Double-machine back pressure output control thermal system of small steam turbine and control method thereof

Abstract

This invention relates to the field of steam turbine technology, and more particularly to a thermodynamic system for controlling the back pressure and output of a dual-unit regenerative small steam turbine. The system includes a main steam turbine, a small steam turbine, a first heater, a second heater, and driven equipment. An inlet regulating valve group is installed on the inlet pipe of the small steam turbine. The exhaust port of the small steam turbine is connected to the first heater, which is connected in parallel with a first bypass. A first regulating valve group is installed on the first bypass. The main steam turbine has a first extraction port, which is connected to the second heater via a first extraction pipe. The second heater is connected in parallel with a second bypass, which is equipped with a second regulating valve group. The invention also relates to a control method for this system, primarily controlling the back pressure and output of the small steam turbine by adjusting the opening degree of one or more of the inlet regulating valve group, the first regulating valve group, and the second regulating valve group. This allows for various back pressure and output control methods for the small steam turbine, meeting the control requirements for different trends in back pressure and output.

Description

Technical Field

[0001] This invention relates to the field of steam turbine technology, and in particular to a thermodynamic system for controlling the back pressure output of a dual-unit regenerative small steam turbine and its control method. Background Technology

[0002] As the parameters of thermal power turbine units increase, the superheat of high-pressure regenerative extraction steam also increases. In order to address the resulting decrease in energy efficiency, increase in irreversible losses, and increase in the cost of high-pressure extraction steam pipelines and high-pressure heaters, a dual-unit regenerative system has been proposed. This system can significantly reduce the superheat of high-pressure regenerative extraction steam, thereby improving the economic efficiency of the unit and reducing the cost of the unit.

[0003] The dual-turbine regenerative system includes a main steam turbine and a small steam turbine. The main steam turbine provides steam for part of the high-pressure heater, the small steam turbine, and part of the low-pressure heater. The small steam turbine is an extraction back-pressure steam turbine. The intermediate extraction and exhaust steam of the small steam turbine are supplied to the regenerative heater. The rotor of the small steam turbine is connected to the working mechanism and the power generation mechanism, providing power to the working mechanism. Excess power generation is balanced through the power generation mechanism.

[0004] The dual-unit regenerative small steam turbine differs from the feedwater pump turbine in conventional thermal power units. It undertakes multiple functions, including driving the working mechanism, coupling multi-stage regeneration, and outputting power to the power generation mechanism. This increases the difficulty of control and places higher demands on the control system. The flexible and reliable operation of the small steam turbine is the foundation for ensuring the safety and economy of the entire unit. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a thermodynamic system and control method for back pressure output control of a dual-unit regenerative small steam turbine, which can meet the control requirements of different trends in back pressure and output of the small steam turbine, so as to overcome the above-mentioned defects of the prior art.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] This invention provides a thermal system for controlling the back pressure and output of a dual-unit regenerative small steam turbine, comprising a main steam turbine, a small steam turbine, a first heater, a second heater, and driven equipment connected to the small steam turbine. The outlet of the second heater is connected to the inlet of the first heater. The steam inlet of the small steam turbine is connected to an inlet pipe, and an inlet regulating valve group is provided on the inlet pipe. The exhaust port of the small steam turbine is connected to the first heater through an exhaust pipe. The first heater is connected in parallel with a first bypass, and a first regulating valve group is provided on the first bypass. The main steam turbine has a first extraction port, which is connected to the second heater through a first extraction pipe. The second heater is connected in parallel with a second bypass, and a second regulating valve group is provided on the second bypass. The back pressure and output of the small steam turbine are controlled by adjusting the opening degree of one or more of the inlet regulating valve group, the first regulating valve group, and the second regulating valve group.

[0008] Preferably, it also includes a heater group, wherein the outlet of the first heater is connected to the inlet of the heater group, the steam inlet pipeline is connected to the main steam turbine, the main steam turbine is provided with a second steam extraction port upstream of the steam inlet pipeline, and the small steam turbine is provided with a small turbine steam extraction port. The second steam extraction port and the small turbine steam extraction port are respectively connected to the heater group through the second steam extraction pipeline and the small turbine steam extraction pipeline.

[0009] Preferably, it also includes a low-pressure heater, the outlet of which is connected to the inlet of the second heater, and a third steam extraction port is provided on the main steam turbine downstream of the first steam extraction port, which is connected to the low-pressure heater through a third steam extraction pipeline.

[0010] Preferably, the driven device includes a working mechanism and a power generation mechanism.

[0011] This invention also provides a control method for the back pressure and output control thermodynamic system of a dual-unit regenerative small steam turbine as described above. Based on the back pressure and output control requirements of the small steam turbine, one or more of the following three control measures are combined to achieve the back pressure and output control requirements of the small steam turbine: Control measure 1: Adjusting the opening of the steam inlet regulating valve group to increase or decrease both the back pressure and output of the small steam turbine; Control measure 2: Adjusting the opening of the first regulating valve group to increase the back pressure and decrease the output of the small steam turbine, and adjusting the opening of the first regulating valve group to decrease the back pressure and increase the output of the small steam turbine; Control measure 3: Adjusting the opening of the second regulating valve group to increase the back pressure and increase the output of the small steam turbine, and adjusting the opening of the second regulating valve group to decrease the back pressure and decrease the output of the small steam turbine.

[0012] Compared with the prior art, the present invention has significant progress:

[0013] The present invention discloses a thermodynamic system and control method for controlling the back pressure and output of a dual-unit regenerative small steam turbine. By providing a first bypass and a first regulating valve group for the first heater, and a second bypass and a second regulating valve group for the second heater, the first and second regulating valve groups can cooperate with the inlet regulating valve group on the steam inlet pipeline of the small steam turbine to coordinate the control of the back pressure and output of the small steam turbine. Individual adjustment of the first, second, and inlet regulating valve groups can each form a control measure. By employing one or more of these control measures in combination, various control methods for controlling the back pressure and output of the small steam turbine can be achieved, thereby meeting the control requirements of different trends in back pressure and output of the small steam turbine and improving the system's flexibility and reliability. Due to the combination of multiple control measures, compared to the control method of simply adjusting the steam inlet flow of the small steam turbine, the present invention can achieve a faster control response. Furthermore, the various control measures in the present invention are independent and do not affect each other. Even if a fault occurs in one control pipeline during field operation, the other control pipelines can still operate in combination to control the back pressure and output of the small steam turbine. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the back pressure output control thermodynamic system of a dual-unit regenerative small steam turbine according to an embodiment of the present invention.

[0015] The reference numerals in the attached figures are explained as follows:

[0016] 1. Main steam turbine

[0017] 101 First extraction steam pipeline

[0018] 102 Second extraction steam pipeline

[0019] 103 Third extraction steam pipeline

[0020] 2 Small steam turbines

[0021] 201 Steam Inlet Pipeline

[0022] 202 Exhaust Pipeline

[0023] 203 Small machine extraction pipeline

[0024] 31 First heater

[0025] 301 First Bypass

[0026] 32 Second heater

[0027] 302 Second Bypass

[0028] 33 Heater group

[0029] 34 Low-pressure heater

[0030] 41. Working Organization

[0031] 42 Power generation units

[0032] 51. Steam Inlet Regulating Valve Assembly

[0033] 52 First regulating valve group

[0034] 53 Second regulating valve group Detailed Implementation

[0035] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0036] In the description of this invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "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" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0038] Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0039] It should be noted that the term "downstream" in this article refers to the downstream direction along the steam flow direction of the main steam turbine, while "upstream" refers to the upstream direction along the steam flow direction of the main steam turbine.

[0040] like Figure 1 As shown, this invention provides an embodiment of a dual-turbine regenerative small steam turbine back pressure output control thermodynamic system. This embodiment's dual-turbine regenerative small steam turbine back pressure output control thermodynamic system includes a main steam turbine 1, a small steam turbine 2, a first heater 31, a second heater 32, and driven equipment.

[0041] Steam enters the main turbine 1 through its inlet, passes through the high-pressure zone, intermediate-pressure zone, and low-pressure zone in sequence, and then exits through its exhaust port. The arrangement of the main turbine 1 in this embodiment is not limited; it can be a single-shaft arrangement or a split-shaft arrangement.

[0042] In this embodiment, the small steam turbine 2 is an extraction back-pressure steam turbine. The steam inlet of the small steam turbine 2 is connected to the steam inlet pipe 201, through which steam is supplied to the small steam turbine 2. The steam inlet pipe 201 is equipped with a steam inlet regulating valve group 51; adjusting the opening of the steam inlet regulating valve group 51 controls the amount of steam entering the small steam turbine 2. The steam source for the steam inlet pipe 201 is not limited; it can be provided by the main steam turbine 1, the boiler system, or other main steam turbines in the same power plant. Preferably, in this embodiment, the steam inlet pipe 201 is connected to the main steam turbine 1, which supplies steam to the small steam turbine 2. The driven equipment is connected to the rotor of the small steam turbine 2. When the steam flows within the small steam turbine 2, it drives the rotor of the small steam turbine 2 to rotate, providing power to the driven equipment and driving its operation; that is, the output power of the small steam turbine 2 drives the operation of the driven equipment. The driven equipment preferably includes a working mechanism 41 and a power generation mechanism 42. Both the working mechanism 41 and the power generation mechanism 42 are connected to the rotor of the small steam turbine 2. The small steam turbine 2 provides power to the working mechanism 41, driving the working mechanism 41 to operate. Excess power generated by the small steam turbine 2 is absorbed and balanced through the power generation mechanism 42. In this embodiment, the working mechanism 41 is mainly a water pump, but may also include other driven equipment; the power generation mechanism 42 is mainly a generator, but may also include a 3S coupling.

[0043] The first heater 31 and the second heater 32 are used to recover heat from the small steam turbine 2 and the main steam turbine 1 to heat the working fluid (such as feedwater or condensate) of the thermodynamic cycle, thereby improving the cycle efficiency. The outlet of the second heater 32 is connected to the inlet of the first heater 31, meaning the second heater 32 is the upstream of the first heater 31. The exhaust port of the small steam turbine 2 is connected to the first heater 31 through the exhaust pipe 202, and the exhaust steam from the small steam turbine 2 enters the first heater 31 through the exhaust pipe 202. The first heater 31 is connected in parallel with the first bypass 301, and the first bypass 301 is equipped with a first regulating valve group 52. The main steam turbine 1 is equipped with a first extraction port, which is connected to the second heater 32 through the first extraction pipe 101. Steam is extracted from the first extraction port of the main steam turbine 1 through the first extraction pipe 101 and sent to the second heater 32. The second heater 32 is connected in parallel with the second bypass 302, and the second bypass 302 is provided with a second regulating valve group 53.

[0044] Preferably, the back pressure output control thermal system of the dual-turbine regenerative small steam turbine in this embodiment may further include a heater group 33. The outlet of the first heater 31 is connected to the inlet of the heater group 33, that is, the heater group 33 is the lower stage of the first heater 31. The steam inlet pipe 201 is connected to the main steam turbine 1. The main steam turbine 1 has a second steam extraction port upstream of the steam inlet pipe 201. The second steam extraction port is connected to the heater group 33 through the second steam extraction pipe 102. Steam is extracted from the second steam extraction port of the main steam turbine 1 by the second steam extraction pipe 102 and sent to the heater group 33. The small steam turbine 2 is provided with a small turbine steam extraction port. The small turbine steam extraction port is connected to the heater group 33 through the small turbine steam extraction pipe 203. Steam is extracted from the small turbine steam extraction port of the small steam turbine 2 by the small turbine steam extraction pipe 203 and sent to the heater group 33.

[0045] Preferably, the back pressure output control thermal system of the dual-unit regenerative small steam turbine in this embodiment may further include a low-pressure heater 34, the outlet of which is connected to the inlet of the second heater 32, i.e., the low-pressure heater 34 is the upper stage of the second heater 32. A third steam extraction port is provided on the main steam turbine 1 downstream of the first extraction port. The third steam extraction port is connected to the low-pressure heater 34 through a third extraction pipe 103. Steam is extracted from the third extraction port of the main steam turbine 1 through the third extraction pipe 103 and sent into the low-pressure heater 34.

[0046] Therefore, in this embodiment, the low-pressure heater 34, the second heater 32, the second bypass 302, the second regulating valve group 53, the first heater 31, the first bypass 301, the first regulating valve group 52, and the heater group 33 constitute a regenerative unit. The regenerative extraction steam is provided to the regenerative unit by the extraction steam from the main turbine 1, the extraction steam from the small turbine 2, and the exhaust steam from the small turbine 2. The condensate passes sequentially through the low-pressure heater 34, the second heater 32 (the second heater 32 and the second bypass 302), the first heater 31 (the first heater 31 and the first bypass 301), and the heater group 33, and is finally heated in the heater group 33 to meet the requirements for feedwater.

[0047] In this embodiment, the condensate from the outlet of the second heater 32 and the condensate in the second bypass 302 are mixed and then enter the first heater 31. If the pressure loss and heat dissipation loss of the second bypass 302 are ignored, the temperature of the condensate in the second bypass 302 is equal to the temperature of the condensate at the outlet of the upper stage (low-pressure heater 34) of the second heater 32, and lower than the temperature of the condensate at the outlet of the second heater 32. As the opening of the second regulating valve group 53 gradually increases, the temperature of the condensate entering the first heater 31 will gradually decrease, and at the same time, the flow rate of the condensate entering the second heater 32 will decrease. The condensate from the outlet of the first heater 31 and the condensate in the first bypass 301 mix and enter the lower stage (heater group 33) of the first heater 31. If the pressure loss and heat loss of the first bypass 301 are ignored, the condensate temperature of the first bypass 301 is equal to the condensate temperature of the outlet of the second heater 32 and lower than the condensate temperature of the outlet of the first heater 31. As the opening of the first regulating valve group 52 gradually increases, the condensate temperature entering the lower stage (heater group 33) of the first heater 31 will gradually decrease, and the condensate flow rate entering the first heater 31 will decrease.

[0048] Since the first heater 31 is connected to the exhaust port of the small steam turbine 2 through the exhaust pipe 202, if the pressure loss of the exhaust pipe 202 is ignored, the exhaust pressure of the small steam turbine 2 is equal to the pressure of the first heater 31. That is, the back pressure of the small steam turbine 2 is equal to the pressure of the first heater 31. Therefore, controlling the pressure of the first heater 31 can achieve back pressure control of the small steam turbine 2. The pressure of the first heater 31 is determined by two sets of parameters. One set is the condensate flow rate, condensate pressure, and condensate temperature at the inlet of the first heater 31. The other set is the flow rate of the regenerative extraction steam. In this embodiment, under the same operating conditions, the condensate pressure at the inlet of the first heater 31 remains basically constant. Therefore, the pressure of the first heater 31 is mainly related to the condensate flow rate, condensate temperature, and regenerative extraction steam flow rate of the first heater 31. The working capacity of the small steam turbine 2 is related to the flow rate of each section of the flow vanes, the inlet thermal parameters, and the outlet thermal parameters. The output of the small steam turbine 2 can be increased by increasing the flow rate of each section of the flow vanes, increasing the inlet thermal parameters, and decreasing the outlet thermal parameters. Conversely, the output of the small steam turbine 2 can be decreased by decreasing the flow rate of each section of the flow vanes, decreasing the inlet thermal parameters, and increasing the outlet thermal parameters.

[0049] Therefore, the back pressure and output control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment can control the back pressure and output of the small steam turbine 2 by adjusting the opening degree of one or more of the steam inlet regulating valve group 51, the first regulating valve group 52, and the second regulating valve group 53. Specifically, the back pressure and output control thermodynamic system of the dual-unit regenerative small steam turbine in this embodiment has the following three control measures to achieve back pressure and output control of the small steam turbine 2.

[0050] Control Measure 1: Adjust the opening of the steam inlet regulating valve group 51 on the steam inlet pipe 201 of the small steam turbine 2 to increase or decrease the back pressure and output of the small steam turbine 2. By adjusting the opening of the steam inlet regulating valve group 51, the steam flow rate at the steam inlet of the small steam turbine 2 can be adjusted. As the opening of the steam inlet regulating valve group 51 gradually increases, more steam enters the small steam turbine 2, increasing the output of the small steam turbine 2. After passing through the regenerator extraction ports of each stage of the small steam turbine 2, more exhaust steam eventually enters the first heater 31 through the exhaust pipe 202, increasing the pressure of the first heater 31. Therefore, increasing the opening of the steam inlet regulating valve group 51 can increase both the back pressure and output of the small steam turbine 2. Conversely, as the opening of the steam inlet regulating valve group 51 gradually decreases, less steam enters the small steam turbine 2, resulting in a reduction in the output of the small steam turbine 2. After the steam passes through the various stages of the regenerated steam extraction ports of the small steam turbine 2, less exhaust steam eventually enters the first heater 31 through the exhaust pipe 202, resulting in a reduction in the pressure of the first heater 31. Therefore, by adjusting the opening of the steam inlet regulating valve group 51 to decrease, both the back pressure and output of the small steam turbine 2 can be reduced.

[0051] Control Measure 2: Increase the opening of the first regulating valve group 52 to raise the back pressure of the small steam turbine 2 and reduce its output; decrease the opening of the first regulating valve group 52 to lower the back pressure of the small steam turbine 2 and increase its output. By adjusting the opening of the first regulating valve group 52 on the first bypass 301, the condensate flow rate at the inlet of the first heater 31 and the condensate temperature at the inlet of the lower stage (heater group 33) of the first heater 31 can be adjusted. As the opening of the first regulating valve group 52 gradually increases, the condensate flow rate entering the first heater 31 decreases, causing the pressure of the first heater 31 to increase. At the same time, the condensate temperature entering the lower stage (heater group 33) of the first heater 31 decreases, causing the regenerative steam extraction rate of the lower stage (heater group 33) of the first heater 31 to increase. The steam flow rate of the last stage of the small steam turbine 2 decreases, and the output of the small steam turbine 2 decreases. Therefore, increasing the opening of the first regulating valve group 52 can raise the back pressure of the small steam turbine 2 and reduce its output. Conversely, as the opening of the first regulating valve group 52 gradually decreases, the condensate flow rate entering the first heater 31 increases, causing the pressure of the first heater 31 to decrease. At the same time, the condensate temperature entering the lower stage (heater group 33) of the first heater 31 increases, causing the regenerative steam extraction rate of the lower stage (heater group 33) of the first heater 31 to decrease. The steam flow rate of the last stage of the small steam turbine 2 increases, and the output of the small steam turbine 2 increases. Therefore, by adjusting the opening of the first regulating valve group 52 to decrease, the back pressure of the small steam turbine 2 can be reduced and the output increased.

[0052] Control Measure 3: Increase the opening of the second regulating valve group 53 to decrease the back pressure of the small steam turbine 2 and increase its output; decrease the opening of the second regulating valve group 53 to increase the back pressure of the small steam turbine 2 and decrease its output. By adjusting the opening of the second regulating valve group 53 on the second bypass 302, the condensate temperature at the inlet of the first heater 31 can be adjusted. As the opening of the second regulating valve group 53 gradually increases, the condensate temperature entering the first heater 31 decreases, causing the pressure in the first heater 31 to decrease, thus decreasing the back pressure of the small steam turbine 2 and increasing its output. Therefore, increasing the opening of the second regulating valve group 53 can decrease the back pressure of the small steam turbine 2 and increase its output. As the opening of the second regulating valve group 53 gradually decreases, the temperature of the condensate entering the first heater 31 increases, which in turn increases the pressure of the first heater 31, increases the back pressure of the small steam turbine 2, and reduces the output of the small steam turbine 2. Therefore, by adjusting the opening of the second regulating valve group 53 to decrease, the back pressure of the small steam turbine 2 can be increased and the output can be reduced.

[0053] Of the three control measures, control measure one controls the back pressure and output of the small steam turbine 2 in the same way; when the back pressure increases, the output also increases. Control measures two and three control the back pressure and output of the small steam turbine 2 in opposite ways; when the back pressure increases, the output decreases. In actual field operation, there will be four different control requirements for the small steam turbine 2: increasing back pressure and increasing output, decreasing back pressure and increasing output, increasing back pressure and decreasing output, and decreasing back pressure and decreasing output. This embodiment can use one or more of the three control measures in combination to form multiple control methods for the back pressure and output of the small steam turbine 2, satisfying the control requirements for the different trends of back pressure and output of the small steam turbine 2, and achieving the back pressure control requirements and output control requirements of the small steam turbine 2.

[0054] Based on the dual-unit regenerative small steam turbine back pressure and output control thermal system described in this embodiment, this embodiment also provides a control method for the dual-unit regenerative small steam turbine back pressure and output control thermal system described in this embodiment. This control method involves using one or more of the following three control measures in combination, according to the back pressure control requirements and output control requirements of the small steam turbine 2, to achieve the back pressure control requirements and output control requirements of the small steam turbine 2: Control measure 1: Adjusting the opening of the steam inlet regulating valve group 51 to increase or decrease, thereby increasing or decreasing both the back pressure and output of the small steam turbine 2; Control measure 2: Adjusting the opening of the first regulating valve group 52 to increase, thereby increasing the back pressure and decreasing the output of the small steam turbine 2; adjusting the opening of the first regulating valve group 52 to decrease, thereby decreasing the back pressure and increasing the output of the small steam turbine 2; Control measure 3: Adjusting the opening of the second regulating valve group 53 to increase, thereby decreasing the back pressure and increasing the output of the small steam turbine 2; adjusting the opening of the second regulating valve group 53 to decrease, thereby increasing the back pressure and decreasing the output of the small steam turbine 2.

[0055] In summary, the dual-unit regenerative small steam turbine back pressure output control thermodynamic system and its control method of this embodiment, by setting a first bypass 301 and a first regulating valve group 52 for the first heater 31, and a second bypass 302 and a second regulating valve group 53 for the second heater 32, allows the first regulating valve group 52 and the second regulating valve group 53 to cooperate with the steam inlet regulating valve group 51 on the steam inlet pipe 201 of the small steam turbine 2 to coordinate the control of the back pressure and output of the small steam turbine 2. The individual adjustment of the first regulating valve group 52, the second regulating valve group 53 and the steam inlet regulating valve group 51 can each form a control measure. By adopting one or more of the three control measures in combination, multiple control methods for the back pressure and output of the small steam turbine 2 can be realized, thereby meeting the control requirements of different trends in the back pressure and output of the small steam turbine 2, and improving the flexibility and reliability of the system. Because it combines multiple control measures, this embodiment can achieve a faster control response compared to the control method of simply adjusting the steam flow of the small steam turbine 2. At the same time, the various control measures in this embodiment are independent of each other and do not affect each other. Even if a certain control pipeline fails during field operation, the other control pipelines can still be combined to achieve the control of the back pressure and output of the small steam turbine 2.

[0056] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A dual-unit regenerative small steam turbine back pressure output control thermodynamic system, comprising a main steam turbine (1), a small steam turbine (2), a first heater (31), a second heater (32), and driven equipment connected to the small steam turbine (2), wherein the outlet of the second heater (32) is connected to the inlet of the first heater (31), characterized in that, The steam inlet of the small steam turbine (2) is connected to the steam inlet pipeline (201), and the steam inlet pipeline (201) is equipped with a steam inlet regulating valve group (51); the steam outlet of the small steam turbine (2) is connected to the first heater (31) through the steam outlet pipeline (202), the first heater (31) is connected in parallel with the first bypass (301), and the first bypass (301) is equipped with a first regulating valve group (52); the main steam turbine (1) is equipped with a first extraction steam outlet, the first extraction steam outlet is connected to the second heater (32) through the first extraction steam pipeline (101), the second heater (32) is connected in parallel with the second bypass (302), and the second bypass (302) is equipped with a second regulating valve group (53); the small steam turbine is controlled by adjusting the opening degree of one or more of the steam inlet regulating valve group (51), the first regulating valve group (52) and the second regulating valve group (53). The back pressure and output of the turbine (2); also includes a heater group (33), the outlet of the first heater (31) is connected to the inlet of the heater group (33), the steam inlet pipe (201) is connected to the main steam turbine (1), the main steam turbine (1) is provided with a second steam extraction port upstream of the steam inlet pipe (201), the small steam turbine (2) is provided with a small steam extraction port, the second steam extraction port and the small steam extraction port are respectively connected to the heater group (33) through the second steam extraction pipe (102) and the small steam extraction pipe (203); also includes a low-pressure heater (34), the outlet of the low-pressure heater (34) is connected to the inlet of the second heater (32), the main steam turbine (1) is provided with a third steam extraction port downstream of the first steam extraction port, the third steam extraction port is connected to the low-pressure heater (34) through the third steam extraction pipe (103).

2. The thermodynamic system for controlling the back pressure output of a dual-unit regenerative small steam turbine according to claim 1, characterized in that, The driven device includes a working mechanism (41) and a power generation mechanism (42).

3. A control method for a dual-unit regenerative small steam turbine back pressure output control thermodynamic system as described in any one of claims 1 to 2, characterized in that, Based on the back pressure control requirements and output control requirements of the small steam turbine (2), one or more of the following three control measures are adopted in combination to achieve the back pressure control requirements and output control requirements of the small steam turbine (2): Control measure 1: Adjust the opening of the steam inlet regulating valve group (51) to increase or decrease, so that the back pressure and output of the small steam turbine (2) increase or decrease. Control measure 2: Increase the opening of the first regulating valve group (52) to increase the back pressure and decrease the output of the small steam turbine (2); decrease the opening of the first regulating valve group (52) to decrease the back pressure and increase the output of the small steam turbine (2). Control measure three: Increase the opening of the second regulating valve group (53) to reduce the back pressure and increase the output of the small steam turbine (2), and decrease the opening of the second regulating valve group (53) to increase the back pressure and decrease the output of the small steam turbine (2).

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