A control method for an electric feed water pump during the unit startup phase

Abstract

The present invention relates to the field of general control technology. Specifically, it relates to a control method for an electric feed water pump during the startup stage of a unit. The steps of this method include: during the startup stage of a grid-connected unit, determine whether only a single steam-driven feed water pump is operating and the outlet valve is open. If not, re-determine whether only a single steam-driven feed water pump is operating and the outlet valve is open. If so, start the electric feed water pump and open the electric feed water pump to a first set degree. Determine whether the steam-driven feed water pump trips. If not, re-determine whether the steam-driven feed water pump trips. If so, open the electric feed water pump to a second set degree and determine whether the feed water volume of the unit meets the first set condition or the second set condition. If so, trigger a boiler MFT and end the process. If not, open the electric feed water pump to a third set degree to make the feed water volume of the unit reach the expected value, complete the control of the electric feed water pump during the startup stage of the unit, and end the process.

Description

Technical Field

[0001] The present invention relates to the technical field of general control, and more particularly, to a control method for an electric feed water pump during the start-up stage of a unit. Background Art

[0002] At present, during the start-up stage of grid-connected units, in order to reduce the power consumption rate of the electric feed water pump, usually only one steam-driven feed water pump is operated, resulting in a weak problem in the unit's feed water operation mode. For example, when one steam-driven feed water pump trips, the electric feed water pump will start automatically. The operator adjusts the scoop tube opening immediately to increase the output of the electric feed water pump, but still cannot instantly meet the minimum boiler water inlet flow rate, resulting in boiler MFT. Based on this, we designed a control method for the electric feed water pump during the start-up stage of the unit to address the above problems. Summary of the Invention

[0003] The purpose of the present invention is to provide a control method for an electric feed water pump during the start-up stage of a unit to solve the above technical problems.

[0004] The embodiments of the present invention are achieved through the following technical solutions:

[0005] A control method for an electric feed water pump during the start-up stage of a unit, the steps of the method include:

[0006] During the start-up stage of a grid-connected unit, determine whether only one steam-driven feed water pump is operating and the outlet valve is open. If not, re-determine whether only one steam-driven feed water pump is operating and the outlet valve is open. If so, start the electric feed water pump and open the electric feed water pump to a first set degree, and enter the next step;

[0007] Determine whether the steam-driven feed water pump trips. If not, re-determine whether the steam-driven feed water pump trips. If so, open the electric feed water pump to a second set degree, and determine whether the feed water volume of the unit meets the first set condition or the second set condition. If so, the boiler (the boiler of the grid-connected unit) MFT, and the process ends; if not, open the electric feed water pump to a third set degree to make the feed water volume of the unit reach the expected value, complete the control of the electric feed water pump during the start-up stage of the unit, and end the process.

[0008] Optionally, when only one steam-driven feed water pump is operating and the outlet valve is open, the specific outlet valve is opened 100%.

[0009] Optionally, when opening the electric feed water pump to a first set degree, specifically, the first set degree is: open the scoop tube of the electric feed water pump to 30% and open the recirculation valve of the electric feed water pump to 100%.

[0010] Optionally, the motor-driven feed water pump is started to a second set level, specifically: the scoop tube of the motor-driven feed water pump is opened to 40%, and the recirculation valve of the motor-driven feed water pump is opened to 50%.

[0011] Optionally, it is determined whether the feed water flow of the unit meets the first set condition or the second set condition. Specifically, the first set condition is: the feed water flow of the unit is less than 280 t / h, and the boiler MFT occurs after a delay of 20 s.

[0012] Optionally, the second set condition is specifically: the feed water flow of the unit is less than 240 t / h, and the boiler MFT occurs after a delay of 3 s.

[0013] Optionally, the motor-driven feed water pump is started to a third set level, specifically: the opening of the scoop tube and the recirculation valve of the motor-driven feed water pump are adjusted.

[0014] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0015] In this embodiment, during the unit startup stage, a turbine-driven feed water pump trip test is carried out. The scoop tube of the motor-driven feed water pump is opened normally in an override manner, and the motor-driven feed water pump automatically participates in the regulation of the feed water flow. The operator only needs to finely adjust the opening of the scoop tube, effectively ensuring the safe operation of the unit and improving the automation level of the control of the motor-driven feed water pump. Brief Description of the Drawings

[0016] Figure 1 It is a schematic flow chart of a control method for a motor-driven feed water pump during the unit startup stage provided by the present invention. Detailed Embodiment

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and illustrated herein can be arranged and designed in various different configurations.

[0018] As Figure 1 shown, the present invention provides one of the embodiments: a control method for a motor-driven feed water pump during the unit startup stage. The steps of the method include:

[0019] During the startup stage of the grid-connected unit, it is determined whether only a single turbine-driven feed water pump is running and the outlet valve is open. If not, it is re-determined whether only a single turbine-driven feed water pump is running and the outlet valve is open. If so, the motor-driven feed water pump is started, and the motor-driven feed water pump is started to a first set level, and the next step is entered;

[0020] Open the motor-driven feed water pump to the first set level to keep the motor-driven feed water pump in rotational hot standby, and open the scoop tube to a certain opening degree, taking into account safety and economy.

[0021] Judge whether the steam-driven feed water pump trips to confirm safety. If not, re-judge whether the steam-driven feed water pump trips. If so, open the motor-driven feed water pump to the second set level, and judge whether the feed water volume of the unit meets the first set condition or the second set condition. If so, trigger the boiler MFT and end the process; if not, open the motor-driven feed water pump to the third set level to make the feed water volume of the unit reach the expected value, complete the control of the motor-driven feed water pump during the unit startup stage, and end the process.

[0022] In this embodiment, a single steam-driven feed water pump is in operation and the outlet valve is open, specifically the outlet valve is opened by 100%.

[0023] In this embodiment, open the motor-driven feed water pump to the first set level. Specifically, the first set level is: open the scoop tube of the motor-driven feed water pump to 30%, and open the recirculation valve of the motor-driven feed water pump to 100%.

[0024] In this embodiment, open the motor-driven feed water pump to the second set level. Specifically, the second set level is: open the scoop tube of the motor-driven feed water pump to 40%, and open the recirculation valve of the motor-driven feed water pump to 50% to ensure that the motor-driven feed water pump increases its output, instantaneously discharges water, and participates in the regulation of the feed water volume.

[0025] In this embodiment, judge whether the feed water volume of the unit meets the first set condition or the second set condition. Specifically, the first set condition is: the feed water volume of the unit is less than 280 t / h, and the boiler MFT is triggered after a delay of 20 s.

[0026] In this embodiment, the second set condition is: the feed water volume of the unit is less than 240 t / h, and the boiler MFT is triggered after a delay of 3 s.

[0027] In this embodiment, open the motor-driven feed water pump to the third set level. Specifically, the third set level is: adjust the opening degree of the scoop tube and the recirculation valve of the motor-driven feed water pump.

[0028] This embodiment is applied to the second-phase units of a certain power plant, and the actual use effect is good: taking the trip test of the steam-driven feed water pump during the startup stage of Unit 4 as an example, after the unit is connected to the grid, it is detected that a single steam-driven feed water pump is in operation and the outlet valve is fully open, and the motor-driven feed water pump is automatically started to maintain rotational hot standby. At this time, manually trip the operating steam-driven feed water pump, the steam-driven feed water pump trips, and the motor-driven feed water pump automatically adjusts the opening degrees of the scoop tube and the recirculation valve to maintain the feed water flow rate, and no boiler MFT due to low feed water flow rate occurs.

[0029] Table 1: Test Data of Turbine-driven Feedwater Pump Tripping during the Startup Phase of Unit 4

[0030]

[0031] As shown in Table 1, when the motor-driven feedwater pump is started by the method described in this embodiment normally, and at the moment when the turbine-driven feedwater pump trips, the scoop tube and recirculation valve of the motor-driven feedwater pump operate normally. The feedwater flow rate drops slightly instantaneously and then immediately returns to normal, indicating that a control method for the motor-driven feedwater pump during the unit startup phase is effective.

[0032] In summary, through the turbine-driven feedwater pump tripping test during the unit startup phase in this embodiment, the scoop tube of the motor-driven feedwater pump overrides and opens normally, and the motor-driven feedwater pump automatically participates in the regulation of the feedwater flow rate. The operator only needs to fine-tune the scoop tube opening, which effectively ensures the safe operation of the unit and improves the automation level of the motor-driven feedwater pump control.

[0033] The above is only the preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A control method for an electric feed water pump during the startup stage of a unit, characterized in that, The steps of the method include: In the startup stage of the grid-connected unit, it is judged whether only a single steam-driven feed water pump is running and the outlet valve is open. If not, it is re-judged whether only a single steam-driven feed water pump is running and the outlet valve is open. If so, the electric feed water pump is started, and the electric feed water pump is opened to a first set degree, and the next step is entered; It is judged whether the steam-driven feed water pump trips. If not, it is re-judged whether the steam-driven feed water pump trips. If so, the electric feed water pump is opened to a second set degree, and it is judged whether the feed water volume of the unit meets the first set condition or the second set condition. If so, the boiler MFT is triggered and the process ends; if not, the electric feed water pump is opened to a third set degree so that the feed water volume of the unit reaches the expected value, the control of the electric feed water pump in the startup stage of the unit is completed, and the process ends; It is judged whether the feed water volume of the unit meets the first set condition or the second set condition. Among them, the first set condition is specifically: the feed water volume of the unit is less than 280 t / h, and the boiler MFT is triggered after a delay of 20 s; Among them, the second set condition is specifically: the feed water volume of the unit is less than 240 t / h, and the boiler MFT is triggered after a delay of 3 s.

2. The method for controlling the electric feedwater pump during the unit startup phase according to claim 1, characterized in that: When a single steam-driven feed water pump is running and the outlet valve is open, the specific outlet valve is opened 100%.

3. The method for controlling an electric feedwater pump during the unit startup phase according to claim 1, characterized in that: The electric feed water pump is opened to a first set degree. Among them, the first set degree is specifically: the scoop tube of the electric feed water pump is opened to 30%, and the recirculation valve of the electric feed water pump is opened to 100%.

4. The method for controlling an electric feedwater pump during the unit startup phase according to claim 1, characterized in that: The electric feed water pump is opened to a second set degree. Among them, the second set degree is specifically: the scoop tube of the electric feed water pump is opened to 40%, and the recirculation valve of the electric feed water pump is opened to 50%.

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