Primary Frequency Regulation Control System of Power Grid Frequency

Abstract

An embodiment of this specification discloses a primary frequency regulation control system for a power grid frequency, which includes a coordinated control system. The coordinated control system includes a first adder, a blocking device, and a first controller. The first adder receives a steam turbine speed signal and calculates a frequency difference between the real-time power grid frequency corresponding to the steam turbine speed signal and the target power grid frequency, so as to output a primary frequency regulation load command. The blocking device receives the primary frequency regulation load command and is used to block the automatic generation control load command when the automatic generation control load command and the primary frequency regulation load command change in the opposite direction. The first controller is connected to the blocking device and is used to perform a first coordinated control on the real-time power grid frequency according to the automatic generation control load command and the primary frequency regulation load command. The embodiment of this specification can improve the response speed of primary frequency regulation and enhance the safety and reliability of the power grid.

Description

Technical Field

[0001] This specification relates to the field of safe operation of steam turbine units, and particularly to a primary frequency regulation control system for power grid frequency. Background Art

[0002] In recent years, with the increase in power grid capacity, the impact of new energy on coal-fired power generation, and the technological innovation of smart grids, the power grid has put forward higher requirements for the power generation quality on the power supply side and the safety guarantee of the power system, including new requirements for the primary frequency regulation performance of coal-fired units.

[0003] As Figure 1 shown, the traditional primary frequency regulation control program has a set of speed-corresponding primary frequency regulation functions in each of the Coordinated Control System (CCS) and the Digital Electro-Hydraulic Control System (DEH). After receiving the steam turbine speed signal, it is input into the corresponding adder ( Figure 1 ② and ⑦ in Figure 1 ① and ⑥ in Figure 1 ③ and ⑧ in Figure 1 ④ in Figure 1 ⑤ in Figure 1 ), calculate the deviation between the speed corresponding to the reference speed and the grid frequency. And according to the speed regulation rate, output a primary frequency regulation command with a correction coefficient of K1 ( ), then superimpose it with the load command corresponding to the unit given load set manually and input it into the adder ( Figure 1 ⑥ in Figure 1 ⑨ in Figure 1 ⑩ in

[0004] The traditional primary frequency regulation control program only has a basically corresponding primary frequency regulation action amount. Although the existing primary frequency regulation program on the power supply side can perform the tasks required by the power grid, in the actual frequency regulation process, due to the rapidity of grid frequency fluctuations, the power supply side regulation often lags behind the actual power grid frequency fluctuations, resulting in poor safety of primary frequency regulation. When reflected in the actual primary frequency regulation compliance test, the primary frequency regulation has no response to small frequency difference disturbances and may be over-regulated for large frequency difference disturbances. Therefore, the safety and reliability of the power grid are reduced. Summary of the Invention

[0005] An embodiment of this specification provides a primary frequency regulation control system for a power grid to solve the problem of low safety and reliability of the existing power grid primary frequency regulation.

[0006] To solve the above technical problems, this specification is implemented as follows:

[0007] In a first aspect, an embodiment of this specification provides a primary frequency regulation control system for a power grid, including a coordinated control system. The coordinated control system includes a first adder, a blocking device, and a first controller.

[0008] The first adder receives a steam turbine speed signal and calculates the frequency difference between the real-time power grid frequency corresponding to the steam turbine speed signal and the target power grid frequency to output a primary frequency regulation load command.

[0009] The blocking device receives the primary frequency regulation load command and is used to block the automatic generation control load command when the automatic generation control load command and the primary frequency regulation load command change in opposite directions.

[0010] The first controller is connected to the blocking device and is used to perform first coordinated control on the real-time power grid frequency according to the automatic generation control load command and the primary frequency regulation load command.

[0011] Optionally, the system further includes:

[0012] A second adder is connected between the blocking device and the first controller and is used to receive the primary frequency regulation load command and the automatic generation control load command and calculate the sum of the first frequency regulation load command and the automatic generation control load command.

[0013] The first controller performs the first coordinated control according to the sum of the first frequency regulation load command and the automatic generation control load command.

[0014] Optionally, the system further includes a frequency difference compensation device and a third adder.

[0015] The frequency difference compensation device is connected to the output end of the first adder and is used to calculate the primary frequency regulation compensation value corresponding to the frequency difference.

[0016] The third adder includes a first input end connected to the output end of the frequency difference compensation device, a second input end connected to the output end of the blocking device, and an output end connected to the input end of the second adder.

[0017] Optionally, the frequency difference compensation device receives the frequency difference value and calculates a primary frequency regulation compensation value corresponding to the frequency difference disturbance after the grid frequency exceeds the primary frequency regulation dead zone according to the frequency difference value.

[0018] Optionally, the first input end is used to receive the primary frequency regulation compensation value, the second input end is used to receive the primary frequency regulation load instruction, and the output end is used to use the sum of the primary frequency regulation compensation value and the primary frequency regulation load instruction as the primary frequency regulation load instruction and output it to the second adder.

[0019] Optionally, the system further includes a digital electro-hydraulic control system, and the digital electro-hydraulic control system includes a second controller.

[0020] The frequency difference compensation device is also connected to the input end of the second controller and is used to output the primary frequency regulation compensation value to the second controller.

[0021] The second controller is connected to the output end of the frequency difference compensation device and is used to perform second coordinated control on the real-time grid frequency according to the primary frequency regulation compensation value.

[0022] Optionally, the second controller performs the second coordinated control according to the primary frequency regulation compensation value and the sum of the first frequency regulation load instruction and the automatic generation control load instruction.

[0023] Optionally, the system further includes a frequency modulation suppression device and a fifth adder.

[0024] The fifth adder is connected between the output end of the second adder and the input end of the first controller.

[0025] The frequency modulation suppression device is connected between the output end of the first adder and the input end of the fifth adder and is used to perform frequency modulation suppression limitation on the real-time grid frequency.

[0026] Optionally, the frequency modulation suppression device calculates the reverse rate of the primary frequency regulation action according to the frequency difference value to perform the frequency modulation suppression limitation.

[0027] Optionally, the first coordinated control is the steam turbine governing valve control of the coordinated control system, and the second coordinated control is the steam turbine governing valve control of the digital electro-hydraulic control system.

[0028] The above at least one technical solution adopted in the embodiments of this specification can achieve the following beneficial effects: By adding a locking device to the traditional primary frequency regulation control, receiving a primary frequency regulation load command obtained from the frequency difference between the real-time grid frequency corresponding to the steam turbine speed signal and the target grid frequency, and locking the automatic generation control load command when the automatic generation control load command and the primary frequency regulation load command change in the opposite direction, ensuring the priority of the primary frequency regulation action and preferentially outputting the primary frequency regulation command. Thereby improving the regulation accuracy of the primary frequency regulation of the grid frequency, enhancing the response speed of the primary frequency regulation, and further enhancing the safety, reliability and power generation quality of the grid. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The drawings described herein are used to provide a further understanding of this specification, and constitute a part of this specification. The illustrative embodiments and descriptions thereof of this specification are used to explain this specification and do not constitute an improper limitation of this specification. In the drawings:

[0030] Figure 1 is a schematic circuit diagram of an existing primary frequency regulation control system for grid frequency.

[0031] Figure 2 is a schematic circuit diagram of the primary frequency regulation control system for grid frequency in the embodiments of this specification. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] To make the purpose, technical solutions and advantages of this specification clearer, the technical solutions of this specification will be clearly and completely described below in conjunction with the specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in this specification without creative efforts shall fall within the scope of protection of this specification.

[0033] The following will describe in detail the technical solutions provided by each embodiment of this specification with reference to the drawings.

[0034] Refer to Figure 2 , Figure 2 is a schematic circuit diagram of the primary frequency regulation control system for grid frequency in the embodiments of this specification.

[0035] Primary frequency regulation refers to an automatic control process in which once the frequency of the power grid deviates from the rated value, the control system of the units in the power grid automatically controls the increase or decrease of the active power of the units, restricts the change of the power grid frequency, and maintains the stability of the power grid frequency.

[0036] As Figure 2 shown, the primary frequency regulation control system for grid frequency includes a coordinated control system 1, and the coordinated control system 1 includes a first adder 12, a locking device 14, and a first controller, that is, a CCS controller 26.

[0037] The first adder 12 receives the steam turbine speed signal and calculates the frequency difference between the real-time grid frequency corresponding to the steam turbine speed signal and the target grid frequency, so as to output a primary frequency modulation load command.

[0038] The real-time grid frequency corresponds to the steam turbine speed and is obtained by conversion through the speed regulation rate. The target grid frequency is obtained by conversion Figure 2 The shown speed reference. That is, the speed deviation obtained by the steam turbine speed signal and the speed reference through the first adder 12 can be converted into the corresponding grid frequency deviation through conversion. The speed deviation is input to the primary frequency modulation function device 20 set in the coordinated control system 1, so that a primary frequency modulation command 22 with a correction coefficient of K1 corresponding to the speed deviation can be obtained.

[0039] The blocking device 14 receives the primary frequency modulation load command 22 and is used to block the automatic generation control (AGC, Automatic Gain Control) load command when the AGC load command and the primary frequency modulation load command 22 change in the opposite direction.

[0040] The AGC load command always exists in the automatic state of the unit, and its change is to increase or decrease on the original basis. The AGC load command is issued by a higher level such as the grid dispatching center and is converted into a unit load given command after reaching the local steam turbine unit. It is the highest level command received by the power plant.

[0041] When the primary frequency modulation command 22 is issued, if the AGC load command changes and the change is in the same direction as the primary frequency modulation load command 22, that is, both increase or both decrease, the blocking device 14 does not block at this time; when the primary frequency modulation load command 22 is issued, if the AGC command changes and the change is in the opposite direction to the primary frequency modulation load command 22, for example, the primary frequency modulation load command increases and the AGC load command decreases, or the primary frequency modulation load command decreases and the AGC load command increases, the blocking device 14 blocks at this time, that is, the original AGC load command basis remains unchanged, the subsequent reverse AGC load command is not issued, and the primary frequency modulation load command 22 is ensured to be issued.

[0042] In this way, it can ensure the correct action of the primary frequency modulation load command 22, the integrated power meets the requirements, the unit load does not change due to the reverse action of the AGC load command, and it is not evaluated by the grid.

[0043] The first controller 26 is connected to the blocking device 14 and is used to perform the first coordinated control on the real-time grid frequency corresponding to the steam turbine speed signal according to the AGC load command and the primary frequency modulation load command 22. Here, the first coordinated control is the steam turbine governor valve control of the coordinated control system.

[0044] Such asFigure 2 As shown in the figure, the primary frequency regulation control system of the power grid frequency further includes a second adder 16. The second adder 16 is connected between the blocking device 14 and the CCS controller 26, and is used to receive the primary frequency regulation load command 22 and the automatic generation control load command, and calculate the sum of the first frequency regulation load command 22 and the automatic generation control load command. The CCS controller then performs the first coordinated control according to the sum of the first frequency regulation load command 22 and the automatic generation control load command.

[0045] If the primary frequency regulation load command 22 is issued and the AGC load command does not change, the second adder 16 superimposes the primary frequency regulation load command 22 on the original AGC load command. If the AGC load command changes and the change is in the same direction as the primary frequency regulation load command 22, and the blocking device 14 does not block the AGC load command, the second adder 16 superimposes the primary frequency regulation load command 22 on the basis of the change of the AGC load command; if the AGC load command changes and the change is in the opposite direction to the primary frequency regulation load command 22, and the blocking device 14 blocks the AGC load command, the second adder 16 superimposes the primary frequency regulation load command 22 on the original AGC load command.

[0046] Once the unit is connected to the grid, the steam turbine speed changes in real time with the power grid frequency. The speed reference is 3000 rpm (50HZ). Frequency regulation is to adjust the power grid frequency to approach the target value of 50HZ. According to the power grid frequency corresponding to the real-time speed signal and the network frequency deviation corresponding to the reference power grid frequency, and combined with the AGC load command, the primary frequency regulation of the power grid frequency is carried out.

[0047] As Figure 2 shown in the figure, the primary frequency regulation control system of the power grid frequency further includes a frequency difference compensation device 28 and a third adder 24. The frequency difference compensation device 28 is connected to the output end of the first adder 12 and is used to calculate the primary frequency regulation compensation value corresponding to the frequency difference. The third adder 24 includes a first input end connected to the output end of the frequency difference compensation device 28, a second input end connected to the output end of the blocking device 14, and an output end connected to the input end of the second adder 16.

[0048] The frequency difference compensation device 28 receives the frequency difference output by the first adder 12 and calculates the primary frequency regulation compensation value corresponding to the frequency difference disturbance of the power grid frequency after exceeding the primary frequency regulation dead zone according to the frequency difference.

[0049] The first input end of the third adder 24 is used to receive the primary frequency regulation compensation value output by the frequency difference compensation device 28. The second input end of the third adder 24 is used to receive the primary frequency regulation load command 22. The output end of the third adder 24 is used to take the sum of the primary frequency regulation compensation value and the primary frequency regulation load command 22 as the primary frequency regulation load command and output it to the second adder 16.

[0050] The primary frequency regulation control system of the power grid frequency also includes a digital electro-hydraulic control system 2, and the digital electro-hydraulic control system 2 includes a second controller, namely the DEH controller 40 shown in the figure. The frequency difference compensation device 28 is also connected to the input end of the DEH controller 40 for outputting a primary frequency regulation compensation value to the DEH controller 40.

[0051] The DEH controller 40 is connected to the output end of the frequency difference compensation device 28 for performing a second coordinated control on the real-time power grid frequency according to the primary frequency regulation compensation value output by the frequency difference compensation device 28. Here, the second coordinated control is the steam turbine control valve control of the digital electro-hydraulic control system.

[0052] When the primary frequency regulation action occurs, by calculating the small frequency difference disturbance within 1 rpm range after the power grid frequency breaks through the dead zone, a dedicated primary frequency regulation compensation value is designed by the frequency difference compensation device 28 and sent to the CCS control system 1, and is superimposed with the load command of the CCS control system 1 to ensure the qualification rate of the primary frequency regulation action of the generating unit under the small frequency difference disturbance less than 3 rpm.

[0053] Meanwhile, a primary frequency regulation compensation value is output to the DEH system 2 to quickly actuate the steam turbine control valve as a feedforward primary frequency regulation compensation command to ensure the quick response of the primary frequency regulation load command.

[0054] The micro-movement of the power generation side rotational speed signal is accurately measured by using a high-precision small-range rotational speed signal, and the power grid side frequency is fitted. And this signal is converted into an adjusted load and directly added to the steam turbine steam admission control valve for load regulation symmetry, and the predicted power grid fluctuation is adjusted quickly and accurately. To achieve the purpose of early response.

[0055] A set of primary frequency regulation function device 32 corresponding to the rotational speed is also set in the digital electro-hydraulic control system 2. After receiving the steam turbine rotational speed signal, it is input to the corresponding adder 30 to calculate the rotational speed deviation corresponding to the steam turbine rotational speed signal and the rotational speed reference to obtain the corresponding power grid frequency deviation. Then, the primary frequency regulation function device 32 outputs a primary frequency regulation load command 34 with a correction coefficient of K1 according to the speed regulation rate, and then is input to the adder 36 for superimposition with the load command corresponding to the unit given load set manually, and then sent to the DEH controller 40, and the DEH controller 40 outputs a control command to the control mode selector 42.

[0056] In addition, the primary frequency regulation function device 32 outputs a primary frequency regulation load command 35 with a correction coefficient of K2 according to the speed regulation rate and inputs it to the adder 38 for superimposition with the control command output by the CCS controller 26, and the output signal of the adder 38 is further input to the control mode selector 42.

[0057] The control mode selector 42 finally outputs to the steam turbine regulating valve according to the control signals sent by the received CCS controller 38 and DEH controller 40, so as to perform corresponding control on the steam turbine valves. For the CCS control mode, a comprehensive valve position command is output; for the DEH control method, a de-electro-hydraulic regulation command is output.

[0058] Optionally, the power grid frequency primary frequency modulation control system further includes a frequency modulation suppression device 28 and a fifth adder 18. The fifth adder 18 is connected between the output end of the second adder 16 and the input end of the CCS controller 26. The frequency modulation suppression device 28 is connected between the output end of the first adder 12 and the input end of the fifth adder 18, and is used to perform frequency modulation suppression limit on the real-time power grid frequency. The frequency modulation suppression device 28 calculates the reverse rate of the primary frequency modulation action according to the power grid frequency difference output by the first adder 12 to perform frequency modulation suppression limit.

[0059] Primary frequency modulation is a regulation program for the single-item network frequency fluctuation on the power grid side. If the frequency callback responds quickly, it will cause secondary interference to the power grid frequency. It is necessary to comprehensively consider the current network frequency and load, and impose a certain rate limit on the callback load amount to prevent the power grid frequency oscillation caused by the rapid callback of the frequency modulation action. In this application, after the existing primary frequency modulation instruction action, a primary frequency modulation action instruction feedforward is added, and at the same time, the primary frequency modulation function is optimized, and a new frequency modulation action reverse rate limit function is designed, which can ensure the correct direction of the primary frequency modulation action, accelerate the regulation rate, and suppress the regulation effect in the non-primary frequency modulation action direction during speed fluctuation.

[0060] It should be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of another identical element in the process, method, commodity or device including the said element.

[0061] The above description is only for the embodiments of this specification and is not used to limit this specification. For those skilled in the art, this specification can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this specification shall be included within the scope of the claims of this specification.

Claims

1. A primary frequency regulation control system for power grid frequency, characterized in that, It includes a coordinated control system, and the coordinated control system includes a first adder, a blocking device, a first controller, a second adder, a frequency modulation suppression device, and a fifth adder. The first adder receives a steam turbine speed signal and calculates the frequency difference between the real-time grid frequency corresponding to the steam turbine speed signal and the target grid frequency to output a primary frequency modulation load command. The blocking device receives the primary frequency modulation load command and is used to block the automatic generation control load command when the automatic generation control load command and the primary frequency modulation load command change in the opposite direction. The first controller is connected to the blocking device and is used to perform first coordinated control on the real-time grid frequency according to the automatic generation control load command and the primary frequency modulation load command. The second adder is connected between the blocking device and the first controller and is used to receive the primary frequency modulation load command and the automatic generation control load command and calculate the sum of the first frequency modulation load command and the automatic generation control load command. The fifth adder is connected between the output end of the second adder and the input end of the first controller. The frequency modulation suppression device is connected between the output end of the first adder and the input end of the fifth adder and is used to perform frequency modulation suppression limitation on the real-time grid frequency. It also includes a frequency difference compensation device and a third adder. The frequency difference compensation device is connected to the output end of the first adder and is used to calculate the primary frequency modulation compensation value corresponding to the frequency difference disturbance after the grid frequency exceeds the primary frequency modulation dead zone according to the frequency difference. The third adder includes a first input end connected to the output end of the frequency difference compensation device, a second input end connected to the output end of the blocking device, and an output end connected to the input end of the second adder.

2. The system according to claim 1, wherein It also includes: The first controller performs the first coordinated control according to the sum of the first frequency modulation load command and the automatic generation control load command.

3. The system according to claim 1, wherein The frequency difference compensation device receives the frequency difference and calculates the primary frequency modulation compensation value corresponding to the frequency difference disturbance after the grid frequency exceeds the primary frequency modulation dead zone according to the frequency difference.

4. The system according to claim 1, wherein The first input end is used to receive the primary frequency modulation compensation value, the second input end is used to receive the primary frequency modulation load command, and the output end is used to use the sum of the primary frequency modulation compensation value and the primary frequency modulation load command as the primary frequency modulation load command and output it to the second adder.

5. The system according to claim 1, wherein It also includes a digital electro-hydraulic control system, and the digital electro-hydraulic control system includes a second controller. The frequency difference compensation device is also connected to the input end of the second controller and is used to output the primary frequency modulation compensation value to the second controller. The second controller is connected to the output end of the frequency difference compensation device and is used to perform second coordinated control on the real-time grid frequency according to the primary frequency modulation compensation value.

6. The system according to claim 5, wherein The second controller performs the second coordinated control according to the primary frequency modulation compensation value and the sum of the first frequency modulation load command and the automatic generation control load command.

7. The system according to claim 1, characterized in that, The frequency modulation suppression device calculates the reverse rate of the primary frequency modulation action according to the frequency difference value to perform the frequency modulation suppression limit.

8. The system according to any one of claims 5 to 6, characterized in that, The first coordinated control is the control of the steam turbine governing valve of the coordinated control system, and the second coordinated control is the control of the steam turbine governing valve of the digital electro-hydraulic control system.

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