A multi-state coupled governing steam turbine unit and a control method thereof

Abstract

The application provides a multi-state coupling regulation steam turbine unit and a control method thereof, wherein the first stage of the high-pressure cylinder is a regulation stage with n parallel nozzle groups, a steam distribution system comprises a main steam pipe and a pre-regulation module, the main steam pipe and the pre-regulation module are selectively connected with a main steam outlet of a boiler, the pre-regulation module is parallel to the main steam pipe, at least two steam outlet ends of the steam distribution system are connected with the regulation stage through a valve switching system, the main steam pipe is connected with i nozzle groups and the pre-regulation module is connected with n-i nozzle groups by controlling the valve switching system. In different working conditions, the proportion of the steam entering the pre-regulation module is adjusted, the number of the nozzle groups connected with the pre-regulation module is changed, when the load is lower, the number of the nozzle groups connected with the pre-regulation module is more, the energy of the main steam is graded by the pre-regulation module, the purpose of regulating the peak load and saving energy of the thermal power generating unit in different load working conditions is achieved, and the unit efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation peak shaving and energy saving technology, and particularly relates to a steam turbine unit with multi-state coupling regulation and its control method. Background Technology

[0002] With increasing domestic carbon reduction requirements, the proportion of new energy sources is rising. Traditional thermal power generating units are facing increasing pressure to regulate peak loads, making deep peak shaving an inevitable trend in this field. However, due to the design characteristics of traditional thermal power generating units, their efficiency drops significantly below design efficiency during peak shaving, especially at low loads. Therefore, improving the efficiency of thermal power generating units under different load conditions during peak shaving has become particularly important. Currently, there are three main ways to improve the efficiency of thermal power generating units during low-load peak shaving:

[0003] I. Combustion Adjustment: Change the state of low boiler combustion efficiency, high oxygen content, and low reheat steam temperature at low load by adjusting combustion to improve combustion efficiency in the low load section.

[0004] II. Improve cold-end efficiency: By modifying the cold-end system, the heat exchange margin of the cold-end system under low load is explored, and the back pressure of the unit is reduced and the unit efficiency is improved while ensuring the safety of the cold-end system.

[0005] 3. Add a small back-pressure steam turbine for heating: When the load is low, higher pressure steam is used for steam supply. By adding a small back-pressure steam turbine, part of the residual pressure is recovered to improve efficiency.

[0006] The above methods are traditional efficiency improvement techniques that only improve the performance of thermal power generating units to a certain extent, taking into account the operating characteristics of low and medium loads. However, they still have the following shortcomings:

[0007] I. The potential for energy consumption reduction after the renovation is limited, not exceeding 5g / kWh;

[0008] Second, some technologies require specific heating (or steam) conditions and are not applicable to all units;

[0009] Third, it is not applicable to all operating conditions; the energy-saving effect is only obvious in a certain operating condition.

[0010] Fourth, for systems like steam back-pressure turbines, the operation involves switching the system on and off under varying operating conditions, making operation adjustments inflexible. Summary of the Invention

[0011] In order to overcome the shortcomings of the prior art, the present invention aims to provide a steam turbine unit with multi-state coupling regulation and its control method, which is mainly used to solve the problems of narrow regulation range, insufficient flexibility and poor energy saving and consumption reduction effect of the existing steam turbine unit.

[0012] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0013] The first inventive point is to provide a multi-state coupled regulation steam turbine unit, including a boiler, a steam distribution system, and a high-pressure cylinder. The first stage of the high-pressure cylinder is a regulating stage with n parallel nozzle groups. The steam distribution system includes a main steam pipeline and a pre-regulating module. The main steam pipeline and the pre-regulating module are selectively connected to the main steam outlet of the boiler. The pre-regulating module is connected in parallel with the main steam pipeline. At least two steam outlets of the steam distribution system are connected to the regulating stage through a valve switching system. By controlling the valve switching system, the main steam pipeline is connected to i of the nozzle groups, and the pre-regulating module is connected to ni of the nozzle groups, where 0 ≤ i ≤ n, and n is an integer greater than 1.

[0014] In some embodiments, the pre-regulation module includes at least one pre-turbine, which is connected in parallel or in series to form a pre-regulation module and then connected in parallel with the main steam pipeline.

[0015] In some embodiments, each of the nozzle groups is provided with an adjustment valve, and at least one pair of nozzle groups are connected by a shut-off valve.

[0016] In some embodiments, the number of nozzle groups is four, namely a first nozzle group, a second nozzle group, a third nozzle group, and a fourth nozzle group. A first regulating valve is provided before the first nozzle group, a second regulating valve is provided before the second nozzle group, a third regulating valve is provided before the third nozzle group, and a fourth regulating valve is provided before the fourth nozzle group. At least one steam outlet end of the pre-regulating module is connected to the first regulating valve and the second regulating valve pipeline through a first steam outlet valve. The steam outlet end of the main steam pipeline is connected to the third regulating valve and the fourth regulating valve pipeline through a main steam outlet valve. The second regulating valve and the third regulating valve are connected by a shut-off valve.

[0017] In some embodiments, there are two front-mounted steam turbines, namely a first front-mounted steam turbine and a second front-mounted steam turbine. The first front-mounted steam turbine and the second front-mounted steam turbine are coaxially arranged and used to drive the auxiliary generator.

[0018] The steam inlet of the first pre-mounted steam turbine is connected to the main steam outlet of the boiler through a first steam inlet valve, and the steam outlet of the first pre-mounted steam turbine is connected to the inlet of the steam distribution system through a first steam outlet valve.

[0019] The steam inlet of the second front-mounted steam turbine is connected to the main steam outlet of the boiler through a second steam inlet valve, and the steam outlet of the second front-mounted steam turbine is connected to the inlet of the steam distribution system through a second steam outlet valve.

[0020] The steam outlet of the second front turbine is also connected to the steam inlet of the first front turbine via a switching valve.

[0021] The second inventive point is to provide a control method for a steam turbine unit applied to the above-mentioned multi-state coupled regulation, comprising the following steps:

[0022] Based on the number of nozzle groups n, determine n+1 state points S. i (0≤i≤n), establish a mapping table between state points and nozzle groups, where state point S i The load rate is X i %, State point S i Load factor X i % greater than state point S i+1 Load factor X i+1 %, State point S i The number of nozzle groups connected to the pre-adjustment module is greater than that at state point S. i+1 Few;

[0023] Detect the current load factor X%.

[0024] When the load factor X i+1 % <X%≤X i When %, select state point S. i The corresponding nozzle group connection status controls the valve switching system and determines the system operation mode.

[0025] When the load factor X% ≤ X n When %, select state point S. n The corresponding nozzle group's on / off status controls the valve switching system and determines the system's operating mode.

[0026] In some embodiments, the load rate corresponding to state point S0 is the maximum load condition X0%, and the nozzle group connection state corresponding to state point S0 is: the main steam outlet of the boiler is connected to the main steam pipeline, the main steam pipeline is connected to n nozzle groups, and the pre-adjustment module is not connected to the nozzle group.

[0027] The load rate corresponding to state point S1 is X1%, and the nozzle group connection state corresponding to state point S1 is: the main steam outlet of the boiler is connected to the main steam pipeline and the pre-regulation module, the main steam pipeline is connected to n-1 of the nozzle groups, and the pre-regulation module is connected to 1 of the nozzle groups;

[0028] State point S nThe corresponding load rate is X n %, State point S n The corresponding nozzle group connection status is as follows: the main steam outlet of the boiler is connected to the pre-regulation module, the main steam pipeline is not connected to the nozzle group, and the pre-regulation module is connected to n nozzle groups.

[0029] In some embodiments, based on the number of nozzle groups n and the number of front turbines included in the front regulating module, the possible number f(m,n) of connections between the main steam outlet of the boiler and the high-pressure cylinder regulating stage via the main steam pipeline, the front regulating module and n nozzle groups are determined.

[0030] Based on the main steam pressure reaching the design value, f(m,n) state points are determined. After theoretical optimization and safety analysis, x state points with poor efficiency are eliminated, resulting in the optimal number of state points f(m,n)-x.

[0031] When the load rate X% is operating between the two preferred load rates, the system operation mode is determined according to the nozzle group connection status at the higher load rate state point, and the pressure is operated by sliding pressure when operating between the two state points.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] The steam distribution system can control the flow of steam, allowing a portion of the main steam to directly enter the nozzle group and another portion to enter the pre-regulation module before entering the nozzle group. Under different operating conditions, the proportion of steam entering the pre-regulation module can be adjusted, thereby changing the number of nozzle groups connected to the pre-regulation module. The lower the load, the more nozzle groups the pre-regulation module connects to. By using the pre-regulation module to utilize the main steam in stages, the system can achieve peak shaving and energy saving for thermal power generating units under different load conditions, thereby improving unit efficiency.

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0035] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of a steam turbine unit with multi-state coupling regulation in one embodiment.

[0037] Figure 2 This is a schematic diagram of a multi-state coupled regulation steam turbine unit in another embodiment.

[0038] Figure 3 This is a schematic diagram of a multi-state coupled regulation steam turbine unit in another embodiment. Detailed Implementation

[0039] The technical solution of the present invention will now be clearly and completely described 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 are within the scope of protection of the present invention.

[0040] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0041] In the description of this invention, when a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device. When a specific device is described as being connected to other devices, the specific device may be directly connected to the other devices without an intermediary device, or it may not be directly connected to the other devices but may have an intermediary device.

[0042] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0043] Firstly, referring to Figure 1 and Figure 3 This invention provides a multi-state coupled regulation steam turbine unit, including a boiler, a steam distribution system, and a high-pressure cylinder. The first stage of the high-pressure cylinder is a regulating stage 30 with n parallel nozzle groups. The steam distribution system includes a main steam pipeline 10 and a pre-regulating module 20. The main steam pipeline 10 and the pre-regulating module 20 can be selectively connected to the main steam outlet of the boiler. The pre-regulating module 20 is connected in parallel with the main steam pipeline 10. At least two steam outlets of the steam distribution system are connected to the regulating stage 30 through a valve switching system. By controlling the valve switching system, the main steam pipeline 10 is connected to i nozzle groups, and the pre-regulating module 20 is connected to ni nozzle groups, where 0≤i≤n and n is an integer greater than 1.

[0044] It should be noted that this turbine unit has multiple selectable states, including the steam distribution ratio between the main steam pipeline 10 and the pre-regulation module 20 in the steam distribution system, as well as the connection state between the nozzle group and the pre-regulation module 20 and the main steam pipeline 10.

[0045] First, the main steam pipeline 10 and the pre-regulating module 20 can be selectively connected to the main steam outlet of the boiler. That is, the main steam coming out of the boiler can, depending on the controlled connection result, enter either the main steam pipeline 10 or the pre-regulating module 20, or a portion can enter the main steam pipeline 10 and a portion can enter the pre-regulating module 20. Furthermore, the mass flow rate ratio of the steam in the main steam pipeline 10 and the pre-regulating module 20 can be adjusted. This is one type of coupling factor.

[0046] In addition, the regulating stage 30 has a total of n nozzle groups. The connection status between different nozzle groups and the pre-regulating module 20 and the main steam pipeline 10 is also another coupling factor. That is, all n nozzle groups can be connected to the pre-regulating module 20, or all n nozzle groups can be connected to the main steam pipeline 10, or some nozzle groups are connected to the pre-regulating module 20 and other nozzle groups are connected to the main steam pipeline 10.

[0047] Furthermore, the steam distribution system, which consists of the main steam pipeline 10 and the pre-regulating module 20, has at least two steam outlets. Each steam outlet can be individually controlled by a valve. The steam outlets are connected to a valve switching system, which includes valves and pipelines with certain connections. By controlling different valve combinations, the steam from the steam outlets passes through a specific nozzle group and enters the regulating stage 30.

[0048] In summary, when the load condition of the steam turbine unit decreases, the proportion of steam passing through the pre-regulation module 20 can be increased, and the number of nozzle groups connected to the pre-regulation module 20 can be gradually increased. This allows main steam of different flow rates to be delivered to the high-pressure cylinder to perform work. At the same time, the pre-regulation module 20 enables the graded utilization of energy from the main steam, reducing the throttling losses caused by peak shaving through the main steam isolation valve in traditional technologies. This achieves the purpose of peak shaving and energy saving for thermal power generating units under different load conditions, improving unit efficiency. Moreover, it does not rely on specific external conditions such as heating or steam supply, and can achieve flexible adjustment. It is suitable for different operating conditions and different types of thermal power generating units, and its operation and adjustment are flexible.

[0049] In this embodiment, the pre-regulation module 20 includes at least one pre-mounted steam turbine. When there is only one pre-mounted steam turbine, the pre-mounted steam turbine is connected in parallel with the main steam pipeline 10. When there is more than one pre-mounted steam turbine, the pre-mounted steam turbines are connected in parallel or in series to form a pre-regulation module 20, which is then connected in parallel with the main steam pipeline 10. That is, the pre-mounted steam turbine can be switched to a parallel state or a series state under the control of the valve. In the parallel state, the pre-regulation module 20 has multiple steam outlets. In the series state, the pre-regulation module 20 has one steam outlet.

[0050] Each nozzle group is equipped with a regulating valve, and at least one pair of nozzle groups are connected by a shut-off valve. The regulating valve can control the on / off state of each nozzle group, while the shut-off valve between nozzle groups can control the same steam source to enter multiple nozzle groups.

[0051] Example 1:

[0052] Combination Figure 1In this embodiment 1, the pre-regulation module 20 includes a pre-turbine 200, with steam valves installed before and after the pre-turbine 200. There are four nozzle groups: a first nozzle group 31, a second nozzle group 32, a third nozzle group 33, and a fourth nozzle group 34. A first regulating valve 41 is installed before the first nozzle group 31, a second regulating valve 42 is installed before the second nozzle group 32, a third regulating valve 43 is installed before the third nozzle group 33, and a fourth regulating valve 44 is installed before the fourth nozzle group 34. The steam outlet of the pre-turbine 200 is connected to a first steam outlet valve. 25 is connected to the first regulating valve 41 and the second regulating valve 42. The steam outlet end of the main steam pipeline 10 is connected to the third regulating valve 43 and the fourth regulating valve 44 via the main steam outlet valve 11. The first regulating valve 41 and the second regulating valve 42 are connected by the first shut-off valve 51, which can be located between the first steam outlet valve 25 and the second regulating valve 42. The second regulating valve 42 and the third regulating valve 43 are connected by the second shut-off valve 52. The third regulating valve 43 and the fourth regulating valve 44 are connected by the third shut-off valve. The valve 53 is connected to the main steam outlet valve 11, and the third shut-off valve 53 can be located between the main steam outlet valve 11 and the third regulating valve 43. The valve switching system consists of the first regulating valve 41, the second regulating valve 42, the third regulating valve 43, the fourth regulating valve 44, the first shut-off valve 51, the second shut-off valve 52, the third shut-off valve 53, and the pipelines between them. Through the coordinated adjustment of these valves, multi-state coupling between the front-mounted steam turbine 200, the main steam pipeline 10, and the first nozzle group 31, the second nozzle group 32, the third nozzle group 33, and the fourth nozzle group 34 can be achieved. The system can be configured in various ways, such as closing the first steam outlet valve 25 and opening the main steam outlet valve 11, so that the main steam flows only through the main steam pipeline 10. Then, the first regulating valve 41, the second regulating valve 42, the third regulating valve 43, the fourth regulating valve 44, the first shut-off valve 51, the second shut-off valve 52, and the third shut-off valve 53 can be opened, so that the steam enters the four nozzle groups. Of course, the system can also be controlled by switching the valves so that the steam at the steam outlet of the front turbine 200 enters three nozzle groups, and the steam at the steam outlet of the main steam pipeline 10 enters one nozzle group, etc.

[0053] Example 2:

[0054] Combination Figure 2This embodiment 2 is essentially based on embodiment 1, but eliminates the first and third shut-off valves, and connects both ends of the second shut-off valve 52 to the outlets of the second regulating valve 42 and the third regulating valve 43 via pipelines. This method uses only one shut-off valve to achieve flexible adjustment of four nozzle groups. For example, when the first regulating valve 41, the second regulating valve 42, and the second shut-off valve 52 are opened, the third regulating valve 43 is closed, and the fourth regulating valve 44 is opened, the steam at the steam outlet of the front turbine 200 enters three nozzle groups, and the steam at the steam outlet of the main steam pipeline 10 enters one nozzle group. Alternatively, when the second shut-off valve 52 is closed and all four regulating valves are opened, the steam at the steam outlet of the front turbine 200 enters two nozzle groups, and the steam at the steam outlet of the main steam pipeline 10 enters two nozzle groups, and so on.

[0055] Example 3:

[0056] Combination Figure 3 In this embodiment 3, there are two front-mounted steam turbines, namely a first front-mounted steam turbine 21 and a second front-mounted steam turbine 22. The first front-mounted steam turbine 21 and the second front-mounted steam turbine 22 are coaxially arranged and used to drive the auxiliary generator 23. The high-pressure cylinder is connected to the main generator, and the high-pressure cylinder and the front-mounted steam turbine are arranged on opposite shafts.

[0057] The steam inlet of the first front-mounted steam turbine 21 is connected to the main steam outlet of the boiler through the first steam inlet valve 24, and the steam outlet of the first front-mounted steam turbine 21 is connected to the inlet of the steam distribution system through the first steam outlet valve 25.

[0058] The steam inlet of the second front-mounted steam turbine 22 is connected to the main steam outlet of the boiler through the second steam inlet valve 26, and the steam outlet of the second front-mounted steam turbine 22 is connected to the inlet of the steam distribution system through the second steam outlet valve 27.

[0059] The steam outlet of the second pre-turbine 22 is also connected to the steam inlet of the first pre-turbine 21 via a switching valve 28. By controlling the opening or closing of the switching valve 28, in conjunction with the opening and closing of the first steam inlet valve 24, the first steam outlet valve 25, the second steam inlet valve 26, and the second steam outlet valve 27, the series and parallel connection of the second pre-turbine 22 and the first pre-turbine 21 can be controlled. In the series state, the pre-regulatory module 20 has two steam outlets connected to the valve switching system; in the parallel state, the pre-regulatory module 20 has only one steam outlet connected to the valve switching system.

[0060] Furthermore, the valve switching system in Embodiment 3 is the same as that in Embodiment 1, that is, there are four nozzle groups, namely the first nozzle group 31, the second nozzle group 32, the third nozzle group 33, and the fourth nozzle group 34. A first regulating valve 41 is provided before the first nozzle group 31, a second regulating valve 42 is provided before the second nozzle group 32, a third regulating valve 43 is provided before the third nozzle group 33, and a fourth regulating valve 44 is provided before the fourth nozzle group 34. The steam outlet end of the first pre-turbine 21 is connected to the first regulating valve 41 and the second regulating valve 42 through the first steam outlet valve 25. The steam outlet end of the main steam pipeline 10 is connected to the third regulating valve 43 and the fourth regulating valve 44 through the main steam outlet valve 11. The steam outlet end of the second pre-turbine 22 is connected to the main steam pipeline 10 through the second steam outlet valve 27. The first regulating valve 41 and the second regulating valve 42 are connected by a first shut-off valve. The valves 51 are connected. The first shut-off valve 51 can be located between the first steam outlet valve 25 and the second regulating valve 42. The second regulating valve 42 and the third regulating valve 43 are connected through the second shut-off valve 52. The third regulating valve 43 and the fourth regulating valve 44 are connected through the third shut-off valve 53. The third shut-off valve 53 can be located between the main steam outlet valve 11 and the third regulating valve 43. The valve switching system is composed of the first regulating valve 41, the second regulating valve 42, the third regulating valve 43, the fourth regulating valve 44, the first shut-off valve 51, the second shut-off valve 52, the third shut-off valve 53 and the pipelines between them. Through the coordination and adjustment of the above valves, the multi-state coupling relationship between the first front turbine 21, the second front turbine 22, the main steam pipeline 10 and the first nozzle group 31, the second nozzle group 32, the third nozzle group 33 and the fourth nozzle group 34 can be realized.

[0061] Example 4:

[0062] This embodiment 4 is essentially based on embodiment 3, except that the first shut-off valve and the third shut-off valve are removed, and the two ends of the second shut-off valve are connected to the outlets of the second regulating valve and the third regulating valve through pipelines. Since this connection method is similar to that of embodiment 2, it will not be described again here. Please refer to the valve switching system in embodiment 2.

[0063] As can be seen from Examples 2 and 4, multi-state coupling and connection between the nozzle group and the pre-regulation module and the main steam pipeline can also be achieved by connecting only a pair of nozzle groups through a shut-off valve.

[0064] Secondly, the present invention also provides a control method for a steam turbine unit with multi-state coupled regulation applied in the above embodiments, comprising the following steps:

[0065] Based on the number of nozzle groups n, determine n+1 state points S. i(0≤i≤n), establish a mapping table between state points and nozzle groups, where state point S i The load rate is X i %, State point S i Load factor X i % greater than state point S i+1 Load factor X i+1 %, State point S i The number of nozzle groups connected to the pre-adjustment module 20 is greater than the number of states at point S. i+1 Few;

[0066] Detect the current load factor X%.

[0067] When the load factor X i+1 % <X%≤X i When %, select state point S. i The corresponding nozzle group connection status controls the valve switching system and determines the system operation mode.

[0068] When the load factor X% ≤ X n When %, select state point S. n The corresponding nozzle group's on / off status controls the valve switching system and determines the system's operating mode.

[0069] It should be noted that when there are 4 nozzle groups, there are a total of 5 state points: S0, S1, S2, S3, and S4. State point S0 corresponds to the highest load rate, and S4 corresponds to the lowest load rate. As the load rate decreases continuously under full load, the state point will gradually decrease from S0 to S4. Each state point is associated with a specific set of nozzle group connection states, for example:

[0070] The load rate corresponding to state point S0 is the maximum load condition X0%. The nozzle group connection state corresponding to state point S0 is: the main steam outlet of the boiler is connected to the main steam pipeline 10, the main steam pipeline 10 is connected to the 4 nozzle groups, and the pre-regulation module 20 is not connected to the nozzle groups. Under this condition, the main steam does not pass through the pre-regulation module 20, but enters the 4 nozzle groups through the main steam pipeline 10. The ratio of the main steam pipeline 10 to the nozzle groups connected to the pre-regulation module 20 is 4:0, which meets the requirements of high load operation.

[0071] The load rate corresponding to state point S1 is X1%, and the nozzle group connection status corresponding to state point S1 is as follows: the main steam outlet of the boiler is connected to the main steam pipeline 10 and the pre-regulation module 20. The main steam pipeline 10 is connected to 3 nozzle groups, and the pre-regulation module 20 is connected to 1 nozzle group. As the load rate decreases, one nozzle group connected to the main steam pipeline 10 is reduced, and one nozzle group connected to the pre-regulation module 20 is added. The ratio of nozzle groups connected to the main steam pipeline 10 and the pre-regulation module 20 is 3:1, which meets the requirements for medium load operation.

[0072] And so on...

[0073] The load rate corresponding to the state point S4 is X4%, and the nozzle group connection state corresponding to the state point S4 is: connecting the main steam outlet of the boiler to the pre-regulating module 20, not connecting the main steam pipeline 10 to the nozzle group, and connecting the pre-regulating module 20 to 4 nozzle groups; as the load rate continues to decrease, one more nozzle group connected to the main steam pipeline 10 is reduced, and one more nozzle group connected to the pre-regulating module 20 is added, so that the ratio of the nozzle groups connected between the main steam pipeline 10 and the pre-regulating module 20 is 0:4, meeting the low-load operation requirements.

[0074] In summary, for the state point S i the number of nozzle groups corresponding to it that are connected to the pre-regulating module 20 is less than that of the state point S i+1 That is, when the load rate decreases, the state points move backward continuously, and the number of nozzle groups connected to the pre-regulating module 20 will increase;

[0075] Therefore, after detecting the current load rate X%, first determine between which two load rates corresponding to the state points it is. For example, when X2% < X% ≤ X1%, select the nozzle group connection state corresponding to the state point S1, control the valve switching system, and determine the system operation mode, so that the ratio of the nozzle groups connected between the main steam pipeline 10 and the pre-regulating module 20 is 3:1 to adapt to the medium-load operation;

[0076] As the load decreases, when X% ≤ X4%, select the nozzle group connection state corresponding to the state point S4, control the valve switching system, and determine the system operation mode, so that the ratio of the nozzle groups connected between the main steam pipeline 10 and the pre-regulating module 20 is 0:4 to adapt to the low-load operation.

[0077] Since there are many implementation methods for the valve switching system, the above Examples 1 to 4 are just one possible implementation method. Those skilled in the art can also set different combinations of valves and pipelines according to conventional technical means to achieve various connection methods between the steam outlet end of the main steam pipeline 10 and the pre-regulating module 20 and each nozzle group, which will not be elaborated here one by one. However, any non-substantive changes and substitutions made based on this invention fall within the scope of protection required by this invention.

[0078] In the above embodiments, the number of state points S i is only related to the number n of nozzle groups. This method is more suitable for the case of a single pre-turbine. However, for this multi-state coupled regulation steam turbine unit, in addition to the coupling factor of the number of nozzle groups, there is another coupling factor, which is the number of pre-turbines included in the pre-regulating module 20;

[0079] Therefore, as another implementation method, based on the number of nozzle groups n and the number of pre-heater turbines included in the pre-heater regulating module 20, the possible number f(m,n) of connections between the main steam outlet of the boiler and the high-pressure cylinder regulating stage 30 through the main steam pipeline 10, the pre-heater regulating module 20 and n nozzle groups is determined. In this step, since there are many flow paths for steam after it leaves the boiler and before it enters the high-pressure cylinder regulating stage 30, these flow paths are determined by the number of pre-heater turbines in operation and the proportion of nozzle groups connected to the main steam pipeline 10 and the pre-heater regulating module 20. Therefore, all possible connection numbers f(m,n) can be obtained from the two parameters m and n.

[0080] Based on the main steam pressure reaching the design value, f(m,n) state points are determined. After theoretical optimization and safety analysis, x state points with poor efficiency are eliminated, resulting in the optimal number of state points f(m,n)-x. To facilitate coupled regulation and control and obtain the required controllable state points more accurately, after calculating the total number of possible state points f(m,n) from the two parameters m and n, x state points with poor efficiency are eliminated based on calculation and analysis, and only the optimal f(m,n)-x state points are controlled.

[0081] When the load rate X% is operating between the two preferred load rates, the system operation mode is determined according to the nozzle group connection status at the higher load rate state point, and the pressure is operated by sliding pressure when operating between the two state points.

[0082] In summary, compared with the prior art, the above embodiments provide a multi-state coupled regulation steam turbine unit and its control method. Through the steam distribution system, a portion of the main steam can be directly fed into the nozzle group, while another portion enters the pre-regulation module 20 before entering the nozzle group. Under different operating conditions, the proportion of steam entering the pre-regulation module 20 can be adjusted, thereby changing the number of nozzle groups connected to the pre-regulation module 20. The lower the load, the more nozzle groups the pre-regulation module 20 connects to. Through the pre-regulation module 20, the energy of the main steam is utilized in stages, thereby achieving the purpose of peak shaving and energy saving for the thermal power generating unit under different load conditions and improving the unit efficiency.

[0083] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A steam turbine unit with multi-state coupled regulation, characterized in that, The system includes a boiler, a steam distribution system, and a high-pressure cylinder. The first stage of the high-pressure cylinder is a regulating stage with n parallel nozzle groups. The steam distribution system includes a main steam pipeline and a pre-regulating module. The main steam pipeline and the pre-regulating module are selectively connected to the main steam outlet of the boiler. The pre-regulating module is connected in parallel with the main steam pipeline. At least two steam outlets of the steam distribution system are connected to the regulating stage through a valve switching system. By controlling the valve switching system, the main steam pipeline is connected to i of the nozzle groups, and the pre-regulating module is connected to ni of the nozzle groups, where 0 ≤ i ≤ n, and n is an integer greater than 1. The pre-regulation module includes at least one pre-mounted steam turbine, which is connected in parallel or in series to form a pre-regulation module and then connected in parallel with the main steam pipeline; Each of the nozzle groups is provided with an adjustment valve, and at least one pair of nozzle groups are connected by a shut-off valve. The number of nozzle groups is four, namely a first nozzle group, a second nozzle group, a third nozzle group, and a fourth nozzle group. A first regulating valve is provided in front of the first nozzle group, a second regulating valve is provided in front of the second nozzle group, a third regulating valve is provided in front of the third nozzle group, and a fourth regulating valve is provided in front of the fourth nozzle group. At least one steam outlet end of the pre-regulating module is connected to the first regulating valve and the second regulating valve pipeline through a first steam outlet valve. The steam outlet end of the main steam pipeline is connected to the third regulating valve and the fourth regulating valve pipeline through a main steam outlet valve. The second regulating valve and the third regulating valve are connected by a shut-off valve.

2. The multi-state coupled regulation steam turbine unit as described in claim 1, characterized in that, The number of front-mounted steam turbines is two, namely a first front-mounted steam turbine and a second front-mounted steam turbine. The first front-mounted steam turbine and the second front-mounted steam turbine are coaxially arranged and used to drive the auxiliary generator. The steam inlet of the first pre-mounted steam turbine is connected to the main steam outlet of the boiler through a first steam inlet valve, and the steam outlet of the first pre-mounted steam turbine is connected to the inlet of the steam distribution system through a first steam outlet valve. The steam inlet of the second front-mounted steam turbine is connected to the main steam outlet of the boiler through a second steam inlet valve, and the steam outlet of the second front-mounted steam turbine is connected to the inlet of the steam distribution system through a second steam outlet valve. The steam outlet of the second front turbine is also connected to the steam inlet of the first front turbine via a switching valve.

3. A control method for a steam turbine unit with multi-state coupled regulation as described in any one of claims 1 to 2, characterized in that, Includes the following steps: Based on the number of nozzle groups n ,Sure n +1 state point S i (0≤) i ≤ n Establish a mapping table between state points and nozzle groups, where state point S i The load rate is X i %, State point S i Load factor X i % greater than state point S i+1 Load factor X i+1 %, State point S i The number of nozzle groups connected to the pre-adjustment module is greater than that at state point S. i+1 Few; Detect the current load factor X%. When the load factor X i+1 % <X%≤X i When %, select state point S. i The corresponding nozzle group connection status controls the valve switching system and determines the system operation mode. When the load factor X% ≤ X n When %, select state point S. n The corresponding nozzle group's on / off status controls the valve switching system and determines the system's operating mode.

4. The control method as described in claim 3, characterized in that, The load rate corresponding to state point S0 is the maximum load condition X0%. The nozzle group connection state corresponding to state point S0 is: the main steam outlet of the boiler is connected to the main steam pipeline, the main steam pipeline is connected to n nozzle groups, and the front-end adjustment module is not connected to the nozzle group. The load rate corresponding to state point S1 is X1%, and the nozzle group connection state corresponding to state point S1 is: the main steam outlet of the boiler is connected to the main steam pipeline and the pre-regulation module, the main steam pipeline is connected to n-1 of the nozzle groups, and the pre-regulation module is connected to 1 of the nozzle groups; State point S n The corresponding load rate is X n %, State point S n The corresponding nozzle group connection status is as follows: the main steam outlet of the boiler is connected to the pre-regulation module, the main steam pipeline is not connected to the nozzle group, and the pre-regulation module is connected to n nozzle groups.

5. The control method as described in claim 4, characterized in that, Based on the number of nozzle groups n The number of front-mounted steam turbines included in the front-mounted regulating module m Determine the possible number of connections between the main steam outlet of the boiler and the high-pressure cylinder regulating stage via the main steam pipeline, the pre-regulating module, and n nozzle groups. f ( m , n ); Determined based on the main steam pressure reaching the design value. f ( m , n From the given number of state points, through theoretical optimization and security analysis, some inefficient ones were eliminated. x From the given number of state points, we obtain the optimal number of state points. f ( m , n )- x ; When the load rate X% is operating between the two preferred load rates, the system operation mode is determined according to the nozzle group connection status at the higher load rate state point, and the pressure is operated by sliding pressure when operating between the two state points.

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