Primary frequency modulation logic optimization method for nuclear power unit

Abstract

The invention relates to the technical field of nuclear turbine control systems, and provides a primary frequency modulation logic optimization method for a nuclear power unit in order to solve the problem that difference adjustment parameters, response time, accumulated output and the like of existing primary frequency modulation cannot meet the requirements of a power grid. When the primary frequency modulation rotating speed signal is recovered to a 4RPM dead zone, the maximum frequency modulation signal is still output in a delayed manner for 30 seconds, and the primary frequency modulation power signal is recovered after 30 seconds; and if the negative primary frequency modulation signal appears, the positive frequency modulation signal is immediately recovered to 0. According to the method, during high-load operation, when the unit participates in primary frequency modulation due to power grid frequency fluctuation, the frequency modulation performance requirements of the unit in different load sections can be met under the condition of ensuring stable operation of other nuclear safety related systems.

Description

Technical Field

[0001] The invention relates to the technical field of nuclear power steam turbine control systems, and in particular to a primary frequency modulation logic optimization method for a nuclear power unit. Background Art

[0002] The maximum rated power output of a nuclear power unit in normal operation is 650-689MW (689MW in winter); the minimum output is 80% of the rated output (520MW). The unit should be operated with basic load under normal circumstances. When the system is under special light load conditions such as power grid holidays, the unit output can be reduced to 520MW (but the time limit is 10 days). The unit's primary frequency regulation parameter is ≤6%, and the speed dead zone is ≤±0.1Hz; the limit is 3% of the rated power. When the unit runs above the 80% power platform, a primary frequency regulation signal needs to be put into operation.

[0003] In addition, an analysis was conducted on the situation in which four units participated in the grid's primary frequency regulation three times, resulting in unit power transient events. Under summer conditions, the turbine control system flow request of the four units reached 96% Fp when the power load was 640MW. Combined with historical trends, in order to ensure the safe and stable operation of the units, the logic of DEH (turbine control system) needs to be optimized again. Summary of the invention

[0004] The purpose of the present invention is to provide a primary frequency regulation logic optimization method for a nuclear power unit, which solves the problem that the adjustment parameters, response time, cumulative output, etc. of the primary frequency regulation cannot meet the requirements of the power grid.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for optimizing primary frequency modulation logic for a nuclear power unit comprises the following steps:

[0007] Step 1: Select several turbine speed probe signals, and output the selected value through the selected module for the logic control of the primary frequency modulation. The selected module has a protection setting. When the speed signals have a large deviation between each other or the number of signal failures is ≥ 2, the primary frequency modulation is exited;

[0008] Step 2: Calculate the deviation between the actual speed selected signal and the set speed, and output the speed deviation as the calculation condition for primary frequency modulation;

[0009] Step 3: The output speed deviation enters the frequency modulation function module, and a total of 10 function inflection points are set;

[0010] Step 4: Multiply the rated power percentage output by the turbine flow request. When the flow request is ≥60%, the output is 1. After multiplication, the primary frequency modulation is performed normally. When the flow request is <60%, the output is 0. After multiplication, the primary frequency modulation signal is 0.

[0011] Step 5: Determine the output primary frequency modulation power signal. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, the maximum frequency modulation signal is still output with a delay of 30 seconds. After 30 seconds, the primary frequency modulation power signal is restored. If a positive primary frequency modulation signal appears, the negative frequency modulation signal is immediately restored to 0.

[0012] Step 6: The output primary frequency modulation power signal is judged by the judgment module. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, the maximum frequency modulation signal is still output with a delay of 30 seconds. After 30 seconds, the primary frequency modulation power signal is restored. If a negative primary frequency modulation signal appears, the positive frequency modulation signal is immediately restored to 0.

[0013] Step 7: Determine whether the primary frequency modulation signal is input.

[0014] In step 1, three turbine speed probe signals are selected.

[0015] In step 2, set the speed to 3000 RPM.

[0016] In step 3, a total of 10 function inflection points are set, X is the speed deviation, Y is the percentage of rated full power, and the function settings are as follows:

[0017]

[0018]

[0019] In step 5 and step 6, when the grid frequency difference recovers to within the dead zone of the unit's participation in primary frequency regulation, the unit output is delayed for a period of time to reset the primary frequency regulation action, thereby extending the unit's primary frequency regulation response time and ensuring the primary frequency regulation power contribution.

[0020] Furthermore, the critical value of the primary frequency modulation dead zone is 0.067 Hz (ie, the speed deviation is plus or minus 4 RPM).

[0021] Furthermore, the delay period for resetting the frequency modulation action is 30s.

[0022] Compared with the prior art, the primary frequency regulation logic optimization method for nuclear power units provided by the present invention has the following beneficial effects:

[0023] The present invention can meet the frequency regulation performance requirements of the unit under different load segments while ensuring the stable operation of other nuclear safety-related systems during high load (80%-100% Fp) operation when the grid frequency fluctuates and causes the unit to participate in primary frequency regulation.

[0024] For example, under 80% rated load condition, the load is stable at 535.3MW, the manual simulation speed control deviation is ±5.8r / min, ±7.6r / min, ±9.4r / min, and the speed control deviation is restored to 0r / min after 1 minute each simulation. The test data are as follows:

[0025]

[0026] The 80% load effect is shown in the following table:

[0027]

[0028]

[0029] Under 90% rated load condition, the load is stable at 601.7MW, the manual simulation speed control deviation is ±5.8r / min, ±7.6r / min, ±9.4r / min, and the speed control deviation is restored to 0r / min after 1 minute each simulation. The test data are as follows:

[0030]

[0031]

[0032] The 90% load effect is shown in the following table:

[0033]

[0034] Under 100% rated load condition, the load is stable at 665.29MW, the manual simulation speed control deviation is ±5.8r / min, ±7.6r / min, ±9.4r / min, and the speed control deviation is restored to 0r / min after 1 minute of each simulation. The test data are as follows:

[0035]

[0036]

[0037] The 100% load effect is shown in the following table:

[0038]

[0039]

[0040] The overall effect is shown in the following table:

[0041]

[0042]

[0043] The effects are summarized as follows:

[0044] The frequency modulation response time is 1s.

[0045] The actual stabilization time of a frequency modulation is 53s;

[0046] The actual load change in 15s reaches 86.81% of the theoretical value;

[0047] The actual load change in 30 seconds reaches 99.67% of the theoretical value.

[0048] All four indicators meet the requirements of the "two regulations" of the East China Power Grid.

[0049] According to the test data analysis, under typical working conditions, when the frequency difference is ±0.097Hz, ±0.127Hz, and ±0.157Hz, the unit can meet the normal requirements of primary frequency regulation and has good regulation performance. The primary frequency regulation control loop of Qinshan Second Nuclear Power Plant Unit 1 functions correctly and the parameters are set reasonably, and the unit has the ability to regulate primary frequency regulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the technical description.

[0051] Figure 1 This is a schematic diagram of a frequency modulation curve before optimization;

[0052] Figure 2 A flow chart of a primary frequency modulation logic optimization method for a nuclear power unit provided by the present invention;

[0053] Figure 3 This is a logic diagram of the primary frequency modulation logic optimization method provided by the present invention. DETAILED DESCRIPTION

[0054] The following is further explained in detail through specific implementation methods.

[0055] The frequency regulation limit of the existing 1# and 2# units participating in the primary frequency regulation is ΔP=±19.5MW (the rated power of the unit is calculated as 650MW, 19.5MW is equivalent to 3% frequency regulation limit), the difference parameter is 6%, and the frequency regulation dead zone is ±0.1HZ (±6RPM). Calculated based on the full power of DEH 700MW, the corresponding primary frequency regulation curve is as follows Figure 1 shown.

[0056] The primary frequency modulation switching area is 80-100%. When the load is lower than 80%, if the primary frequency modulation is activated, the primary frequency modulation circuit will be automatically exited.

[0057] The present invention first optimizes the parameters of primary frequency modulation, changes the frequency control dead zone to 50±0.067Hz, and adjusts the modulation difference coefficient δ% and the maximum load limit of the unit.

[0058] Although the unit's primary frequency regulation performance is good under the test condition of a long duration of large frequency difference, the actual frequency fluctuation of the power grid is that except for large frequency differences, the time for the frequency difference to cross ±0.067Hz (the unit's primary frequency regulation dead zone) is usually short (about 2 to 10 seconds). This results in a short primary frequency regulation action time for the unit, poor load response, and difficulty in meeting the power grid assessment requirements.

[0059] In view of the frequency fluctuation characteristics of the power grid with short-term and small frequency differences, the following adaptive modifications are made to the primary frequency regulation related logic in DEH, and the "fast investment and slow return" optimization measures are taken. When the power grid frequency exceeds the dead zone range, there is an immediate ±0.5% output response. After the power grid frequency returns to the dead zone, the unit output still maintains the frequency regulation output delay of 30s to meet the assessment requirements of the power grid.

[0060] In order to meet the requirements of short-term frequency fluctuations in the power grid to reduce and increase loads, the response measures for delayed output recovery of 30S are optimized to meet the requirements of the power grid. By modifying the DEH primary frequency regulation related configuration logic, the load-adding and load-adding frequency regulation instructions and delayed reset functions are realized when the primary frequency regulation is increased or decreased.

[0061] (1) Add the function of locking the primary frequency modulation load instruction when the primary frequency modulation reduces the load, that is, the primary frequency modulation load instruction maintains the minimum value during the primary frequency modulation load reduction action, so as to improve the response capability of the primary frequency modulation under small frequency difference.

[0062] (2) On the basis of the primary frequency regulation load reduction lockout function, a 30s reset function for the primary frequency regulation load reduction is added. That is, when the grid frequency difference recovers to within the dead zone (0.067Hz) of the unit's participation in the primary frequency regulation, the unit output is delayed for 30s to reset the primary frequency regulation action, thereby extending the unit's primary frequency regulation response time and ensuring the primary frequency regulation output contribution.

[0063] (3) Add the function of locking the primary frequency modulation load instruction reduction when the primary frequency modulation adds load, that is, the primary frequency modulation load instruction maintains the maximum value during the primary frequency modulation load adding action, so as to improve the response capability of the primary frequency modulation under small frequency difference.

[0064] (4) On the basis of the primary frequency regulation load lockout reduction function, a primary frequency regulation load delay reset function is added, that is, when the grid frequency difference recovers to within the primary frequency regulation dead zone (0.067Hz) of the unit, the unit output is delayed for a period of time to reset the primary frequency regulation action (for example, 30s), thereby extending the primary frequency regulation response time of the unit and ensuring the primary frequency regulation power contribution.

[0065] Based on the Westinghouse Ovation 3.5.1 operating platform, the present invention takes Qinshan Nuclear Power Unit 1 as an example to provide a method for optimizing primary frequency regulation for nuclear power units, achieving a "zero breakthrough" for nuclear power units in the East China Power Grid. Although other nuclear power units use different steam turbine control system platforms and have different initial control logics, they can all be implemented using this logic optimization method.

[0066] The unit has good primary frequency regulation performance under the test condition of long duration of large frequency difference. However, the actual frequency fluctuation of the power grid is that except for the large frequency difference, the time when the frequency difference crosses ±0.067Hz (the primary frequency regulation dead zone of the unit) is usually short (about 2 to 10s). This results in the short time of the primary frequency regulation action of the unit, poor load response, and difficulty in meeting the assessment requirements of the power grid. In order to meet the assessment requirements of the primary frequency regulation of the power grid, on the basis of the primary frequency regulation test parameters, the primary frequency regulation function of the unit needs to be further improved. The optimization content includes moderately increasing the amplitude of the next frequency regulation response under small frequency difference, the frequency regulation instruction locking reduction function when the primary frequency regulation is loaded, and the delayed reset function of the primary frequency regulation when adding load and reducing load.

[0067] like Figure 2 and Figure 3 As shown, the primary frequency modulation logic optimization method for a nuclear power unit provided by the present invention comprises the following steps:

[0068] Step 1: Select 3 turbine speed probe signals, and output the selected value through the selected module for the logic control of the primary frequency modulation. The selected module has a protection setting. When the speed signals have a large deviation between each other or the number of signal failures is ≥ 2, the primary frequency modulation is exited;

[0069] Step 2: Calculate the deviation between the actual speed signal and the set speed 3000, and output the speed deviation as a frequency modulation calculation.

[0070] Step 3: The output speed deviation enters the frequency modulation function module f(x). The function settings are as shown in the following table. A total of 10 function inflection points are set. X is the speed deviation and Y is the percentage of the rated full power.

[0071] X-coordinate 1 -9.4 Y-coordinate 1 3.65 X-coordinate 2 -7.6 X-coordinate 2 2.75 X-coordinate 3 -5.8 Y-coordinate 3 1.4 X-coordinate 4 -4.02 Y-coordinate 4 0.5 X-coordinate 5 -4 Y-coordinate 5 0 X-coordinate 6 4 Y-coordinate 6 0 X-coordinate 7 4.02 Y-coordinate 7 -0.5 X-coordinate 8 5.8 Y-coordinate 8 -1.2 X-coordinate 9 7.6 Y-coordinate 9 -2.2 X-coordinate 10 9.4 Y-coordinate 10 -3.0 Output Top of Scale 3.65 Output Bottom of Scale -3.0

[0072] Step 4: Multiply the rated power percentage of the output by the turbine flow request. When the flow request is ≥60%, the output is 1, and after multiplication, it participates in the primary frequency modulation normally. When the flow request is <60%, the output is 0, and the primary frequency modulation signal is 0 after multiplication.

[0073] Step 5: By adding a 30s reset function for the primary frequency modulation load reduction delay. The output primary frequency modulation power signal passes through the judgment module. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, it still maintains a 30-second delay to output the maximum frequency modulation signal. After 30 seconds, the primary frequency modulation power signal is restored; if a positive primary frequency modulation signal appears, it is restored immediately.

[0074] Step 6: Add a 30s reset function by adding a primary frequency modulation load reduction delay. The output primary frequency modulation power signal passes through the judgment module. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, it still maintains a 30-second delay to output the maximum frequency modulation signal. After 30 seconds, the primary frequency modulation power signal is restored; if a negative primary frequency modulation signal appears, it is restored immediately.

[0075] Step 7: By adding a judgment module to determine whether the primary frequency modulation is put into use, if the primary frequency modulation is put into use, the actual frequency modulation signal is output; if the primary frequency modulation is not put into use, 0 is output.

[0076] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for optimizing primary frequency modulation logic of a nuclear power unit, characterized in that: The following steps are involved: Step 1: Select several turbine speed probe signals, and output the selected value through the selected module for the logic control of the primary frequency modulation. The selected module has a protection setting. When the speed signals have a large deviation between each other or the number of signal failures is ≥ 2, the primary frequency modulation is exited; Step 2: Calculate the deviation between the actual speed selected signal and the set speed, and output the speed deviation as the calculation condition for primary frequency modulation; Step 3: The output speed deviation enters the frequency modulation function module, and a total of 10 function inflection points are set; Step 4: Multiply the rated power percentage output by the turbine flow request. When the flow request is ≥60%, the output is 1. After multiplication, the primary frequency modulation is performed normally. When the flow request is <60%, the output is 0. After multiplication, the primary frequency modulation signal is 0. Step 5: Determine the output primary frequency modulation power signal. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, the maximum frequency modulation signal is still output with a delay of 30 seconds. After 30 seconds, the primary frequency modulation power signal is restored. If a positive primary frequency modulation signal appears, the negative frequency modulation signal is immediately restored to 0. Step 6: The output primary frequency modulation power signal is judged by the judgment module. When the primary frequency modulation speed signal returns to the dead zone of 4RPM, the maximum frequency modulation signal is still output with a delay of 30 seconds. After 30 seconds, the primary frequency modulation power signal is restored. If a negative primary frequency modulation signal appears, the positive frequency modulation signal is immediately restored to 0. Step 7: Determine whether the primary frequency modulation signal is input.

2. The primary frequency modulation logic optimization method for a nuclear power unit according to claim 1, characterized in that: In step 1, three turbine speed probe signals are selected.

3. The primary frequency modulation logic optimization method for a nuclear power unit according to claim 1, characterized in that: In step 2, set the speed to 3000RPM.

4. The primary frequency modulation logic optimization method for a nuclear power unit according to claim 1, characterized in that: In step 3, a total of 10 function inflection points are set, X is the speed deviation, Y is the percentage of rated full power, and the function settings are as follows:

5. The method for optimizing primary frequency modulation logic for a nuclear power unit according to claim 1, characterized in that: In step 5 and step 6, when the grid frequency difference recovers to within the dead zone of the unit's participation in primary frequency regulation, the unit output is delayed for a period of time to reset the primary frequency regulation action, thereby extending the unit's primary frequency regulation response time and ensuring the primary frequency regulation power contribution.

6. The method for optimizing primary frequency modulation logic for a nuclear power unit according to claim 1, characterized in that: The critical value of the primary frequency modulation dead zone is 0.067Hz.

7. The primary frequency modulation logic optimization method for a nuclear power unit according to claim 1, characterized in that: The delay time for resetting the frequency modulation action is 30s.

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