample value of zero is 4, and a = 4.

[0045] Count the total number of times the MCU output state D is "1" within one observation period N. (2) Count represents the total number of times the MCU output state D is "1" within an observation period N. If Count > M, the input state is considered valid and the input state is set to "1"; otherwise, it is considered that the input state is changed due to AC interference or other disturbances, the input state is considered invalid and the input state is set to "0".

[0046] Using the above method, Figure 3 In the middle, when a 220V AC power supply is connected in series with the positive power supply side of a 110V DC power supply ( Figure 3 At point A, the voltage waveform input to the optocoupler is as follows: Figure 4 As shown, the Count value within an observation window is ( If the number of input points is 18, which is less than the set value M (20), it is considered that the input quantity change is caused by AC interference or other interference. The input quantity status is determined to be invalid, and the input quantity status is set to "0", which effectively prevents the influence of AC interference on DC input.

[0047] In one or more embodiments, a gas turbine unit protection anti-AC DC input control system is also provided, which can be implemented in software. The gas turbine unit protection anti-AC DC input control system includes the following software modules: The output status determination module is used to obtain the output voltage value of the optocoupler of the gas turbine unit's input circuit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, the output status is set to "1"; otherwise, the output status is set to "0". The input status judgment module is used to select an observation period for the output status, continuously count the total number of output statuses of "1" within the observation period and compare it with a set threshold. If the total number of output statuses of "1" is not less than the set threshold, the input status is judged to be valid and the input status is set to "1"; otherwise, the input status is judged to be invalid and the input status is set to "0". Here, N is the number of sampling points per cycle.

[0048] It should be noted that each module in the gas turbine protection anti-AC DC input control system of the present invention corresponds one-to-one with each step in the gas turbine protection anti-AC DC input control method in the above embodiments, and their specific implementation processes are the same, so they will not be repeated here.

[0049] In other embodiments, a gas turbine generator set protection device is also provided. The structure of the gas turbine generator set protection device according to embodiments of the present invention is described in detail below. The gas turbine generator set protection device includes: at least one microcontroller, a memory, a user interface, and at least one network interface. The various components in the gas turbine generator set protection anti-AC-DC input control system are coupled together through a bus system. It can be understood that the bus system is used to realize the connection and communication between these components. In addition to a data bus, the bus system also includes a power bus, a control bus, and a status signal bus.

[0050] It is understood that the memory can be volatile memory or non-volatile memory, or both. The memory in this embodiment of the invention is capable of storing data to support the operation of the terminal. Examples of this data include any computer programs used to operate on the terminal, such as operating systems and applications. The operating system includes various system programs, such as the framework layer, core library layer, driver layer, etc., used to implement various basic services and handle hardware-based tasks. Applications can include various applications.

[0051] In some embodiments, the input control system for protecting gas turbine units against AC-DC interference provided in this invention can be implemented using a combination of hardware and software. For example, the input control system for protecting gas turbine units against AC-DC interference provided in this invention can be a processor in the form of a hardware decoding processor, programmed to execute the input control method for protecting gas turbine units against AC-DC interference provided in this invention. For instance, the processor in the form of a hardware decoding processor can employ one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), or other electronic components.

[0052] As an example, a microcontroller can be an integrated circuit chip with signal processing capabilities, such as a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0053] As an example of the hardware implementation of the AC-DC interference prevention control system for gas turbine protection provided in this embodiment of the invention, the device provided in this embodiment of the invention can be directly executed by a processor in the form of a hardware decoding processor. For example, it can be executed by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), or other electronic components to implement the AC-DC interference prevention control method for gas turbine protection provided in this embodiment of the invention.

[0054] The memory in this embodiment of the invention is used to store various types of data to support the operation of the gas turbine unit protection anti-AC DC input control system, or to store data for execution. Figure 1The program code for the method shown. Examples of this data include: any executable instructions for operation on an input control system for gas turbine protection against AC-DC interference, such as executable instructions that can be included in the executable instructions to implement the input control method for gas turbine protection against AC-DC interference according to embodiments of the present invention.

[0055] Specifically, according to embodiments of this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program including functions for executing... Figure 1 The program code for the method shown. In such an embodiment, the computer program can be downloaded and installed from a network via a communication component, and / or installed from a removable medium. When the computer program is executed by the central processing unit, it performs the various functions defined in the apparatus of this application.

[0056] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, as well as combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0057] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for controlling input quantities to prevent AC interference with DC current in a gas turbine unit, characterized in that, It is executed within the microcontroller of the gas turbine unit protection device, and specifically includes the following steps: Obtain the output voltage value of the optocoupler in the input circuit of the gas turbine unit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, set the output status to "1"; otherwise, set the output status to "0". Select an observation period for the output status, continuously count the total number of times the output status is "1" within that observation period, and compare it with a set threshold. If the total number of times the output status is "1" is not less than the set threshold, the input status is determined to be valid and the input status is set to "1"; otherwise, the input status is determined to be invalid and the input status is set to "0".

2. The input control method for protecting gas turbine units against AC-DC interference as described in claim 1, characterized in that, The observation period for the selected output state is set to N, and its value is the number of sampling points per cycle.

3. The input control method for protecting gas turbine units against AC-DC interference as described in claim 2, characterized in that, Set the threshold to M, and its value is Na; where a is the number of points with a sample value of zero.

4. The input control method for protecting gas turbine units against AC interference with DC as described in claim 1, characterized in that, The observation period is selected as the previous week's wavelength at the current sampling point.

5. The input control method for protecting gas turbine units against AC-DC interference as described in claim 1, characterized in that, The voltage threshold that matches the current input circuit voltage level is: ； in, This represents the current input circuit voltage level, i.e., the rated DC power supply voltage of the input; Percent% is the voltage threshold percentage value.

6. The input control method for protecting a gas turbine unit against AC interference with DC as described in claim 5, characterized in that, Percent% ranges from 55% to 70%.

7. The input control method for protecting a gas turbine unit against AC interference with DC as described in claim 1, characterized in that, Different levels of input circuit voltage and their matching voltage thresholds are pre-stored in different buffer areas.

8. A gas turbine unit protection control system for AC-DC interference prevention, characterized in that, The input control method for protecting gas turbine units against AC-DC interference as described in any one of claims 1-7 includes: The output status determination module is used to obtain the output voltage value of the optocoupler of the gas turbine unit's input circuit and compare it with the voltage threshold that matches the current input circuit voltage level. If the former is greater than the latter, the output status is set to "1"; otherwise, the output status is set to "0". The input status judgment module is used to select an observation period for the output status, continuously count the total number of output statuses of "1" within the observation period and compare it with a set threshold. If the total number of output statuses of "1" is not less than the set threshold, the input status is judged to be valid and the input status is set to "1"; otherwise, the input status is judged to be invalid and the input status is set to "0". Here, N is the number of sampling points per cycle.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by the microcontroller, the program implements the steps in the input control method for protecting gas turbine units against AC interference with DC as described in any one of claims 1-7.

10. A gas turbine generator set protection device, comprising a memory, a microcontroller, and a computer program stored in the memory and executable on the microcontroller, characterized in that, When the microcontroller executes the program, it implements the steps in the input control method for gas turbine unit protection against AC interference with DC as described in any one of claims 1-7.

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