A primary frequency modulation method for a million-level nuclear power steam turbine

Abstract

A kind of million level nuclear power steam turbine primary frequency modulation method, in order to solve the problem that the primary frequency modulation function of existing is not set frequency modulation dead zone, leading to the life of steam turbine generator unit is low, and frequency modulation response speed is slow, the speed of reaching steady state is slow;According to the unit not equal rate and power grid peak shaving requirement design primary frequency modulation function curve;The speed difference value of actual speed and set speed of steam turbine is obtained, find the primary frequency modulation component instruction value corresponding to the difference value on the ordinate axis of primary frequency modulation function curve;When receiving primary frequency modulation input or cut-off condition, according to the current actual load of steam turbine, adjust the current primary frequency modulation component instruction value, obtain the adjusted primary frequency modulation component instruction value;According to the adjusted primary frequency modulation component instruction value, power closed loop instruction value, load limiter instruction value and load regulator instruction value of steam turbine, control steam turbine generator unit regulating valve valve opening degree.This application is used to control steam turbine generator unit regulating valve valve opening degree.

Description

Technical Field

[0001] This invention relates to primary frequency modulation design and belongs to the field of frequency modulation technology. Background Technology

[0002] According to the "Technical Supervision Guidelines for Grid-Connected Steam Turbine Regulation Systems (DL / T338-2010)" and the "Grid Operation Guidelines (DL1040-2007)," all generating units connected to the grid should participate in primary frequency regulation. Therefore, the control system of a 1,000 MW nuclear power turbine needs to have primary frequency regulation functionality. Currently, the primary frequency regulation function lacks a deadband, leading to frequent operation of the turbine generator unit's regulating valves, which affects the turbine generator unit's lifespan. Furthermore, the existing primary frequency regulation function's frequency response speed in the turbine generator unit's closed-loop power mode cannot meet the grid's required frequency regulation response speed, and it cannot enable the turbine generator unit to reach steady state within the specified time. Therefore, when the grid frequency changes, the lack of a deadband in the existing primary frequency regulation function results in a short lifespan for the turbine generator unit, slow frequency regulation response speed, and slow steady-state attainment, failing to meet the power industry standards for primary frequency regulation. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of existing primary frequency regulation functions, such as the lack of a frequency regulation dead zone, which leads to short lifespan of steam turbine generator sets, slow frequency regulation response speed, and slow speed to reach steady state, thus failing to meet the requirements of power industry standards for primary frequency regulation. This invention proposes a primary frequency regulation method for megawatt-class nuclear power steam turbines.

[0004] A method for primary frequency regulation of a megawatt-class nuclear power turbine, the method comprising the following:

[0005] Step 1: Design the primary frequency regulation function curve based on the unit imbalance rate and grid peak shaving requirements. The horizontal axis of the primary frequency regulation function curve is the turbine speed deviation, and the vertical axis is the primary frequency regulation component command value.

[0006] Step 2: Obtain the speed difference between the actual speed and the set speed of the steam turbine, and find the command value of the primary frequency regulation component corresponding to this difference on the vertical axis of the primary frequency regulation function curve;

[0007] Step 3: When the primary frequency regulation is activated or deactivated, adjust the current primary frequency regulation component command value according to the actual load of the turbine to obtain the adjusted primary frequency regulation component command value.

[0008] Step 4: Based on the adjusted primary frequency regulation component command value, the turbine power closed-loop command value, the load limiter command value, and the load regulator command value, control the valve opening of the turbine generator set regulating valve, thereby realizing the control of the turbine generator set regulating valve opening through primary frequency regulation.

[0009] Preferably, in step 3, the current primary frequency regulation component command value is adjusted according to the current actual load of the steam turbine. The specific process is as follows:

[0010] If the current actual load of the steam turbine is equal to or less than the set lower limit threshold, and the current primary frequency regulation component command value is greater than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is less than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment.

[0011] If the current actual load of the steam turbine is equal to or greater than the set upper limit threshold, and the current primary frequency regulation component command value is less than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is greater than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment.

[0012] Preferably, the specific process of step 4 is as follows:

[0013] The power closed-loop command value of the steam turbine is obtained. The power closed-loop command value of the steam turbine and the primary frequency regulation component command value are summed to obtain the summed command value. The minimum value is selected from the summed command value and the value 100. The maximum value is selected from the minimum value and the value 0. The difference between the maximum value and the current actual load of the steam turbine is calculated by PID to generate the valve position control command. The valve position control command value, the load limiter command value and the primary frequency regulation component command value of the previous moment are summed to obtain the load closed-loop command value. At the same time, the load regulator command value and the primary frequency regulation component command value of the previous moment are summed to obtain the regulator loop command value. The minimum value between the load closed-loop command value and the regulator loop command value is selected as the comprehensive valve position command value, which is used to control the valve opening of the steam turbine generator set regulating valve.

[0014] Preferably, in step 1, the following settings are made on the primary frequency modulation function curve: the frequency modulation dead zone range is -0.25Hz to 0.25Hz, the frequency modulation upper and lower limits are -10% of rated power to 10% of rated power, and the primary frequency modulation inequality rate is 4.5%.

[0015] Preferably, in step 3, the conditions for primary frequency regulation to be engaged or disengaged include: manual engagement, manual disengagement, speed fault, engine outlet circuit breaker disconnection, rapid load, and delayed load increase.

[0016] Preferably, the rate at which the current primary frequency modulation component command value is adjusted is 1% / s.

[0017] Preferably, step 3 further includes:

[0018] The adjusted primary frequency modulation component command value is converted into the corresponding load value, which is then displayed on the human-machine interface.

[0019] The beneficial effects of this invention are:

[0020] To meet the grid's requirements for the primary frequency regulation performance of the connected generating units, the original functions and performance indicators of the control system are kept unchanged, and only the primary frequency regulation control strategy is optimized and improved based on the original million-kilowatt steam turbine control logic.

[0021] First, a primary frequency regulation function curve is designed based on the unit's unequal speed and grid peak-shaving requirements. The curve includes a deadband range of -0.25Hz to 0.25Hz (adjustable according to the grid frequency response sensitivity requirements of the turbine generator set); upper and lower frequency regulation limits are set to -10% of rated power to 10% of rated power (adjustable according to the grid peak-shaving requirements of the turbine generator set); and a primary frequency unequal speed is set at 4.5%. Based on the speed difference between the actual turbine speed and the set speed, the corresponding primary frequency regulation component command value is obtained. According to the actual turbine load, the primary frequency regulation component command value is continuously adjusted to control the valve opening of the turbine generator set's regulating valve. Therefore, the purpose of designing the frequency regulation dead zone range in this application is that the primary frequency regulation will only start to operate when the frequency regulation dead zone range is exceeded. Within the primary frequency regulation dead zone range, the primary frequency regulation component command value is zero, so the primary frequency regulation will not operate within the dead zone. Therefore, frequent operation of the turbine generator set regulating valve is avoided. Compared with the existing frequency regulation method, this application improves the service life of the turbine generator set.

[0022] In addition, the primary frequency regulation function of this application, during power closed-loop operation (i.e., when the power closed-loop command value of the steam turbine is obtained), directly superimposes the power closed-loop command value of the steam turbine and the primary frequency regulation component command value onto the final command to achieve rapid response; and when the primary frequency regulation is activated, the rate can be adjusted to 1% / s, which is fast, thereby ensuring that the primary frequency regulation component command value is not over-adjusted after it is generated, and that the steam turbine generator unit can reach steady state within a specified time.

[0023] For example, a technical standard for power grids is: when the grid frequency change exceeds the primary frequency regulation dead zone of the generating unit, the generating unit should fully respond according to the unit response target within 15 seconds; when the grid frequency change exceeds the primary frequency regulation dead zone for 45 seconds, the average deviation between the actual power of the generating unit and the unit response target should be within ±3% of the rated active power of the generating unit, including the addition of a feedforward loop and a frequency regulation command generation rate setting. This application, because it sets a primary frequency regulation function curve, can perform primary frequency regulation when the primary frequency regulation dead zone of the generating unit is exceeded; and the rate of the primary frequency regulation component command value of this application is 1% / s, fully meeting the corresponding requirements within 15 seconds. Therefore, this application fully meets the requirements of the power grid. Attached Figure Description

[0024] Figure 1 A flowchart of a primary frequency regulation method for a million-kilowatt-class nuclear power turbine;

[0025] Figure 2 This is a graph of the primary frequency modulation function;

[0026] Figure 3 A flowchart for generating the adjusted primary frequency modulation component command value;

[0027] Figure 4 A flowchart for generating integrated valve position command values. Detailed Implementation

[0028] 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.

[0029] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0031] Specific implementation method one: Combining Figure 1 and Figure 2 This embodiment describes a primary frequency regulation method for a megawatt-class nuclear power turbine, which includes the following:

[0032] Step 1: Design the primary frequency regulation function curve based on the unit imbalance rate and grid peak shaving requirements. The horizontal axis of the primary frequency regulation function curve is the turbine speed deviation, and the vertical axis is the primary frequency regulation component command value.

[0033] Step 2: Obtain the speed difference between the actual speed and the set speed of the steam turbine, and find the command value of the primary frequency regulation component corresponding to this difference on the vertical axis of the primary frequency regulation function curve;

[0034] Step 3: When the primary frequency regulation is activated or deactivated, adjust the current primary frequency regulation component command value according to the actual load of the turbine to obtain the adjusted primary frequency regulation component command value.

[0035] Step 4: Based on the adjusted primary frequency regulation component command value, the turbine power closed-loop command value, the load limiter command value, and the load regulator command value, control the valve opening of the turbine generator set regulating valve, thereby realizing the control of the turbine generator set regulating valve opening through primary frequency regulation.

[0036] In this embodiment, primary frequency regulation is effective in all three load control modes: load regulator, load limiter, and load closed loop.

[0037] The advantage of primary frequency regulation is that it can adjust the turbine output according to the local power grid requirements to adapt to the real-time power demand of the power grid.

[0038] Specific Implementation Method Two: Combining Figure 3 This embodiment further defines the primary frequency regulation method for a megawatt-class nuclear power turbine described in Specific Embodiment 1. In this embodiment, in step 3, the current primary frequency regulation component command value is adjusted according to the actual load of the turbine. The specific process is as follows:

[0039] If the current actual load of the steam turbine is equal to or less than the set lower limit threshold, and the current primary frequency regulation component command value is greater than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is less than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment.

[0040] If the current actual load of the steam turbine is equal to or greater than the set upper limit threshold, and the current primary frequency regulation component command value is less than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is greater than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment.

[0041] Figure 3 In the diagram, F(x) represents the command value of the primary frequency modulation component corresponding to the difference found on the ordinate axis of the primary frequency modulation function curve. The relationship between the horizontal and vertical axes of the primary frequency modulation function curve is as follows:

[0042]

[0043]

[0044] Figure 3 In this context, LIMIT indicates that the switching rate during a single frequency modulation switch is 1% / s, ensuring that the switch is completed within 10 seconds (frequency modulation complete). The lower threshold can be 373.71 MW (30% of rated load), and the upper threshold can be 1245.7 MW (100% of rated load).

[0045] If the current actual load of the steam turbine is equal to or less than the set lower threshold, it means that the actual load is already very low. If the primary frequency control component command is less than zero at this time, in order to prevent the primary frequency control component command value from further reducing the load, the primary frequency control component command value is kept at the command value of the previous moment. Similarly, if the current actual load of the steam turbine is equal to or greater than the set upper threshold, it means that the actual load is already very high. If the primary frequency control component command value is greater than zero at this time, in order to prevent the primary frequency control component command value from further increasing the load, the primary frequency control component command value is kept at the command value of the previous moment.

[0046] Figure 3 In this context, K represents the primary frequency modulation command unit conversion factor, which converts the primary frequency modulation component command value, which is in percentage (%), into a value in MW. If the normal rated power is 1245.7MW, the corresponding command value should be 100%. Using 1245.7 / 100 = 12.457 as the conversion factor, the conversion factor is 12.457.

[0047] Specific implementation method three: Combining Figure 4 This embodiment further defines the primary frequency regulation method for a megawatt-class nuclear power turbine described in specific embodiment one or two. In this embodiment, the specific process of step 4 is as follows:

[0048] The power closed-loop command value of the steam turbine is obtained. The power closed-loop command value of the steam turbine and the primary frequency regulation component command value are summed to obtain the summed command value. The minimum value is selected from the summed command value and the value 100. The maximum value is selected from the minimum value and the value 0. The difference between the maximum value and the current actual load of the steam turbine is calculated by PID to generate the valve position control command. The valve position control command value, the load limiter command value and the primary frequency regulation component command value of the previous moment are summed to obtain the load closed-loop command value. At the same time, the load regulator command value and the primary frequency regulation component command value of the previous moment are summed to obtain the regulator loop command value. The minimum value between the load closed-loop command value and the regulator loop command value is selected as the comprehensive valve position command value, which is used to control the valve opening of the steam turbine generator set regulating valve.

[0049] Figure 4 In this context, the ALR command value represents the power closed-loop command value of the steam turbine.

[0050] from Figure 4 It can be seen that when the primary frequency regulation is activated, the valve position control command consists of the sum of the primary frequency regulation command value and the ALR command value. The purpose is to avoid the closed loop from adjusting in the opposite direction when the primary frequency regulation is activated in the power closed-loop control mode.

[0051] The minimum value is selected from the summed instruction value and the value 100. The value 100 is set to prevent the total instruction value after summing from exceeding 100, which would pose a risk of overpowering the nuclear reactor.

[0052] The existing steam turbine control system is designed with three power control loops (load regulator control, load limiter control, and load closed-loop control). Among them, the load regulator control and load limiter control are open-loop control, and the valve control command values ​​are manually given by the operator without the need for power feedback to participate in the logical operation. Therefore, the load limiter command value and the load regulator command value are set values. The power closed-loop control requires power feedback to participate in the logical operation to generate the valve control command value. Therefore, the power closed-loop command value of the steam turbine needs to be collected in real time.

[0053] Specific Implementation Method Four: This implementation method further defines the primary frequency regulation method for a million-kilowatt-class nuclear power turbine described in Specific Implementation Method One. In this implementation method, in step 1, the primary frequency regulation function curve is set with the following settings: frequency regulation dead zone range of -0.25Hz to 0.25Hz, frequency regulation upper and lower limit values ​​of -10% rated power to 10% rated power, and primary frequency regulation inequality rate of 4.5%.

[0054] In this embodiment, Figure 1 The designed frequency modulation function curve can reflect frequency modulation inequality, frequency modulation dead zone, and frequency modulation amplitude.

[0055] Specific Implementation Method 5: This implementation method further defines the primary frequency regulation method for a million-kilowatt nuclear power turbine described in Specific Implementation Method 1. In this implementation method, the conditions for primary frequency regulation to be engaged or disengaged in step 3 include: manual engagement, manual disengagement, speed fault, engine outlet circuit breaker disconnection, rapid load increase, and delayed load increase.

[0056] Figure 3 The text shows the conditions for frequency modulation activation or deactivation.

[0057] Specific Implementation Method Six: This implementation method further defines the primary frequency regulation method for a million-kilowatt nuclear power turbine described in Specific Implementation Method One. In this implementation method, the rate at which the current primary frequency regulation component command value is adjusted is 1% / s.

[0058] Figure 3 The frequency modulation rate is shown as 1% / s.

[0059] Specific Implementation Method Seven: This implementation method further defines the primary frequency regulation method for a megawatt-class nuclear power turbine described in Specific Implementation Method One. In this implementation method, step 3 further includes:

[0060] The adjusted primary frequency modulation component command value is converted into the corresponding load value, which is then displayed on the human-machine interface.

[0061] In this embodiment, a primary frequency regulation command unit conversion coefficient K is designed, and the MMI human-machine interface can display the primary frequency regulation command value (unit: %) as the corresponding load value (unit: MW).

[0062] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for primary frequency regulation of a megawatt-class nuclear power turbine, characterized in that, The method includes the following: Step 1: Design the primary frequency regulation function curve based on the unit imbalance rate and grid peak shaving requirements. The horizontal axis of the primary frequency regulation function curve is the turbine speed deviation, and the vertical axis is the primary frequency regulation component command value. Step 2: Obtain the speed difference between the actual speed and the set speed of the steam turbine, and find the command value of the primary frequency regulation component corresponding to this difference on the vertical axis of the primary frequency regulation function curve; Step 3: When the primary frequency regulation is activated or deactivated, adjust the current primary frequency regulation component command value according to the actual load of the turbine to obtain the adjusted primary frequency regulation component command value. Step 4: Based on the adjusted primary frequency regulation component command value, the turbine power closed-loop command value, the load limiter command value, and the load regulator command value, control the valve opening of the turbine generator set regulating valve, thereby realizing the control of the turbine generator set regulating valve opening through primary frequency regulation. In step 3, the current primary frequency regulation component command value is adjusted according to the actual load of the steam turbine. The specific process is as follows: If the current actual load of the steam turbine is equal to or less than the set lower limit threshold, and the current primary frequency regulation component command value is greater than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is less than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment. If the current actual load of the steam turbine is equal to or greater than the set upper limit threshold, and the current primary frequency regulation component command value is less than or equal to zero, then the steam turbine frequency is regulated according to the current primary frequency regulation component command value. If the current primary frequency regulation component command value is greater than zero, then the current primary frequency regulation component command value is adjusted to the primary frequency regulation component command value of the previous moment.

2. The method for primary frequency regulation of a megawatt-class nuclear power turbine according to claim 1, characterized in that, The specific process of step 4 is as follows: The power closed-loop command value of the steam turbine is obtained. The power closed-loop command value of the steam turbine and the primary frequency regulation component command value are summed to obtain the summed command value. The minimum value is selected from the summed command value and the value 100. The maximum value is selected from the minimum value and the value 0. The difference between the maximum value and the current actual load of the steam turbine is calculated by PID to generate the valve position control command. The valve position control command value, the load limiter command value and the primary frequency regulation component command value of the previous moment are summed to obtain the load closed-loop command value. At the same time, the load regulator command value and the primary frequency regulation component command value of the previous moment are summed to obtain the regulator loop command value. The minimum value between the load closed-loop command value and the regulator loop command value is selected as the comprehensive valve position command value, which is used to control the valve opening of the steam turbine generator set regulating valve.

3. The method for primary frequency regulation of a megawatt-class nuclear power turbine according to claim 1, characterized in that, In step 1, the following settings are made on the primary frequency modulation function curve: frequency modulation dead zone range is -0.25Hz to 0.25Hz, frequency modulation upper and lower limits are -10% of rated power to 10% of rated power, and primary frequency modulation inequality is 4.5%.

4. The primary frequency regulation method for a megawatt-class nuclear power turbine according to claim 1, characterized in that, In step 3, the conditions for frequency regulation to be put into or cut off include: manual initiation, manual cut-off, speed fault, engine outlet circuit breaker opening, rapid load, and delayed load increase.

5. The primary frequency regulation method for a megawatt-class nuclear power turbine according to claim 1, characterized in that, The rate at which the current primary frequency modulation component command value is adjusted is 1% / s.

6. The primary frequency regulation method for a megawatt-class nuclear power turbine according to claim 1, characterized in that, Step 3 also includes: The adjusted primary frequency modulation component command value is converted into the corresponding load value, which is then displayed on the human-machine interface.

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