Load low-frequency oscillation detection processing system of thermal power generating unit

Abstract

The invention relates to a load low-frequency oscillation detection and processing system of a thermal power generating unit. The system comprises a normal state judgment module, a load response delay detection module, a unit load response transition module and a logic AND module, wherein the normal state judgment module comprises a unit load response lagging detection module, a unit load response transition module and a logic AND module; the input end of the logic AND module is connected with the unit load response lag detection module and the unit load response transition module; the oscillation amplitude overrun recording module comprises a positive value oscillation overrun recording module, a negative value oscillation overrun recording module and a logic OR module; the input end of the logic OR module is connected with the positive value oscillation overrun recording module and the negative value oscillation overrun recording module; the input end of the frequency counting module is connected with the output end of the logic OR module and the output end of the logic AND module; the input end of the frequency detection module is connected with the oscillation frequency presetting module and the frequency counting module; the input end of the manual control module is connected with the output end of the frequency detection module; the input end of the low-frequency alarm module is connected with the output end of the frequency detection module.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic control of thermal power generation, and in particular to the technical field of a load low-frequency oscillation detection and processing system for a thermal power unit. Background Art

[0002] With the rapid construction of UHV power grid and new energy power generation, my country's power structure has changed significantly. The pattern of a national power grid has basically taken shape. While facilitating the allocation of energy resources across the country, it has also exacerbated problems such as low-frequency oscillations in the power system and insufficient primary frequency regulation capabilities of the power grid. Low-frequency oscillations in the power system usually refer to the oscillation phenomenon of active power below 2.5Hz after the power system is disturbed. If not handled in time, it may cause serious consequences such as power grid collapse.

[0003] In recent years, thermal power units have frequently experienced low-frequency load oscillations due to their participation in the primary frequency regulation of the power grid, which has become a new source of oscillation. The primary frequency regulation circuit usually has no inertia and delay links and responds quickly, but this also makes it very easy to cause low-frequency load oscillation accidents when the turbine speed fluctuates near the dead zone due to poor valve linearity or unreasonable control system parameter settings. Therefore, if the control system can quickly and accurately detect low-frequency oscillations after the occurrence of low-frequency oscillations and exit the coordination and primary frequency regulation circuits in time, the continuation of low-frequency load oscillations of thermal power units can be avoided, thereby significantly improving the operating safety and stability of the units and power systems. Summary of the invention

[0004] The technical problem to be solved by the present invention is how to exit the coordination and primary frequency modulation loop in time after detecting low-frequency oscillation to prevent the oscillation from continuing for a long time, thereby improving the safety and stability of the unit and the power system.

[0005] In order to solve the above technical problems, a load low-frequency oscillation detection and processing system for a thermal power unit is provided according to the present invention. The system comprises:

[0006] A normal state judgment module, the normal state judgment module includes a unit load response hysteresis detection module, a unit load response excessive module and a logic and module; the input end of the logic and module is connected to the unit load response hysteresis detection module and the unit load response excessive module;

[0007] An oscillation amplitude over-limit recording module, wherein the oscillation amplitude over-limit recording module comprises a positive oscillation over-limit recording module, a negative oscillation over-limit recording module and a logic OR module; an input end of the logic OR module is connected to the positive oscillation over-limit recording module and the negative oscillation over-limit recording module;

[0008] A frequency counting module, wherein an input end of the frequency counting module is connected to an output end of the logic OR module and an output end of the logic AND module;

[0009] A frequency detection module, wherein an input end of the frequency detection module is connected to the frequency counting module;

[0010] A manual control module, the input end of the manual control module is connected to the output end of the frequency detection module;

[0011] A low frequency alarm module, wherein the input end of the low frequency alarm module is connected to the output end of the frequency detection module.

[0012] Furthermore, the unit load response lag detection module includes a signal processing module, a first high alarm module and a first inversion module; the input end of the signal processing module is connected to the unit load input end and the unit actual load input end; the input end of the first high alarm module is connected to the signal processing module and the oscillation detection amplitude end; the first inversion module is connected to the output end of the first high alarm module.

[0013] Furthermore, the unit load response excessive detection module includes the signal processing module, a first low alarm module, a negative value module and a second inversion module; the input end of the first low alarm module is connected to the signal processing module and the negative value module connected to the oscillation detection amplitude end, and the second inversion module is connected to the output end of the first low alarm module.

[0014] Furthermore, the positive oscillation out-of-limit recording module includes the first high alarm module, the first RS module, and the second low alarm module; the input end of the second low alarm module is connected to the signal processing module and the zero value input end; the Set pin of the first RS module is connected to the output end of the first high alarm module, and the Reset pin of the first RS trigger module is connected to the output end of the second low alarm module.

[0015] Furthermore, the negative oscillation over-limit recording module includes the second high alarm module, the second RS module and the first low alarm module; the input end of the second high alarm module is connected to the signal processing module and the zero value input end; the Set pin of the second RS module is connected to the output end of the first low alarm module, and the Reset pin of the second RS module is connected to the output end of the second high alarm module.

[0016] Furthermore, the frequency counting module includes a counting module and a signal delay module; the input end of the signal delay module is connected to the output end of the logic and module; the counting input end of the counting module is connected to the output end of the logic or module, and the reset input end of the counting module is connected to the output end of the signal delay module.

[0017] Furthermore, the frequency detection module includes a preset numerical module, a preset multiplication coefficient module, a multiplication module and a third high alarm module; the input end of the multiplication module is connected to the preset numerical module and the preset multiplication coefficient module; the output end of the multiplication module is connected to the input end of the third high alarm module, and the input end of the third high alarm module is also connected to the output end of the counting module.

[0018] Furthermore, the manual control module includes a primary frequency modulation module and a steam turbine main control manual switching module; the start ends of the primary frequency modulation module and the steam turbine main control manual switching module are both connected to the output end of the third high alarm module.

[0019] A control method for a load low-frequency oscillation detection and processing system of a thermal power unit includes the above-mentioned load low-frequency oscillation detection and processing system of a thermal power unit. The control method includes:

[0020] Step 1: Detect whether the response of the unit load is delayed or excessive by the unit load response delay detection module and the unit load excessive response module;

[0021] Step 2: Using an oscillation amplitude exceeding limit recording module to record positive and negative oscillation exceeding limit events, and superimposing them into a first output signal;

[0022] Step 3: Calculate the occurrence frequency of the oscillation exceeding limit event of the first output signal by the frequency counting module;

[0023] Step 4: Detecting, by the frequency detection module, whether the frequency calculated by the frequency counting module exceeds a preset threshold;

[0024] Step 5: When the frequency calculated by the frequency counting module exceeds a preset threshold, the primary frequency modulation module and the turbine master control manual switch module are started and manually controlled; at the same time, the low frequency alarm module sounds an alarm.

[0025] Furthermore, the counting method of the frequency counting module includes:

[0026] Step 1, the signal delay module determines whether to delay timing according to the unit load response lag detection module and the unit load response over-detection module;

[0027] Step 2: When the signal delay module determines that the timing needs to be delayed, the signal delay module internally counts for 60 seconds; at the same time, the counting module still counts each rising edge of the first output signal until 60 seconds are over;

[0028] Step 3, the counting module sends the count value within 60 seconds as the oscillation frequency to the third high alarm module, and then the counting module is reset;

[0029] Step 4: Repeat steps 1 to 3 until the frequency counting module stops working.

[0030] Compared with the prior art, the technical solution provided by the embodiments of the present invention can at least achieve the following beneficial effects:

[0031] First, the present invention can more accurately determine whether the unit is in a normal state and promptly discover the problem of response lag or overload through the unit load response lag detection module and the unit load overload response overload detection module.

[0032] Second, the oscillation amplitude over-limit recording module and the frequency counting module of the present invention can quickly record and count oscillation events, providing timely data support for subsequent frequency detection and processing.

[0033] Third, the frequency detection module can detect low-frequency oscillations in time, triggering the manual control module and the low-frequency alarm module, allowing the operator to take quick action or automatically issue an alarm, thereby avoiding the impact of low-frequency oscillations on grid stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings in the following description only relate to some embodiments of the present invention, but are not intended to limit the present invention.

[0035] Figure 1 The present invention is a schematic diagram of a load low-frequency oscillation detection and processing system for a thermal power unit.

[0036] In the figure:

[0037] Unit load response hysteresis detection module: 11

[0038] Signal processing module: 111

[0039] First high alarm module: 112

[0040] First negation module: 113

[0041] Oscillation detection amplitude end: 114

[0042] Negative value modules: 115

[0043] Unit load response over-detection module: 12

[0044] First low alarm module: 121

[0045] The second inversion module: 123

[0046] Logic and modules: 13

[0047] Positive oscillation over-limit recording module: 21

[0048] First RS module: 211

[0049] Second low alarm module 212

[0050] Negative oscillation over-limit recording module: 22

[0051] Second highest alarm module: 221

[0052] Second RS module: 222

[0053] Logical or module: 23

[0054] Counting modules: 31

[0055] Signal delay module: 32

[0056] Preset value module: 41

[0057] Preset multiplication factor module: 42

[0058] Multiplication module: 43

[0059] The third highest alarm module: 44

[0060] Primary frequency modulation module: 51

[0061] Steam turbine master control manual module: 52

[0062] Low frequency alarm module: 6

[0063] Signal: 71-710

[0064] Zero value analog signal: 81 and 82 DETAILED DESCRIPTION

[0065] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0066] Unless otherwise defined, the technical or scientific terms used herein shall have the common meanings understood by persons with ordinary skills in the field to which the present invention belongs. The words "first", "second" and similar words used in the patent application specification and claims of the present invention do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "a" do not indicate a quantity limitation, but indicate the existence of at least one.

[0067] refer to Figure 1 The present invention provides a load low-frequency oscillation detection and processing system for a thermal power unit, the system comprising:

[0068] A normal state judgment module, which includes a unit load response hysteresis detection module 11, a unit load response excess detection module 12 and a logic AND module 13; the input end of the logic AND module 13 is connected to the unit load response hysteresis detection module 11 and the unit load response excess detection module 12;

[0069] An oscillation amplitude over-limit recording module, the oscillation amplitude over-limit recording module comprises a positive oscillation over-limit recording module 21, a negative oscillation over-limit recording module 22 and a logic OR module 23; an input end of the logic OR module 23 is connected to the positive oscillation over-limit recording module 21 and the negative oscillation over-limit recording module 22;

[0070] A frequency counting module, the input end of the frequency counting module is connected to the output end of the logic OR module 23 and the output end of the logic AND module 13;

[0071] A frequency detection module, wherein an input end of the frequency detection module is connected to a frequency counting module;

[0072] A manual control module, the input end of the manual control module is connected to the output end of the frequency detection module;

[0073] The low frequency alarm module 6 has an input end connected to the output end of the frequency detection module.

[0074] The present invention can accurately determine whether the unit is in a normal state through the normal state judgment module, and timely discover the problem of delayed or excessive response. In addition, the oscillation amplitude overlimit recording module and frequency counting module of the present invention can quickly record and count oscillation events, providing timely data support for subsequent frequency detection and processing. Finally, the frequency detection module of the present invention can detect low-frequency oscillations in time, trigger the manual control module and the low-frequency alarm module 6, so that the operator can take quick action or automatically issue an alarm, thereby avoiding the impact of low-frequency oscillations on the stability of the power grid.

[0075] In a preferred embodiment, the unit load response lag detection module 11 includes a signal processing module 111, a first high alarm module 112 and a first inversion module 113; the input end of the signal processing module 111 is connected to the unit load input end (for the first low alarm module 121 to receive signal 71, i.e., the input unit load signal) and the unit actual load input end (for the first low alarm module 121 to receive signal 72, i.e., the unit actual load signal); the input end of the first high alarm module 112 is connected to the signal processing module 111 and the oscillation detection amplitude end 114; the first inversion module 113 is connected to the output end of the first high alarm module 112.

[0076] In a preferred embodiment, the function of the signal processing module 111 is to process the signal 71 and the signal 72, that is, to subtract the signal 72 (actual load of the unit) from the signal 71 (unit load instruction) to generate the signal 73. The first high alarm module 112 makes a judgment based on 73 and the signal 74 to generate the signal 75; specifically, the signal 74 inputted by the oscillation detection amplitude end 114 is used as the high limit signal, that is, when the value of the signal 73 exceeds the signal 74, the first high alarm module 112 will output a high level signal; when the first high alarm module 112 outputs a high level signal, it actually means that the signal 71 (unit load instruction) minus the signal 72 (actual load of the unit) is greater than the signal 74 (the oscillation detection amplitude allowed by the system), at which time, the hysteresis of the actual load of the unit exceeds the allowable range.

[0077] In a preferred embodiment, the unit load response excessive detection module 12 includes a signal processing module 111, a first low alarm module 121, a negative value module 122 and a second inversion module 123; the input end of the first low alarm module 121 is connected to the signal processing module 111 (for the first low alarm module 121 to receive signal 71) and the negative value module 115 connected to the oscillation detection amplitude end 114 (for the first low alarm module 121 to receive signal 76, signal 76 is the negative value of the oscillation detection amplitude), and the second inversion module 123 is connected to the output end of the first low alarm module 121.

[0078] In a preferred embodiment, the first low alarm module 121 makes a judgment based on 73 and signal 76 to generate signal 77; the function of the first low alarm module 121 is to use signal 76 as the lower limit signal, that is, when the value of signal 73 is lower than signal 76, signal 77 of the first low alarm module 121 will become a high level signal; in fact, it means that when signal 72 (actual load of the unit) minus signal 71 (unit load instruction) is greater than signal 76 (system allowed oscillation detection amplitude), at this time, the response of the actual load of the unit is excessive, and the excessive exceeds the allowable range.

[0079] In a preferred embodiment, the first inversion module 113 generates a signal 77 after inverting the signal 75; the function of the first inversion module 113 is to enable the signal delay module 32 to start timing when the signal 73 is less than the signal 74, that is, to start timing when the lag amplitude of the actual load of the unit is received is normal.

[0080] Similarly, the second inversion module 123 inverts the signal 77 to generate the signal 78; the function of the second inversion module 123 is to enable the signal delay module 32 to start timing when the signal 73 is greater than the signal 76, that is, to start timing when the response amplitude of the actual load of the unit is normal.

[0081] Therefore, the function of the logic module 13 is to superimpose the signal 75 and the signal 78. When the signal 77 and the signal 78 are at a high level, that is, the response amplitude and the hysteresis amplitude of the actual load of the unit are both within the normal range, that is, when the signal 72 (actual load of the unit) is normal, the signal delay module 32 will start timing, and then the counting module 31 will use the number of oscillation amplitude exceeding limit events occurring within the next 60 seconds as the frequency.

[0082] In a preferred embodiment, the positive oscillation over-limit recording module 21 includes a first high alarm module 112, a first RS module 211, and a second low alarm module 212; the input end of the second low alarm module 212 is connected to the signal processing module 111 and the zero value input end 213; the Set pin of the first RS module 211 is connected to the output end of the first high alarm module 112, and the Reset pin of the first RS module 211 is connected to the output end of the second low alarm module 212.

[0083] In a preferred embodiment, the second low alarm module 212 receives the signal 73 and the zero-value analog signal 81 input from the zero-value input terminal 213; the second low alarm module 212 uses the zero-value analog signal 81 as the lower limit signal, that is, when the value of the signal 73 is lower than the zero-value analog signal 81, the output signal 79 of the second low alarm module 212 will become a high-level signal.

[0084] In a preferred embodiment, the first RS module 211 is a Reset-Set trigger. Specifically, the first RS module 211 has the following operations:

[0085] Set Operation: When the Set input receives a high signal (logic 1), the state of the flip-flop is set to high (logic 1), regardless of the state of the Reset input.

[0086] Reset Operation: When the Reset input receives a high signal (logic 1), the state of the flip-flop is reset to a low level (logic 0), regardless of the state of the Set input.

[0087] Keep state: If the Set and Reset inputs receive a low-level signal (logic 0) at the same time, the RS flip-flop will maintain its current state.

[0088] Therefore, when signal 73 (signal 71 minus signal 72) is greater than signal 74, the output of the first RS module 211 is a high level; when signal 73 is less than the zero-value analog signal 81, the output of the first RS module 211 is a low level; when signal 73 is less than or equal to signal 74, and signal 73 is greater than or equal to the zero-value analog signal 81, the output signal 710 of the first RS module 211 remains in its original state.

[0089] In a preferred embodiment, the negative oscillation over-limit recording module 22 includes a second high alarm module 221, a second RS module 222 and a first low alarm module 223; the input end of the second high alarm module 221 is connected to the signal processing module 111 and the zero value input end 214; the Set pin of the second RS module 222 is connected to the output end of the first low alarm module 223, and the Reset pin of the second RS module 222 is connected to the output end of the second high alarm module.

[0090] The second RS module 222 is also a Reset-Set trigger, and its specific operations are as follows:

[0091] Set Operation: When the Set input receives a high signal (logic 1), the state of the flip-flop is set to high (logic 1), regardless of the state of the Reset input.

[0092] Reset Operation: When the Reset input receives a high signal (logic 1), the state of the flip-flop is reset to a low level (logic 0), regardless of the state of the Set input.

[0093] Keep state: If the Set and Reset inputs receive a low-level signal (logic 0) at the same time, the RS flip-flop will maintain its current state.

[0094] Therefore, when signal 73 (signal 71 minus signal 72) is less than signal 76, the output of the second RS module 222 is a high level; when signal 73 is greater than the zero-value analog signal 82, the output of the second RS module 222 is a low level; when signal 73 is greater than or equal to signal 76, and signal 7 is less than or equal to the zero-value analog signal 82, the output signal 710 of the second RS module 222 remains in its original state.

[0095] In a preferred embodiment, the frequency counting module includes a counting module 31 and a signal delay module 32; the input end of the signal delay module 32 is connected to the output end of the logic and module 13; the counting input end of the counting module 31 is connected to the output end of the logic or module 23, and the reset input end of the counting module 31 is connected to the output end of the signal delay module 32. For the specific working method of the frequency counting module, refer to the above description of the first negation module 113 and the second negation module 123.

[0096] In a preferred embodiment, the frequency detection module includes a preset numerical module 41, a preset multiplication coefficient module 42, a multiplication module 43 and a third high alarm module 44; the input end of the multiplication module 43 is connected to the preset numerical module 41 and the preset multiplication coefficient module 42; the output end of the multiplication module 43 is connected to the input end of the third high alarm module 44, and the input end of the third high alarm module 44 is also connected to the output end of the counting module 31.

[0097] In a preferred embodiment, the preset multiplication coefficient of the preset multiplication coefficient module 42 is 60, so that the preset value input by the preset value module 41 can be multiplied by 60, and then the result can be used as a threshold for detecting the oscillation frequency.

[0098] In a preferred embodiment, the manual control module includes a primary frequency modulation module 51 and a turbine main control manual switching module 52 ; the start ends of the primary frequency modulation module 51 and the turbine main control manual switching module 52 are both connected to the output end of the third high alarm module 44 .

[0099] In addition to the embodiments of the modules of the present invention described above, a control method of a load low-frequency oscillation detection and processing system of a thermal power unit of the present invention is as follows:

[0100] Step 1: Detect whether the response of the unit load is delayed or excessive by the unit load response delay detection module 11 and the unit load response excess detection module 12;

[0101] Step 2: Using an oscillation amplitude exceeding limit recording module to record positive and negative oscillation exceeding limit events, and superimposing them into a first output signal;

[0102] Step 3: Calculate the frequency of the oscillation exceeding limit event of the first output signal 710 through a frequency counting module;

[0103] Step 4: Detect whether the frequency calculated by the frequency counting module exceeds a preset threshold through the frequency detection module;

[0104] Step 5: When the frequency calculated by the frequency counting module exceeds the preset threshold, the primary frequency modulation module 51 and the turbine master control manual switching module 52 are started and manual control is performed; at the same time, the low frequency alarm module 6 sounds an alarm.

[0105] Furthermore, the counting method of the frequency counting module includes:

[0106] Step 1: The signal delay module 32 determines whether to perform delay timing according to the unit load response lag detection module 11 and the unit load response over-detection module 12;

[0107] Step 2: When the signal delay module 32 determines that the timing needs to be delayed, the signal delay module 32 internally counts for 60 seconds; at the same time, the counting module 31 still counts each rising edge of the first output signal 710 until 60 seconds are over;

[0108] Step 3, the counting module 31 sends the count value as the oscillation frequency to the third high alarm module 44, and then the counting module 31 is reset;

[0109] Step 4: Repeat steps 1 to 3 until the frequency counting module stops working.

[0110] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the protection scope of the present invention. The protection scope of the present invention is determined by the appended claims.

Claims

1. A load low-frequency oscillation detection and processing system for a thermal power unit, characterized in that: The system comprises: A normal state judgment module, the normal state judgment module includes a unit load response hysteresis detection module, a unit load response excessive module and a logic and module; the input end of the logic and module is connected to the unit load response hysteresis detection module and the unit load response excessive module; An oscillation amplitude over-limit recording module, wherein the oscillation amplitude over-limit recording module comprises a positive oscillation over-limit recording module, a negative oscillation over-limit recording module and a logic OR module; an input end of the logic OR module is connected to the positive oscillation over-limit recording module and the negative oscillation over-limit recording module; A frequency counting module, wherein an input end of the frequency counting module is connected to an output end of the logic OR module and an output end of the logic AND module; A frequency detection module, wherein an input end of the frequency detection module is connected to the frequency counting module; A manual control module, the input end of the manual control module is connected to the output end of the frequency detection module; A low frequency alarm module, wherein the input end of the low frequency alarm module is connected to the output end of the frequency detection module.

2. According to claim 1, a load low-frequency oscillation detection and processing system for a thermal power unit is characterized in that: The unit load response lag detection module includes a signal processing module, a first high alarm module and a first inversion module; the input end of the signal processing module is connected to the unit load input end and the unit actual load input end; the input end of the first high alarm module is connected to the signal processing module and the oscillation detection amplitude end; the first inversion module is connected to the output end of the first high alarm module.

3. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 2, characterized in that: The unit load response excessive detection module includes the signal processing module, a first low alarm module, a negative value module and a second inversion module; the input end of the first low alarm module is connected to the signal processing module and the negative value module connected to the oscillation detection amplitude end, and the second inversion module is connected to the output end of the first low alarm module.

4. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 3, characterized in that: The positive oscillation over-limit recording module includes the first high alarm module, the first RS module, and the second low alarm module; the input end of the second low alarm module is connected to the signal processing module and the zero value input end; the Set pin of the first RS module is connected to the output end of the first high alarm module, and the Reset pin of the first RS trigger module is connected to the output end of the second low alarm module.

5. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 3, characterized in that: The negative oscillation over-limit recording module includes the second high alarm module, the second RS module and the first low alarm module; the input end of the second high alarm module is connected to the signal processing module and the zero value input end; the Set pin of the second RS module is connected to the output end of the first low alarm module, and the Reset pin of the second RS module is connected to the output end of the second high alarm module.

6. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 1, characterized in that: The frequency counting module includes a counting module and a signal delay module; the input end of the signal delay module is connected to the output end of the logic and module; the counting input end of the counting module is connected to the output end of the logic or module, and the reset input end of the counting module is connected to the output end of the signal delay module.

7. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 6, characterized in that: The frequency detection module includes a preset numerical module, a preset multiplication coefficient module, a multiplication module and a third high alarm module; the input end of the multiplication module is connected to the preset numerical module and the preset multiplication coefficient module; the output end of the multiplication module is connected to the input end of the third high alarm module, and the input end of the third high alarm module is also connected to the output end of the counting module.

8. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 6, characterized in that: The manual control module includes a primary frequency modulation module and a steam turbine main control manual switching module; the start ends of the primary frequency modulation module and the steam turbine main control manual switching module are both connected to the output end of the third high alarm module.

9. A control method for a load low-frequency oscillation detection and processing system of a thermal power unit, comprising a load low-frequency oscillation detection and processing system of a thermal power unit according to claims 1 to 8, the control method comprising: Step 1: Detect whether the response of the unit load is delayed or excessive by the unit load response delay detection module and the unit load excessive response module; Step 2: Using an oscillation amplitude exceeding limit recording module to record positive and negative oscillation exceeding limit events, and superimposing them into a first output signal; Step 3: Calculate the occurrence frequency of the oscillation exceeding limit event of the first output signal by the frequency counting module; Step 4: Detecting, by the frequency detection module, whether the frequency calculated by the frequency counting module exceeds a preset threshold; Step 5: When the frequency calculated by the frequency counting module exceeds a preset threshold, the primary frequency modulation module and the turbine master control manual switch module are started and manually controlled; at the same time, the low frequency alarm module sounds an alarm.

10. A load low-frequency oscillation detection and processing system for a thermal power unit according to claim 9, characterized in that: The counting method of the frequency counting module includes: Step 1, the signal delay module determines whether to delay timing according to the unit load response lag detection module and the unit load response excessive module; Meanwhile, the counting module counts each rising edge of the first output signal. Step 2: When the signal delay module determines that a delay is required, the signal delay module internally counts for 60 seconds; meanwhile, the counting module still counts each rising edge of the first output signal; When the signal delay module determines that no delay timing is required, the signal delay module does not act; at the same time, the counting module still counts each rising edge of the first output signal; Step 3: After the signal delay module counts for 60 seconds, the signal delay module reminds the counting module to return to zero and sends the count of the counting module to the frequency detection module; Step 4: Repeat steps 1 to 3 until the frequency counting module stops working.

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