External cooling water temperature fault-tolerant control method, system and distributed control system

Abstract

The present invention discloses a fault-tolerant control method, system, and distributed control system for external cooling water temperature in the field of external cooling water temperature control technology. The external cooling water system is used to cool a heat source, and the external cooling water system includes a cooling tower equipped with a cooling fan; external cooling water enters the heat source from the cooling tower water collection tank, and the external cooling water cools the heat source and becomes hot water, which then enters the cooling tower water collection tank again after being cooled by the cooling tower equipped with a cooling fan; at least two external cooling water temperature measurement points are set in the external cooling water inlet pipe of each heat source; the method includes: screening the inlet water temperature values ​​detected by each external cooling water temperature measurement point of each heat source, and calculating the average inlet water temperature of each heat source; when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, issuing a cooling fan start-up command. The present invention can effectively control the external cooling water temperature, keep the external cooling water temperature stable, and avoid overheating and damage to the heat source equipment caused by the loss of control of the external cooling water temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of external cooling water temperature control, and in particular relates to an external cooling water temperature fault-tolerant control method, system and distributed control system. Background Art

[0002] Phase-shifting systems (CMs) can rapidly provide reactive power support during UHV transmission system failures, supporting the safe operation of large power grids. CMs are installed at converter stations or substations and typically use tap water for cooling. Mechanically ventilated cooling towers dissipate heat from the CMs' external cooling water, resulting in a small evaporation area. Natural evaporative cooling requires forced phase change heat absorption (achieved by interlocking the cooling fan) to meet heat exchange requirements under all operating conditions. Forced phase change heat absorption interlocks with the cooling fan, increasing the amount of liquid water transformed into vapor, promoting heat absorption and rapidly reducing the external cooling water temperature. (Thermodynamic wet-bulb temperature (adiabatic saturation temperature) refers to the temperature of the system when the air in the system reaches saturation and thermal equilibrium, when the latent heat required for evaporation of a large amount of water in contact with a limited amount of moist air is derived entirely from the sensible heat released by the lowering of the moist air temperature. The liquefaction of moist air promotes heat release from the external cooling water.) This temporarily increases the external cooling water's cooling capacity to meet the CMs' heat exchange requirements.

[0003] The external cooling water temperature control of the condenser generally selects the average inlet water temperature of the condenser as the controlled variable, and the inlet water temperature measurement points are configured with dual redundancy. Taking the main pipe external cooling water system of four condensers as an example, each condenser is configured with two inlet water temperature measurement points, and the average of the two is obtained by averaging the two to obtain the average inlet water temperature of the condenser. When the average inlet water temperature of any condenser is greater than the high set value of the condenser's external cooling water temperature, the cooling fan is started. The above external cooling water temperature control method has two defects: (1) The average inlet water temperature calculation has no fault tolerance. A single thermal resistor failure will cause the average inlet water temperature to be calculated too high; (2) The water temperature-linked fan start logic has no fault tolerance. If the average inlet water temperature of a single unit is too high, the cooling fan will be started interlocked. The above defects make the external cooling water temperature entering the condenser (heat source) unstable and easy to lose control. The temperature of the condenser and other equipment that serve as heat sources fluctuates too much, increasing the risk of safe operation. Summary of the Invention

[0004] To address the deficiencies in the prior art, the present invention provides a fault-tolerant control method, system, and distributed control system for external cooling water temperature, which can effectively control the external cooling water temperature, keep the external cooling water temperature stable, and avoid overheating and damage to heat source equipment caused by runaway external cooling water temperature.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present embodiment provides a fault-tolerant control method for external cooling water temperature, wherein the external cooling water system is used to cool down a number of heat sources, and the external cooling water system includes a cooling tower equipped with a cooling fan; wherein the external cooling water enters each heat source from the cooling tower water collection tank, and the external cooling water cools down the heat source and becomes hot water, and the hot water enters the cooling tower water collection tank again after being cooled by the cooling tower equipped with a cooling fan; at least two external cooling water temperature measuring points are set for the external cooling water inlet pipe of each of the heat sources; the method includes: screening the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source, and calculating the average inlet water temperature of each heat source; when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, a cooling fan start-up instruction is issued.

[0007] Furthermore, the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is compared with the total average value of the inlet water temperature. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the total average value of the inlet water temperature is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point will not be included in the calculation of the inlet water temperature average value of the heat source to which the external cooling water temperature measuring point belongs; wherein, the total average value of the inlet water temperature is the temperature value obtained by averaging the average values ​​of the inlet water temperatures of each heat source.

[0008] Furthermore, the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is screened, and the average inlet water temperature of each heat source is calculated, including: collecting the external cooling water temperature in the cooling tower collection tank and recording it as a first temperature value; comparing the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source with the first temperature value. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the first temperature value is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point does not participate in the calculation of the average inlet water temperature of the heat source to which the external cooling water temperature measuring point belongs.

[0009] Furthermore, the preset value ranges from 5°C to 8°C.

[0010] Furthermore, the high setting value of the external cooling water temperature ranges from 26 to 30°C.

[0011] Furthermore, when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, a cooling fan start-up instruction is issued after a delay setting time.

[0012] In a second aspect, an external cooling water temperature fault-tolerant control system is provided, wherein the external cooling water system is used to cool down several heat sources, and the external cooling water system includes a cooling tower equipped with a cooling fan; wherein, external cooling water enters each heat source from the cooling tower water collection tank, and the external cooling water cools down the heat source and becomes hot water, and the hot water enters the cooling tower water collection tank again after being cooled by the cooling tower equipped with a cooling fan; at least two external cooling water temperature measuring points are set for the external cooling water inlet pipe of each heat source; the system includes: an average temperature calculation module, which is used to screen the inlet water temperature values ​​detected by each external cooling water temperature measuring point of each heat source, and calculate the average inlet water temperature of each heat source; a fan start judgment module, which is used to issue a cooling fan start instruction when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature.

[0013] In a third aspect, a distributed control system is provided, wherein the distributed control system is configured with the external cooling water temperature fault-tolerant control system described in the second aspect.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention screens the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source and calculates the average inlet water temperature of each heat source; when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, a cooling fan start-up instruction is issued; the external cooling water temperature can be effectively controlled to keep the external cooling water temperature stable, thereby avoiding overheating and damage to the heat source equipment caused by the loss of control of the external cooling water temperature;

[0016] (2) The present invention has dual fault-tolerant functions. The failure of a single external cooling water temperature measuring point no longer affects the water temperature control, effectively suppressing the occasional interference caused by the failure of the temperature measuring point, improving the control stability of the external cooling water temperature, and being beneficial to the stabilization of the stator coil, rotor coil, stator core and lubricating oil temperature of the phase regulator, and providing a valuable window period for maintenance and troubleshooting. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the external cooling water temperature fault-tolerant logic (average temperature calculation) in a method for controlling the external cooling water temperature fault-tolerant provided by an embodiment of the present invention;

[0018] Figure 2 This is a schematic diagram of the external cooling water temperature fault-tolerant logic (fan start-up judgment) in an external cooling water temperature fault-tolerant control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] Example 1:

[0021] like Figure 1 、 Figure 2 As shown, a fault-tolerant control method for external cooling water temperature is shown, wherein the external cooling water system is used to cool down several heat sources, and the external cooling water system includes a cooling tower equipped with a cooling fan; wherein the external cooling water enters each heat source from the cooling tower water collection tank, and the external cooling water cools down the heat source and becomes hot water, and the hot water enters the cooling tower water collection tank again after being cooled by the cooling tower equipped with a cooling fan; at least two external cooling water temperature measuring points are set in the external cooling water inlet pipe of each heat source; the method includes: screening the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source, and calculating the average inlet water temperature of each heat source; when the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, issuing a cooling fan start-up instruction.

[0022] This example uses a main-pipe external cooling water system configured for four condensers as an example. In this example, the condensers serve as the heat source, and external cooling water is used to cool them. Each condenser has two inlet water temperature measurement points, for a total of eight temperature measurement points across the four units.

[0023] Under the main pipe operation mode, the water inlet of each phase regulator is taken from the mechanical ventilation cooling tower collection tank. The temperature difference during actual operation will not be too large, which can be used as a reference for the fault tolerance criterion of "average temperature calculation" and "fan start-up judgment".

[0024] This embodiment includes two parts: "average temperature calculation" and "fan start-up judgment".

[0025] "Average temperature calculation" includes: comparing the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source with the total average value of the inlet water temperature. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the total average value of the inlet water temperature is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point will not be included in the calculation of the average value of the inlet water temperature of the heat source to which the external cooling water temperature measuring point belongs; wherein, the total average value of the inlet water temperature is the temperature value obtained by averaging the average values ​​of the inlet water temperatures of each heat source.

[0026] The specific steps are as follows:

[0027] 1) Compare the water inlet temperature of condenser No. 1 with the total average water inlet temperature;

[0028] 2) If the difference between the inlet water temperature of condenser 1 and the average value of the inlet water temperature is less than 5°C, the inlet water temperature of condenser 1 will be included in the calculation of the average value of the inlet water temperature of condenser 1;

[0029] 3) If the difference between the inlet water temperature of condenser No. 1 and the total average value of the inlet water temperature is greater than 5°C, the inlet water temperature of condenser No. 1 will not be included in the calculation of the average value of the inlet water temperature of condenser No. 1;

[0030] 4) Calculate the average water inlet temperature of the No. 2, No. 3 and No. 4 condensers using the above method.

[0031] The steps for "starting the fan judgment" include:

[0032] 1) Calculate the average water inlet temperature of condenser No. 1 based on the two water inlet temperature measurement points of the condenser.

[0033] 2) Compare the average inlet water temperature of condenser 1 with the high set value of the external cold water temperature of the condenser. If the average value is greater than the set value (28℃), the comparison result is set to "1".

[0034] 3) Compare the average inlet water temperature of condensers 2 to 4 with the high set value of the external cold water temperature of the condenser in sequence. If the average value is greater than the set value (28°C), the comparison result is set to "1".

[0035] 4) When the average inlet water temperature of two or more condensers is greater than the high set value of the condenser's external cold water temperature, the output is "Inlet water temperature is higher than the set value".

[0036] 5) Delay 5s before issuing the cooling fan start command.

[0037] In this embodiment, the delay time is set to 5s to eliminate jitter and prevent false operation. The delay time can be adjusted according to operational needs.

[0038] In this embodiment, the range of the difference between the phase shifter inlet water temperature (the inlet water temperature value detected by the external cooling water temperature measuring point) and the first temperature value is adjusted according to the unit operation conditions, and is generally set to 5-8°C. In this embodiment, it is set to 5°C.

[0039] In this embodiment, the range of the high setting value of the external cooling water temperature is adjusted according to the operating conditions of the unit, and is generally set to 26~30°C. In this embodiment, it is set to 28°C.

[0040] A converter station is equipped with four phase-converters, and the external cooling water system operates on a main control. Prior to implementing the method described in this invention, the following issues occurred. On March 4, 2021, the external cooling water inlet temperature measurement point 1 (20PCB01CT101) for phase-converter 2 failed (approximately 6°C above normal). At 10:36 a.m., the average external cooling water inlet temperature for phase-converter 2 exceeded 27°C (the value for the combined fan start), and fan 5 started. The average inlet temperature of the remaining phase-converters was less than 26°C, and fan 5 was shut down at 10:38 a.m. (Combined fan shutdown requires any phase-converter inlet temperature to be less than 26°C, and the already started cooling fans to run at a low frequency of less than 32 Hz for two minutes). At this point, the external cooling water inlet temperature measurement point for phase-converter 2 was still above 31°C. The input of the pulse function block controlling the fan start command failed to flip back to trigger a second time, preventing subsequent fan start and causing the external cooling water temperature to continue to rise. At 11:53 a.m., all five fans were urgently started.

[0041] After adopting the method described in the present invention, the temperature control method has dual fault tolerance functions. The failure of a single external cooling water temperature measuring point no longer affects the water temperature control, effectively suppressing the occasional interference caused by the failure of the temperature measuring point, improving the control stability of the external cooling water temperature, and being beneficial to the stabilization of the stator coil, rotor coil, stator core and lubricating oil temperature, and providing a valuable window period for maintenance and fault elimination.

[0042] Example 2:

[0043] Because the water inlet to each phase regulator is taken from the cooling tower sump, the temperature difference during actual operation is not too large and can be used as a reference for "average temperature calculation". The difference between this embodiment and the first embodiment is that the "average temperature calculation" in this embodiment adopts the following method:

[0044] The "average temperature calculation" includes: collecting the external cooling water temperature in the cooling tower sump and recording it as a first temperature value; comparing the inlet water temperature value detected by each external cooling water temperature measuring point of each heat source with the first temperature value; when the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the first temperature value is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point is not included in the calculation of the average inlet water temperature of the heat source to which the external cooling water temperature measuring point belongs;

[0045] The specific steps are as follows:

[0046] 1) Compare the water inlet temperature of condenser No. 1 with the first temperature value;

[0047] 2) If the difference between the first temperature and the water inlet temperature of the first condenser is less than 5°C, the water inlet temperature of the first condenser will be included in the calculation of the average water inlet temperature of the first condenser;

[0048] 3) If the difference between the first temperature and the water inlet temperature of the first condenser is greater than 5°C, the water inlet temperature of the first condenser will not be included in the calculation of the average water inlet temperature of the first condenser;

[0049] 4) Calculate the average water inlet temperature of the No. 2, No. 3 and No. 4 condensers using the above method.

[0050] Example 3:

[0051] Based on the external cooling water temperature fault-tolerant control method described in Example 1 and Example 2, this embodiment provides an external cooling water temperature fault-tolerant control system, wherein the external cooling water system is used to cool a plurality of heat sources, and the external cooling water system includes a cooling tower equipped with a cooling fan; wherein external cooling water enters each heat source from a cooling tower water collection tank, and the external cooling water cools the heat source and becomes hot water, and the hot water enters the cooling tower water collection tank again after being cooled by the cooling tower equipped with a cooling fan; at least two external cooling water temperature measuring points are set in the external cooling water inlet pipe of each heat source; the system includes:

[0052] The average temperature calculation module is used to screen the inlet water temperature values ​​detected by each external cooling water temperature measurement point of each heat source and calculate the average inlet water temperature of each heat source;

[0053] The fan start judgment module is used to issue a cooling fan start instruction when the average water inlet temperature of at least two heat sources is greater than the high set value of the external cooling water temperature.

[0054] Example 4:

[0055] Based on the external cooling water temperature fault-tolerant control system described in the third embodiment, this embodiment provides a distributed control system, which is configured with the external cooling water temperature fault-tolerant control system described in the third embodiment.

[0056] The external cooling water temperature fault-tolerant control method described in the present invention has been successfully applied in a 4×300MVar phase-shifting unit project built in conjunction with a converter station. It can be directly implemented through configuration in various distributed control systems (DCS).

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A fault-tolerant control method for external cooling water temperature, characterized in that: The external cooling water system is used to cool down several heat sources. The external cooling water system includes a cooling tower equipped with a cooling fan. The external cooling water enters each heat source from the cooling tower water collection tank. The external cooling water cools the heat source and turns into hot water. The hot water is cooled by the cooling tower equipped with a cooling fan and then enters the cooling tower water collection tank again. At least two external cooling water temperature measurement points are set in the external cooling water inlet pipe of each heat source. The method comprises: Screen the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source, and calculate the average inlet water temperature of each heat source; When the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, a cooling fan start command is issued; The method of screening the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source and calculating the average inlet water temperature of each heat source includes: The inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is compared with the total average value of the inlet water temperature. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the total average value of the inlet water temperature is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point will not be included in the calculation of the inlet water temperature average value of the heat source to which the external cooling water temperature measuring point belongs; wherein, the total average value of the inlet water temperature is the temperature value obtained by averaging the average values ​​of the inlet water temperatures of each heat source.

2. A fault-tolerant control method for external cooling water temperature, characterized in that: The external cooling water system is used to cool down several heat sources. The external cooling water system includes a cooling tower equipped with a cooling fan. The external cooling water enters each heat source from the cooling tower water collection tank. The external cooling water cools the heat source and turns into hot water. The hot water is cooled by the cooling tower equipped with a cooling fan and then enters the cooling tower water collection tank again. At least two external cooling water temperature measurement points are set in the external cooling water inlet pipe of each heat source. The method comprises: Screen the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source, and calculate the average inlet water temperature of each heat source; When the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, a cooling fan start command is issued; The method of screening the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source and calculating the average inlet water temperature of each heat source includes: Collect the external cooling water temperature in the cooling tower sump and record it as the first temperature value; The inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is compared with the first temperature value. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the first temperature value is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point is not included in the calculation of the average inlet water temperature of the heat source to which the external cooling water temperature measuring point belongs.

3. The fault-tolerant control method for external cooling water temperature according to claim 1 or 2, characterized in that: The preset value ranges from 5 to 8°C.

4. The fault-tolerant control method for external cooling water temperature according to claim 1 or 2, characterized in that: The maximum set value of the external cooling water temperature ranges from 26 to 30°C.

5. The fault-tolerant control method for external cooling water temperature according to claim 1 or 2, characterized in that: When the average inlet water temperature of at least two heat sources is greater than the high set value of the external cooling water temperature, the cooling fan start command is issued after the set delay time.

6. An external cooling water temperature fault-tolerant control system, characterized in that: The external cooling water system is used to cool down several heat sources. The external cooling water system includes a cooling tower equipped with a cooling fan. The external cooling water enters each heat source from the cooling tower water collection tank. The external cooling water cools the heat source and turns into hot water. The hot water is cooled by the cooling tower equipped with a cooling fan and then enters the cooling tower water collection tank again. At least two external cooling water temperature measurement points are set in the external cooling water inlet pipe of each heat source. The control system comprises: The average temperature calculation module is used to screen the inlet water temperature values ​​detected by each external cooling water temperature measurement point of each heat source and calculate the average inlet water temperature of each heat source; The fan start judgment module is used to issue a cooling fan start instruction when the average water inlet temperature of at least two heat sources is greater than the high set value of the external cooling water temperature; The method of screening the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source and calculating the average inlet water temperature of each heat source includes: The inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is compared with the total average value of the inlet water temperature. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the total average value of the inlet water temperature is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point will not be included in the calculation of the inlet water temperature average value of the heat source to which the external cooling water temperature measuring point belongs; wherein, the total average value of the inlet water temperature is the temperature value obtained by averaging the average values ​​of the inlet water temperatures of each heat source.

7. An external cooling water temperature fault-tolerant control system, characterized in that: The external cooling water system is used to cool down several heat sources. The external cooling water system includes a cooling tower equipped with a cooling fan. The external cooling water enters each heat source from the cooling tower water collection tank. The external cooling water cools the heat source and turns into hot water. The hot water is cooled by the cooling tower equipped with a cooling fan and then enters the cooling tower water collection tank again. At least two external cooling water temperature measurement points are set in the external cooling water inlet pipe of each heat source. The control system comprises: The average temperature calculation module is used to screen the inlet water temperature values ​​detected by each external cooling water temperature measurement point of each heat source and calculate the average inlet water temperature of each heat source; The fan start judgment module is used to issue a cooling fan start instruction when the average water inlet temperature of at least two heat sources is greater than the high set value of the external cooling water temperature; The method of screening the inlet water temperature values ​​detected at each external cooling water temperature measuring point of each heat source and calculating the average inlet water temperature of each heat source includes: Collect the external cooling water temperature in the cooling tower sump and record it as the first temperature value; The inlet water temperature value detected by each external cooling water temperature measuring point of each heat source is compared with the first temperature value. When the difference between the inlet water temperature value detected by a certain external cooling water temperature measuring point and the first temperature value is greater than a preset value, the inlet water temperature value detected by the external cooling water temperature measuring point is not included in the calculation of the average inlet water temperature of the heat source to which the external cooling water temperature measuring point belongs.

8. A distributed control system, characterized in that: The distributed control system is equipped with the external cooling water temperature fault-tolerant control system according to claim 6 or 7.

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