Supercritical carbon dioxide cycle optimal shunting coefficient control system and method

Abstract

The invention discloses a supercritical carbon dioxide cycle optimal split-flow coefficient control system and method. The system comprises a split-flow coefficient control module, a flow control module and a split-flow recompression cycle system. The method comprises the following steps: fitting a function of an optimal shunting coefficient alpha opt changing along with a rotating speed RS based on the optimal shunting coefficient alpha opt corresponding to each working condition point; the function serves as a judgment standard to be input into a shunting coefficient control module, and variable load optimal shunting coefficient alpha opt tracking control is carried out; after receiving a feedback signal of a real-time shunting coefficient alpha, the shunting coefficient control module calculates an optimal shunting coefficient alpha opt corresponding to the current rotating speed RS in real time, judges the difference value between the actual shunting coefficient alpha and alpha opt, and continuously adjusts the opening degree of a main path valve and the opening degree of a bypass valve, so that the shunting coefficient of the main path valve and the bypass valve is obtained. Therefore, the shunting coefficient alpha under each working condition is equal to the optimal shunting coefficient alpha opt under the variable load working condition. According to the method, the problem of low-efficiency power generation caused by using a constant design optimal shunting coefficient in the variable-load operation process of the unit is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of new circulation system control, and particularly relates to a control system and method for the optimal splitting coefficient of a supercritical carbon dioxide cycle. Background Art

[0002] In the field of supercritical carbon dioxide cycle power generation, the split re-compression technology is one of the key means to improve the power generation efficiency of the system. Its core lies in precisely regulating the splitting coefficient to adjust the matching relationship between the turbine work output and the compressor power consumption. The splitting coefficient is defined as the ratio of the bypass flow rate to the total flow rate of the main cycle. The change of the splitting coefficient will directly affect the power generation efficiency of the system. In the system design stage, the aim is to find the optimal splitting coefficient to maximize the designed power generation efficiency of the unit.

[0003] The specific value of the optimal splitting coefficient depends on multiple key parameters of the unit, such as the main gas pressure, the main gas temperature, the turbine efficiency, the compressor efficiency, etc. During the dynamic change process of the unit load, the value of the optimal splitting coefficient under each specific working condition will also be adjusted accordingly, rather than simply being fixed as the optimal value under the design working condition. When the unit deviates from the design point operation, the fixed splitting ratio will destroy the thermodynamic coupling balance of the turbine and compressor systems, resulting in the dual adverse effects of the decrease in the turbine work output and the increase in the compressor power consumption. Therefore, in order to ensure that the system can maintain efficient operation under different working conditions, a dynamic splitting coefficient control strategy needs to be implemented. Summary of the Invention

[0004] The purpose of the present invention is to provide a control system and method for the optimal splitting coefficient of a supercritical carbon dioxide cycle to solve the problem of low-efficiency power generation caused by using a constant designed optimal splitting coefficient during the variable load operation of the unit.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A control system for the optimal splitting coefficient of a supercritical carbon dioxide cycle includes a splitting coefficient control module, a flow control module, and a split re-compression cycle system;

[0007] In a split re-compression cycle system, the hot-side outlet of the low-temperature recuperator is connected to the inlet of the main path valve and at the same time to the inlet of the bypass valve; the outlet of the main path valve is connected to the inlet of the pre-cooler, the outlet of the pre-cooler is connected to the inlet of the pressure stabilizing tank, the outlet of the pressure stabilizing tank is connected to the inlet of the main compressor, the outlet of the main compressor is connected to the cold-side inlet of the low-temperature recuperator, and the cold-side outlet of the low-temperature recuperator is connected to the cold-side inlet of the high-temperature recuperator; the outlet of the bypass valve is connected to the inlet of the bypass flowmeter, the outlet of the bypass flowmeter is connected to the inlet of the re-compressor, and the outlet of the re-compressor is connected to the cold-side inlet of the high-temperature recuperator; the cold-side outlet of the high-temperature recuperator is connected to the cold-side inlet of the intermediate heat exchanger; the cold-side outlet of the intermediate heat exchanger is connected to the inlet of the turbine, the outlet of the turbine is connected to the inlet of the main circulation flowmeter, the outlet of the main circulation flowmeter is connected to the hot-side inlet of the high-temperature recuperator, and the hot-side outlet of the high-temperature recuperator is connected to the hot-side inlet of the low-temperature recuperator;

[0008] In the flow control module, the input signal is the flow rate detected by the main circulation flowmeter, and rotational speed signals are output to the turbine, the main compressor, and the re-compressor; in the split coefficient control module, the input signals are the flow rates detected by the main circulation flowmeter and the bypass flowmeter, and opening signals are output to the main path valve and the bypass valve.

[0009] A further improvement of the present invention lies in that the turbine, the main compressor, and the re-compressor are coaxially arranged.

[0010] A further improvement of the present invention lies in that the rotational speeds of the turbine, the main compressor, and the re-compressor are equal.

[0011] A further improvement of the present invention lies in that in the flow control module, the rotational speed RS is set as the control variable, and the total closed-system flow rate m is set as the controlled variable.

[0012] A further improvement of the present invention lies in that the measuring point of the rotational speed RS is arranged on the coaxial system of the turbine, the main compressor, and the re-compressor.

[0013] A further improvement of the present invention lies in that the measuring point of the total closed-system flow rate m is the main circulation flowmeter; the main circulation flowmeter is arranged between the outlet of the turbine and the hot-side inlet of the high-temperature recuperator.

[0014] A further improvement of the present invention lies in that in the split coefficient control module, the bypass valve is set as the direct control device, the main path valve is set as the reverse linkage control device, wherein the opening of the bypass valve is the direct control variable, the opening of the main path valve is the indirect control variable, and the split coefficient α is the controlled variable.

[0015] A further improvement of the present invention lies in that the main path valve is arranged between the hot-side outlet of the low-temperature recuperator and the inlet of the pre-cooler; the bypass valve is arranged between the hot-side outlet of the low-temperature recuperator and the inlet of the bypass flowmeter; the bypass flowmeter is arranged between the outlet of the bypass valve and the inlet of the re-compressor.

[0016] A further improvement of the present invention lies in that the calculated value of the diversion coefficient α is the ratio of the flow monitoring value of the bypass flowmeter to the flow monitoring value of the main circulation flowmeter.

[0017] An optimal diversion coefficient control method for a supercritical carbon dioxide cycle, which is based on the above-mentioned optimal diversion coefficient control system for a supercritical carbon dioxide cycle, includes:

[0018] Set the opening degrees of the main valve and the bypass valve to always satisfy the constraint: it is required that the opening degrees of both the main valve and the bypass valve are greater than 0% and less than or equal to 100%;

[0019] Under the conditions of the rotational speed RS being 100%, 95%, 90%, 85%, 80%, 75%, and 70% of the rated speed, calculate the load that can be output at this operating point and the corresponding optimal diversion coefficient α opt ;

[0020] Based on the optimal diversion coefficient α corresponding to each operating point opt , fit the optimal diversion coefficient α opt varying with the rotational speed RS, the function α opt = f(RS);

[0021] Input this function as a judgment criterion into the diversion coefficient control module to carry out the optimal diversion coefficient α opt tracking control;

[0022] During the process of the unit operating with variable load, after receiving the feedback signal of the real-time diversion coefficient α, the diversion coefficient control module calculates the optimal diversion coefficient α corresponding to the current rotational speed RS in real time opt , determines the difference between the actual diversion coefficient α and α opt , and continuously adjusts the opening degrees of the main valve and the bypass valve, so as to ensure that the diversion coefficient α is equal to the optimal diversion coefficient α under variable load conditions opt ;

[0023] When α > α opt , increase the opening degree of the bypass valve and decrease the opening degree of the main valve until α = α opt ;

[0024] When α < α opt , decrease the opening degree of the bypass valve and increase the opening degree of the main valve until α = α opt .

[0025] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0026] An optimal split coefficient control system and method for a supercritical carbon dioxide cycle provided by the present invention integrate an optimal split coefficient tracking mode in the split coefficient control module, ensuring that the system can automatically adjust the opening degrees of the main path valve and the bypass valve under various variable load conditions to match the optimal split coefficient for operation, thereby solving the problem of poor dynamic performance of the fixed split ratio system when the unit operates deviating from the design point, effectively avoiding the compressor surge problem that may occur in the traditional fixed split coefficient operation mode, further improving the power generation efficiency of the system, and enhancing the safety and stability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0028] Figure 1 It is a schematic structural diagram of an optimal split coefficient control system for a supercritical carbon dioxide cycle of the present invention.

[0029] Description of the reference numerals:

[0030] 1 - Compressor, 2 - Low-temperature recuperator, 3 - High-temperature recuperator, 4 - Intermediate heat exchanger, 5 - Turbine, 6 - Recompressor, 7 - Pre-cooler, 8 - Pressure stabilizing tank, 9 - Generator, F1 - Main circulation flowmeter, F2 - Bypass flowmeter, V1 - Main path valve, V2 - Bypass valve, CM-m - Flow control module, CM-α - Split coefficient control module. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] In the following text, only some exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present invention. Therefore, the drawings and the description are considered to be exemplary in nature rather than restrictive.

[0032] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0033] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0034] In the present invention, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or a communication connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may include the direct contact between the first and second features, or may include the situation where the first and second features are not in direct contact but in contact through other features between them. Moreover, the first feature being "above", "over" and "on top of" the second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "under", "beneath" and "underneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than that of the second feature.

[0036] It should also be understood that the terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0037] It should be further understood that the term "and / or" used in the specification and appended claims of the present invention refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0038] Various structural schematic diagrams according to the disclosed embodiments of the present invention are shown in the drawings. These figures are not drawn to scale, where for the purpose of clear expression, some details are enlarged and some details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary. In practice, there may be deviations due to manufacturing tolerances or technical limitations, and those skilled in the art can design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0039] The embodiments of the present invention will be described in detail below with reference to the drawings:

[0040] Embodiment 1

[0041] As Figure 1 shown, a supercritical carbon dioxide cycle optimal split coefficient control system provided by the present invention includes: a split coefficient control module CM-α, a flow control module CM-m, and a split recompression cycle system.

[0042] The flow control module CM-m controls the rotational speeds of the turbine 5, the main compressor 1, and the recompressor 6 by monitoring the flow rate of the main circulation flowmeter F1.

[0043] The split coefficient control module CM-α controls the opening degrees of the main path valve V1 and the bypass valve V2 by monitoring the flow rate of the main circulation flowmeter F1 and the flow rate of the bypass flowmeter.

[0044] In the described split re-compression cycle system, the hot-side outlet of the low-temperature recuperator 2 is connected to the inlet of the main path valve V1 and simultaneously to the inlet of the bypass valve V2. The outlet of the main path valve V1 is connected to the inlet of the precooler 7, the outlet of the precooler 7 is connected to the inlet of the pressure stabilizing tank 8, the outlet of the pressure stabilizing tank 8 is connected to the inlet of the main compressor 1, the outlet of the main compressor 1 is connected to the cold-side inlet of the low-temperature recuperator 2, and the cold-side outlet of the low-temperature recuperator 2 is connected to the cold-side inlet of the high-temperature recuperator 3. The outlet of the bypass valve V2 is connected to the inlet of the bypass flowmeter F2, the outlet of the bypass flowmeter F2 is connected to the inlet of the re-compressor 6, and the outlet of the re-compressor 6 is connected to the cold-side inlet of the high-temperature recuperator 3. The cold-side outlet of the high-temperature recuperator 3 is connected to the cold-side inlet of the intermediate heat exchanger 4. The cold-side outlet of the intermediate heat exchanger 4 is connected to the inlet of the turbine 5, the outlet of the turbine 5 is connected to the inlet of the main circulation flowmeter F1, the outlet of the main circulation flowmeter 5 is connected to the hot-side inlet of the high-temperature recuperator 3, and the hot-side outlet of the high-temperature recuperator 3 is connected to the hot-side inlet of the low-temperature recuperator 2. The turbine 5, the main compressor 1, and the re-compressor 6 are coaxially arranged.

[0045] The turbine 5, the main compressor 1, and the re-compressor 6 always rotate at the same speed.

[0046] The working process / working principle of the present invention is as follows:

[0047] Part of the low-pressure fluid at the cold-side outlet of the low-temperature recuperator 2 enters the re-compressor 6 to be compressed to a high-pressure and low-temperature state after the flow rate is controlled by the bypass valve V2 and the flow rate is measured by the bypass flowmeter F2; the other part enters the hot side of the precooler 7 to release heat to a temperature near the supercritical state point after the flow rate is controlled by the main path valve V1, and after the pressure fluctuation is stabilized by the pressure stabilizing tank 8, it enters the main compressor 1 to be compressed into a high-pressure and low-temperature fluid, and then enters the cold side of the low-temperature recuperator 2 to absorb heat and increase the temperature; after the two high-pressure fluids converge at the cold-side outlet of the low-temperature recuperator 2, they sequentially pass through the cold side of the high-temperature recuperator 3 and the cold side of the intermediate heat exchanger 4 to absorb heat to form a high-pressure and high-temperature state fluid and enter the turbine 5 for adiabatic expansion work, which is converted into a low-pressure and high-temperature fluid. After the flow rate of this fluid is measured by the main circulation flowmeter F1, it sequentially passes through the hot side of the high-temperature recuperator 3 and the hot side of the low-temperature recuperator 2 to release heat and reduce the temperature, and is ready to enter the next cycle.

[0048] When the working medium adiabatically expands in the turbine 5, it pushes the blades to rotate. The rotational motion of the turbine 5 drives the generator 9 to generate electric energy through a mechanical transmission device, realizing the conversion of thermal energy into electric energy, and at the same time driving the main compressor 1 and the re-compressor 6 to rotate, reducing the mechanical energy loss when the turbine and the compressor are arranged on separate shafts.

[0049] During the variable load process, the flow control module CM-m controls the rotational speeds of the turbine 5, the main compressor 1, and the recompressor 6 by monitoring the flow rate of the main circulation flowmeter F1. If the monitored main circulation flow rate increases, the rotational speeds of the turbine 5, the main compressor 1, and the recompressor 6 are increased; if the monitored main circulation flow rate decreases, the rotational speeds of the turbine 5, the main compressor 1, and the recompressor 6 are decreased.

[0050] During the variable load process, the split coefficient control module CM-α monitors the flow rates of the main circulation flowmeter F1 and the bypass flowmeter, calculates the split coefficient α based on the ratio of the two, and compares the calculated value of the split coefficient α with the set value, thereby controlling the opening degrees of the main path valve V1 and the bypass valve V2. If the calculated value of the split coefficient α is smaller than the set value, the opening degree of the main path valve V1 is decreased and the opening degree of the bypass valve V2 is increased; if the calculated value of the split coefficient α is larger than the set value, the opening degree of the main path valve V1 is increased and the opening degree of the bypass valve V2 is decreased.

[0051] Embodiment 2

[0052] An optimal split coefficient control method for a supercritical carbon dioxide cycle provided by the present invention includes:

[0053] Set the opening degrees of the main path valve and the bypass valve to always satisfy the constraint: it is required that the opening degrees of both the main path valve V1 and the bypass valve V2 are greater than 0% and less than or equal to 100%; under operating conditions such as when the rotational speed RS is 100%, 95%, 90%, 85%, 80%, 75%, 70% of the rated rotational speed, calculate the load that can be output at this operating condition point and the corresponding optimal split coefficient α opt 。

[0054] Maximize the power generation efficiency by adjusting the matching relationship between the split coefficient α and the rotational speed RS. Fix the rotational speed at 95% of its rated rotational speed RS d and set the split coefficient α to linearly decrease from 0.5 to 0.2 to obtain the changing trend of the power generation efficiency. Identify the optimal split coefficient value corresponding to the highest power generation efficiency at this rotational speed (i.e., 95% of the rated rotational speed).

[0055] Subsequently, successively reduce the rotational speed to 90%, 85%, 80%, 75%, and 70% of the rated rotational speed, and repeat the above process at each rotational speed to find and determine the optimal split coefficient value at this rotational speed.

[0056] Based on the distribution of the optimal split coefficient values at each rotational speed, fit a function α opt with the rotational speed as the independent variable and the optimal split coefficient as the dependent variable. Input this function as an input signal into the split coefficient control module CM-α.

[0057] During the entire variable load process, the set speed RS decreases linearly, and the shunt coefficient control module CM-α is set to the automatic adjustment mode.

[0058] During the unit's load reduction operation, after the shunt coefficient control module CM-α receives the feedback signal of the real-time shunt coefficient α, it calculates the optimal shunt coefficient value α corresponding to the current speed RS. opt , compare α and α opt , and thus adjust the opening degrees of the main path valve V1 and the bypass valve V2.

[0059] When α < α opt , increase the opening degree of the bypass valve V2 and decrease the opening degree of the main path valve V1, so that the bypass flow rate increases and the main path flow rate decreases, thereby increasing the real-time shunt coefficient α to make it equal to α opt .

[0060] When α > α opt , decrease the opening degree of the bypass valve V2 and increase the opening degree of the main path valve V1, so that the bypass flow rate decreases and the main path flow rate increases, thereby decreasing the real-time shunt coefficient α to make it equal to α opt .

[0061] During the entire operation process of the unit, the instantaneous value of α is basically equal to α opt , which can effectively improve the average power generation efficiency of the unit during the variable working conditions. At the same time, the working state of the recompressor gradually moves away from the surge line, which can ensure the safe and stable operation of the unit.

[0062] Example 3

[0063] In this example, a 1MW supercritical carbon dioxide split recompression cycle power generation system is taken as the implementation object, and the system design parameters are: rated speed RS d = 44000 rpm, and the designed optimal shunt coefficient α d = 0.33.

[0064] Comparative example - fixed shunt coefficient control method:

[0065] During the entire variable load process, the set speed decreases linearly according to RS = RS d ×(1 - 1.22t), where t is the time variable with the unit of second. The control module CM-α adopts a fixed parameter strategy, and the set value of the shunt coefficient is locked at α d = 0.33. During the variable load process, the calculated value of the shunt coefficient α increases. In order to counter this trend and maintain the shunt coefficient value at α dRemaining unchanged, the flow coefficient control module CM-α gradually increases the opening of the main path valve V1 and simultaneously decreases the opening of the bypass valve V2. As the rotational speed RS further decreases, the opening of the main path valve V1 reaches 100% and remains unchanged, while the opening of the bypass valve V2 continues to decrease. Since the volumetric flow rate of the working fluid passing through the recompressor 6 decreases more rapidly, this brings the actual operating state of the recompressor 6 closer to the surge line. Since the real-time flow coefficient is constantly the design condition value α d , during the load change process, the main gas pressure, main gas temperature, turbine efficiency, and compressor efficiency change, resulting in the power generation efficiency of the unit not matching the optimal value of the current operating condition. Real-time monitoring data shows that the time-averaged power generation efficiency of the unit is 18.72%.

[0066] The present invention - the optimal flow coefficient control method:

[0067] During the entire load change process, the set rotational speed decreases linearly according to RS = RS d ×(1 - 1.22t), where t is the time variable in seconds. The control module CM-α adopts the optimal flow coefficient strategy and calculates the corresponding α for the current rotational speed RS in real time through the cubic spline interpolation algorithm opt value, as shown in Table 1. During the load change process, after receiving the feedback signal of the calculated flow coefficient value α, the control module CM-α adjusts the openings of the main path valve V1 and the bypass valve V2 continuously by calculating the difference between the current flow coefficient α and α opt to ensure that α equals α under various operating conditions opt . In this mode, the time-averaged power generation efficiency of the unit is 19.13%, which is higher than the time-averaged power generation efficiency in the fixed flow coefficient control mode. Therefore, it is recommended that the unit operate using the optimal flow coefficient method during the actual load change process.

[0068] Table 1

[0069] RS <![CDATA[α opt > 30800 0.37491 33000 0.35399 35200 0.33994 37400 0.32531 39600 0.31287 41800 0.31367

[0070] The above shows and describes the basic principles, main features, and advantages of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, from any perspective, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be encompassed by the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0071] In addition, it should be understood that although this specification is described in terms of embodiments, not every embodiment contains only an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any modification made on the basis of the technical solution according to the technical idea proposed by the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A supercritical carbon dioxide cycle optimal split coefficient control system, characterized in that: It includes a flow splitting coefficient control module (CM-α), a flow control module (CM-m) and a flow splitting recompression circulation system; In the split-flow recompression cycle system, the hot side outlet of the low-temperature regenerator (2) is connected to the inlet of the main valve (V1) and the inlet of the bypass valve (V2); the outlet of the main valve (V1) is connected to the inlet of the precooler (7), the outlet of the precooler (7) is connected to the inlet of the pressure stabilizing tank (8), the outlet of the pressure stabilizing tank (8) is connected to the inlet of the main compressor (1), the outlet of the main compressor (1) is connected to the cold side inlet of the low-temperature regenerator (2), the cold side outlet of the low-temperature regenerator (2) is connected to the cold side inlet of the high-temperature regenerator (3); the outlet of the bypass valve (V2) is connected to the bypass flow meter (F2 ), the outlet of the bypass flowmeter (F2) is connected to the inlet of the recompressor (6), the outlet of the recompressor (6) is connected to the cold side inlet of the high-temperature regenerator (3); the cold side outlet of the high-temperature regenerator (3) is connected to the cold side inlet of the intermediate heat exchanger (4); the cold side outlet of the intermediate heat exchanger (4) is connected to the inlet of the turbine (5), the outlet of the turbine (5) is connected to the inlet of the main circulation flowmeter (F1), the outlet of the main circulation flowmeter (F1) is connected to the hot side inlet of the high-temperature regenerator (3), and the hot side outlet of the high-temperature regenerator (3) is connected to the hot side inlet of the low-temperature regenerator (2); In the flow control module (CM-m), the input signal is the flow detected by the main circulation flow meter (F1), and the speed signal is output to the turbine (5), the main compressor (1) and the re-compressor (6); in the diversion coefficient control module (CM-α), the input signal is the flow detected by the main circulation flow meter (F1) and the bypass flow meter (F2), and the opening signal is output to the main valve (V1) and the bypass valve (V2).

2. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 1, characterized in that: The turbine (5), the main compressor (1) and the recompressor (6) are coaxially arranged.

3. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 1, characterized in that: The rotation speeds of the turbine (5), the main compressor (1) and the recompressor (6) are equal.

4. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 1, characterized in that: In the flow control module (CM-m), the speed RS is set as the control variable and the total flow m of the closed system is set as the controlled variable.

5. A supercritical carbon dioxide cycle optimal split coefficient control system according to claim 4, characterized in that: The measuring point of the speed RS is arranged on the coaxial system of the turbine, main compressor and recompressor.

6. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 4, characterized in that: The measuring point of the total flow m of the closed system is the main circulation flow meter (F1); the main circulation flow meter (F1) is arranged between the outlet of the turbine (5) and the hot side inlet of the high-temperature regenerator (3).

7. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 4, characterized in that: In the diversion coefficient control module (CM-α), the bypass valve (V2) is set as a direct control device, and the main valve (V1) is set as a reverse linkage control device, wherein the opening of the bypass valve (V2) is the direct control quantity, the opening of the main valve (V1) is the indirect control quantity, and the diversion coefficient α is the controlled quantity.

8. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 7, characterized in that: The main valve (V1) is arranged between the hot side outlet of the low-temperature regenerator (2) and the inlet of the precooler (7); the bypass valve (V2) is arranged between the hot side outlet of the low-temperature regenerator (2) and the inlet of the bypass flowmeter (F2); and the bypass flowmeter (F2) is arranged between the outlet of the bypass valve (V2) and the inlet of the recompressor (6).

9. The optimal split coefficient control system for supercritical carbon dioxide circulation according to claim 7, characterized in that: The calculated value of the flow splitting coefficient α is the ratio of the flow rate monitoring value of the bypass flow meter (F2) to the flow rate monitoring value of the main circulation flow meter (F1).

10. A method for controlling the optimal split coefficient of supercritical carbon dioxide circulation, characterized in that: The method is based on a supercritical carbon dioxide cycle optimal split coefficient control system according to claim 7, comprising: The openings of the main valve and the bypass valve are set to always satisfy the constraint: the openings of the main valve (V1) and the bypass valve (V2) are required to be greater than 0% and less than or equal to 100%; When the speed RS is 100%, 95%, 90%, 85%, 80%, 75%, 70% of the rated speed, calculate the load that can be output at this operating point and the corresponding optimal flow split coefficient α opt ; Based on the optimal split coefficient α corresponding to each operating point opt , fitting the optimal split coefficient α opt Function α that changes with the speed RS opt =f(RS); This function is used as a criterion to input into the flow splitting coefficient control module (CM-α) to carry out the optimal flow splitting coefficient α of variable load. opt Tracking control; During the variable load operation of the unit, after receiving the feedback signal of the real-time split coefficient α, the split coefficient control module (CM-α) calculates the optimal split coefficient α corresponding to the current speed RS in real time. opt , determine the actual split coefficients α and α opt The difference between the opening of the main valve (V1) and the opening of the bypass valve (V2) is continuously adjusted to ensure that the diversion coefficient α under each working condition is equal to the optimal diversion coefficient α under variable load conditions. opt ; When α>α opt When the bypass valve (V2) is opened, the opening of the main valve (V1) is reduced until α = α opt ; When α<α opt When the bypass valve (V2) is turned down, the main valve (V1) is turned up until α=α opt .

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