Optimal control method for primary frequency regulation of power grid under grid connection of new energy

Abstract

The application discloses a power grid primary frequency modulation optimization control method under new energy grid connection, and particularly relates to the field of power grid frequency modulation optimization, and comprises the following steps: obtaining current load of thermal power unit and power grid frequency difference; determining directional limit value pair; selecting corresponding limit value pair primary frequency modulation output instruction based on the direction of power grid frequency difference; and outputting the limited frequency modulation output instruction for execution. The power grid primary frequency modulation optimization control method under new energy grid connection narrows down in five linear continuous sections of normal area, first transition area, low voltage area, second transition area and safety protection area through limit value reduction, and meets the constraint that the load after reduction is not lower than the sum of stable combustion safety load lower limit and safety margin, so as to realize low load reduction without boiler stable combustion margin consumption; the upper limit value is constant as the maximum in the full load section, so as to maintain the upward frequency support capacity in the low load interval; the lower load removal reduction channel is kept available while the upper increase channel is kept available, so as to further guarantee the safety of deep peak shaving and eliminate the frequency support vacuum.

Description

Technical Field

[0001] This invention relates to the field of power grid frequency regulation optimization technology, and more specifically, to a method for optimizing primary frequency regulation control of a power grid under the integration of new energy sources. Background Technology

[0002] With the continuous increase in the proportion of new energy power generation and the normalization of deep peak shaving operation of thermal power units, the primary frequency regulation of the power grid, that is, the function of grid-connected units to quickly adjust the active power output through the speed regulation system to suppress frequency deviation when the frequency deviates from the rated value, has become a core engineering link in the grid-connected control of thermal power units in the context of new energy grid connection. This is because the control of the primary frequency regulation of the power grid is directly related to frequency stability and is also subject to the assessment of the power auxiliary service market.

[0003] To address the aforementioned needs, the mainstream technical approach in the industry involves setting directional switches and limits for the primary frequency modulation action in the digital electro-hydraulic regulation system and coordinated control loop, based on load ranges: bidirectional adjustment is allowed in the rated load range, only downward adjustment is retained in the near-full load range to prevent over-generation, only upward adjustment is retained in the low load range, and the frequency modulation action is set to zero and completely discontinued in the low load range. This approach is implemented after being verified by a simulator before installation, ensuring that the downward adjustment action does not cross the lower limit of stable combustion under normal loads, thus meeting basic frequency modulation requirements.

[0004] However, in actual use, it still has some shortcomings. For example, its limit adopts a fixed symmetrical value and uses a directional switch for binarization. It does not distinguish the directional safety asymmetry where the downward adjustment margin disappears as the load decreases and the upward adjustment capacity is basically unrelated to the load. During the deep peak shaving period, the downward adjustment action overdraws the boiler's stable combustion margin, causing large fluctuations in main steam pressure and steam temperature, or even the risk of non-shutdown. In the low-load range, the frequency modulation effect is reduced to zero in both directions, causing the low-load section to lose its ability to support the frequency upward, creating a frequency support vacuum and triggering the commissioning rate assessment. Summary of the Invention

[0005] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method for optimizing the primary frequency regulation control of the power grid under the grid connection of new energy sources, and solves the problems mentioned in the background art through the following scheme.

[0006] To achieve the above objectives, the present invention provides the following technical solution: The primary frequency regulation optimization control method for power grids under new energy grid integration includes: S1: Obtain the current load L of the thermal power unit and the grid frequency difference Δf; S2: Based on the current load L and the preset stable combustion safety load lower limit The lower limit D(L) and the upper limit U(L) are determined. The lower limit D(L) is a continuous monotonically non-increasing function with load L as the independent variable, and the upper limit U(L) is independently maintained at a preset maximum upper limit. ; The lower limit D(L) is set in a first transition zone between the normal zone and the low-pressure zone. Within the first transition zone, the lower limit is adjusted from the preset maximum lower limit. With the first slope Linear transition to low-pressure zone preset lower limit - A second transition zone is established between the low-pressure area and the safety protection zone, and the limit value is lowered from - in the second transition zone. With the second slope Linear transition to zero; within the safety protection zone, the limit is lowered to zero; within the normal zone, the limit is lowered to zero. Furthermore, the lowering limit D(L) satisfies the constraint. Where Le is the rated load of the unit, and ΔL is the preset safety margin; S3: Based on the direction of the power grid frequency difference Δf, select a lower limit D(L) or an upper limit U(L) to limit the primary frequency regulation output command, and generate a limited frequency regulation output command; S4: Execute the frequency modulation output command after the amplitude limiting.

[0007] Preferably, step S1, obtaining the current load L of the thermal power unit, specifically includes: Acquire the load signal from the DCS power transmitter and the load reference value from the DEH; The validity of the load signal from the DCS power transmitter is verified. When the load signal of the DCS power transmitter passes the validity check, the DCS power transmitter load signal is preferentially used as the current load L; When the load signal of the DCS power transmitter fails the validity check, it automatically switches to the DEH load reference value or the turbine regulating stage pressure equivalent load as the current load L.

[0008] Preferably, step S1, obtaining the power grid frequency difference Δf, specifically includes: Calculation of measured grid frequency f based on DEH system speed signal; The measured power grid frequency f is compared with the rated frequency. The original frequency difference is obtained by subtraction. ; When the original frequency difference When the absolute value is not greater than the preset dead zone threshold, the power grid frequency difference Δf is set to zero; When the original frequency difference When the absolute value is greater than the preset dead zone threshold, the original frequency difference is... The frequency difference Δf of the power grid; When the original frequency difference When the absolute value of the frequency difference exceeds the preset frequency difference threshold, the power grid frequency difference Δf is determined to be invalid.

[0009] Preferably, S1 further includes: Determine the lower limit benchmark value of the safe combustion load based on the boiler's minimum stable combustion load test data or minimum stable combustion load calibration value. ; Based on the received volatile matter obtained from the online coal quality analyzer Flame detection signal fluctuation rate Absolute value of main steam pressure change rate The lower limit benchmark value of the stable combustion safety load is adjusted by a preset correction function. Online dynamic correction is performed, and the correction results are clamped at upper and lower limits to obtain the preset lower limit of stable combustion safety load. ; Specifically, the upper and lower limit clamping is expressed as follows: ,in, The upper limit protection value of the lower limit of the safe load for stable combustion. The lower limit of the stable combustion safety load is corrected for the kth sampling period but without upper and lower limit clamping.

[0010] Preferably, the method for determining the load interval boundary in S2 specifically includes: Preset lower limit of safe combustion load The sum of the safety margin ΔL and the preset safety margin ΔL is used as the upper limit B0 of the safety protection zone, i.e., B0 = +ΔL; The upper boundary of the safety protection zone B0 is sequentially superimposed with the width of the second transition zone W2, the width of the low-pressure zone W1, and the width of the first transition zone W3 to determine the upper boundary of the second transition zone B1, the upper boundary of the low-pressure zone B2, and the lower boundary of the normal zone B3, respectively. The boundary of the load range follows the preset lower limit of the stable combustion safety load. It is dynamically translated through online dynamic correction.

[0011] Preferably, in step S2, when the downward adjustment limit D(L) does not satisfy the constraint... At that time, the limiting parameters are adjusted sequentially according to preset priority, specifically including: The first priority is to adjust the width of the transition zone, and adjust the upper limit B1 of the second transition zone towards the high load direction; The second priority is to adjust the slope parameter, increasing the second slope. Or the first slope ; The third priority is the preset lowering limit value for the low-pressure area. The amplitude is adjusted to reduce the absolute value of the preset downward limit value of the low-voltage zone; After adjusting the parameters, re-execute the constraints. Verification.

[0012] Preferably, after generating the limited frequency modulation output command, step S3 further includes: The frequency modulation output command after amplitude limiting is subject to a command change rate limitation. When the deviation between the frequency modulation output command after the amplitude limit and the final frequency modulation output command of the previous control cycle exceeds the preset maximum load change rate With control cycle When multiplying by , the frequency modulation output command is clamped within the allowable range of the rate of change.

[0013] Preferably, step S4, while executing the output command of the limited frequency modulation power, also includes: Monitor the current load L of the thermal power unit and the lower limit of the stable combustion safe load. The relationship between the sum of the preset safety margin ΔL and the safety margin ΔL; When the current load L is lower than When +ΔL, the down-adjustment channel is cut off, the frequency modulation output command output in the negative direction is blocked, and the up-adjustment channel remains available. When the current load L rises to no less than If the +ΔL value is increased and the duration exceeds the preset recovery delay, the down-adjustment channel will be automatically restored.

[0014] The technical effects and advantages of this invention are as follows: 1. This invention decouples the downward adjustment limit and the upward adjustment limit in a directional manner, so that the downward adjustment limit narrows continuously as the load decreases, while the upward adjustment limit does not narrow with load changes. This achieves an asymmetric limiting where the safety margin in the downward adjustment direction is negatively correlated with the load level, and the frequency regulation capability in the upward adjustment direction is independent of the load level. This effectively alleviates the problems in the prior art where fixed symmetrical limiting does not distinguish between directional safety asymmetry and the downward adjustment action during deep peak shaving periods overdraws the boiler's stable combustion margin. 2. This invention achieves a continuous and smooth transition of the reduction limit by linearly narrowing it from the maximum reduction value in the normal zone through the first transition zone to the rated load in the low-pressure zone, and then accelerating its narrowing to zero through the second transition zone. This avoids the impact of step switching on the unit. At the same time, it accelerates the decay of the reduction limit when it approaches the lower limit of the stable combustion safety load, ensuring that the reduction action in the low-load section will not exceed the safety boundary. 3. This invention directly links the value of the downward adjustment limit with the lower limit of the stable combustion safe load and the preset safety margin, and forcibly constrains the load prediction value after any downward adjustment action to not be lower than the safety protection line. This ensures that the first frequency adjustment action in the downward adjustment direction will not overdraw the minimum stable combustion margin of the boiler, and avoids the risk of large fluctuations in main steam pressure and steam temperature or even non-shutdown. 4. This invention maintains the upward adjustment limit at the maximum value across all load ranges and independently selects the corresponding limit based on the frequency difference direction, thereby achieving uninterrupted maintenance of the frequency support capability in the upward adjustment direction in low load ranges. This effectively solves the problems of vacuum in upward frequency support and substandard frequency modulation input rate assessment caused by the overall bidirectional zeroing in low load ranges in the prior art. 5. This invention links the upper boundary of the safety protection zone, the boundaries of each transition zone, and the lower limit of the stable combustion safety load after online correction, so that the safety protection line is always covered by the safety protection zone. This enables the automatic upward shift of the safety boundary when combustion conditions deteriorate, ensuring that the logic for narrowing the lower limit value always matches the actual stable combustion capability of the boiler. 6. This invention combines offline traversal verification with online real-time verification and self-corrects according to priority parameters, ensuring that the limit parameters still meet safety constraints after coal quality fluctuations or changes in combustion conditions, effectively avoiding hidden safety risks caused by parameter mismatch, and minimizing the impact on frequency regulation capability. 7. This invention limits the sudden change rate of the regulating valve opening command by clamping the change in frequency regulation output command within a single control cycle within the range of the preset maximum load change rate, thereby avoiding the impact of rapid and large frequency regulation on boiler combustion stability and main steam pressure, and further reducing the risk of non-outage induced by frequency regulation in low load sections. 8. This invention achieves hard protection for down-modulation and up-modulation in low-load segments and uninterrupted up-modulation capability by independently controlling the down-modulation channel and up-modulation channel at the execution level, and only shielding the down-modulation command while maintaining the normal transmission of the up-modulation command within the safety protection zone. This forms a directional safety interlock and further consolidates the frequency support capability in low-load segments. 9. This invention avoids input errors in the limit function caused by distortion of a single load signal through redundancy verification and automatic switching of multi-source load signals, ensuring the accuracy of the current load on which the lower limit calculation is based, thereby indirectly ensuring the effectiveness of safety constraint verification. 10. This invention incorporates the actual combustion stability index of the boiler into the calculation of the lower safety limit in real time, enabling the safety protection line to be dynamically adjusted according to changes in coal quality and combustion disturbances. This enhances the adaptability of the limit function to real operating conditions and avoids the risk of overdraft due to the failure to adjust the lower safety limit in time when the combustion stability capacity decreases. Attached Figure Description

[0015] Figure 1 This is a flowchart illustrating the steps of the power grid primary frequency regulation optimization control method for new energy grid connection provided in the embodiments of this application.

[0016] Figure 2 This is a flowchart of data acquisition and preprocessing provided according to an embodiment of this application.

[0017] Figure 3 This is a flowchart for determining the frequency difference direction according to an embodiment of this application.

[0018] Figure 4 This is a flowchart of the output execution and protection logic provided according to the embodiments of this application.

[0019] Figure 5 This is a flowchart of the correction and constraint verification of the lower limit of stable combustion safety load provided according to the embodiments of this application. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification of this application, the singular expressions “a,” “an,” “the,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to and includes any or all possible combinations of one or more of the listed items.

[0022] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0023] As attached Figure 1 The grid primary frequency regulation optimization control method shown for new energy grid integration includes the following steps: S1: Obtain the current load L of the thermal power unit and the grid frequency difference Δf; S2: Based on the current load L and the preset stable combustion safety load lower limit The lower limit D(L) and the upper limit U(L) are determined. The lower limit D(L) is a continuous monotonically non-increasing function with load L as the independent variable, and the upper limit U(L) is independently maintained at a preset maximum upper limit. ; The lower limit D(L) is set in a first transition zone between the normal zone and the low-pressure zone. Within the first transition zone, the lower limit is adjusted from the preset maximum lower limit. With the first slope Linear transition to low-pressure zone preset lower limit - A second transition zone is established between the low-pressure area and the safety protection zone, and the limit value is lowered from - in the second transition zone. With the second slope Linear transition to zero; within the safety protection zone, the limit is lowered to zero; within the normal zone, the limit is lowered to zero. Furthermore, the lowering limit D(L) satisfies the constraint. Where Le is the rated load of the unit, and ΔL is the preset safety margin; S3: Based on the direction of the power grid frequency difference Δf, select a lower limit D(L) or an upper limit U(L) to limit the primary frequency regulation output command, and generate a limited frequency regulation output command; S4: Execute the frequency modulation output command after the amplitude limiting.

[0024] In this embodiment, a boiler with a rated capacity of Le=300MW and a minimum stable combustion load is used. The implementation target is an 80MW subcritical drum boiler thermal power unit.

[0025] In S1, based on DCS power transmitter signals, DEH speed signals, boiler stable combustion test data, and online coal quality analyzer signals, a data acquisition process is constructed that includes load validity verification, frequency difference dead zone processing, data preprocessing, and online correction of the stable combustion safety load lower limit. This process generates the current load L after validity verification, the grid frequency difference Δf after dead zone processing, and the online dynamically corrected stable combustion safety load lower limit. .

[0026] The generator active power is obtained from the power transmitter signal in the DCS system as the current load L.

[0027] The power transmitter converts the generator's active power Pe into a 4-20mA current signal. The DCS analog input card calculates the active power value based on the following formula: ,in, This is the current value output by the power transmitter; In this embodiment, the power is the full-scale power of the power transmitter. =360MW.

[0028] Simultaneously, redundant load signals are obtained from the load reference values ​​in the DEH system. It originates from the load reference value calculated by DEH based on the valve opening and main steam pressure, and can be cross-verified with the DCS power transmitter signal.

[0029] The validity of the DCS power transmitter signal and the DEH load reference value is verified. The verification rules include: whether the signal value falls within the preset load validity range [0, 330MW]; whether the signal has not been updated for three consecutive sampling cycles; and whether the signal change rate exceeds the unit's maximum allowable load change rate.

[0030] When the DCS power transmitter signal passes the validity check, it is preferred to use...

[0031] As the current load L; when the DCS power transmitter signal is abnormal or fails the validity check, it automatically switches to the DEH load reference value. Or turbine regulating stage pressure equivalent load As the current load L.

[0032] Regulating stage pressure equivalent load It is obtained from the static correspondence between the pressure and load of the turbine regulating stage, and can be obtained through conventional turbine thermodynamic characteristic tests.

[0033] The unit's rated load is 300MW, and it is allowed to temporarily exceed 330MW (i.e., 110% of the rated load) during normal operation. A load below 0MW is invalid. The maximum allowable rate of change of the unit's load is usually no more than 15MW / min.

[0034] In this embodiment, the load sampling period is 100ms. The normal load change within three consecutive sampling periods is much less than 5MW, while a power transmitter disconnection or a sudden change in the DEH load reference value often produces a step change of more than 50MW. Therefore, the bad point threshold is set to 50MW. Table 1 shows the configuration of key parameters for data acquisition and preprocessing.

[0035] Table 1

[0036] The grid frequency f is calculated from the rotational speed signal of the DEH system.

[0037] The DEH speed measuring device measures the grid frequency corresponding to the turbine speed with a resolution of 0.001 Hz. The grid frequency f is compared with the rated frequency. By subtracting the frequencies, we obtain the original frequency difference. Where, 𝑓 is the measured power grid frequency; The rated frequency is 50Hz.

[0038] For the original frequency difference Dead zone processing is performed to obtain the power grid frequency difference. In this embodiment, a preset frequency difference exceeding threshold is used. .

[0039] When the absolute value of the frequency difference exceeds 0.5Hz, a frequency regulation action will lose the normal physical meaning of the power grid frequency deviation, the corresponding frequency difference data will be judged as invalid, and the frequency regulation output command will be locked to zero.

[0040] After obtaining the current load L of the thermal power unit and the grid frequency difference Δf, first-order inertial filtering is performed on both to eliminate high-frequency noise.

[0041] The specific expression for first-order inertial filtering is: , ,in, This is the current filter output value; This is the filtered output value from the previous sampling period; This is the current original sample value; The sampling period is specified in this embodiment. ; This is the filtering time constant.

[0042] The filtered load L and frequency difference Δf are subjected to defect elimination and effectiveness assessment.

[0043] When the net change in load L over three consecutive sampling periods exceeds the preset load step threshold When the current load value is determined to be an anomaly, the previous effective load value is used as a replacement; the determination criteria are as follows: ,in, This represents the load value in the kth sampling period; The load value is from 3 sampling periods ago; In this embodiment, a preset load step threshold is used. .

[0044] When the absolute value of the power grid frequency difference Δf exceeds the preset frequency difference over-limit threshold When the frequency difference data is invalid, the load data is deemed invalid. When the load L exceeds the preset effective load range [0, 330MW], the load data is deemed invalid.

[0045] For bad pixels or invalid data, use the previous valid value or set it to unusable and issue an alarm signal.

[0046] The above load signal failure determination is based solely on the quality of the load signal itself and does not depend on whether the DEH command is abnormal. When the power transmitter disconnects or the load reference value suddenly changes, causing the load signal to become invalid, it automatically switches to the redundant source. If the load signal changes by more than 50MW within three consecutive sampling periods and the redundant source is also unavailable, it is set to unavailable and an alarm is issued.

[0047] When the load signal changes by more than 50MW within three consecutive sampling periods and a DEH command anomaly occurs simultaneously, it is set to unavailable and automatically switched to a redundant source.

[0048] In this embodiment, a load signal validity status flag is introduced. When the load signal is valid When the load signal is invalid This flag is used in the S4 abnormal operating condition command locking loop to determine whether to execute the frequency modulation output command to zero.

[0049] Alarm signals are output using a tiered DCS alarm point system: Level 1 alarms indicate invalid load signals or excessive frequency deviations, serving as a notification to operators; Level 2 alarms indicate that the unit's current load is lower than [a certain value]. Furthermore, the down-regulation channel is cut off to indicate the safety risks of deep peak shaving; the level three alarm is triggered when the frequency modulation output command is locked to zero under abnormal operating conditions, to indicate the protective action of the control system.

[0050] All alarms at all levels have an automatic reset function. When the abnormal operating condition is eliminated, the alarm signal will automatically disappear and the control system will return to normal operation.

[0051] Determine from the boiler's minimum stable combustion load test data or the boiler design minimum stable combustion load calibration value provided by the equipment manufacturer. The benchmark value In this embodiment .

[0052] The minimum stable combustion load test of the boiler is carried out after the unit is newly put into operation or after major overhaul. By gradually reducing the load and monitoring combustion stability parameters such as furnace negative pressure, flame detection signal, and main steam pressure fluctuation, the minimum load value at which the boiler can maintain stable combustion is determined.

[0053] Coal quality parameters (based on volatile matter) obtained from an online coal quality analyzer Ash content calorific value Intensity and volatility of flame detection signals Main steam pressure change rate By using a preset correction function The baseline value is corrected in real time. The standard deviation of the flame intensity signal within a 5-second sliding window is used and normalized. The absolute value of the slope of the linear regression is represented by a 100ms sampling and a 1s sliding window.

[0054] The specific expression of the preset correction function is as follows: ;in, The lower limit of the stable combustion safety load is corrected for the kth sampling period but without upper and lower limit clamping; The lower limit of the safe load for stable combustion is 80MW in this embodiment; The received volatile matter content measured by the online coal quality analyzer; In this embodiment, a preset threshold is set for the volatile matter content of coal. =18%; For flame detection signal fluctuation; In this embodiment, a preset threshold is set for the flame intensity fluctuation rate. =15%; The absolute value of the rate of change of main steam pressure; In this embodiment, a preset threshold is set for the main steam pressure change rate. MPa / min; This is an indicator function that takes the value 1 when the condition inside the parentheses is true, and 0 otherwise. , , To correct the coefficient, in this embodiment MW / %, MW / %, MW / (MPa / min), This is an additional positive correction amount when there are abnormalities in ash content or calorific value.

[0055] For ash and heat generation In this embodiment, the correction amount is affected in the following way: when Higher than the preset ash threshold or Below the preset low heat generation threshold At that time, add an additional positive correction amount. ,in .

[0056] In this embodiment, both threshold values ​​mentioned above are empirical values ​​for conventional coal quality stable combustion evaluation.

[0057] For the revised Upper and lower limit clamping protection is specifically expressed as follows: ,in, The upper limit protection value of the lower limit of the stable combustion safety load is taken in this embodiment. =86MW, to ensure the corrected safety protection line Not exceeding 91MW, thus coordinating with the fixed-width transition zone boundary.

[0058] When coal quality parameters return to normal or flame fluctuation rate falls below the threshold, the indicator function is set to 0, and the corresponding correction term is automatically eliminated. It has fallen back to the baseline value.

[0059] Current load L, grid frequency difference Δf, and online dynamically corrected lower limit of safe fuel load for stable operation It forms the input basis for the limit generation layer in S2.

[0060] In S2, the current load L, which has been validated based on the output of S1, and the dynamically corrected lower limit of the safe load for stable combustion are used. and a preset set of limiting parameters. A five-segment load interval division framework with the current load L as the independent variable is constructed, along with a piecewise linear and continuous downward adjustment limit function D(L) and an independent and constant upward adjustment limit function U(L), generating a system that satisfies the fuel stability safety constraints. The directional limit pair [D(L),U(L)].

[0061] The load range is divided based on the dynamically adjusted lower limit of the safe load for stable combustion. The sum of the safety margin ΔL and the preset safety margin ΔL is used as the upper limit B0 of the safety protection zone, i.e., B0 = +ΔL. The upper boundary of the second transition zone B1 = B0 + W2, the upper boundary of the low-pressure zone B2 = B1 + W1, and the lower boundary of the normal zone (i.e., the upper boundary of the first transition zone) B3 = B2 + W3; where W2 is the width of the second transition zone, W1 is the width of the low-pressure zone, and W3 is the width of the first transition zone. In this embodiment, W2 = 6MW, W1 = 4MW, and W3 = 10MW. The boundaries of the five intervals follow... Dynamic translation ensures the safety protection zone remains covered at all times. +ΔL.

[0062] Under the baseline operating conditions of this embodiment, the following is selected: Given a base load of 80MW and a voltage of ΔL=5MW, then B0=85MW, B1=91MW, B2=95MW, and B3=105MW. The safety protection zone is the load range where L<85MW; the second transition zone is 85MW≤L<91MW; the low-voltage zone is 91MW≤L<95MW; the first transition zone is 95MW≤L≤105MW; and the normal zone is L>105MW. The above baseline operating condition boundaries are consistent with the original fixed boundaries.

[0063] The load width of each transition zone is greater than the unit's minimum load regulation dead zone of 3MW to ensure the engineering feasibility of the transition process. The above-mentioned interval widths were obtained through boiler heat storage tests and load reduction disturbance tests. During the tests, the furnace negative pressure, flame intensity fluctuation rate, and main steam pressure change rate were recorded, and the load difference corresponding to the inflection point of combustion stability was taken as the transition zone width.

[0064] Table 2 gives the five load ranges and limit values ​​(baseline operating condition). =80MW, ΔL=5MW).

[0065] Table 2

[0066] Table 2 shows that the load boundary values ​​and the values ​​of D(L) for each interval together define the complete form of the asymmetric limit function. The lower limit D(L) is adjusted from the normal zone... =-5%, narrowing to the low-pressure area after the first transition zone - =-2%, then narrowed from the second transition zone to 0 in the safety protection zone; the upward adjustment limit U(L) remains constant in all intervals. =+5%, which does not narrow as the load decreases.

[0067] The downward adjustment limit D(L) is defined as a piecewise linear continuous function with load L as the independent variable. The expression for each interval is determined by the constraint that the function values ​​are equal at the interval boundaries. Dynamic boundaries B0, B1, B2, and B3 are used to represent it. ,in, In this embodiment, the absolute value of the preset maximum downward limit is used. ; In this embodiment, a preset absolute value for the downward adjustment limit is provided for the low-pressure area. ; As the first slope, in this embodiment ; In this embodiment, the absolute value of the narrowing rate of the second transition region is... = % / MW≈0.3333% / MW.

[0068] The value of D(L) in each zone is a dimensionless ratio expressed as a percentage of the rated load, that is, it represents the percentage of the reduced load limit relative to the rated load.

[0069] First slope The value is based on the transition zone width W3 = 10MW. =3%, calculated using the following formula: =0.3% / MW; The narrowing rate of the second transition zone is determined by the transition zone width W2 = 6MW. =2% is determined, its absolute value It is calculated using the following formula: % / MW≈0.333% / MW.

[0070] D(L) takes the form of a linear function within each interval; at the boundary of adjacent intervals, the function value is forced to be equal. Simultaneously, D(L) monotonically increases as the load L decreases within each of the above intervals, with the increase rates in the first and second transition zones being 0.3% / MW and [missing data]. % / MW, and .

[0071] The upward adjustment limit U(L) is independently maintained at the preset maximum upward adjustment limit. Specifically In this embodiment, we take... = =5%, that is, U(L) = +5%.

[0072] In this embodiment, =5% and speed regulation discrepancy rate =5% corresponds to. The typical speed regulation unevenness range is 4% to 6%. In this embodiment, by setting the maximum upper and lower adjustment limits to 5% of the rated load, the excess part is limited, avoiding excessive frequency regulation actions that could impact boiler safety.

[0073] The upward adjustment limit U(L) remains constant in all load intervals (including the second transition zone and the safety protection zone) and does not narrow with changes in the current load L.

[0074] Limited by the unit type and parameters of this embodiment, the upward adjustment action releases boiler heat storage or increases the combustion rate to increase the load by increasing the opening of the turbine control valve.

[0075] The value of the lower limit function D(L) must satisfy the following combustion safety constraints: Where L is the current load of the unit; D(L) is the percentage of the load that is reduced to the limit corresponding to the current load; Le is the rated load of the unit, and in this embodiment Le=300MW; The lower limit of the safe load for stable combustion; ΔL is the preset safety margin, which is 5MW in this embodiment.

[0076] After performing a frequency regulation operation in the downward direction, the actual load forecast value of the unit is... It must not be lower than the dynamic safety protection line. +ΔL. Under the baseline operating condition, this safety protection limit is 85MW. When After online correction, the safety protection line changes dynamically accordingly, and the lower limit constraint verification should use the corrected version. +ΔL is executed. Within the safety protection zone, the down-channel cutoff is not affected by this constraint.

[0077] Constraint verification is implemented by combining offline traversal verification with online real-time verification.

[0078] During the offline parameter design phase, under the baseline operating conditions With a load capacity of 80MW and a ΔL = 5MW, the entire load range [0, 330MW] is traversed, and 331 verification load points are generated with a step size of 1MW. Calculations are performed for each load point. and with the safety protection line Comparison. In this embodiment, eight typical loads listed in Table 3 are selected for detailed verification calculations.

[0079] Table 3 (Baseline Operating Conditions) =80MW, ΔL=5MW)

[0080] In Table 3, the constraint judgment results for all typical load points are satisfied. The minimum load after reduction is equal to the safety protection line of 85MW (appearing at L=91MW and L=88MW), and is not lower than 85MW. This indicates that the limit parameter design in this embodiment can ensure that the load after reduction is not lower than the safety protection line.

[0081] when After online correction, offline verification should still be performed, but the security protection line should be replaced with the corrected one. +ΔL; If a load point that does not meet the constraints is found, the parameters are adjusted in the following preset priority order: the first priority is to adjust the transition zone width, moving the upper boundary B1 of the second transition zone towards the high load direction; the second priority is to adjust the slope parameter, increasing... or The third priority is The amplitude is adjusted to further reduce the absolute value of the preset lower limit in the low-voltage zone. After parameter adjustment, the constraint verification of S2 is re-executed.

[0082] Adjusting the boundary position of the transition zone has the least impact on the shape of the limit curve and the mildest sacrifice in frequency modulation capability. Adjusting the amplitude directly compresses the down-regulation capability in the low-voltage region, which has the greatest impact on frequency modulation assessment, and therefore is placed last.

[0083] In S3, the grid frequency difference Δf after dead-zone processing is based on the output of S1, the directional limit pair [D(L),U(L)] output of S2, and the primary frequency regulation output command generated by the DEH frequency difference-load conversion function. The system constructs sequential execution logic for frequency direction determination, independent limit selection, saturation limiting calculation, and command rate of change limitation to generate the frequency modulation output command after limiting. .

[0084] The power grid frequency difference direction determination sub-process generates a direction marker based on the sign of the power grid frequency difference Δf.

[0085] When the grid frequency difference Δf is positive and exceeds the dead zone threshold +0.033Hz, the direction indicator is "downward adjustment"; when the grid frequency difference Δf is negative and its absolute value exceeds the dead zone threshold 0.033Hz, the direction indicator is "upward adjustment"; when the absolute value of the grid frequency difference Δf is less than or equal to the dead zone threshold 0.033Hz, the direction indicator is "no action".

[0086] Original primary frequency modulation output command The DEH frequency offset-load conversion function is calculated using the following formula: Where Δf is the power grid frequency difference after dead zone processing; =50Hz; Le=300MW; δ=5%. The physical meaning of this formula is: when the grid frequency difference Δf is positive, A negative value corresponds to a downward adjustment direction; when Δf is negative... If it is a positive value, it corresponds to an upward adjustment direction.

[0087] Select the corresponding limit value independently from the directional limit value pair [D(L),U(L)] based on the directional indicator.

[0088] When adjusting the load direction, the lower limit value D(L) is selected as the lower limit value, and D(L) is multiplied by the rated load Le of the unit to convert it into the lower limit load amount. When adjusting the direction upward, select the upward adjustment limit value U(L) as the upper limit amplitude value, and multiply U(L) by the rated load Le of the unit to convert it into the upward adjustment limit load amount U(L)·Le (positive value).

[0089] In this embodiment, the value of D(L) in each load interval is determined by Table 3 above, and U(L) is always +5% in all load intervals, corresponding to an upward adjustment of the load limit of always +15MW. The logical correspondence between frequency difference direction determination and limit selection is shown in Table 4.

[0090] Table 4

[0091] After completing the limit selection, the primary frequency modulation output command is executed. Perform saturation limiting calculation to generate the frequency modulation output command after limiting. The specific expression for saturation limiting is: ,in, This is the original primary frequency modulation output command; The frequency regulation output command after the current control cycle has passed the saturation limit; D(L) is the percentage of the load that is lowered to the limit (negative value) corresponding to the current load; U(L) is the percentage of the load that is raised to the limit (positive value), in this embodiment U(L)=+5%; Le is the rated load of the unit, in this embodiment Le=300MW.

[0092] The saturation limiting calculation is explained under the following optional load conditions: In the normal zone, the load L=120MW, and the grid frequency difference Δf At +0.08Hz (downward adjustment direction), D(120) = -5%, corresponding to a downward adjustment of the limiting load. =-15MW; Original primary frequency regulation output command =-9.6MW. Since Δf>+0.033Hz and =-9.6MW>-15MW, satisfying the "other" branch condition, therefore =-9.6MW.

[0093] When the load in the second transition zone is L=88MW and the grid frequency difference is Δf=-0.1Hz (upward adjustment direction), D(88)=-1.0%, corresponding to a reduction of the load limit by -3MW; U(88)=+5%, corresponding to an upper limit of +15MW; =+12MW. Because =+12MW<+15MW, satisfying the "other" branch, therefore =+12MW.

[0094] When the load in the safety protection zone is L=83MW and the grid frequency difference is Δf=+0.1Hz (downward adjustment direction), D(83)=0, and the downward adjustment limit load is 0; =-12MW. Since Δf>+0.033Hz and =-12MW<0, triggering the first branch. =0MW, down-adjustment command is disabled. When Δf = -0.1Hz (up-adjustment direction), =+12MW, since +12MW<+15MW, the "other" branch is satisfied. =+12MW, the unit is still performing upward frequency regulation.

[0095] After the saturation limiting operation, the frequency modulation output command after limiting is executed. The generation and update cycle is consistent with the DEH control cycle, which is 100ms in this embodiment.

[0096] right The execution command rate of change is limited to generate the final frequency modulation output command. The specific expression of the instruction rate of change limit is as follows: ,in, This is the frequency modulation output command after saturation limiting for the current control cycle; This is the final frequency modulation output command after the command change rate limit of the previous control cycle; This is the final frequency modulation output command after the command change rate is limited for the current control cycle; To preset the maximum load change rate, in this embodiment... =15MW / min=0.25MW / s, only used for recovery section or steady-state load recovery, frequency regulation transient allows for faster valve operation; To control the cycle, in this embodiment =100ms=0.1s. The maximum allowable instruction change in a single control cycle is =0.025MW.

[0097] In this embodiment, a maximum load change rate is preset. =15MW / min. Under normal operating conditions, the maximum load change rate allowed by the coordinated control system is usually 3% / min to 5% / min; in this embodiment, 5% / min of the rated load is taken, i.e., 15MW / min.

[0098] In S4, the final frequency modulation output command is based on the output of S3 after being limited by the command rate of change. S1 output load signal validity status flag S2 determines the safety protection line The mapping relationship of the valve opening of the DEH side f2(X) function is used to construct the conversion execution path from frequency regulation output command to turbine valve opening increment, low load down-adjustment channel cut-off interlock, abnormal operating condition command locking and command-response data recording execution logic, generate valve opening command acting on turbine valve mechanism and form data record for limit parameter feedback verification.

[0099] The frequency modulation output command after limiting from S3 The output is the f2(X) function on the DEH side. The f2(X) function is located at the front end of the valve opening control loop in the DEH control logic, and its input interface receives a frequency modulation output command in the load dimension. The output is the turbine control valve opening increment Δμ. It should be noted that execution does not change the PID main loop or the main structure of the coordinated control, i.e. It does not enter the load command generation loop of the coordinated control system, nor is it used as the setpoint bias of the PID controller. It only forms the valve opening increment independently through the f2(X) function.

[0100] The f2(X) function is the original load-valve opening feedforward mapping function in the DEH digital electro-hydraulic control system. The improved f2(X) function only... The original linear mapping relationship is converted into the valve opening increment without changing the external interface, calling timing, or connection relationship with the main control loop of function f2(X). S3 has already completed the direction decoupling and limiting, so the limiting logic will not be repeated here.

[0101] The f2(X) function is embedded in the DEH control logic at the reference value of the regulating gate opening in the main coordinated control loop. After generation, before the gate actuator. Gate opening reference value. The load is generated by the coordinated control main loop based on the unit's target load and main steam pressure via a PID controller. This embodiment operates under a 300MW rated load condition. Approximately 85%. The output Δμ of the f2(X) function is... The commands are superimposed at the adder to form the valve opening command acting on the turbine control valve mechanism. .

[0102] valve opening reference value Under steady-state conditions, the values ​​are approximately 85%, 79%, and 63% for 300MW, 120MW, and 88MW, respectively. These values ​​are only used to illustrate the superposition process in this embodiment; the actual values ​​are obtained through real-time calculations by the DEH.

[0103] Within the f2(X) function, the frequency modulation output command after limiting is... Converted to turbine control valve opening increment The conversion formula is: , ,in, This is the increment of the turbine control valve opening; The valve opening-load linear mapping coefficient; This is the frequency regulation output command after amplitude limiting; Le is the rated load of the unit, which is 300MW in this embodiment. The load adjustment amount of the frequency regulation output command is linearly converted into the valve opening increment according to the rated load ratio.

[0104] In this embodiment, the f2(X) function adopts a linear mapping model, and the mapping coefficients are... =0.333% / MW, its value is based on the fact that the static characteristics of the turbine's control valve opening and load are approximately linear near the rated load.

[0105] Increment the turbine control valve opening Superimposed on the turbine control valve opening reference value The above generates a valve opening command that acts on the turbine regulating valve mechanism. The superposition formula is: .

[0106] In an optional embodiment, the second transition zone load L = 88MW, and the grid frequency difference Δf = -0.1Hz (upward adjustment direction). S3 output =+12MW. DEH control cycle =When it arrives in 100ms, =+12MW is written to the f2(X) function input register. Press =0.333% / MW Calculation of valve opening increment =+4%. Reference value for valve opening in the main control circuit under the current load of 88MW. =63%. The result after adding both is... =67%, written to the DEH output register and applied to the regulating valve actuator. After the regulating valve actuator operates, the steam flow rate increases, completing the upward frequency regulation action.

[0107] In another optional embodiment, the load in the safety protection zone L = 83MW, and the grid frequency difference Δf = +0.1Hz (downward adjustment direction). S3 output =0MW. (The rest of the text appears to be incomplete and requires further context.) =0MW is written into the f2(X) function. =0% = Meanwhile, due to the current load L=83MW< =85MW, triggering low-load cutoff interlock, the down-regulation channel was cut off, even if Even if any upstream anomaly results in a non-zero negative value, the cut-off status of the down-adjustment channel can still ensure that the negative value instruction is not sent to the gate actuator.

[0108] In another optional embodiment, the normal zone load L = 120MW, and the grid frequency difference Δf = +0.08Hz (downward adjustment direction). S3 output =-9.6MW. =-3.2%. Under a current load of 120MW. =79%. After superposition =75.8%, the valve opening decreased, the unit load decreased by about 9.6MW to 110.4MW, and the downward frequency regulation action was completed.

[0109] While executing the frequency regulation output command after the amplitude limit is applied, the current load L of the unit and the safety protection line are continuously monitored. The relationship. When When this occurs, an alarm is issued and the downlink channel is automatically disconnected, while the uplink channel remains available. Under baseline operating conditions... =85MW. When After online correction, the safety protection line is dynamically updated, and the interlock is disconnected using the corrected version. +ΔL.

[0110] The down-adjustment channel is defined as the channel that executes the down-adjustment direction frequency modulation output command, that is, when When <0, the output to the input side of the f2(X) function is allowed; the up-adjustment channel is defined as the channel that executes the up-adjustment direction frequency modulation output command, that is, when When the value is greater than 0, the output path to the input side of the function f2(X) is allowed.

[0111] When the current load L of the unit is lower than When the load recovers, a level 2 alarm is issued to indicate the safety risks associated with deep peak shaving. This alarm automatically resets when the load returns to normal. This continues for 3 control cycles.

[0112] In each DEH control cycle =Within 100ms, the current load L and Compare. When L < At that time, set the down-channel enable flag. =0, masks any negative values. The transfer to the function f2(X); as L rises to When the above conditions are met and the duration exceeds 3 control cycles, the channel enable flag will be automatically lowered. =1. In actual implementation, the upward channel does not have load-based disconnection interlocks enabled; the enable flag is... Always 1.

[0113] Introducing a down-channel enable flag and increase the channel enable flag Its definition is as follows: , ,in, ; To keep the load continuously at or above the minimum The duration count is incremented if L(k) ≥ +ΔL, increment by 1 for each control cycle; when L(k) < +ΔL is cleared to zero. When, negative value Blocked; When, negative value Normal transmission. A value of 1 always indicates that the up channel is always available.

[0114] In an alternative embodiment, during the process of the unit slowly reducing load from 88MW to 83MW, when L is at 84.5MW (below) =85MW), the down-regulation channel is cut off; if a positive frequency difference disturbance occurs in the grid frequency difference, even if S3 has already been closed due to the safety protection zone D(L)=0. Setting the channel to zero still provides additional protection; when L rises back to 86MW and is maintained for 3 control cycles, the channel automatically recovers.

[0115] In this embodiment, injection is performed at L=84MW. In the verification of -10MW, negative outputs were masked, and the up-adjustment channel availability remained at 100%.

[0116] While executing the frequency modulation output command after amplitude limiting, the validity status flag of the load signal is continuously monitored. The value of the grid frequency difference Δf. When an invalid load signal is detected or the absolute value of the grid frequency difference Δf exceeds the preset frequency difference over-limit threshold. At that time, the frequency modulation output command after amplitude limiting is set to zero, and an alarm signal is issued. In this embodiment... =0.5Hz.

[0117] When an invalid load signal is detected or the absolute value of the grid frequency difference Δf exceeds the preset frequency difference over-limit threshold, a level one alarm is issued to alert the operators.

[0118] The automatic reset condition is that the load signal is restored to a valid state and the absolute value of the frequency difference falls back to below 0.5Hz.

[0119] In each DEH control cycle An anomaly check is performed every 100ms. The check condition is: =0 or |Δf|>0.5Hz. When the detection conditions are met, Force the value to zero and write it to the input register of function f2(X) to increment the valve opening. =0, regulating valve opening command Keep as Simultaneously, the DCS alarm point is triggered. After the anomaly is cleared, the alarm automatically resets. Restore the output value of S3 to its normal value.

[0120] In an alternative embodiment, if the load signal fails due to a power transmitter disconnection, The command output module detects the change from 1 to 0 within 50ms and will... Set the load signal to zero and issue an alarm; wait for the load signal to recover after redundancy switching. The jump to 1 indicates that the instruction output module will resume operation in the next control cycle. Normal output.

[0121] While executing the limited FM output command, the value of the limited FM output command is recorded. Compared with the actual load response value of the unit The corresponding data is stored in the DCS historical database. The recording frequency is consistent with the DEH control cycle, with one data record recorded per control cycle, including a timestamp. , Current load L, grid frequency difference Δf, and valve opening command There are 6 fields in total. The stored data is used for subsequent feedback verification of the reasonableness of the parameters of the lower limit D(L) and the upper limit U(L).

[0122] When the percentage of records with deviations exceeding ±2MW exceeds 5%, the limit parameters are deemed to require correction; the correction method involves adjusting the transition zone boundary, slope, or... in a preset sequence. The amplitude is adjusted, and the constraint check of S2 is re-executed.

[0123] Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other. In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing primary frequency regulation control of a power grid under new energy grid integration, characterized in that, include: S1: Obtain the current load L of the thermal power unit and the grid frequency difference Δf; S2: Based on the current load L and the preset stable combustion safety load lower limit The lower limit D(L) and the upper limit U(L) are determined. The lower limit D(L) is a continuous monotonically non-increasing function with load L as the independent variable, and the upper limit U(L) is independently maintained at a preset maximum upper limit. ; The lower limit D(L) is set in a first transition zone between the normal zone and the low-pressure zone. Within the first transition zone, the lower limit is adjusted from the preset maximum lower limit. With the first slope Linear transition to low-pressure zone preset lower limit - A second transition zone is established between the low-pressure area and the safety protection zone, and the limit value is lowered from - in the second transition zone. With the second slope Linear transition to zero; within the safety protection zone, the limit is lowered to zero; within the normal zone, the limit is lowered to zero. Furthermore, the lowering limit D(L) satisfies the constraint. Where Le is the rated load of the unit, and ΔL is the preset safety margin; S3: Based on the direction of the power grid frequency difference Δf, select a lower limit D(L) or an upper limit U(L) to limit the primary frequency regulation output command, and generate a limited frequency regulation output command; S4: Execute the frequency modulation output command after the amplitude limiting.

2. The method for optimizing primary frequency regulation of the power grid under new energy grid connection as described in claim 1, characterized in that: S1, obtaining the current load L of the thermal power unit, specifically includes: Acquire the load signal from the DCS power transmitter and the load reference value from the DEH; The validity of the load signal from the DCS power transmitter is verified. When the load signal of the DCS power transmitter passes the validity check, the DCS power transmitter load signal is preferentially used as the current load L; When the load signal of the DCS power transmitter fails the validity check, it automatically switches to the DEH load reference value or the turbine regulating stage pressure equivalent load as the current load L.

3. The method for optimizing primary frequency regulation of the power grid under new energy grid connection according to claim 1, characterized in that: S1, obtaining the power grid frequency difference Δf, specifically includes: Calculation of measured grid frequency f based on DEH system speed signal; The measured power grid frequency f is compared with the rated frequency. The original frequency difference is obtained by subtraction. ; When the original frequency difference When the absolute value is not greater than the preset dead zone threshold, the power grid frequency difference Δf is set to zero; When the original frequency difference When the absolute value is greater than the preset dead zone threshold, the original frequency difference is... The frequency difference Δf of the power grid; When the original frequency difference When the absolute value of the frequency difference exceeds the preset frequency difference threshold, the power grid frequency difference Δf is determined to be invalid.

4. The method for optimizing primary frequency regulation of the power grid under new energy grid connection as described in claim 1, characterized in that: The S1 further includes: Determine the lower limit benchmark value of the safe combustion load based on the boiler's minimum stable combustion load test data or minimum stable combustion load calibration value. ; Based on the received volatile matter obtained from the online coal quality analyzer Flame detection signal fluctuation rate Absolute value of main steam pressure change rate The lower limit benchmark value of the stable combustion safety load is adjusted by a preset correction function. Online dynamic correction is performed, and the correction results are clamped at upper and lower limits to obtain the preset lower limit of stable combustion safety load. ; Specifically, the upper and lower limit clamping is expressed as follows: ,in, The upper limit protection value of the lower limit of the safe load for stable combustion. The lower limit of the stable combustion safety load is corrected for the kth sampling period but without upper and lower limit clamping.

5. The method for optimizing the primary frequency regulation of the power grid under new energy grid connection as described in claim 1, characterized in that: The method for determining the load interval boundary, S2, specifically includes: Preset lower limit of safe combustion load The sum of the safety margin ΔL and the preset safety margin ΔL is used as the upper limit B0 of the safety protection zone, i.e., B0 = +ΔL; The upper boundary of the safety protection zone B0 is sequentially superimposed with the width of the second transition zone W2, the width of the low-pressure zone W1, and the width of the first transition zone W3 to determine the upper boundary of the second transition zone B1, the upper boundary of the low-pressure zone B2, and the lower boundary of the normal zone B3, respectively. The boundary of the load range follows the preset lower limit of the stable combustion safety load. It is dynamically translated through online dynamic correction.

6. The method for optimizing primary frequency regulation of the power grid under new energy grid connection according to claim 1, characterized in that: In step S2, when the downward adjustment limit D(L) does not satisfy the constraint... At that time, the limiting parameters are adjusted sequentially according to preset priority, specifically including: The first priority is to adjust the width of the transition zone, and adjust the upper limit B1 of the second transition zone towards the high load direction; The second priority is to adjust the slope parameter, increasing the second slope. Or the first slope ; The third priority is the preset lowering limit value for the low-pressure area. The amplitude is adjusted to reduce the absolute value of the preset downward limit value of the low-voltage zone; After adjusting the parameters, re-execute the constraints. Verification.

7. The method for optimizing primary frequency regulation of the power grid under new energy grid connection according to claim 1, characterized in that: After generating the limited frequency modulation output command, step S3 further includes: The frequency modulation output command after amplitude limiting is subject to a command change rate limitation. When the deviation between the frequency modulation output command after the amplitude limit and the final frequency modulation output command of the previous control cycle exceeds the preset maximum load change rate With control cycle When multiplying by , the frequency modulation output command is clamped within the allowable range of the rate of change.

8. The method for optimizing primary frequency regulation of the power grid under new energy grid connection according to claim 1, characterized in that: S4, while executing the limited frequency modulation output command, also includes: Monitor the current load L of the thermal power unit and the lower limit of the stable combustion safe load. The relationship between the sum of the preset safety margin ΔL and the safety margin ΔL; When the current load L is lower than When +ΔL, the down-adjustment channel is cut off, the frequency modulation output command output in the negative direction is blocked, and the up-adjustment channel remains available. When the current load L rises to no less than If the +ΔL value is increased and the duration exceeds the preset recovery delay, the down-adjustment channel will be automatically restored.

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