High-pressure main throttle valve activity test method

Abstract

The invention discloses a high-pressure main throttle valve activity test method, which comprises the following steps of: presetting a safety median of a control valve instruction and additionally arranging a control valve instruction compensator, and testing the difference between a downstream control valve instruction on the same side of a high-pressure main throttle valve and the safety median in a high-pressure main throttle valve activity test process; the method comprises the following steps: superposing on each control valve instruction at the downstream of a main throttle valve on the other side in real time, and taking auxiliary measures such as linearly setting a DEH steam distribution function, limiting test boundary conditions, quitting a DEH remote control mode, quitting a primary frequency modulation loop, quitting a regulating stage pressure loop, quitting an auxiliary engine fault rapid load reduction loop, quitting a power feedback loop, shortening test time and the like; the stability of the generator power during the test is maintained, and the low-frequency oscillation risk of the generator power is reduced.

Description

Technical Field

[0001] The invention relates to a high-pressure main steam valve activity test method, belonging to the technical field of thermal power generation. Background Art

[0002] Modern steam turbine units widely use digital electro-hydraulic control systems (DEH) for valve management. Considering the requirements of fast opening and closing and sealing, the turbine regulating valve usually uses a fast-opening regulating valve, and its flow characteristics (numerically represented as the functional relationship between the stroke percentage and the steam inlet flow percentage) are generally linear within the first 40% of the valve core stroke, and then become significantly flat, with typical nonlinear characteristics. The DEH system steam distribution function is responsible for the nonlinear correction and comprehensive management of the steam inlet flow of the regulating valve (group) by converting the received total valve position command into each regulating valve command, thereby realizing precise linear control of the speed and power of the steam turbine generator set.

[0003] According to the National Energy Administration's "Twenty-Five Key Requirements for Preventing Power Production Accidents", in order to prevent turbine overspeed accidents, steam turbine units should adhere to the regulations to conduct main steam valve, regulating steam valve, low-pressure supplementary steam valve closing time test, steam valve tightness test, overspeed protection test, valve activity test. Compared with other test items, the high-pressure main steam valve activity test is carried out regularly by the operating personnel during the normal operation of the unit after the unit is connected to the grid. The technical details of the test plan and related safety measures are often not considered in detail and comprehensively. During the high-pressure main steam valve activity test, many units experienced violent fluctuations in generator power and steam parameters, and even power oscillation failures.

[0004] The steam turbine units in service are usually equipped with two sets of high-pressure main steam valves, and each set of high-pressure main steam valves has 1-3 regulating valves connected in series downstream. The high-pressure main steam valve activity test often requires the exit of the AGC automatic generation control (AGC) in advance and is carried out in single-valve mode. The steps of the high-pressure main steam valve activity test are: first close the regulating valve on the same side of the test high-pressure main steam valve at a certain rate; after all the regulating valves on the same side are fully closed, the test high-pressure main steam valve automatically closes quickly and then immediately fully opens, completing the full-stroke activity test of the test high-pressure main steam valve (during the test, the non-test high-pressure main steam valve on the other side is always in the fully open state). Afterwards, the operator clicks "End of Test", and the regulating valves on the same side open at a certain rate at the same time and return to the position before the test.

[0005] Obviously, during the high-pressure main steam valve activity test, the various control valve instructions are completely different from the steam distribution function instructions of the DEH system (i.e., normal operating state). During the high-pressure main steam valve activity test on one side, along with the closing of the control valve on the same side, the steam turbine gradually changes from double-side steam inlet to single-side steam inlet (i.e., all steam from the boiler enters the steam turbine through the main steam valve and the control valve on the other side). The control valve on the other side is insufficient to compensate for the deviation of the steam inlet flow rate, which will inevitably cause a sharp drop in generator power and a sharp fluctuation in the main steam pressure. At the same time, since the flow diameter of the single-side steam inlet is only half of that of the double-side steam inlet, the steam flow rate is significantly reduced under the same pressure difference, resulting in a significant change in the control valve flow characteristics. Simulation calculations show that the originally linear throttle flow characteristics under double-sided synchronous steam inlet conditions will present a nonlinear characteristic of superposition of flat and steep areas under single-sided steam inlet and other non-synchronous steam inlet conditions; especially when the main steam valve / main throttle valve on one side is fully closed to form single-sided steam inlet, the throttle flow characteristics present serious nonlinearity, which can easily lead to over-adjustment of the DEH system power closed-loop control, and then generate low-frequency oscillation of the generator power.

[0006] In order to reduce the fluctuation of generator power during the test, the industry usually adopts CCS coordination control system (CCS) or DEH system power closed loop (method 1), and maintains the generator power unchanged by changing the steam turbine command (the opening of the other side of the throttle valve follows the steam distribution function command); there is also a method that uses the throttle valve command balance loop to evenly distribute the total flow command reduced by all the throttle valves on the same side and superimpose it on the flow command of all the throttle valves on the other side (method 2). The former directly balances the generator power and has a better actual effect; but due to the slow steam turbine main control adjustment rate of the CCS system or DEH system, on the one hand, the main control PID parameters need to be enhanced, and on the other hand, the switch rate of the throttle valve on the same side of the test main steam valve must be slowed down, which makes the unit stay in the non-double-side synchronous steam inlet state for a long time (usually 10 to 15 minutes). Therefore, during the test, the strong PID parameters are superimposed on the severely nonlinear flow characteristics, resulting in frequent low-frequency oscillations of the generator power. The latter directly balances the flow command, which follows the turbine principle to a certain extent; however, due to the nonlinear characteristics of the fast-opening throttle valve, not only is the actual flow balance effect poor, it is difficult to maintain the stability of the generator power, but also the throttle valve command on the other side changes too quickly, which easily causes fluctuations in the EH oil pressure. Therefore, no matter which method is used, there are clear safety risks.

[0007] In order to prevent large fluctuations or low-frequency oscillations in the generator power during the test and ensure the regular and safe implementation of the high-pressure main steam valve activity test, the present invention proposes a high-pressure main steam valve activity test method. Summary of the invention

[0008] The purpose of the present invention is to prevent large fluctuations or low-frequency oscillations in the generator power during the test and ensure the regular and safe implementation of the high-pressure main steam valve activity test. The present invention proposes a high-pressure main steam valve activity test method.

[0009] The technical solution implemented by the present invention is as follows: a high-pressure main steam valve activity test method, which presets a safety median value of a throttle command and adds a throttle command compensator, and during the high-pressure main steam valve activity test, the difference between the throttle command on the same side of the test high-pressure main steam valve and the safety median is superimposed in real time on each throttle command downstream of the other side of the main steam valve, and adopts auxiliary measures such as linearizing and adjusting the DEH steam distribution function, limiting the test boundary conditions, exiting the DEH remote control mode, exiting the primary frequency regulation loop, exiting the regulating stage pressure loop, exiting the auxiliary machine failure rapid load reduction loop, exiting the power feedback loop, and shortening the test time, so as to maintain the stability of the generator power during the test and reduce the risk of low-frequency oscillation of the generator power.

[0010] Before carrying out the high-pressure main steam valve activity test, the method needs to linearly adjust the single-valve steam distribution function of the DEH system to achieve a 1:1 correspondence between the steam turbine command and the steam inlet flow rate percentage.

[0011] The method generates a two-dimensional curve of "total valve position command-throttle control command" according to a single-valve steam distribution function; a relatively linear throttle control command area is marked on the curve, and the median value of the throttle control command in the area is recorded as a "safe median value".

[0012] The method confirms that the generator power is less than 50% of the rated load and the valve adjustment command is at a "safe mid-value" before conducting the high-pressure main steam valve activity test.

[0013] The method confirms that the unit is in a single valve operation mode and exits the DEH remote control mode before conducting a high-pressure main steam valve activity test.

[0014] The method confirms that the unit exits the primary frequency regulation loop of the CCS system and the DEH system before conducting the high-pressure main steam valve activity test.

[0015] The method confirms that the unit exits the regulating stage pressure circuit and the auxiliary machine failure rapid load reduction circuit before conducting the high-pressure main steam valve activity test.

[0016] The method confirms that the unit exits the power feedback loop of the CCS system and the DEH system before carrying out the high-pressure main steam valve activity test.

[0017] In the method, during the high-pressure main steam valve activity test, the closing rate and opening rate of the same-side regulating valve instruction of the high-pressure main steam valve are both set to 2% / second.

[0018] The method uses the safety median value as the starting reference value during the high-pressure main steam valve activity test, and calculates the difference between the same-side valve adjustment command of the test high-pressure main steam valve and the safety median value in real time; and superimposes the difference on the same-side valve adjustment command of the non-test high-pressure main steam valve on the other side.

[0019] The beneficial effect of the present invention is that, during the high-pressure main steam valve activity test, by presetting the regulating valve command safety median, adding a regulating valve command compensator and taking a series of auxiliary measures, full use is made of the relatively linear command area of ​​the regulating valve flow characteristic, and the stability of the turbine steam inlet flow is maintained more ideally, the fluctuation of the generator power and the main steam pressure is reduced, and the action range of the regulating valve during the main steam valve activity test is controlled within the relatively linear command area of ​​the flow, and various loops are exited, and at the same time, the non-bilateral synchronous steam intake time is shortened to about 1 minute, effectively eliminating various potential factors inducing low-frequency oscillations. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the safe median value of the throttle command according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is shown in the figure. Figure 1 , clearly and completely describe the technical solutions in the embodiments of the present invention.

[0022] A high-pressure main steam valve activity test method according to an embodiment of the present invention comprises the following steps:

[0023] The method presets a safe median value of a throttle command and adds a throttle command compensator, superimposes the difference between the downstream throttle command on the same side of the test high-pressure main steam valve and the safe median value during the high-pressure main steam valve activity test on each throttle command downstream of the other side of the main steam valve in real time, and adopts auxiliary measures such as linearizing and adjusting the DEH steam distribution function, limiting the test boundary conditions, exiting the DEH remote control mode, exiting the primary frequency regulation loop, exiting the regulating stage pressure loop, exiting the auxiliary machine failure rapid load reduction loop, exiting the power feedback loop, and shortening the test time, so as to maintain the stability of the generator power during the test and reduce the risk of low-frequency oscillation of the generator power.

[0024] Before carrying out the high-pressure main steam valve activity test, the method needs to linearly adjust the single-valve steam distribution function of the DEH system to achieve a 1:1 correspondence between the steam turbine command and the steam inlet flow rate percentage.

[0025] The method generates a two-dimensional curve of "total valve position command-throttle control command" according to a single-valve steam distribution function; a relatively linear throttle control command area is marked on the curve, and the median value of the throttle control command in the area is recorded as a "safe median value".

[0026] The method confirms that the generator power is less than 50% of the rated load and the valve adjustment command is at a "safe mid-value" before conducting a high-pressure main steam valve activity test.

[0027] The method confirms that the unit is in a single valve operation mode and exits the DEH remote control mode before conducting a high-pressure main steam valve activity test.

[0028] The method confirms that the unit exits the primary frequency regulation loop of the CCS system and the DEH system before conducting the high-pressure main steam valve activity test.

[0029] The method confirms that the unit exits the regulating stage pressure circuit and the auxiliary machine failure rapid load reduction circuit before conducting the high-pressure main steam valve activity test.

[0030] The method confirms that the unit exits the power feedback loop of the CCS system and the DEH system before carrying out the high-pressure main steam valve activity test.

[0031] In the method, during the high-pressure main steam valve activity test, the closing rate and opening rate of the same-side regulating valve instruction of the high-pressure main steam valve are both set to 2% / second.

[0032] The method uses the safety median value as the starting reference value during the high-pressure main steam valve activity test, and calculates the difference between the same-side valve adjustment command of the test high-pressure main steam valve and the safety median value in real time; and superimposes the difference on the same-side valve adjustment command of the non-test high-pressure main steam valve on the other side.

[0033] The above is a detailed introduction to the high-pressure main steam valve activity test method provided by the present invention. In this embodiment, a specific example is used to illustrate the principle and implementation method of the present invention. The description of the above embodiment is only used to help understand the method and core idea of ​​the present invention. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A high-pressure main steam valve activity test method, characterized in that: The method presets a safe median value of a throttle command and adds a throttle command compensator, superimposes the difference between the downstream throttle command on the same side of the high-pressure main steam valve and the safe median value during the high-pressure main steam valve activity test on each throttle command downstream of the other side of the main steam valve in real time, and linearly adjusts the DEH steam distribution function, limits the test boundary conditions, exits the DEH remote control mode, exits the primary frequency regulation loop, exits the regulating stage pressure loop, exits the auxiliary machine failure rapid load reduction loop, exits the power feedback loop, and shortens the test time, so as to maintain the stability of the generator power during the test and reduce the risk of low-frequency oscillation of the generator power.

2. A high-pressure main steam valve activity test method according to claim 1, characterized in that: Before carrying out the high-pressure main steam valve activity test, the method needs to linearly adjust the single-valve steam distribution function of the DEH system to achieve a 1:1 correspondence between the steam turbine command and the steam inlet flow rate percentage.

3. A high-pressure main steam valve activity test method according to claim 2, characterized in that: The method generates a two-dimensional curve of "total valve position command-throttle control command" according to a single-valve steam distribution function; a relatively linear throttle control command area is marked on the curve, and the median value of the throttle control command in the area is recorded as a "safe median value".

4. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method confirms that the generator power is less than 50% of the rated load and the valve adjustment command is at a "safe mid-value" before conducting the high-pressure main steam valve activity test.

5. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method confirms that the unit is in a single valve operation mode and exits the DEH remote control mode before conducting a high-pressure main steam valve activity test.

6. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method confirms that the unit exits the primary frequency regulation loop of the CCS system and the DEH system before conducting the high-pressure main steam valve activity test.

7. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method confirms that the unit exits the regulating stage pressure circuit and the auxiliary machine failure rapid load reduction circuit before conducting the high-pressure main steam valve activity test.

8. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method confirms that the unit exits the power feedback loop of the CCS system and the DEH system before carrying out the high-pressure main steam valve activity test.

9. A high-pressure main steam valve activity test method according to claim 1, characterized in that: In the method, during the high-pressure main steam valve activity test, the closing rate and opening rate of the same-side regulating valve instruction of the high-pressure main steam valve are both set to 2% / second.

10. A high-pressure main steam valve activity test method according to claim 1, characterized in that: The method uses the safety median value as the starting reference value during the high-pressure main steam valve activity test, and calculates the difference between the same-side valve adjustment command of the test high-pressure main steam valve and the safety median value in real time; and superimposes the difference on the same-side valve adjustment command of the non-test high-pressure main steam valve on the other side.

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