A Digital Steam Turbine Controller Intrusion Monitoring Method and System Based on Step Response Identification

Abstract

The present invention discloses a method and system for intrusion monitoring of a digital steam turbine controller based on step response identification, which relates to the technical field of steam turbine control. The present invention first determines whether the grid-side load and the grid dispatching instruction are stable. When they are stable, the output value of the controller is recorded as the received signal of the electro-hydraulic converter; a timed step excitation signal is input into the controller, and the response curve at the output end of the controller is saved; a response signal is superimposed on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller; the controller parameters are identified by using the saved response curve; the identified controller parameters are compared with the known controller parameters to determine whether the controller parameters are abnormal. The present invention can realize network attack monitoring without affecting the normal operation of the steam turbine control system and without relying on network traffic analysis means.

Description

Technical Field

[0001] The present invention relates to the technical field of steam turbine control, and particularly to a monitoring method when a steam turbine control system is under a cyber attack and the controller parameters are modified. More specifically, the present invention relates to a digital steam turbine controller intrusion monitoring method and system based on step response identification. Background Art

[0002] With the development of information and communication technologies, industrial control systems widely apply computer and network communication technologies to improve the control level, enabling power plants to develop into cyber-physical systems that can achieve real-time perception, dynamic control, and information service integration. At the same time, this also brings many network security problems to power plants.

[0003] To achieve speed and power control, the DEH system of a steam turbine collects the actual speed and power of the steam turbine through sensors, compares them with the target speed and power, and uses a classical PI control algorithm to implement the control logic. The control parameters affect the regulation characteristics of the system. Existing network security monitoring methods usually rely on network traffic analysis, which has a high false alarm rate and missed alarm rate. Currently, there is a lack of effective monitoring means for the problem of malicious modification of controller parameters. Especially when encountering interference attacks, operators are deceived by false data, and the operator station interface maintains the pre-attack screen, making it difficult to detect parameter changes. Summary of the Invention

[0004] In order to overcome the defects and deficiencies existing in the above-mentioned prior art, the present invention provides a digital steam turbine controller intrusion monitoring method and system based on step response identification. The object of the present invention is to solve the problem in the prior art that there is a lack of effective monitoring means for malicious modification of controller parameters. The present invention provides a digital steam turbine controller intrusion monitoring method based on step response identification, which can identify the system model parameters of the controller and determine whether the parameters are abnormal after the steam turbine control system is under a cyber attack and the controller parameters and set values are modified, and realize network attack monitoring without affecting the normal operation of the steam turbine control system and without relying on network traffic analysis means.

[0005] In order to solve the problems existing in the above-mentioned prior art, on the one hand, the present invention provides a digital steam turbine controller intrusion monitoring method based on step response identification, which includes the following steps:

[0006] S1. Determine whether the grid-side load and grid dispatching instructions are stable. If stable, send a high-level signal; if unstable, send a low-level signal.

[0007] S2. When the grid-side load and grid dispatching instructions are stable, record the output value of the controller, and use the output value of the controller as the received signal of the electro-hydraulic converter.

[0008] S3. Input a timed step excitation signal to the controller and save the response curve at the output end of the controller;

[0009] S4. Superimpose a response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller;

[0010] S5. Use the response curve saved in step S3 for identification, adopt the least squares method to identify the controller parameters, and output the proportional coefficient and integral coefficient;

[0011] S6. Compare the controller parameters identified in step S5 with the known controller parameters to determine whether the controller parameters are abnormal. If the controller parameters are abnormal, output a high level as an alarm signal indicating that the turbine controller parameters have been maliciously modified.

[0012] Furthermore, in step S1, determining whether the grid-side load and grid dispatching instructions are stable refers to monitoring whether the load following waveform in the turbine model is stable. If the highest and lowest points of the waveform remain within the set range within a period of time, it is considered stable.

[0013] The timed step excitation signal refers to periodically inputting a signal that first jumps from 0 to 0.1, lasts for a period of time, then jumps from 0.1 to -0.1, lasts for the same time, and finally jumps back to 0; the part where the signal is 0.1 is used as the excitation, and the controller response signal during the period when the signal is 0.1 is recorded. The part where the signal is -0.1 is used to restore the controller output value.

[0014] Furthermore, during the duration of the timed step excitation signal, the following judgment is made: within the period when the excitation signal is added, judge whether the dispatching and load instructions have changed;

[0015] If there is no change, after the excitation signal ends, use the controller response curve recorded in step S3 for parameter identification;

[0016] If there is a change, put the controller back into use again, interrupt the current identification, and wait for the next cycle of the excitation signal.

[0017] Step S4 is specifically as follows: According to the structure and parameters of the known controller, calculate in advance the response signal generated by the controller for the excitation signal in step S3, and superimpose this response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller.

[0018] Step S5 is specifically as follows: Use the response curve saved in step S3 for identification. When the excitation signal is -0.1, adopt the least squares method for fitting to obtain the proportional coefficient and integral coefficient of the controller.

[0019] The second aspect of the present invention provides a digital steam turbine controller intrusion monitoring system based on step response identification. The system includes

[0020] A load scheduling stability judgment module, which is used to obtain the grid-side load and scheduling instructions, and judge whether the grid-side charge and scheduling instructions are stable. If they are stable, the load scheduling stability judgment module sends out a high-level signal; if they are not stable, the load scheduling stability judgment module sends out a low-level signal.

[0021] A signal latch, which is used to record the output value of the controller when the load scheduling stability judgment module sends out a high level, and use the output value of the controller as the received signal of the electro-hydraulic converter.

[0022] A step excitation signal generator, which is used to generate a timed step excitation signal and input the generated timed step excitation signal into the controller.

[0023] A parameter identification module, which is used to receive the response curve output by the controller when the controller inputs a timed step excitation signal. When the excitation signal is generated, the parameter identification module generates a high-level signal and saves the response curve of the controller within the time period when the step excitation signal is 0.1. When the step excitation signal is -0.1, the parameter identification module uses the least squares method to fit the saved response curve to identify the integral coefficient and proportional coefficient of the controller.

[0024] An abnormality judgment module, which is used to compare the integral coefficient and proportional coefficient of the controller identified by the parameter identification module with the known controller parameters. If they are consistent, it is judged that the controller is normal and outputs a low level; if they are not consistent, it is judged that the controller parameters are abnormal and outputs a high-level alarm signal.

[0025] Furthermore, in the load scheduling stability judgment module, judging whether the grid-side load and grid scheduling instructions are stable means monitoring whether the load following waveform in the steam turbine model is stable. If the highest and lowest points of the waveform remain within the set range within a period of time, it is considered stable.

[0026] The timed step excitation signal generated by the step excitation signal generator refers to a signal that is periodically input, first jumps from 0 to 0.1, lasts for a period of time, then jumps from 0.1 to -0.1, lasts for the same time, and finally jumps to 0. The part where the signal is 0.1 is used as the excitation, and the response signal of the controller within the time period when the signal is 0.1 is recorded. The part where the signal is -0.1 is used to restore the output value of the controller.

[0027] Furthermore, within the duration of the timed step excitation signal, the load scheduling stability judgment module makes the following judgment: judge whether the scheduling and load instructions have changed;

[0028] If there is no change, after the excitation signal ends, parameter identification is performed using the controller response curve recorded by the parameter identification module.

[0029] If there is a change, this excitation is invalid, the current identification is interrupted, and the controller is put back into use, waiting for the next cycle of the excitation signal.

[0030] Compared with the prior art, the beneficial technical effects brought by the present invention are as follows:

[0031] The present invention can accurately and quickly identify the current operating state parameters of the steam turbine controller, while ensuring the stable operation of the steam turbine control system, providing a means for monitoring that the parameters of the steam turbine controller are attacked by the network and modified, and providing a certain basis for identifying network attacks against the modification of controller parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a flowchart of the intrusion monitoring method for a digital steam turbine controller based on step response identification according to the present invention;

[0033] Figure 2 It is a structural diagram of the intrusion monitoring system for a digital steam turbine controller based on step response identification according to the present invention;

[0034] Figure 3 It is a Simulink model of the steam turbine control system shown in the embodiment for testing the present invention;

[0035] Figure 4 It is a step excitation signal of the intrusion monitoring method for a digital steam turbine controller based on step response identification shown in the embodiment of the present invention;

[0036] Figure 5 It is to simulate that the simulation system is attacked by the network and the control parameters are modified;

[0037] Figure 6 They are the original controller control parameters;

[0038] Figure 7 They are the control parameters after the simulation system is attacked by the network and modified;

[0039] Figure 8 It is the stable judgment of the load and the scheduling signal;

[0040] Figure 9 It is the control parameter identification diagram before and after the simulation system is attacked by the network;

[0041] Figure 10 It is the parameter anomaly warning signal;

[0042] Figure 11 It is that the scheduling signal changes during the identification process;

[0043] Figure 12 To determine whether the scheduling value has changed and suspend identification;

[0044] Figure 13 For the normal power adjustment curve of the simulation system. Specific implementation manner

[0045] The following further elaborates the technical solution of the present invention in detail in conjunction with the accompanying drawings of the specification and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work fall within the protection scope of the present invention.

[0046] Embodiment 1

[0047] As a preferred embodiment of the present invention, referring to the accompanying drawings of the specification Figure 1 , this embodiment discloses a digital steam turbine controller intrusion monitoring method based on step response identification, and the method includes the following steps:

[0048] S1. Determine whether the grid-side load and the grid scheduling instruction are stable. If stable, send a high-level signal; if unstable, send a low-level signal.

[0049] S2. When the grid-side load and the grid scheduling instruction are stable, record the output value of the controller, and use the output value of the controller as the received signal of the electro-hydraulic converter; First, it is difficult to perform identification in a closed-loop system. Keeping the received signal of the electro-hydraulic converter constant is to make the controller equivalent to an open-loop, so that the excitation signal added in S3 will not affect the input signal through the feedback channel; Second, considering that adding an excitation signal will have a certain impact on the normal operation of the system, the received signal of the electro-hydraulic converter is kept at a stable value.

[0050] S3. Input a timed step excitation signal into the controller and save the response curve at the output end of the controller;

[0051] S4. Superimpose a response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller;

[0052] S2 and S4 are related, and S3 and S4 are carried out simultaneously. Because the excitation signal will last for a period of time, if the system needs to be adjusted during this period, that is, it is judged as unstable in S1, the closed-loop adjustment function of the controller must be restored. However, the output signal of the controller has been changed. The role of S4 is to superimpose the response signal corresponding to the excitation signal on the output in reverse, so that the total output signal remains unchanged.

[0053] Assume the initial value is A, and the excitation signal changes it to A+X, which is also the curve for identification (the response curve saved in step S3); the signal A+X is then superimposed with a signal -X to restore it to A, aiming to enable the controller to resume the adjustment function at any time (for the signal latch to record and use it as the received signal of the electro-hydraulic converter).

[0054] S5. Use the response curve saved in step S3 for identification, adopt the least squares method to identify the controller parameters, and output the proportional coefficient and integral coefficient;

[0055] S6. Compare the controller parameters identified in step S5 with the known controller parameters to determine whether the controller parameters are abnormal. If the controller parameters are abnormal, output a high level as an alarm signal indicating that the turbine controller parameters have been maliciously modified.

[0056] Furthermore, in step S1, determining whether the grid-side load and the grid dispatching instruction are stable refers to monitoring whether the load-following waveform in the turbine model is stable. If the highest and lowest points of the waveform remain within the set range within a period of time, it is considered stable.

[0057] The timed step excitation signal refers to periodically inputting a signal that first jumps from 0 to 0.1, lasts for a period of time, then jumps from 0.1 to -0.1, lasts for the same time, and finally jumps back to 0; the part of the signal with a value of 0.1 is used as the excitation, and the controller response signal during the period when the signal value is 0.1 is recorded. The part of the signal with a value of -0.1 is used to restore the controller output value.

[0058] Furthermore, during the duration of the timed step excitation signal, the following judgment is made: within the period when the excitation signal is added, determine whether the dispatching and load instructions have changed;

[0059] If there is no change, after the excitation signal ends, use the controller response curve recorded in step S3 for parameter identification;

[0060] If there is a change, reactivate the controller, interrupt the current identification, and wait for the next cycle of the excitation signal. The above process is carried out in the stablejudge module in Appendix Figure 2 corresponding to step S1. The execution of step S1 runs through the entire process of each cycle of identification. On the one hand, it determines whether the conditions for identification are met, and on the other hand, it also determines whether this excitation process is effective. If it is ineffective (the system undergoes an adjustment effect and becomes unstable during the excitation process), the identification is terminated, and the controller is restored and put into use for adjustment.

[0061] Step S4 specifically is to calculate in advance, according to the structure and parameters of the known controller, the response signal generated by the excitation signal controller in Step S3, and superimpose this response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller.

[0062] Step S5 specifically is to perform identification by using the response curve saved in Step S3. When the excitation signal is -0.1, the least squares method is used for fitting to obtain the proportional coefficient and integral coefficient of the controller.

[0063] Embodiment 2

[0064] As another preferred embodiment of the present invention, referring to the attached Figure 2 of the specification, this embodiment discloses a digital steam turbine controller intrusion monitoring system based on step response identification. The system includes

[0065] A load dispatch stability judgment module, which is used to obtain the grid-side load and dispatch instructions, and judge whether the grid-side charge and dispatch instructions are stable. If stable, the load dispatch stability judgment module sends out a high-level signal; if not stable, the load dispatch stability judgment module sends out a low-level signal.

[0066] A signal latch, which is used to record the output value of the controller when the load dispatch stability judgment module sends out a high level, and use the output value of the controller as the received signal of the electro-hydraulic converter.

[0067] A step excitation signal generator, which is used to generate a timed step excitation signal and input the generated timed step excitation signal into the controller.

[0068] A parameter identification module, which is used to receive the response curve output by the controller when the controller inputs a timed step excitation signal. When the excitation signal is generated, the parameter identification module generates a high-level signal and saves the response curve of the controller within the time period when the step excitation signal is 0.1. When the step excitation signal is -0.1, the parameter identification module uses the least squares method to fit the saved response curve to identify the integral coefficient and proportional coefficient of the controller.

[0069] An abnormality judgment module, which is used to compare the integral coefficient and proportional coefficient of the controller identified by the parameter identification module with the known controller parameters. If they are consistent, it is judged that the controller is normal and outputs a low level; if not consistent, it is judged that the controller parameters are abnormal and outputs a high-level alarm signal.

[0070] Further, in the load dispatch stability judgment module, judging whether the grid-side load and grid dispatch instructions are stable means monitoring whether the load following waveform in the steam turbine model is stable. If the highest point and the lowest point of the waveform are kept within the set range within a period of time, it is considered stable.

[0071] The timed step excitation signal generated by the step excitation signal generator refers to a signal that is periodically input, first jumping from 0 to 0.1, lasting for a period of time, then jumping from 0.1 to -0.1, lasting for the same time, and finally jumping back to 0; the part where the signal is 0.1 is used as the excitation, and the response signal of the controller during the period when the signal is 0.1 is recorded, and the part where the signal is -0.1 is used to restore the output value of the controller.

[0072] Furthermore, the step excitation signal generator makes the following judgments on the timed step excitation signal: during the period when the excitation signal is added, it is judged whether the scheduling and load commands change;

[0073] If there is no change, after the excitation signal ends, parameter identification is carried out using the controller response curve recorded in step S3;

[0074] If there is a change, the controller is put back into use again, the current identification is interrupted, and waiting for the excitation signal in the next cycle.

[0075] The step excitation signal generator calculates in advance the response signal generated by the controller when the excitation signal is input according to the structure and parameters of the known controller, and superimposes this response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller.

[0076] Embodiment 3

[0077] As another preferred embodiment of the present invention, referring to the attached drawings of the specification Figure 1 、 2 and shown in Figure 3, this embodiment discloses a digital steam turbine controller intrusion monitoring method based on step response identification provided by the present invention, including:

[0078] S1. Judge whether the grid-side load and the grid scheduling command are stable, and send a high-level signal when stable. Judging whether the grid-side load and the grid scheduling command are stable means monitoring the load following waveform in the steam turbine model. If the highest point and the lowest point of the waveform remain within a certain range within a period of time, the system can be considered stable and a high-level signal is sent to enter the identification link;

[0079] S2. Record the output value of the controller when stable, and record the output of the controller in the current stable state through the signal latch module as the input signal of the electro-hydraulic converter;

[0080] S3. Input a timed step excitation signal to the controller and save the response curve at the output end. The timed step excitation signal refers to a signal that is periodically input, which first jumps from 0 to 0.1, lasts for a period of time, then jumps from 0.1 to -0.1, lasts for the same time, and finally jumps back to 0. The part of the signal with a value of 0.1 is used as the excitation, and the response curve of the controller during this period is recorded. The part of the signal with a value of -0.1 is used to restore the output value of the controller to prevent the accumulation of the integral term.

[0081] S4. Superimpose a response signal on the output end of the controller. Since the structure and parameters of the controller are known, the response signal generated by the controller for the excitation signal in step 3 can be calculated in advance. This response signal is superimposed on the output end to eliminate the influence of the excitation signal on the final output of the controller. During the identification process, if there are significant changes in the grid-side load and grid dispatching instructions, the regulation function of the controller can be maintained to ensure the stability of the unit operation.

[0082] S5. Use the response curve saved in step 3 for identification. When the excitation signal is -0.1, the least squares method is used to identify the controller parameters, and the waveform diagrams of the proportional coefficient and integral coefficient are output.

[0083] S6. Compare with the known controller parameters to determine whether the controller parameters are abnormal. If abnormal, output a high level as an alarm signal indicating that the parameters of the steam turbine controller have been maliciously modified.

[0084] Furthermore, as Figure 1 shown, a digital steam turbine controller intrusion monitoring method based on step response identification has the following specific process:

[0085] (1) Make the following judgment: Whether the load and dispatching are stable. If stable, output a high level; otherwise, output a low level. The output signal is denoted as A.

[0086] (2) Signal A is used as the switching signal for the controller output signal latch and parameter identification. When A is at a high level, record the current controller output signal as the command signal for the electro-hydraulic converter. If a step excitation signal is generated at this time, record the controller response curve.

[0087] (3) For the periodic step excitation signal, make the following judgment: Whether there are changes in the dispatching and load instructions during the period when the excitation signal is added.

[0088] ① If not, after the excitation signal ends, use the recorded controller response curve for parameter identification.

[0089] ② If so, put the controller back into use, interrupt this identification, and wait for the next periodic excitation signal.

[0090] (4)The parameter identification uses the least squares method to identify the proportional and integral coefficients and makes the following judgments: Compare whether there are significant changes in the identification results with the known parameters.

[0091] ① If the result is consistent with the reference value, the system is normal, and it returns to perform the next cycle detection.

[0092] ② If the result is inconsistent with the reference value, it is judged that the parameter is abnormal, and a high-level alarm signal is output.

[0093] As Figure 2 shown, a Simulink simulation model for intrusion monitoring of a digital steam turbine controller based on step response identification includes six parts:

[0094] (1)In the figure, the stabejudge module is used for load dispatching stability judgment. Its function is to judge whether the load and dispatching remain stable. When stable, it generates a high-level signal.

[0095] (2)In the figure, the step excitation signal generator. Its function is to generate a periodic step signal. First, it jumps from 0 to 0.1 and lasts for 4 s, then jumps from 0.1 to -0.1 and lasts for 4 s, and finally jumps to 0. On the one hand, it serves as the excitation signal in the parameter identification process. On the other hand, the response signal corresponding to this signal is subtracted from the output end of the controller to prevent the system from needing to be adjusted during the identification process, and the controller can be adjusted in time.

[0096] (3)In the figure, the signal latch. Its function is to record the output signal of the controller in the stable state when the stabejudge module generates a high-level signal and serve as the command signal for the electro-hydraulic converter.

[0097] (4)In the figure, the identification module is used for parameter identification. Its function is to save the response curve of the controller within 4 s when the step excitation is 0.1 when the excitation signal is generated and the stabejudge module generates a high-level signal. When the step excitation is -0.1, the least squares method is used to fit the saved response curve to identify the integral coefficient I and the proportional coefficient P.

[0098] (5)In the figure, the jinggao module is used for abnormality judgment. Its function is to judge whether the identification result is consistent with the reference value. If it is consistent, the system is normal and outputs a low level. If it is inconsistent, it is judged that the parameter is abnormal and outputs a high-level alarm signal.

[0099] (6)In the figure, the PI controller module is the controller in the normal state. The function of the "parameter modification" module is to simulate the scenario of tampering with control parameters after the control system is invaded.

[0100] Example 4

[0101] Scenario 1: AsFigure 5 , Figure 6 , Figure 7 As shown, in this paper, the scenario of tampering with control parameters after the system is invaded is simulated by switching the PI controller at 50 seconds, where Figure 6 , Figure 7 are the control parameter diagrams before and after the system is invaded, respectively.

[0102] As Figure 8 shown, the system reaches a stable state at the 20s moment, and the output signal is 1, meeting the prerequisite conditions for system identification. After the parameter change occurs at 50s, the system reaches a stable state at the 61s moment, and the output signal is 1, meeting the prerequisite conditions for system identification. Figure 4 As shown in the input step excitation signal, the output signal of the controller is collected during 30 - 34s and 70 - 74s after the system stabilizes for parameter identification.

[0103] As Figure 9 shown in the parameter identification diagram, after the first - cycle step signal is generated, the control parameters P and I are identified at 34s; before the second - cycle step signal is generated, since the controller parameters have changed, the changed controller parameters P and I are identified at 74s. As Figure 10 shown, when the controller parameter abnormality is detected, a high - level alarm signal is sent at 74s.

[0104] Scenario 2:

[0105] As follows Figure 11 shown, in this paper, the scenario of system adjustment during the parameter identification process is simulated by changing the scheduling signal at the 71s moment, and the scheduling signal rises from 1 to 1.2.

[0106] Figure 12 It is judged that the scheduling changes at the 71s moment, and the parameter identification is paused; Figure 13 is the output power diagram of the system's normal response to the scheduling change.

Claims

1. A digital steam turbine controller intrusion monitoring method based on step response identification, characterized in that, The method includes the following steps: S1. Determine whether the grid-side load and the grid dispatching instruction are stable. If they are stable, a high-level signal is sent; if not, a low-level signal is sent. S2. When the grid-side load and the grid dispatching instruction are stable, record the output value of the controller and use the output value of the controller as the received signal of the electro-hydraulic converter. S3. Input a timed step excitation signal to the controller and save the response curve at the output end of the controller. S4. Superimpose a response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller. S5. Use the response curve saved in step S3 for identification, adopt the least squares method to identify the controller parameters, and output the proportional coefficient and the integral coefficient. S6. Compare the controller parameters identified in step S5 with the known controller parameters to determine whether the controller parameters are abnormal. If the controller parameters are abnormal, output a high level as an alarm signal indicating that the turbine controller parameters have been maliciously modified.

2. The digital steam turbine controller intrusion monitoring method based on step response identification according to claim 1, characterized in that: In step S1, determining whether the grid-side load and the grid dispatching instruction are stable means monitoring whether the load following waveform in the turbine model is stable. If the highest point and the lowest point of the waveform remain within the set range within a period of time, it is considered stable.

3. The digital steam turbine controller intrusion monitoring method based on step response identification according to claim 1, wherein: The timed step excitation signal refers to a signal that is periodically input, first jumping from 0 to 0.1, lasting for a period of time, then jumping from 0.1 to -0.1, lasting for the same time, and finally jumping to 0. The part of the signal with a value of 0.1 is used as the excitation, and the controller response signal during the period when the signal value is 0.1 is recorded. The part of the signal with a value of -0.1 is used to restore the output value of the controller.

4. A digital steam turbine controller intrusion monitoring method based on step response identification according to any one of claims 1-3, characterized in that: During the duration of the timed step excitation signal, the following judgment is made: within the period when the excitation signal is added, determine whether the dispatching and load instructions have changed. If there is no change, after the excitation signal ends, use the controller response curve recorded in step S3 for parameter identification. If there is a change, put the controller back into use again, interrupt the current identification, and wait for the next cycle of the excitation signal.

5. A digital steam turbine controller intrusion monitoring method based on step response identification according to any one of claims 1-3, characterized in that: Step S4 is specifically as follows: According to the structure and parameters of the known controller, calculate in advance the response signal generated by the controller for the excitation signal in step S3, and superimpose this response signal on the output end of the controller to eliminate the influence of the excitation signal on the final output of the controller.

6. The digital steam turbine controller intrusion monitoring method based on step response identification according to claim 3, wherein: Step S5 is specifically as follows: Use the response curve saved in step S3 for identification. When the excitation signal is -0.1, adopt the least squares method for fitting to obtain the proportional coefficient and the integral coefficient of the controller.

7. A digital steam turbine controller intrusion monitoring system based on step response identification, characterized in that, The system includes: A load dispatching stability judgment module, which is used to obtain the grid-side load and the dispatching instruction, and determine whether the grid-side charge and the dispatching instruction are stable. If they are stable, the load dispatching stability judgment module sends a high-level signal; if not, the load dispatching stability judgment module sends a low-level signal. A signal latch, which is used to record the output value of the controller when the load dispatching stability judgment module sends a high level, and use the output value of the controller as the received signal of the electro-hydraulic converter. A step excitation signal generator, which is used to generate a timed step excitation signal and input the generated timed step excitation signal into the controller. The parameter identification module is used to receive the response curve of the controller output when the controller inputs a timed step excitation signal. When the excitation signal is generated, the parameter identification module generates a high-level signal and saves the response curve of the controller within the time period when the step excitation signal is 0.

1. When the step excitation signal is -0.1, the parameter identification module uses the least squares method to fit the saved response curve to identify the integral coefficient and proportional coefficient of the controller. The abnormality judgment module is used to compare the integral coefficient and proportional coefficient of the controller identified by the parameter identification module with the known controller parameters. If they are consistent, it is judged that the controller is normal and a low-level signal is output. If they are inconsistent, it is judged that the controller parameter is abnormal and a high-level alarm signal is output.

8. A digital steam turbine controller intrusion monitoring system based on step response identification as claimed in claim 7, characterized in that: In the load dispatch stability judgment module, judging whether the grid-side load and the grid dispatch instruction are stable means monitoring whether the load following waveform in the steam turbine model is stable. If the highest and lowest points of the waveform are within the set range within a period of time, it is considered stable.

9. The digital steam turbine controller intrusion monitoring system based on step response identification according to claim 7, characterized in that: The timed step excitation signal generated by the step excitation signal generator refers to a signal that is periodically input, first jumping from 0 to 0.1, lasting for a period of time, then jumping from 0.1 to -0.1, lasting for the same time, and finally jumping back to 0. The part where the signal is 0.1 is used as the excitation, and the response signal of the controller within the time period when the signal is 0.1 is recorded. The part where the signal is -0.1 is used to restore the controller output value.

10. A digital steam turbine controller intrusion monitoring system based on step response identification as claimed in claim 7 or 8, characterized in that: During the duration of the timed step excitation signal, the load dispatch stability judgment module makes the following judgments: Judge whether the dispatch and load instructions have changed. If there is no change, after the excitation signal ends, parameter identification is performed using the controller response curve recorded by the parameter identification module. If there is a change, this excitation is invalid, the current identification is interrupted, and the controller is put back into use again, waiting for the next cycle of the excitation signal.

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