A method for improving extraction steam heating and primary frequency regulation capabilities under deep peak shaving conditions

Abstract

This invention relates to a method for enhancing the extraction steam heating and primary frequency regulation capabilities under deep peak shaving conditions. This method utilizes a supplementary steam valve to enhance the extraction steam heating capacity and rapidly responds to primary frequency regulation through the short-term action of the supplementary steam valve, thereby improving the primary frequency regulation performance of the unit under low load conditions. Compared with existing technologies, this invention has the advantages of meeting the heating requirements of extraction steam heating units across the entire load range and effectively solving the shortcomings in heating and frequency regulation capabilities of units under deep peak shaving conditions.

Description

Technical Field

[0001] This invention relates to the field of thermal power generating unit heating technology, and in particular to a method for improving steam extraction heating and primary frequency regulation capabilities under deep peak shaving conditions. Background Technology

[0002] Under the dual carbon targets, my country's renewable energy development has entered an accelerated stage. In order to improve the power system's peak shaving and new energy absorption capacity, thermal power units must undertake the task of grid peak shaving, which increases the requirements for the flexible operation of the units. The deep peak shaving operation of thermal power units at low loads is also gradually becoming the norm.

[0003] For thermal power units with extraction steam heating needs, the impact on heating supply is significant during deep peak shaving (30% or below rated load). Units typically select #1 extraction steam or cold reheat as the high-pressure extraction steam source for external heating. At low loads, the unit's main operating parameters drop sharply. Low-parameter turbine intake steam leads to a decrease in extraction steam source parameters, inevitably reducing the unit's heating capacity. High-temperature, high-pressure steam heating becomes unsustainable. Under deep peak shaving operation, the unit often struggles to meet the needs of heat users, exhibiting insufficient heating capacity, stability, and reliability.

[0004] Furthermore, under deep peak-shaving conditions, as the load decreases, the unit's heat storage capacity declines rapidly, and its primary frequency regulation capability also shows a significant downward trend. To improve the unit's frequency regulation performance under low-load conditions, it is usually necessary to increase the throttling degree of the turbine's high-voltage control valve, but this sacrifices the unit's operating economy and also has an adverse impact on the safe and stable operation of the unit under deep peak-shaving conditions. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art and provide a method for improving the steam extraction heating and primary frequency regulation capabilities under deep peak shaving conditions.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] According to one aspect of the present invention, a method for improving the extraction steam heating and primary frequency regulation capabilities under deep peak shaving conditions is provided. The method improves the extraction steam heating capability by using a supplementary steam valve for heating and quickly responds to primary frequency regulation through short-time action of the supplementary steam valve, thereby improving the primary frequency regulation performance of the unit under low load conditions.

[0008] As a preferred technical solution, the method specifically includes:

[0009] (1) When the extraction steam heating unit is under low load conditions, the original extraction steam source parameters decrease. With the make-up steam valve closed, the extraction steam port of the make-up steam valve is selected as the extraction steam source. The steam is extracted from the high-pressure cylinder through the pipeline after the steam turbine make-up steam valve. The steam source is delivered to the heat user after the high-pressure cylinder is de-cooled and depressurized.

[0010] (2) If the unit load is further reduced and a higher-parameter heating steam source is required, the make-up steam valve is opened and the make-up steam valve is used to directly supply heat. The steam is extracted from the main steam pipeline and supplied through the make-up steam valve, and then de-temperatured and depressurized before reaching the heat user.

[0011] As a preferred technical solution, a primary frequency regulation on / off function is set up when the steam injection valve is turned on for heating.

[0012] As a preferred technical solution, the setting of the frequency modulation switching function specifically includes:

[0013] When the frequency regulation function of the steam replenishment valve is not in use, the opening degree of the steam replenishment valve is manually set according to the heating demand; after the frequency regulation function of the steam replenishment valve is in use, if the frequency regulation is allowed according to the heating status, the opening degree of the steam replenishment valve is increased or decreased rapidly in a short time to respond to the primary frequency regulation.

[0014] As a preferred technical solution, the method of responding to primary frequency regulation by rapidly increasing or decreasing the opening of the steam replenishment valve in a short time specifically includes the following steps:

[0015] Step 1: When the unit has frequency regulation requirements, according to the response characteristics of the unit load to the change in heat supply, the primary frequency regulation command is converted into the change in steam extraction, and the corresponding change in steam extraction requirement is determined when the primary frequency regulation action is taken.

[0016] Step 2: Based on the valve flow characteristics of the steam replenishment valve and the direction of the primary frequency regulation action, determine the corresponding valve position opening change.

[0017] Step 3: Quickly change the valve position response and adjust the frequency once based on the current opening degree of the steam replenishment valve.

[0018] As a preferred technical solution, the step 1 of converting the primary frequency regulation command into the steam extraction change specifically involves converting the primary frequency regulation command into the steam extraction change using the F(X) function.

[0019] As a preferred technical solution, determining the corresponding valve position opening change in step 2 specifically involves:

[0020] By converting valve flow rate to valve position change, the corresponding change in valve opening degree is determined.

[0021] As a preferred technical solution, when the frequency regulation function of the make-up steam valve is put into use, a limit is set on the high and low of the change of the opening of the make-up steam valve to avoid the impact of the steam turbine shaft system on the make-up steam valve opening being too large.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. This invention utilizes a steam injection valve for heating to solve the problems of low extraction steam source parameters and insufficient heating capacity of the unit under low load conditions, thus meeting the heating requirements of the extraction steam heating unit across the entire load range.

[0024] 2. Furthermore, by using the short-term action of the steam injection valve to quickly respond to the primary frequency regulation, the primary frequency regulation performance of the unit under low load conditions can be improved, which can effectively solve the problem of insufficient heating and frequency regulation capabilities of the unit under deep peak shaving conditions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the heating process with the steam replenishment valve closed according to the present invention;

[0026] Figure 2 This is a schematic diagram of the heating process when the steam replenishment valve of the present invention is open;

[0027] Figure 3 This is a flowchart of the present invention, showing the rapid response of frequency regulation through a short-time action of the steam injection valve. 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, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0029] This invention discloses a method for comprehensively improving the extraction steam heating and primary frequency regulation capabilities of thermal power units under deep peak shaving conditions. It utilizes a supplementary steam valve for heating to address issues such as low extraction steam source parameters and insufficient heating capacity under low load conditions, meeting the heating requirements of extraction steam heating units across the entire load range. Furthermore, by using the supplementary steam valve for short-term rapid response to primary frequency regulation, it enhances the primary frequency regulation performance of the unit under low load conditions, effectively solving the problem of insufficient heating and frequency regulation capabilities under deep peak shaving conditions.

[0030] Under low-load conditions, the parameters of the original extraction steam source decrease in extraction steam units. Therefore, extraction steam is used from the pipeline after the turbine's make-up steam valve to the high-pressure cylinder for heating, thus increasing the heating capacity. When the unit is at low load, with the make-up steam valve closed, extraction steam is drawn from the turbine's high-pressure cylinder, increasing the extraction parameters to achieve high-pressure heating. If the unit load further decreases or a heating steam source with higher parameters is required, the make-up steam valve is opened, and the steam source is directly supplied from the main steam pipeline through the make-up steam valve.

[0031] Under low-load, deep-adjustment conditions, opening the make-up steam valve results in steam flowing from the main steam pipeline through the make-up steam valve for heating. A small amount of steam will also enter the high-pressure cylinder from the make-up steam valve. Using the make-up steam valve for direct heating is equivalent to using fresh boiler steam for heating, resulting in the highest steam source parameter level and maximizing the extraction steam parameters and extraction steam heating capacity.

[0032] In the steam-injection valve heating mode, a primary frequency regulation on / off function is set. When the steam-injection valve frequency regulation function is not activated, the steam-injection valve opening is manually set according to the heating demand. After the steam-injection valve frequency regulation function is activated, if the frequency regulation is allowed based on the heating status, the steam-injection valve opening is briefly and rapidly increased or decreased to respond to the primary frequency regulation.

[0033] When the unit has frequency regulation requirements, the frequency regulation command is converted into a change in steam extraction based on the response characteristics of the unit load to changes in heat supply, thus obtaining the corresponding change in steam extraction demand when the frequency regulation is activated. Then, based on the valve flow characteristics of the make-up steam valve, the corresponding valve position change is determined through valve flow-valve position change conversion processing. The valve position is then quickly changed based on the current opening degree of the make-up steam valve to respond to the primary frequency regulation.

[0034] When the frequency regulation function is put into use, the upper and lower limits of the steam injection valve opening are set to avoid the impact of excessive steam injection valve opening on the turbine shaft system and ensure the safe operation of the unit. Specific Implementation

[0036] The method of this invention can be applied to thermal power generating units equipped with steam turbine make-up valves, provided that the material of the corresponding extraction steam pipe meets the heating requirements.

[0037] Taking a 1000MW ultra-supercritical coal-fired power generating unit as an example, the turbine is an ultra-supercritical, single-shaft, four-cylinder, four-exhaust, dual-backpressure, eight-stage regenerative extraction, reaction condensing turbine designed and manufactured by Shanghai Automotive Industry Corporation (SAIC) using Siemens technology. Before deep peak shaving, based on heating demand, cold reheat extraction steam is selected as the steam source. After desuperheating and pressure reduction at the desuperheating and pressure-reducing station, high-pressure or medium-pressure steam is supplied externally. Primary extraction steam serves as a backup steam source. During low load, cold reheat is switched to primary extraction for heating. Under deep peak shaving conditions, the steam source parameters decrease, and cold reheat or primary extraction steam cannot meet the heating requirements.

[0038] like Figure 1 As shown, under low-load conditions, the original steam source parameters at the extraction steam port of the extraction steam unit decrease. Therefore, extraction steam is used from the pipeline after the turbine's make-up steam valve to the high-pressure cylinder for heating, thereby increasing the heating capacity. When the unit is under low load and the make-up steam valve is closed, the extraction steam port of the make-up steam valve is selected as the extraction steam source. Extracted steam from the high-pressure cylinder is led out through the pipeline after the turbine's make-up steam valve to the high-pressure cylinder. The steam source is then depressurized and de-cooled from the high-pressure cylinder before reaching the heat users.

[0039] like Figure 2As shown, when the unit load further decreases, the make-up steam valve is opened, and direct heating is achieved through the make-up steam valve. Extracted steam is supplied from the main steam pipeline via the make-up steam valve, and after desuperheating and pressure reduction, it reaches the heat users. This improves the heating steam parameters and heat output. The corresponding steam flow direction is from the main steam pipeline through the make-up steam valve for heating, with a small amount of steam also entering the high-pressure cylinder from the make-up steam valve. Using the make-up steam valve for direct heating is equivalent to using fresh boiler steam for heating, resulting in the highest steam source parameter level and maximizing the extraction steam parameters and heat output.

[0040] like Figure 3 As shown, under the heating mode of the supplementary steam valve, the primary frequency regulation function is activated. When the primary frequency regulation is activated, according to the response characteristics of the unit load to changes in heating capacity, the primary frequency regulation command is converted into a change in steam extraction using the F(X) function to determine the corresponding change in steam extraction demand during the frequency regulation action. Then, based on the valve flow characteristics of the supplementary steam valve and the direction of the primary frequency regulation action, the amount of change in the valve opening that needs to be altered is determined, thereby enabling the supplementary steam valve to quickly increase or decrease its opening in response to the primary frequency regulation.

[0041] When the steam injection valve is opened too wide, the axial thrust of the turbine and the vibration of the high-pressure cylinder bearing may change. Through verification calculations and experimental testing, the maximum opening of the steam injection valve during the first frequency regulation operation is limited to about 30% to ensure the safe operation of the unit when the steam injection valve provides heating and regulates the frequency.

[0042] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for improving the extraction steam heating and primary frequency regulation capabilities under deep peak shaving conditions, characterized in that, This method utilizes the supplementary steam valve to enhance the extraction steam heating capacity, and improves the primary frequency regulation performance of the unit under low load conditions by quickly responding to the primary frequency regulation through the short-term action of the supplementary steam valve. The method specifically includes: (1) When the extraction steam heating unit is under low load conditions, the original extraction steam source parameters decrease. With the make-up steam valve closed, the extraction steam port of the make-up steam valve is selected as the extraction steam source. The steam is extracted from the high-pressure cylinder through the pipeline from the turbine make-up steam valve to the high-pressure cylinder. The steam source is delivered to the heat user after the high-pressure cylinder is de-cooled and depressurized. (2) If the unit load is further reduced and a higher parameter heating steam source is required, open the steam supply valve and use the steam supply valve to directly supply heat. The steam is extracted from the main steam pipeline and supplied through the steam supply valve, and then de-temperatured and depressurized before reaching the heat user. When the steam injection valve is activated for heating, a primary frequency regulation on / off function is set up. Specifically, this function involves: When the frequency regulation function of the steam replenishment valve is not in use, the opening degree of the steam replenishment valve is manually set according to the heating demand; after the frequency regulation function of the steam replenishment valve is in use, if the frequency regulation is allowed according to the heating status, the opening degree of the steam replenishment valve is increased or decreased rapidly in a short time to respond to the primary frequency regulation.

2. The method for improving steam extraction heating and primary frequency regulation capabilities under deep peak shaving conditions according to claim 1, characterized in that, The method of responding to primary frequency regulation by rapidly increasing or decreasing the opening of the make-up steam valve in a short time includes the following steps: Step 1: When the unit has frequency regulation requirements, according to the response characteristics of the unit load to the change in heat supply, the primary frequency regulation command is converted into the change in steam extraction, and the corresponding change in steam extraction requirement is determined when the primary frequency regulation action is taken. Step 2: Based on the valve flow characteristics of the steam replenishment valve and the direction of the primary frequency regulation action, determine the corresponding valve position opening change. Step 3: Quickly change the valve position response frequency once based on the current opening degree of the steam replenishment valve.

3. The method for improving steam extraction heating and primary frequency regulation capabilities under deep peak shaving conditions according to claim 2, characterized in that, The step 1 of converting the primary frequency regulation command into the steam extraction change specifically involves converting the primary frequency regulation command into the steam extraction change using the F(X) function.

4. The method for improving steam extraction heating and primary frequency regulation capabilities under deep peak shaving conditions according to claim 2, characterized in that, The specific steps in step 2 of determining the corresponding valve position opening change are as follows: By converting valve flow rate to valve position change, the corresponding change in valve opening degree is determined.

5. The method for improving extraction steam heating and primary frequency regulation capabilities under deep peak shaving conditions according to claim 2, characterized in that, When the frequency regulation function of the make-up steam valve is put into use, a limit is set on the opening degree of the make-up steam valve to avoid the impact of excessive opening of the make-up steam valve on the turbine shaft system.

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