Variable-frequency optimization control method for high-pressure water supply shared by multiple systems

Abstract

The invention relates to a frequency conversion optimization control method for multi-system shared high-pressure water supply, which comprises the following steps of: dynamically adjusting a pressure set value of high-pressure water supply frequency conversion control according to the maximum value of the pressure demand of each user, and dynamically adjusting the independent pressure setting of each user through function correction under an emergency working condition; and the set final pressure value of the high-pressure water supply system is automatically changed. Compared with the prior art, the method has the advantages that high-pressure water supply systems of multiple system users are fully considered, full-working-condition frequency conversion automatic efficient control is achieved, safe and stable operation of a unit is met, energy-saving operation of a high-pressure pump is considered, throttling loss is reduced, and the like.

Description

Technical Field

[0001] The invention relates to a high-pressure water supply control system for a heavy-duty fuel engine, and in particular to a frequency conversion optimization control method for high-pressure water supply for multiple systems. Background Art

[0002] Under the dual carbon goals, combined cycle gas turbine power generation has developed rapidly across the country in recent years because it meets the conditions of fast start and stop and low emissions. The most important auxiliary machine in the waste heat boiler of the combined cycle gas turbine unit is the high-pressure feed water pump, which usually adopts frequency conversion control. In the preparation stage before the start of the gas turbine, it cooperates with the boiler drum to fill water. After starting, in addition to cooperating with the boiler drum to fill water in response to load demand, it is also necessary to deal with possible overtemperature and spray water to cool the high-pressure system; at the same time, in order to improve the combustion efficiency of the gas turbine, the natural gas must also be heat exchanged. Water reduction is required during the shutdown stage, and full water operation is required to reduce the temperature difference of the drum wall after the boiler is shut down. As a peak-shaving unit, frequent start and stop bring greater challenges to the control of the high-pressure feed water system.

[0003] Most F-class units have only one stage of performance heater, which is used to heat natural gas and improve the combustion efficiency of gas turbines. The temperature of natural gas at the inlet of the first-stage performance heater does not change much with the seasons throughout the year, and the heat exchange capacity is relatively stable. The heat source is high-pressure feed water, that is, the flow rate of high-pressure feed water used for the performance heater is relatively fixed, which basically does not affect other users of high-pressure feed water, such as high-pressure cooling water and high-pressure drum water flow. H-class gas turbine units have two stages of performance heaters, the first stage uses medium-pressure feed water as the heat source, and the second stage uses high-pressure feed water as the heat source. There is one more stage of heat exchange, and the heat exchange source does not belong to the same system, which causes the natural gas temperature at the inlet of the second-stage performance heater to fluctuate. This brings changes to the amount of high-pressure feed water used as the heat source of the second-stage heater, and increases the difficulty of controlling the high-pressure feed water system.

[0004] Due to its high parameter requirements, the H-class gas turbine has a compressor exhaust system that is different from the F-class unit. In a gas turbine, the compressor exhaust system is an important system. Whether it is surge prevention during compressor start-up and shutdown, or the supply of cooling air for each level of turbine blades during unit operation, it is all completed through the compressor exhaust system. The air temperature after heat exchange in the H-class unit is relatively high, and an OTC (Once-Through Coolers) cooling system (OTC system for short) is required to cool the high-temperature air to a suitable temperature and re-enter the compressor inlet. High-pressure feed water is used as a cooling medium. After heat exchange, superheated steam is generated and returned to the steam pipeline of the high-pressure system of the waste heat boiler. The system has certain pressure requirements for the high-pressure feed water used for cooling, and whether the system operates stably will directly affect the safe operation of the gas turbine. The requirements for the control of the high-pressure feed water system have been further improved.

[0005] Compared with other gas turbine combined cycle units, units equipped with secondary performance heaters and OTC systems have more complex high-pressure water supply users. The water consumption and pressure requirements of each system vary in different load sections. If the high-pressure water supply frequency conversion is controlled based on the user with the highest pressure demand, the throttle opening of other users will be greatly reduced, resulting in a large amount of throttling losses. The previous control ideas only ensured that the water supply pressure was met. When there are unstable factors for multiple high-pressure water supply users, how to make good use of the high-pressure water supply frequency conversion control system to ensure the safe and stable operation of the unit under all operating conditions while avoiding throttling losses as much as possible is the main problem at present.

[0006] After searching, Chinese patent publication number CN104456524A discloses a high-pressure water supply system for waste heat boilers of gas-steam combined cycle power generation units. There are two high-pressure water supply pumps, one for supplying water to the TCA heat exchanger and the other for supplying water to the boiler economizer, forming two independent water supply branches. The use of sub-pumps can solve the problem that when users with different water supply needs are supplied by the same pump, large users dominate and small users suffer large throttling losses.

[0007] Chinese patent publication number CN106774472A discloses a variable frequency energy-saving control method for a high-medium pressure feed pump combined pump system. During the start-up and shutdown process of the unit and the low-load stage, the feed pump controls the high-medium pressure feed water differential pressure, and the high-medium pressure feed water regulating valve controls the high-medium pressure drum water level; during the high-load stage of the unit, the feed pump controls the high-pressure drum water level, while ensuring the minimum differential pressure of the medium-pressure feed water; the high-pressure feed water regulating valve performs auxiliary control of the high-pressure water level, that is, fully opens the regulating valve when the water level is normal, and closes the regulating valve when the water level is high to assist in regulating the water level; the medium-pressure regulating valve controls the medium-pressure drum water level. The high-medium pressure feed pump combined pump system uses the high-pressure feed pump to control the high-pressure water level, and the high-pressure feed water regulating valve is fully opened to control the high-pressure water level, while taking into account the water pressure of the medium-pressure system, achieving the purpose of reducing throttling losses and making the unit operation more energy-efficient.

[0008] Chinese patent publication number CN107178779A discloses a control method for variable speed operation of a variable speed water supply pump. A water supply pressure measuring point is set at each water supply outlet, and a water supply pressure demand value is set for each user system. The control system adjusts the speed of the variable speed water supply pump according to the maximum value of the difference between the water supply pressure demand value of each user system and the actual pressure value measured at the corresponding water supply pressure measuring point, so that the maximum value of the difference between the water supply pressure demand value of each user system and the actual pressure value at the corresponding water supply pressure measuring point is reduced or increased to zero. It can reduce energy consumption as much as possible while ensuring that the actual pressure of each water supply outlet of the variable speed water supply pump meets the water supply pressure demand of the corresponding user system, and at the same time prevent the valve core of the valve from being damaged due to excessive water supply pressure, thereby ensuring the safety of the unit.

[0009] However, the above existing patents still have the following problems:

[0010] 1. The independent control of sub-pumps cannot meet the energy-saving needs of more than two high-pressure water supply users, and there is no backup pump to deal with special working conditions such as insufficient pressure and pump blockage.

[0011] 2. In a specific mode, the high-pressure feed water valve is fully open, and the method of using the high-pressure feed water pump to control the drum water level by frequency conversion cannot meet the changes in water demand of other systems, and cannot meet the control requirements of the H-class gas turbine with the high pressure of the waste heat boiler as a direct current furnace.

[0012] 3. Although it can cope with complex multi-user systems, the pressure setting of each user is a non-dynamic pressure setting value, and it does not seek the optimal pressure demand value of multiple users under the current working conditions from the root; it adopts the form of large selection of the difference between the pressure setting value and the actual pressure value, and each user side must be configured with a pressure measurement point; due to the different control quality of the valves on each system side, it is easy to cause frequent back and forth adjustments of the variable frequency pressure control.

[0013] Therefore, how to solve the energy consumption loss of the variable frequency pump caused by the water pressure difference of the single control of high-pressure water supply for multiple systems of heavy-duty gas turbines, the throttling loss of the user-side regulating valve, and the inability to effectively cope with the harsh working conditions of each system itself, so as to improve the safety and economic operation capability of the high-pressure water supply control system of heavy-duty gas turbines, has become a technical problem that needs to be solved. Summary of the invention

[0014] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a frequency conversion optimization control method for high-pressure water supply used by multiple systems.

[0015] The purpose of the present invention can be achieved by the following technical solutions:

[0016] According to the first aspect of the present invention, there is provided a variable frequency optimization control method for high-pressure water supply shared by multiple systems. The method dynamically adjusts the pressure setting value of the variable frequency control of the high-pressure water supply according to the maximum value of the pressure demand of each user. At the same time, under emergency conditions, the independent pressure setting of each user is dynamically adjusted through function correction, and the final pressure setting value of the high-pressure water supply system is automatically changed.

[0017] As a preferred technical solution, the method provides a pressure bias interface for automatically superimposing correction values.

[0018] As a preferred technical solution, the method specifically comprises the following steps:

[0019] Step S1, based on the separator outlet pressure P 分 Calculate the set value SP1 of the water pressure of the waste heat boiler high pressure system based on the load of the gas turbine;

[0020] Step S2, according to the high pressure superheater outlet pressure P高 , calculate the high-pressure system desuperheating water pressure setting value SP2 based on the gas turbine load and exhaust gas temperature;

[0021] Step S3, calculating the water pressure setting value SP3 of the secondary performance heater according to the natural gas flow, the natural gas temperature at the outlet of the primary performance heater and the fixed water supply pressure requirement of the secondary performance heater;

[0022] Step S4, calculating the OTC system water pressure setting value SP4 according to the gas turbine load and the OTC outlet compressed air temperature;

[0023] Step S5, selecting the four set values ​​of the high-pressure system water supply pressure set value SP1, the high-pressure system desuperheating water pressure set value SP2, the secondary performance heater water pressure set value SP3, and the OTC system water pressure set value SP4 as the comprehensive set values ​​of the high-pressure water supply frequency conversion control under normal circumstances;

[0024] Step S6, when the opening of any user's front regulating valve approaches the opening corresponding to the maximum flow according to its own flow curve, its pressure setting value is superimposed with the set offset.

[0025] As a preferred technical solution, the high-pressure system water pressure setting value SP1 is specifically calculated as:

[0026] SP1=P 分 +P 负荷修 , where P 负荷修 Set the correction value for the water supply pressure that changes with the engine load. The higher the engine load, the higher the P 负荷修 The bigger.

[0027] As a preferred technical solution, the high-pressure system desuperheating water pressure setting value SP2 is specifically calculated as:

[0028] SP2=P 高 +P 排温修 *K 烟气修 , where P 高 is the high pressure superheater outlet pressure, P 排温修 K is the pressure setting correction value that changes with the difference between the exhaust gas temperature and the desuperheating water temperature setting value. 烟气修 It is a correction coefficient obtained based on the amount of flue gas flow at the tail end of the gas turbine reflected by the IGV opening.

[0029] As a preferred technical solution, the larger the difference is, the larger the pressure setting correction value is, and the faster the response is to the high-pressure cooling water demand; at the same time, the larger the IGV opening is, the larger the flue gas flow is, and the larger the correction coefficient is.

[0030] As a preferred technical solution, the water pressure setting value SP3 of the secondary performance heater is specifically calculated as follows:

[0031] SP3=P 固 +P 天然气 *K 一级修 , where P 固 Fixed water pressure for the secondary performance heater, P 天然气 The high-pressure feed water pressure correction for the secondary performance heater heat exchange is estimated based on the current natural gas flow rate, K 一级修 It is the correction factor obtained based on the natural gas temperature at the outlet of the primary performance heater.

[0032] As a preferred technical solution, the higher the outlet natural gas temperature of the first-level performance heater, the smaller the correction coefficient.

[0033] As a preferred technical solution, the OTC system water pressure setting value SP4 is specifically calculated as follows:

[0034] SP4=P 负荷预 *K 空温修 , where P 负荷预 is the water pressure value of the OTC system predicted by the gas turbine load, K 空温修 To determine P according to the OTC outlet compressed air temperature 负荷预 The correction factor of .

[0035] As a preferred technical solution, the higher the OTC outlet compressed air temperature, the more high-pressure water supply is required. 空温修 The bigger.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] 1) The present invention fully considers the high-pressure water supply system of multiple system users, realizes automatic and efficient control of frequency conversion under all working conditions, and at the same time ensures the safe and stable operation of the unit, takes into account the energy-saving operation of the high-pressure water supply pump and reduces throttling losses.

[0038] 2) The present invention realizes automatic energy-saving control of high-pressure water supply pump frequency conversion in a multi-system shared high-pressure water supply system, flexibly applies dynamic high-pressure water supply pressure setting values, and tries to lower the frequency output of the high-pressure water supply pump inverter in each load section and each working condition, thereby increasing the opening of the regulating valve on the high-pressure water supply user side and reducing throttling losses.

[0039] 3) The present invention responds to water demand under special working conditions and automatically increases the pressure setting for emergency treatment, thereby ensuring safe and stable operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of the high-pressure water supply user system of the present invention;

[0041] Figure 2 This is a logic block diagram of the comprehensive set value of the high-pressure water supply frequency conversion of the present invention. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0043] The present invention is aimed at a high-pressure water supply system shared by multiple systems. The pressure setting value of the high-pressure water supply frequency conversion control is designed to be dynamically adjusted according to the maximum value of the pressure demand of each user, thereby reducing the water supply frequency of the high-pressure water supply frequency converter, opening the valve, and reducing throttling losses. At the same time, in order to ensure safe and stable operation, the function correction is used under emergency conditions to dynamically adjust the independent pressure setting of each user, automatically change the final value of the pressure setting of the high-pressure water supply system, and provide a pressure bias interface to automatically superimpose the correction value as a pressure setting adjustment means in emergency situations.

[0044] The present invention is applied to the Ansaldo GT36-H gas-steam combined cycle unit. Its high-pressure water supply users include water from the high-pressure system of the waste heat boiler to control the superheat of the direct-flow furnace separator; high-pressure desuperheating water to control the outlet temperature of the high-pressure superheater, that is, the main steam temperature; water for the secondary performance heater to increase the natural gas temperature at the outlet of the secondary performance heater; and water for the OTC (Once-Through Coolers) cooling system to cool the high-temperature air to a suitable temperature and re-enter the compressor inlet.

[0045] like Figure 1 and Figure 2 As shown, the detailed technical solution of the present invention includes:

[0046] 1) After the outlet of the high-pressure feedwater pump passes through the feedwater regulating valve (including the main feedwater regulating valve and the bypass feedwater regulating valve), it passes through the high-pressure economizer and high-pressure evaporator in turn, and then enters the water storage tank after steam-water separation. Comprehensively considering the combined cycle boiler water supply requirements and energy conservation and emission reduction requirements, based on the separator outlet pressure P 分 The water pressure setting SP1 of the waste heat boiler high pressure system is calculated based on the gas turbine load. The calculation formula is as follows:

[0047] SP1=P 分 +P 负荷修 , where P 分 is the average pressure at the separator outlet, P 负荷修 The correction value is set for the water supply pressure that changes with the load of the gas turbine. The higher the load of the gas turbine, the larger the correction value. While ensuring that the water supply can be normal in all working conditions at full load, the dynamic characteristics of the separator outlet pressure changing with the load of the gas turbine are fully considered. Under some working conditions, the water supply pressure is dynamically corrected to reduce the high-pressure water supply frequency conversion output, thereby achieving energy saving effect.

[0048] 2) The outlet of the high-pressure feedwater pump passes through the two-stage cooling water regulating valve and is sprayed into the high-pressure superheater outlet pipe to ensure that the main steam temperature does not exceed the temperature. The high-pressure system cooling water pressure setting value SP2 is calculated based on the high-pressure superheater outlet pressure and exhaust gas temperature. The calculation formula is as follows:

[0049] SP2=P 高 +P 排温修 *K 烟气修 , where P 高 is the value selected from the three high-pressure superheater outlet pressure, P 排温修 It is the pressure correction value corresponding to the difference between the exhaust gas temperature and the set value of the cooling water temperature. The larger the difference, the larger the correction value. K 烟气修 It is a correction factor obtained based on the amount of flue gas flow at the tail of the gas turbine reflected by the IGV opening. The larger the IGV opening, the larger the flue gas flow, and the larger the correction factor.

[0050] 3) Calculate the water pressure setting value SP3 of the secondary performance heater according to the natural gas flow, the natural gas temperature at the outlet of the primary performance heater and the fixed water supply pressure requirement of the secondary performance heater. The calculation formula is as follows:

[0051] SP3=P 固 +P 天然气 *K 一级修 , where P 固 Fixed water pressure for the secondary performance heater, P 天然气 K is the correction value of the high-pressure feed water pressure for heat exchange of the secondary performance heater estimated according to the current natural gas flow rate. The larger the natural gas flow rate, the larger the correction value. 一级修 It is a correction factor obtained based on the temperature of the natural gas at the outlet of the first-stage performance heater. The higher the temperature, the smaller the correction factor. When the first-stage performance heater reaches the upper limit of heat exchange capacity due to various reasons, the second-stage performance heater increases the water pressure to compensate for the insufficient heat exchange of the first-stage performance heater.

[0052] 4) Calculate the OTC system water pressure setting value SP4 according to the gas turbine load and the OTC outlet compressed air temperature. The calculation formula is as follows:

[0053] SP4=P 负荷预 *K 空温修 , where P 负荷预 The water pressure value of the OTC system predicted by the gas turbine load. The higher the gas turbine load, the greater the water pressure value. 空温修 To determine P according to the OTC outlet compressed air temperature 负荷预 The higher the temperature, the greater the correction coefficient.

[0054] 5) The four set values ​​of the high-pressure system water supply pressure set value SP1, the high-pressure system cooling water pressure set value SP2, the secondary performance heater water pressure set value SP3, and the OTC system water pressure set value SP4 are selected as the comprehensive set values ​​of the high-pressure water supply frequency conversion control under normal circumstances.

[0055] 6) When the opening of the regulating valve in front of any user (CV1-CV4) is greater than the opening corresponding to the maximum flow, it indicates that the current water supply pressure is insufficient to meet the water demand of the user. A certain offset is added to the pressure setting value to promptly relieve the water pressure and avoid further deterioration of the working condition.

[0056] The present invention is aimed at a multi-user high-pressure water supply system, predicts the water supply pressure demand of each user, and adopts a dynamic water supply pressure setting method to cope with the instability of water supply demand of different users under various working conditions. Under the premise of only two high-pressure water supply pumps, one is variable frequency operation and the other is industrial frequency standby, without the need for branch pump operation, thus increasing the operating reliability. The whole process is automatic and no manual intervention is required.

[0057] The present invention can be effectively applied to the variable frequency control of the high-pressure water supply system of the gas turbine combined cycle unit. In recent years, the number of gas turbine projects in various parts of my country, especially the H-class models with higher parameters, has increased year by year. Regardless of the number of users of the high-pressure water supply system, the technical solution of the invention can be applied to achieve safe, stable and energy-saving operation of the high-pressure water supply system. At the same time, the invention technology is also applicable to multi-user water supply systems such as closed cooling water and condensate water.

[0058] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the present invention, and these modifications or replacements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A frequency conversion optimization control method for high-pressure water supply for multiple systems, characterized in that: This method dynamically adjusts the pressure setting value of the high-pressure water supply frequency conversion control according to the maximum pressure demand of each user. At the same time, it dynamically adjusts the independent pressure setting of each user through function correction under emergency conditions and automatically changes the final pressure setting value of the high-pressure water supply system.

2. According to claim 1, a frequency conversion optimization control method for high-pressure water supply for multiple systems is characterized in that: This method provides a pressure offset interface for automatically superimposing correction values.

3. According to claim 1, a frequency conversion optimization control method for high-pressure water supply for multiple systems is characterized in that: The method specifically comprises the following steps: Step S1, based on the separator outlet pressure P 分 Calculate the set value SP1 of the water pressure of the waste heat boiler high pressure system based on the load of the gas turbine; Step S2, according to the high pressure superheater outlet pressure P 高 , calculate the high-pressure system desuperheating water pressure setting value SP2 based on the gas turbine load and exhaust gas temperature; Step S3, calculating the water pressure setting value SP3 of the secondary performance heater according to the natural gas flow, the natural gas temperature at the outlet of the primary performance heater and the fixed water supply pressure requirement of the secondary performance heater; Step S4, calculating the OTC system water pressure setting value SP4 according to the gas turbine load and the OTC outlet compressed air temperature; Step S5, selecting the four set values ​​of the high-pressure system water supply pressure set value SP1, the high-pressure system desuperheating water pressure set value SP2, the secondary performance heater water pressure set value SP3, and the OTC system water pressure set value SP4 as the comprehensive set values ​​of the high-pressure water supply frequency conversion control under normal circumstances; Step S6, when the opening of any user's front regulating valve approaches the opening corresponding to the maximum flow according to its own flow curve, its pressure setting value is superimposed with the set offset.

4. According to claim 3, a frequency conversion optimization control method for high-pressure water supply for multiple systems is characterized in that: The water pressure setting value SP1 of the high-pressure system is specifically calculated as: SP1=P 分 +P 负荷修 , where P 负荷修 Set the correction value for the water supply pressure that changes with the engine load. The higher the engine load, the higher the P 负荷修 The bigger.

5. According to claim 3, a frequency conversion optimization control method for high-pressure water supply for multiple systems is characterized in that: The high-pressure system desuperheating water pressure setting value SP2 is specifically calculated as: SP2=P 高 +P 排温修 *K 烟气修 , where P 高 is the high pressure superheater outlet pressure, P 排温修 K is the pressure setting correction value that changes with the difference between the exhaust gas temperature and the desuperheating water temperature setting value. 烟气修 It is a correction coefficient obtained based on the amount of flue gas flow at the tail end of the gas turbine reflected by the IGV opening.

6. A frequency conversion optimization control method for high-pressure water supply for multiple systems according to claim 5, characterized in that: The larger the difference is, the larger the pressure setting correction value is, and the faster the response is to the high-pressure cooling water demand; at the same time, the larger the IGV opening is, the larger the flue gas flow is, and the larger the correction coefficient is.

7. According to claim 3, a frequency conversion optimization control method for high-pressure water supply for multiple systems is characterized in that: The water pressure setting value SP3 of the secondary performance heater is specifically calculated as follows: SP3=P 固 +P 天然气 *K 一级修 , where P 固 Fixed water pressure for the secondary performance heater, P 天然气 The high-pressure feed water pressure correction for the secondary performance heater heat exchange is estimated based on the current natural gas flow rate, K 一级修 It is the correction factor obtained based on the natural gas temperature at the outlet of the primary performance heater.

8. The frequency conversion optimization control method for high-pressure water supply for multiple systems according to claim 7 is characterized in that: The higher the outlet natural gas temperature of the primary performance heater, the smaller the correction coefficient.

9. The frequency conversion optimization control method for high-pressure water supply for multiple systems according to claim 3 is characterized in that: The OTC system water pressure setting value SP4 is specifically calculated as follows: SP4=P 负荷预 *K 空温修 , where P 负荷预 is the water pressure value of the OTC system predicted by the gas turbine load, K 空温修 To determine P according to the OTC outlet compressed air temperature 负荷预 The correction factor of .

10. The frequency conversion optimization control method for high-pressure water supply for multiple systems according to claim 9 is characterized in that: The higher the OTC outlet compressed air temperature, the more high-pressure water supply is required, K 空温修 The bigger.

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