FCB bypass control method of 9HA gas turbine

Abstract

The invention provides an FCB bypass control method for a 9HA gas turbine. The FCB bypass control method comprises the following steps that S1, an analog quantity switching function block is adopted to memorize the gas turbine load Pg at the FCB triggering moment; s2, converting a gas turbine load Pg into a steam turbine load Pt according to F1 (x), and dividing the steam turbine load Pt by a gain K to form a percentage in a per unit range of 0-100%; s3, according to a valve flow opening degree curve provided by a bypass pressure reducing valve manufacturer, obtaining an initial preset bypass opening degree through F1 (x) by using the per-unit main steam flow; s4, acquiring a bypass opening curve according to 50% and 100% load steam turbine sliding stop and gas turbine load shedding tests, and correcting the initial preset bypass opening curve; by means of the method, accurate bypass control under different load FCB working conditions can be achieved, meanwhile, rapid pressure relief of a bypass system is met, it is guaranteed that main steam pressure is transited stably, the boiler is kept not overpressure, and it is guaranteed that the waste heat boiler drum water level change does not exceed a protection constant value to trigger MFT.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power generation, and in particular to a FCB bypass control method for a 9HA gas turbine. Background Art

[0002] The basic function of FCB is: when the unit is in normal operation (no MFT, turbine tripping, generator tripping), and the power grid collapses due to external reasons, the unit FCB function will be automatically activated, and the load will be quickly shed to operate with the factory power supply, and if the power grid permits, it will be reconnected to the grid to supply power to the system. During the unit island operation, it is required to ensure that the operating parameters are within the safe range, without causing protection action and endangering the safety of the equipment.

[0003] Theoretically, a 9H gas turbine equipped with a 100% BMCR bypass system meets the control requirements under FCB conditions. At present, there is no precedent for the successful FCB test of a 9H gas turbine in China, and the configuration and control strategy of the bypass system are particularly critical to the success of FCB.

[0004] When FCB occurs, the bypass system must not only release pressure quickly to ensure a smooth transition of the main steam pressure and keep the boiler from overpressure, but also ensure that the temperature after the bypass valve does not overheat. For gas-steam combined cycle units, during the bypass opening process, it is necessary to ensure that the main steam pressure does not change too much and that the water level change in the waste heat boiler drum does not exceed the protection set value to trigger the MFT.

[0005] Therefore, how to solve the above problems and propose a new gas turbine FCB bypass control method has become a technical problem that needs to be solved urgently by people in this field. Summary of the invention

[0006] The purpose of the present invention is to solve the shortcomings of the prior art and propose a FCB bypass control method for a 9HA gas turbine. The method is suitable for bypass control of thermal power generating units that are intended to have or already have black start capability, and can achieve precise bypass control under FCB conditions with different loads. The bypass control is fully automatic without manual intervention and has strong safety.

[0007] A FCB bypass control method for a 9HA gas turbine of the present invention comprises: an FCB trigger control method and a PID valve control method;

[0008] The FCB trigger control method includes the following steps:

[0009] S1. Use analog switching function block to memorize the engine load Pg at the FCB triggering time;

[0010] S2. According to the gas engine load Pg, the steam engine load Pt is converted according to F1(x), and the steam engine load Pt is divided by the gain K to be converted into a percentage in the range of 0-100%;

[0011] S3. According to the valve flow opening curve provided by the bypass pressure reducing valve manufacturer, the initial preset bypass opening is obtained by passing the normalized main steam flow through F1(x);

[0012] S4. Collect bypass opening curves based on 50% and 100% load turbine coasting and turbine load rejection tests, and modify the initial preset bypass opening curves;

[0013] In the PID valve control method, the high, medium and low bypass temperature control target values ​​need to be controlled to be 10°C lower than the protection action value, or the temperature that should be controlled when the FCB is triggered can be determined according to the operating procedures.

[0014] Preferably, in the FCB trigger control method, the high, medium and low bypass pressure reducing regulating valves open the preset bypass opening according to the different engine load overrides at the FCB triggering moment, and are put into automatic control after 5 seconds. The pressure target value is the pressure value 5 seconds before the trigger, so as to achieve precise bypass control under different load FCB conditions and ensure the stability of the main steam pressure and the drum water level.

[0015] Preferably, in the FCB trigger control method, the input switch quantity judgment condition in the analog function block SAMA used to memorize the gas engine load Pg at the FCB triggering moment is the FCB signal, the input analog quantity is the real-time load Pg of the gas engine load, the analog output is Pgout, and when the FCB signal is 1, the analog output Pgout can memorize the gas engine load Pg at the FCB triggering moment.

[0016] Preferably, in the FCB trigger control method, the gas turbine load Pg is converted into the steam turbine load Pt according to F1(x), and its piecewise function F1(x) has three segments; among them, (X1, Y1) is (0, 0), (X2, Y2) is the correspondence between the gas turbine load and the steam turbine load under low load and can be modified according to actual conditions, (X3, Y3) is the gas turbine load and the steam turbine load under rated conditions, and the per-unit coefficient K=Y3 / 100.

[0017] Preferably, in the FCB trigger control method, the main steam flow percentage F1(x) after standardization obtains the initial preset bypass opening, and its valve flow opening curve data comes from the factory manual of the bypass valve manufacturer. The input X is the main steam flow percentage after standardization, and the output Y is the initial preset bypass pressure reducing valve opening; different bypass pressure reducing valves, such as high, medium and low bypass pressure reducing valves, have different valve flow opening curve functions F2(x).

[0018] Preferably, in the FCB trigger control method, the method for correcting the initial preset bypass opening curve can be adopted, the real-time data or previous historical data of the turbine coasting down, 50% and 100% load rejection test of the gas turbine; if the conditions do not allow the gas turbine to be subjected to 50% and 100% load rejection test, and there is no previous historical data, the initial bypass preset opening can be corrected based on the relationship between the 50% FCB bypass opening and the main steam pressure change, or the initial bypass preset opening can be corrected based on the empirical data of the same type of units.

[0019] Preferably, in the PID valve control method, the high and low bypass cooling water regulating valves control the valve opening according to the PID, and the temperature target value is 10°C lower than the protection action temperature after the valve; the middle bypass cooling water regulating valve is overrun to 100% opening for 5S after the FCB is triggered, and is put into automatic control after 5S, and the temperature target value is 10°C lower than the protection action temperature after the valve.

[0020] The advantages and technical effects of the present invention are:

[0021] The present invention provides a FCB bypass control method for a 9HA gas turbine. The present invention proposes a bypass system control method under FCB working conditions of a 9HA gas turbine, which can achieve precise bypass control under FCB working conditions with different loads. The bypass control is fully automatic and does not require manual intervention.

[0022] The content of the present invention has been successfully applied to the first domestic 9HA gas-steam combined cycle one-to-one unit. The unit's 50% FCB and 100% FCB to island belt power dynamic tests were successful at one time, and it has black start capability. The successful case of this unit provides a technical basis and experience data for future domestic FCB tests of similar units. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a layout diagram of the steam turbine bypass system of the present invention;

[0024] Figure 2 This is a flow chart for calculating the preset opening of the steam turbine bypass pressure reducing valve FCB of the present invention;

[0025] Figure 3 It is the SAMA diagram of the engine load analog quantity switching block for the memory FCB triggering moment of the present invention;

[0026] Figure 4 This is a main steam pressure diagram of a gas turbine in a power plant under 50% FCB working condition in an embodiment of the present invention;

[0027] Figure 5 This is a diagram of the bypass system parameters under 50% FCB condition of a gas turbine in a power plant in an embodiment of the present invention;

[0028] Figure 6This is a main steam pressure diagram of a gas turbine in a power plant under 100% FCB working condition in an embodiment of the present invention;

[0029] Figure 7 This is a diagram of related parameters of the bypass system of a power plant gas turbine under 100% FCB conditions in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The embodiments of the invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the invention, and cannot be understood as limiting the invention.

[0031] The present invention proposes a bypass control method under FCB conditions of 9HA gas turbine, which can realize precise bypass control under different load FCB conditions, and at the same time meet the requirement of rapid pressure relief of the bypass system, ensure the smooth transition of main steam pressure to maintain the boiler without overpressure, and ensure that the change of water level of waste heat boiler drum will not exceed the protection setting value to trigger MFT. At the same time, it can also ensure that the temperature after bypass valve does not exceed the temperature to ensure that bypass fast closing will not be triggered, causing FCB test failure.

[0032] A bypass system control method for a 9HA gas turbine under FCB conditions, the control strategy is as follows:

[0033] A high, medium and low bypass pressure reducing regulating valve opens the preset bypass opening according to the different turbine load override at the time of FCB triggering. It is put into automatic control after 5 seconds. The pressure target value is the pressure value 5 seconds before triggering, so as to realize precise bypass control under different load FCB conditions and ensure the stability of main steam pressure and drum water level.

[0034] B high and low bypass cooling water regulating valves control valve opening according to PID, and the temperature target value is 10℃ lower than the valve rear protection action temperature. The middle bypass cooling water regulating valve is overrun to 100% opening for 5S after FCB is triggered, and is put into automatic control after 5S, and the temperature target value is 10℃ lower than the valve rear protection action temperature.

[0035] As described in control strategy A, the calculation process of the preset bypass opening degree for different gas turbine load override at the FCB triggering time is as follows: Figure 2 As shown, the first step is to use the analog switching function block to memorize the gas turbine load Pg at the FCB triggering moment; the second step is to convert the gas turbine load Pg into the steam turbine load Pt according to F1(x), and divide it by the gain K to standardize it into a percentage in the range of 0-100%; the third step is to obtain the initial preset bypass opening by using the valve flow opening curve provided by the bypass pressure reducing valve manufacturer through F1(x) with the standardized main steam flow; the fourth step is to collect the bypass opening curve according to the 50% and 100% load steam turbine coasting and gas turbine load rejection test, and correct the initial preset bypass opening curve.

[0036] Furthermore, the analog function block SAMA diagram for memorizing the engine load Pg at the time of FCB triggering is shown in the following figure: Figure 3 As shown, the input switch quantity judgment condition is the FCB signal, the input analog quantity is the real-time load Pg of the gas turbine, and the analog quantity output is Pgout. When the FCB signal is 1, the analog quantity output Pgout can memorize the gas turbine load Pg at the time of FCB triggering.

[0037] Furthermore, the gas engine load Pg is converted into the steam engine load Pt according to F1(x), and its piecewise function F1(x) has three sections. Among them, (X1, Y1) is (0, 0), (X2, Y2) is the corresponding relationship between the gas engine load and the steam engine load under low load, which can be modified according to actual conditions, (X3, Y3) is the gas engine load and the steam engine load under rated conditions, and the per unit coefficient K = Y3 / 100.

[0038] Furthermore, the percentage of the main steam flow after standardization F1(x) is used to obtain the initial preset bypass opening, and the valve flow opening curve data is from the factory manual of the bypass valve manufacturer. The input X is the percentage of the main steam flow after standardization, and the output Y is the initial preset bypass pressure reducing valve opening. Different bypass pressure reducing valves, such as high, medium, and low bypass pressure reducing valves, have different valve flow opening curve functions F2(x).

[0039] Furthermore, the method for correcting the initial preset bypass opening curve can be the real-time data or the historical data of the turbine coasting, 50% and 100% load rejection test of the gas turbine. If the conditions do not allow the 50% and 100% load rejection test of the gas turbine, and there is no historical data, the initial bypass preset opening can be corrected based on the relationship between the 50% FCB bypass opening and the main steam pressure change, or based on the empirical data of the same type of units.

[0040] As described in control strategy B, the high, medium and low bypass temperature control target values ​​are 10°C lower than the protection action value, or the temperature to be controlled when the FCB is triggered is determined according to the operating procedures. The protection action value is derived from the existing logic description of the plant.

[0041] In order to further highlight the superiority of the present invention, this implementation case adopts the first domestic GE 9H gas-steam combined cycle one-to-one unit in which the present invention has been successfully applied, and fully and detailedly explains the technical solutions and features of the present invention.

[0042] Based on the successful implementation of the present invention, the main equipment of the unit is introduced as follows:

[0043] The unit is a 9H.01 gas-steam combined cycle unit with one-to-one, multi-axis arrangement, produced by GE. The power generation capacity of the whole combined cycle is 661MW, and there is no bypass chimney. The turbine bypass is configured as a high-pressure and medium-pressure two-stage series bypass, and the low-pressure bypass is connected in parallel with the high-pressure and medium-pressure bypass. The bypass system diagram is as follows Figure 1 As shown. The bypass pressure regulating valves and desuperheating water regulating valves at all levels are produced by HORA of Germany, and their actuators are hydraulically driven. The bypass control system (BPS) is fully implemented on the DCS, using the maxDNA system of Nanzi.

[0044] The steam turbine adopts the three-pressure reheat, three-cylinder and two-exhaust steam reaction condensing steam turbine generator set produced by Harbin Steam Turbine Factory. Its main parameters are shown in Table 1:

[0045] Table 1: Main parameters of steam turbine

[0046]

[0047] The main parameters of the bypass system are shown in Table 2:

[0048] Table 2: Main parameters of bypass system

[0049]

[0050] This implementation case refines the parameters of the bypass control strategy of the method of the present invention, as follows:

[0051] During the normal load stage of the unit, the high, medium and low bypass pressure regulating valves are generally closed to 0%. After the unit has FCB, the main transformer high-voltage circuit breaker is disconnected, the gas turbine is dumped of all loads to maintain the plant power operation, the turbine trips and the main steam valve is fully closed, and the excess steam needs to be recovered to the reheater and condenser through the bypass.

[0052] In this implementation case, the bypass control strategy is as follows:

[0053] A high, medium and low bypass pressure reducing regulating valves open the preset bypass opening according to the different engine load overrides at the time of FCB triggering. After 5 seconds, they are put into automatic control, and the pressure target value is the pressure value 5 seconds before the triggering.

[0054] The gas engine load Pg is converted into the steam engine load Pt according to F1(x), and then divided by the gain K to normalize it into a percentage ranging from 0 to 100%. Specifically, F1(x) is divided into three sections, namely ((0,0), (328.57,150), (460,210)); the normalization coefficient K = 210 / 100 = 2.1.

[0055] The main steam flow after standardization is converted into the preset opening of the bypass valve through F2(x). The specific corresponding relationship is as follows:

[0056] ①The flow opening relationship of the high-pressure bypass regulating valve is ((0,0)(1.76,10)(35,30)(50,40)(73.5,60)(90,80)(96,80)(100,80));

[0057] ②The flow opening relationship of the medium-pressure bypass regulating valve is ((0,0)(2.15,4.5)(10,10)(22.5,20)(55,50)(74.8,70)(92.3,80)(100,80));

[0058] ③The flow opening relationship of the low-pressure bypass regulating valve is ((0,0)(2.5,1.0)(5.5,10)(19,20)(30,30)(50,50)(80,80)(100,80)).

[0059] Preferably, when the high, medium and low pressure main steam flow rates are 100%, the high, medium and low bypass openings are 80%, which is a valve opening curve corrected based on historical operation data.

[0060] B high and low bypass cooling water regulating valves control valve opening according to PID, and the temperature target value is 10℃ lower than the valve rear protection action temperature. The middle bypass cooling water regulating valve is overrun to 100% opening for 5S after FCB is triggered, and is put into automatic control after 5S, and the temperature target value is 10℃ lower than the valve rear protection action temperature.

[0061] Specifically, in this implementation case, the high-pressure bypass cooling water control target temperature is 365°C, the medium-pressure bypass cooling water control target temperature is 160°C, and the low-pressure bypass cooling water control target temperature is 160°C.

[0062] 50% FCB test bypass action

[0063] At 22:30:03 on April 18, 2024, the 52L (2012) switch on the high-voltage side of the gas turbine main transformer tripped, triggering the FCB signal, the #12 gas turbine running with plant power, and the #13 steam turbine generator set tripped. The maximum speed of the steam turbine reached 3023.8r / min; the maximum speed of the gas turbine reached 3108.5r / min, and the minimum speed reached 2998.8r / min, and the gas turbine ran with 6.44MW plant power.

[0064] At 22:44 on April 18, 2024, the unit was restored to the grid through the 52L (2012) switch on the high-voltage side of the gas turbine main transformer and resumed operation under load.

[0065] After FCB is triggered, the high-pressure, medium-pressure, and low-pressure bypass pressure reducing valves open quickly to the preset opening, and then automatically after 5 seconds, the bypass temperature reduction water regulating valve controls the current temperature according to PID. The 50% FCB process curve is as follows: Figure 4 and Figure 5As shown, the process parameters are shown in Table 3:

[0066] Table 3: Related parameters of bypass system under 50% FCB condition of gas turbine

[0067]

[0068]

[0069] During the FCB operation, the main parameters of the unit, such as high, medium and low pressure main steam pressures, high and low bypass valve rear temperatures, etc., are regulated smoothly, and the maximum fluctuation range does not exceed the unit trip limit;

[0070] The temperature after the middle bypass valve rose rapidly from 159°C at 22:30:45, reached a peak of 207.02°C at 22:31:08, and dropped to 160°C at 22:31:32. Then the temperature slowly dropped and stabilized, and finally stabilized to 110.80°C. The parameter exceeded the limit for 47 seconds. Since the temperature increased too quickly during the process and exceeded the rate rise protection limit of 10°C / S, the rate rise was triggered, so the protection was automatically cut off.

[0071] As a preference, in order to better control the temperature after the middle bypass valve at 100% FCB, the middle bypass cooling water control mode is changed to overrun and open to 100% opening for 5S after FCB is triggered, and then put into automatic control after 5S.

[0072] 100% FCB test bypass action

[0073] At 09:45 on April 19, 2024, the 52L (2012) switch on the high-voltage side of the gas turbine main transformer tripped, triggering the FCB signal, the #12 gas turbine operated with plant power, and the #13 steam turbine generator set tripped. The maximum speed of the steam turbine reached 3033.2r / min; the maximum speed of the gas turbine reached 3236.1r / min, and the minimum speed reached 2998.1r / min, and the gas turbine operated with 8.34MW plant power.

[0074] At 10:03 on April 19, 2024, the unit was restored to the grid through the 52L (2012) switch on the high-voltage side of the gas turbine main transformer and resumed operation under load.

[0075] After FCB is triggered, the high-pressure, medium-pressure, and low-pressure bypass pressure reducing valves open quickly to the preset opening, and automatically switch after 5 seconds. The medium bypass temperature reducing water regulating valve opens quickly to 100%, and automatically switches after 5 seconds. The high bypass and low bypass temperature reducing water regulating valves control the current temperature according to PID. The 100% FCB process curve is as follows: Figure 6 and Figure 7 , process parameters are shown in Table 4:

[0076] Table 4: Related parameters of bypass system under 100% FCB condition of gas turbine

[0077]

[0078] During the 100% FCB operation, the high, medium and low main steam pressures, the high, medium and low bypass valve rear temperatures and other main parameters of the unit are adjusted smoothly, and the maximum fluctuation range does not exceed the unit tripping limit.

[0079] The above specific implementation cases have made a complete and detailed description of the method of the present invention, reflecting the superiority and flexibility of the technical solution of the present invention. The 50% FCB and 100% FCB to island belt power plant dynamic tests of the unit were both successful at one time, which is the first successful case in China for GE 9H gas-steam combined unit. The bypass system control method under FCB conditions of a 9HA gas turbine proposed in the present invention can provide a technical basis and experience data for future FCB tests of similar units in China.

[0080] Finally, all the unexplained parts of the invention adopt mature products and mature technical means in the existing technology.

[0081] In the description of this specification, reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in the embodiment or example of the invention.

[0082] Although embodiments of the invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A FCB bypass control method for a 9HA gas turbine, characterized in that: include: FCB trigger control method, and PID valve control method; The FCB trigger control method comprises the following steps: S1. Use analog switching function block to memorize the engine load Pg at the FCB triggering time; S2. According to the gas engine load Pg, the steam engine load Pt is converted according to F1(x), and the steam engine load Pt is divided by the gain K to be converted into a percentage in the range of 0-100%; S3. According to the valve flow opening curve provided by the bypass pressure reducing valve manufacturer, the initial preset bypass opening is obtained by passing the normalized main steam flow through F1(x); S4. Collect bypass opening curves based on 50% and 100% load turbine coasting and turbine load rejection tests, and modify the initial preset bypass opening curves; In the PID valve control method, the high, medium and low bypass temperature control target values ​​need to be controlled to be 10°C lower than the protection action value, or the temperature to be controlled when the FCB is triggered is determined according to the operating procedures.

2. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the FCB trigger control method, the high, medium and low bypass pressure reducing regulating valves open the preset bypass opening according to the different engine load overrides at the time of FCB triggering, and are put into automatic control after 5 seconds. The pressure target value is the pressure value 5 seconds before the triggering, so as to realize precise bypass control under different load FCB working conditions and ensure the stability of main steam pressure and drum water level.

3. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the FCB trigger control method, the input switch quantity judgment condition in the analog function block SAMA used to memorize the engine load Pg at the FCB triggering moment is the FCB signal, the input analog quantity is the real-time load Pg of the engine load, and the analog quantity output is Pgout. When the FCB signal is 1, the analog quantity output Pgout can memorize the engine load Pg at the FCB triggering moment.

4. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the FCB trigger control method, the gas turbine load Pg is converted into the steam turbine load Pt according to F1(x), and its piecewise function F1(x) has three segments; among them, (X1, Y1) is (0, 0), (X2, Y2) is the corresponding relationship between the gas turbine load and the steam turbine load under low load and can be modified according to actual conditions, (X3, Y3) is the gas turbine load and the steam turbine load under rated conditions, and the per-unit coefficient K=Y3 / 100.

5. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the FCB trigger control method, the main steam flow percentage F1(x) after standardization obtains the initial preset bypass opening, and the valve flow opening curve data comes from the factory manual of the bypass valve manufacturer. The input X is the main steam flow percentage after standardization, and the output Y is the initial preset bypass pressure reducing valve opening; Different bypass pressure reducing valves, such as high, medium and low bypass pressure reducing valves, have different valve flow opening curve functions F2(x).

6. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the FCB trigger control method, the method for correcting the initial preset bypass opening curve can be based on the real-time data or past historical data of the turbine coasting, 50% and 100% load rejection test of the gas turbine; If the conditions do not allow the gas turbine to be tested for 50% or 100% load shedding, and there is no historical data, a post-correction can be made based on the relationship between the 50% FCB bypass opening and the change in main steam pressure, or the initial bypass preset opening can be corrected based on the empirical data of the same type of units.

7. The FCB bypass control method of a 9HA gas turbine according to claim 1, characterized in that: In the PID valve control method, the high and low bypass cooling water regulating valves control the valve opening according to the PID, and the temperature target value is 10°C lower than the valve rear protection action temperature; the middle bypass cooling water regulating valve is overrun to 100% opening for 5S after the FCB is triggered, and is put into automatic control after 5S, and the temperature target value is 10°C lower than the valve rear protection action temperature.

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