A high-speed load reduction peak shaving system and method for thermal power units

Abstract

A high-speed load reduction peak shaving system and method for thermal power units. For each coal-fired power generation unit, a high-precision frequency meter is used to measure the grid frequency at the terminal where the unit is connected to the power grid and send it to the upper limit crossing trigger module. When the grid frequency rises rapidly due to the loss of a large number of loads or a rapid increase in the power generation load, until it is higher than the set upper limit frequency for high-speed load reduction peak shaving operation, the upper limit crossing trigger module outputs 1 or true and sends it to the AND gate for load reduction peak shaving operation. When both the upper limit crossing trigger module and the allowable RB operation switch instruction from the coal-fired power generation unit output 1 or true, the output of the AND gate for load reduction peak shaving operation is 1 or true and is sent to the RB control loop of the coal-fired power generation unit to trigger the RB function of the coal-fired power generation unit. The present invention does not require remote triggering by the power grid dispatching, has good response speed and reliability, and is used for the power grid dispatching in emergency situations, especially having important practical significance for the sending-end power grids in the three northern regions of China.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic control of thermal power plants, and particularly to a high-speed load reduction peak shaving system and method for thermal power units. Background Art

[0002] In the three-north regions of China, there are rich wind and light resources. In recent years, the installed capacities of wind power and photovoltaic power have continued to grow rapidly, gradually forming a large number of clean energy external power supply points or energy bases, and adopting a large-capacity and long-distance power transmission method to supply power to the central and eastern power load centers. The local power grids at the power transmission ends of these power supplies are called sending-end power grids.

[0003] An important feature of the sending-end power grid is that the power generation is far greater than the local power load. Although the excess power is sent away, this brings a huge risk to the operation of the power grid, that is, the fault tripping of the high-power long-distance power transmission line will cause the power generation of the sending-end power grid to be much higher than the power load, resulting in a huge power imbalance. This imbalance will cause the frequency of the sending-end power grid to rise rapidly, thus driving the rapid increase in the speeds of a large number of electrical and generating rotating machinery, bringing the risk of excessive centrifugal force of the rotating components and inducing safety risks. Seriously, it will also instantaneously lose a large amount of power generation due to the overspeed protection of the generating equipment, forming a power oscillation of the power grid until it collapses, resulting in huge economic losses.

[0004] Therefore, the sending-end power grid attaches great importance to the control of power grid power stability. However, at present, neither wind power nor photovoltaic power can cope with the regulation of such rapid and large-capacity power imbalance. Instead, due to the characteristics of wind and light energy itself, it is extremely easy to frequently have additional intermittent power disturbances. Therefore, in the three-north regions of China, the peak shaving relies on the main thermal power units, and it is very important to greatly improve the high-speed load reduction peak shaving ability of the power generation.

[0005] The conventional load reduction regulation of thermal power units includes primary frequency modulation, secondary frequency modulation, tertiary frequency modulation, and electrical overspeed protection (unit tripping) functions.

[0006] (1) Primary Frequency Modulation

[0007] Primary frequency modulation is that the unit actively adjusts the load according to the change of the power grid frequency. When the grid frequency soars due to the tripping of the sending-end power grid tie line, it will automatically reduce the power rapidly, which is the short-time and rapid frequency modulation function of the unit. The requirement for its regulation ability is generally to reach 70% of the regulation target in 15 s and 90% of the regulation target in 30 s. The regulation range for large-capacity thermal power units above 300 MW is generally 5-8%, and in most regional power grids, it is 6% Pe (rated power). Calculated according to the upper limit of 6% Pe, the primary frequency modulation rate within 15 s is about 16.8% Pe / min, and the average primary frequency modulation rate in 30 s is 10.8% Pe / min. However, such a high-speed frequency modulation process is doomed to have a short regulation duration and a small amplitude, and the cumulative amplitude upper limit is about 6%.

[0008] (2) AGC (Automatic Generation Control)

[0009] The secondary frequency regulation of the power grid generally refers to AGC. The power grid dispatching automatically issues load adjustment instructions to the unit side through the control system according to the grid frequency and the power trading situation of the tie line. The unit control system responds to the AGC instructions, thereby achieving the goal of load adjustment. Since the AGC adjustment range is required to be relatively large, generally 45%-100% Pe, and the adjustment direction in the next instruction cycle is random, the adjustment rate is relatively low. The power grid requirement is generally higher than 1.5% Pe / min, and most actual units are between 1% Pe / min and 1.5% Pe / min.

[0010] (3) Tertiary frequency regulation

[0011] The tertiary frequency regulation of the power grid generally means that the power grid dispatcher informs the unit operators by phone according to the peak shaving and power flow requirements of the power grid, and executes the required large-scale load increase and decrease demands. It is equivalent to a supplement to the AGC regulation. Except for start / stop requirements, since it does not involve performance assessment, the response rate and amplitude are not higher than the AGC index requirements.

[0012] (4) Electrical overspeed protection OPC (engine trip)

[0013] Modern high-power thermal power unit control systems are generally equipped with electrical overspeed protection functions. The original purpose is to prevent the steam turbine generator unit from overspeed and avoid the steam turbine from tripping due to the unit speed exceeding 110% of the rated speed. When the unit speed (using a synchronous generator, so the speed and the corresponding grid frequency) exceeds 103% of the rated value, the electrical overspeed protection acts, quickly closes the steam turbine inlet control valve, and opens the steam turbine inlet control valve after the unit speed returns to the rated speed. The purpose is to maintain the unit's online operation under load rejection or grid high-frequency engine trip conditions without tripping the unit. Since this mode is relatively extreme and its reliability and stability need to be determined by regular tests, it is an extreme measure as a last resort and is unlikely to be used for unit peak shaving under the existing technical conditions.

[0014] The comparison of the above four potential technologies that can be used for load reduction and peak shaving is shown in the following table.

[0015]

[0016] Through the above analysis, it can be found that the high-speed primary frequency regulation ability cannot last, and the large-scale and persistent AGC and tertiary frequency regulation functions cannot achieve high-speed peak shaving. This is also the biggest problem faced by the load dispatching of the sending-end power grid at present, that is, the lack of a high-speed and large-scale load reduction and peak shaving means to cope with large-scale load disturbances. Summary of the Invention

[0017] To solve the above problems, the object of the present invention is to propose a high-speed load reduction peak shaving system and method for thermal power units. The triggering condition is actively executed by the unit according to the measured result of the terminal frequency of the connected power grid, without remote triggering by the power grid dispatching. The response speed and reliability are good, and it is used for the power grid dispatching in emergency situations. Especially for the sending-end power grid in the three-north regions of China, it has important practical significance.

[0018] To achieve the above object, the present invention adopts the following technical solutions:

[0019] A high-speed load reduction peak shaving system for thermal power units includes multiple coal-fired generating units 6 operating in parallel on the power grid. Between each coal-fired generating unit 6 and the terminal of the connected regional power grid 1, a high-precision frequency meter 2, an over-limit trigger module 3, and a load reduction peak shaving action AND gate 4 are sequentially arranged. The load reduction peak shaving action AND gate 4 is connected to the RB control loop 5 of the coal-fired generating unit 6.

[0020] The frequency measurement range of the high-precision frequency meter 2 should cover at least the frequency range of 50 - 51.5 Hz.

[0021] The high-speed load reduction peak shaving action upper limit frequency f of the over-limit trigger module 3 H is set to 50.2 Hz to 51.5 Hz.

[0022] For the high-speed load reduction peak shaving method of the high-speed load reduction peak shaving system of thermal power units, each coal-fired generating unit 6 uses a high-precision frequency meter 2 at the terminal of the connected power grid to measure the grid frequency f of the access terminal and sends it to the over-limit trigger module 3; when the grid frequency f increases rapidly due to the loss of a large number of loads or the rapid increase of the power generation load, until it is higher than the set high-speed load reduction peak shaving action upper limit frequency f H at this time, the over-limit trigger module 3 outputs 1 or true and sends it to the load reduction peak shaving action AND gate 4; another input terminal of the load reduction peak shaving action AND gate 4 comes from the allowable RB action switch command of the coal-fired generating unit 6. When the over-limit trigger module 3 and the allowable RB action switch command from the coal-fired generating unit 6 both output 1 or true at the same time, the load reduction peak shaving action AND gate 4 outputs 1 or true and sends it to the RB control loop 5 of the coal-fired generating unit 6 to trigger the RB function of the coal-fired generating unit.

[0023] The allowable RB action switch command from the coal-fired generating unit 6 includes three signal sources in an AND relationship: (1) the allowable execution condition for the input of the RB control loop of the target coal-fired generating unit itself; (2) the set deviation between the grid frequency and the rotational speed of the coal-fired generating unit is less than ±0.5%; (3) the signal for manually inputting the high-speed load reduction peak shaving function.

[0024] For different grid-connected generating units, different action upper limits f H are adopted, and the specific method is as follows:

[0025] Rank the coal-fired generating units participating in high-speed load rejection peak shaving according to their test performance and process safety stability tested in the RB test report, and then conduct accident simulation for the main operation modes of the regional power grid according to the power grid dynamic simulation calculation model. When the accident surplus power is greater than 20% of the rated power of the coal-fired generating unit ranked first and less than 20% of the sum of the rated powers of the first two coal-fired generating units, if the upper limit of the grid fly-up frequency in the simulation result is f L1 It means that if the coal-fired generating unit ranked first triggers the high-speed load rejection peak shaving function when the accident occurs, it can just be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f L1 Is set as the upper limit of the high-speed load rejection peak shaving action frequency f H1 Of the coal-fired generating unit ranked first; similarly, when the simulated accident surplus power is greater than 20% of the sum of the rated powers of the top two coal-fired generating units and less than 20% of the sum of the rated powers of the top three, the corresponding upper limit of the grid fly-up frequency f L2 It means that if the top two coal-fired generating units trigger the high-speed load rejection peak shaving function, it can just be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f L2 Is set as the upper limit of the high-speed load rejection peak shaving action frequency f H2 Of the coal-fired generating unit ranked second; and so on, when the simulated accident surplus power is greater than 20% of the sum of the rated powers of the top N coal-fired generating units and less than 20% of the sum of the rated powers of the top N+1, the corresponding upper limit of the grid fly-up frequency f LN It means that if the top N coal-fired generating units trigger the high-speed load rejection peak shaving function, it can just be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f LN Can be set as the upper limit of the high-speed load rejection peak shaving action frequency f HN Of the coal-fired generating unit ranked N; this can not only avoid over-regulation of the grid frequency caused by a large number of units triggering high-speed load rejection peak shaving at the same time, but also provide a relatively accurate high-speed load shedding peak shaving function during accidents.

[0026] The present invention has the following characteristics and advantages compared with the prior art:

[0027] (1) The trigger condition of the high-speed load rejection peak shaving system of the present invention is actively executed by the unit according to the measured result of the terminal frequency of the connected power grid, without remote triggering by the power grid dispatching, and the response speed and reliability are good.

[0028] (2) The adjustment rate of the high-speed load shedding and peak shaving system of the present invention is much higher than that of the AGC function, and the adjustment range is much higher than that of the primary frequency modulation function, providing a new means of load shedding and peak shaving for the power grid. It is especially applicable to the large-power clean energy sending-end power grids in the three-north regions of China. Once a large-power transmission line is blocked and tripped, the high proportion of surplus power cannot be handled by the conventional primary frequency modulation, and the AGC control far fails to meet the requirements of accident handling. The application of the high-speed load shedding and peak shaving system will greatly improve the accident response ability of the sending-end power grid, avoid power oscillations and even grid disconnection caused by large-scale generator tripping relying only on OPC actions, and is of great strategic significance for coping with the long-distance difference between China's energy and electricity load centers and improving the safety of the UHV large-power long-distance transmission system.

[0029] (3) The high-speed load shedding and peak shaving system of the present invention utilizes the RB function circuit commonly existing in large-power thermal power units. Therefore, the optimization and progress of related RB technologies are also effective for the high-speed load shedding and peak shaving system. The application of the high-speed load shedding and peak shaving system is also beneficial to the unit to further improve its RB function, which is of great significance to the accident response ability of the unit's own auxiliary equipment tripping. Because the high-speed load shedding and peak shaving system is triggered under extreme conditions and may not operate once a year, it forces the unit to strengthen the effectiveness and reliability maintenance of its RB function, which plays an important role in reducing unit outages and improving safety and reliability.

[0030] (4) The high-speed load shedding and peak shaving method for thermal power units can be relatively accurately configured according to the power grid dynamic simulation, which can avoid the over-adjustment of the power grid frequency caused by a large number of units triggering high-speed load shedding and peak shaving at the same time, and can also provide a relatively accurate high-speed load shedding and peak shaving function during accidents. Brief Description of the Drawings

[0031] Figure 1 is a schematic structural diagram of the high-speed load shedding and peak shaving system for thermal power units of the present invention.

[0032] In the figure: 1 - regional power grid; 2 - high-precision frequency meter; 3 - over-limit trigger module; 4 - load shedding and peak shaving action AND gate; 5 - RB control circuit; 6 - coal-fired generating unit. Detailed Embodiment

[0033] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0034] First of all, large-power units are all configured with the RUNBACK (auxiliary equipment failure load shedding, also called load fast return, abbreviated as RB) function, which is defined as a control measure to quickly reduce the unit load when the main auxiliary equipment (such as feed water pump, forced draft fan, induced draft fan) fails and partially withdraws from operation, making the unit unable to carry the rated load.

[0035] When the above-mentioned auxiliary equipment of the unit fails and trips, the unit can quickly reduce the load and maintain stability. Taking the RB test results of a certain large-capacity unit as an example, the load reduction rate and amplitude are shown in the following table:

[0036] RB project Load reduction rate Pe / min Load reduction amplitude Forced draft fan RB 6.1％ 20.4％ Primary air fan RB 9.8％ 19.6％ Coal mill RB 9.9％ 21.5％

[0037] Just from the above test results, it can be seen that the actual unit equipment fully has the ability to continuously reduce the load by about 20% at a rate of about 10% Pe / min. The whole process takes about 2 - 5 minutes, which is just in the same order of magnitude as the time of the large power disturbance process caused by the locking failure of the transmission-end grid tie line or the low-voltage ride-through failure of the wind farm, etc. The transmission-end grid can utilize this ability to achieve high-speed load reduction and peak regulation in emergency situations, effectively improving the stability of the transmission-end grid.

[0038] Based on this principle, the present invention adopts the following technical solutions:

[0039] As Figure 1 shown, a high-speed load reduction and peak regulation system for a thermal power unit of the present invention includes a plurality of coal-fired generating units 6 operating in parallel on the power grid. Between each coal-fired generating unit 6 and the terminal of the accessed regional power grid 1, a high-precision frequency meter 2, an over-limit trigger module 3, and a load reduction and peak regulation action AND gate 4 are sequentially arranged. The load reduction and peak regulation action AND gate 4 is connected to the RB control loop 5 of the coal-fired generating unit 6.

[0040] For the high-speed load reduction and peak regulation method of the high-speed load reduction and peak regulation system for a thermal power unit of the present invention, each coal-fired generating unit 6 uses a high-precision frequency meter 2 at the terminal of the accessed power grid to measure the power grid frequency f of the accessed terminal and send it to the over-limit trigger module 3; when the power grid frequency f increases rapidly due to the loss of a large number of loads or the rapid increase of power generation loads such as wind and light, until it is higher than the set high-speed load reduction and peak regulation action upper limit frequency f H at this time, the over-limit trigger module 3 outputs 1 (or true) and sends it to the load reduction and peak regulation action AND gate 4; another input terminal of the load reduction and peak regulation action AND gate 4 comes from the allowable RB action switch command of the coal-fired generating unit 6. When the over-limit trigger module 3 and the allowable RB action switch command from the coal-fired generating unit 6 both output 1 (or true) at the same time, the load reduction and peak regulation action AND gate 4 outputs 1 (or true) and sends it to the RB control loop 5 of the coal-fired generating unit 6 to trigger the RB function of the coal-fired generating unit.

[0041] The RB function designs of different coal-fired generating units are slightly different, but basically when RB is triggered, the steam turbine is switched to the TF mode (i.e., the turbine following mode, where the steam turbine no longer adjusts the unit load but instead controls the main steam pressure, which is equivalent to automatically changing the unit load according to the level of steam evaporated by the boiler); the boiler is switched to the manual mode, and the RB loop gives a lower RB load command according to different trigger conditions. At this time, the coal-fired generating unit will cut off a certain number of coal mills according to the actual situation, quickly reduce the fuel participating in combustion, thereby greatly reducing the boiler evaporation, reducing the working steam flow rate entering the steam turbine, and achieving high-speed load shedding for peak shaving. In addition to the above conventional RB functions, generally to ensure the safety and stability of the RB process, the relevant loops such as desuperheating spray water and feed water are optimized and adjusted according to the characteristics of the coal-fired generating unit. Generally, the RB function of the coal-fired generating unit is also tested through RB tests to ensure that the unit meets the goal of not tripping and extinguishing after RB is triggered, which also equivalently guarantees the reliable high-speed load shedding and peak shaving ability of the coal-fired generating unit.

[0042] Since the operation process of the aforementioned high-speed load shedding and peak shaving system is similar to the RB process and has the characteristics of non-interruptibility and short-term irreversibility, it is only applicable to the high-speed and large-scale load shedding requirements under emergency conditions, especially suitable for the sending-end power grids in the three-north regions of China. For situations such as the blocking and tripping of large-proportion power transmission tie lines or the rapid increase in the output power of a large number of wind farms caused by instantaneous strong winds, it can achieve a high-speed load shedding and peak shaving ability with a range of 6 - 10% Pe / min up to 20% Pe.

[0043] Therefore, the action upper limit f of the upper limit trigger module 3 in the high-speed load shedding and peak shaving system of the thermal power unit of the present invention HSet between 50.2 Hz and 51.5 Hz. The reason is that the upper limit of the primary frequency regulation power of a thermal power unit is generally 5%-8% Pe, and the grid requires the speed regulation inequality rate to be lower than 5%. That is, the upper limit frequency deviation corresponding to the upper limit of the rapid primary frequency regulation response of 8% Pe of the thermal power unit is 5%×8%×50 Hz = 0.2 Hz. Therefore, when the grid frequency is higher than 50.2 Hz, it has exceeded the response range of the primary frequency regulation action of the thermal power unit. As the frequency continues to increase, the primary frequency regulation function will not continue to reduce power to maintain grid stability. Therefore, setting the action frequency of the high-speed load shedding peak shaving system higher than 50.2 Hz can prevent it from operating in most grid disturbances, while it can make up for the deficiency of the primary frequency regulation ability in the case of extreme load imbalance in the grid. On the other hand, the action speed of the over-speed protection (OPC) of the thermal power unit is 103% of the rated speed, corresponding to a synchronous generator frequency of 51.5 Hz. That is, when the grid frequency exceeds 51.5 Hz, all thermal power units will trigger the OPC action and directly cut off the steam supply to the steam turbine, which will occur in special extreme cases such as grid disconnection or islanded grid operation. At this time, high-speed load shedding peak shaving has lost its meaning. Therefore, the action frequency of high-speed load reduction peak shaving needs to be lower than 51.5 Hz.

[0044] As described above, the measurement result of the grid frequency plays a crucial role in the high-speed load shedding peak shaving action. Therefore, the high-precision frequency meter in the high-speed load shedding peak shaving system of the thermal power unit of the present invention needs to adopt a relatively high measurement resolution. According to the action upper limit f of the aforementioned upper limit trigger module 3 H Set between 50.2 Hz and 51.5 Hz. Therefore, the frequency measurement range of the high-precision frequency meter 2 selected here is different from the measurement range used for primary frequency regulation (49.8 - 50.2 Hz) or the measurement range of the display frequency meter configured in a conventional power plant (generally 0 - 60 Hz), and should at least cover the frequency range of 50 - 51.5 Hz.

[0045] In the high-speed load shedding peak shaving system of the thermal power unit of the present invention, the allowable RB action switch command from the coal-fired generating unit 6 includes at least three signal sources in an AND relationship: (1) the input execution allowable condition of the RB control loop of the target coal-fired generating unit itself; (2) since the reliability requirement for the grid frequency is relatively high, the deviation between the grid frequency and the corresponding speed of the coal-fired generating unit is set to be less than ±0.5% as the second allowable condition. In this way, when the frequency meter is abnormal, there will be a certain deviation from the corresponding synchronous speed, and the corresponding action will not be allowed at this time; (3) the manual input of the high-speed load shedding peak shaving function signal, so that when problems occur in other systems or equipment of the coal-fired generating unit, the relevant actions can be manually blocked to avoid unnecessary losses caused by the high-speed load shedding peak shaving action.

[0046] The high-speed load shedding peak shaving method for the thermal power unit of the present invention is to adopt different action upper limits f for different grid-connected generating unitsH , so when grid accidents or the like cause different levels of substantial excess power generation, the resulting grid frequency rise heights are different, and the number of load-reducing units corresponding to triggering the high-speed load reduction peak shaving function of the unit is different. In this way, the risk of grid frequency rise at the sending end can be more flexibly and accurately addressed, and it is also more conducive to eliminating the limitations that the high-speed load reduction peak shaving process of the present invention cannot be interrupted and is irreversible in a short time.

[0047] The high-speed load reduction peak shaving method for thermal power units of the present invention adopts different action upper limits f for different grid-connected generating units H , and the specific method is as follows: Sort the coal-fired generating units that can participate in high-speed load reduction peak shaving according to their test performance and process safety stability tested in the RB test report, and then conduct accident simulation and simulation under the main operating mode of the regional power grid according to the grid dynamic simulation calculation model. When the accident excess power is greater than 20% Pe of the rated power of the coal-fired generating unit ranked first and less than 20% of the sum of the rated powers of the first two coal-fired generating units, if the grid frequency rise upper limit of the simulation result at this time is f L1 , it means that if the coal-fired generating unit ranked first triggers the high-speed load reduction peak shaving function when the accident occurs, it can just be used to make up for the excess power of this accident. The frequency rise upper limit f L1 at this time is set as the high-speed load reduction peak shaving action frequency upper limit f of the coal-fired generating unit ranked first H1 . Similarly, when the simulated accident excess power is greater than 20% of the sum of the rated powers of the top two coal-fired generating units and less than 20% of the sum of the rated powers of the top three, the corresponding grid frequency rise upper limit f L2 , which means that triggering the high-speed load reduction peak shaving function of the top two coal-fired generating units can just be used to make up for the excess power of this accident. The frequency rise upper limit f L2 at this time can be set as the high-speed load reduction peak shaving action frequency upper limit f of the coal-fired generating unit ranked second H2 . And so on, when the simulated accident excess power is greater than 20% of the sum of the rated powers of the top N coal-fired generating units and less than 20% of the sum of the rated powers of the top N + 1, the corresponding grid frequency rise upper limit f LN , which means that triggering the high-speed load reduction peak shaving function of the top N coal-fired generating units can just be used to make up for the excess power of this accident. The frequency rise upper limit f LN at this time can be set as the high-speed load reduction peak shaving action frequency upper limit f of the coal-fired generating unit ranked Nth HN . In this way, it can not only avoid over-adjustment of the grid frequency caused by a large number of units triggering high-speed load reduction peak shaving at the same time, but also provide a relatively accurate high-speed load reduction peak shaving function during accidents.

Claims

1. A peak shaving method for a thermal power unit with high-speed load reduction in a thermal power unit high-speed load reduction peak shaving system. The system includes multiple coal-fired generating units (6) operating in parallel on the power grid, and is characterized in that: For each coal-fired power generation unit (6), a high-precision frequency meter (2), an over-limit trigger module (3), and a load reduction peak shaving action AND gate (4) are sequentially arranged between the terminals of the connected regional power grid (1). The load reduction peak shaving action AND gate (4) is connected to the RB control loop (5) of the coal-fired power generation unit (6). The high-speed load reduction peak shaving method for thermal power units: For each coal-fired power generation unit (6), a high-precision frequency meter (2) is used to measure the grid frequency f at the terminal where the unit is connected to the grid and send it to the upper limit crossing trigger module (3); when the grid frequency f increases rapidly due to the loss of a large number of loads or the rapid increase of the power generation load until it is higher than the set upper limit frequency f H at which time, the upper limit crossing trigger module (3) outputs 1 or true and sends it to the load reduction peak shaving action AND gate (4); another input terminal of the load reduction peak shaving action AND gate (4) comes from the allowable RB action switch command of the coal-fired power generation unit (6). When the upper limit crossing trigger module (3) and the allowable RB action switch command from the coal-fired power generation unit (6) both output 1 or true at the same time, the load reduction peak shaving action AND gate (4) outputs 1 or true and sends it to the RB control loop (5) of the coal-fired power generation unit (6) to trigger the RB function of the coal-fired power generation unit; Adopt different action upper limits f for different grid-connected generating units H , and the specific method is as follows: Rank the coal-fired power generating units participating in high-speed load reduction peak shaving according to their test performance and process safety stability tested in the RB test report, and then conduct accident simulation for the main operation modes of the regional power grid based on the power grid dynamic simulation calculation model. When the accident surplus power is greater than 20% of the rated power of the coal-fired power generating unit ranked first and less than 20% of the sum of the rated powers of the first two coal-fired power generating units, if the upper limit of the grid fly-up frequency in the simulation result is f L1 , it means that if the coal-fired power generating unit ranked first triggers the high-speed load reduction peak shaving function when the accident occurs, it can be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f L1 is set as the upper limit of the high-speed load reduction peak shaving action frequency f H1 of the coal-fired power generating unit ranked first; when the simulation accident surplus power is greater than 20% of the sum of the rated powers of the top two coal-fired power generating units and less than 20% of the sum of the rated powers of the top three, the corresponding upper limit of the grid fly-up frequency f L2 , which means that the high-speed load reduction peak shaving functions triggered by the top two coal-fired power generating units can be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f L2 is set as the upper limit of the high-speed load reduction peak shaving action frequency f H2 of the coal-fired power generating unit ranked second; and so on. When the simulation accident surplus power is greater than 20% of the sum of the rated powers of the top N coal-fired power generating units and less than 20% of the sum of the rated powers of the top N+1, the corresponding upper limit of the grid fly-up frequency f LN , which means that the high-speed load reduction peak shaving functions triggered by the top N coal-fired power generating units can just be used to make up for the surplus power of this accident. The upper limit of the fly-up frequency f LN can be set as the upper limit of the high-speed load reduction peak shaving action frequency f HN of the coal-fired power generating unit ranked N; in this way, it can not only avoid over-regulation of the grid frequency caused by a large number of units triggering high-speed load reduction peak shaving at the same time, but also provide a high-speed load reduction peak shaving function during accidents.

2. The peak shaving method for high-speed load reduction of a thermal power unit in the high-speed load reduction peak shaving system of a thermal power unit according to claim 1, characterized in that: The frequency measurement range of the high-precision frequency meter (2) should cover at least the frequency range of 50 - 51.5 Hz.

3. The peak shaving method for high-speed load reduction of a thermal power unit in the high-speed load reduction peak shaving system of a thermal power unit according to claim 1, characterized in that: The upper limit frequency f of the high-speed load reduction peak shaving action of the upper limit trigger module (3) H is set to 50.2 Hz to 51.5 Hz.

4. The peaking method for high-speed load reduction of a thermal power unit in the high-speed load reduction peaking system of a thermal power unit according to claim 1, characterized in that: The allowed RB action switch command from the coal-fired power generation unit (6) includes three signal sources in an AND relationship: (1) the input execution permission condition of the RB control loop of the target coal-fired power generation unit itself; (2) the set deviation between the grid frequency and the rotational speed of the coal-fired power generation unit is less than ±0.5%; (3) the manually input high-speed load reduction peak shaving function signal.

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