A supercritical carbon dioxide cycle optimal split coefficient control system and method

Abstract

The application discloses a supercritical carbon dioxide cycle optimal split coefficient control system and method, and belongs to the field of supercritical carbon dioxide cycle optimal split coefficient control. opt The method comprises the following steps: fitting an optimal split coefficient alpha opt of each working condition point as a function of a rotating speed RS; inputting the function as a judgment standard into a split coefficient control module to carry out optimal split coefficient alpha opt tracking control under variable loads; after receiving a feedback signal of a real-time split coefficient alpha opt , the split coefficient control module determines a difference between the actual split coefficient alpha and the optimal split coefficient alpha opt corresponding to the current rotating speed RS by real-time calculation, and continuously adjusts the opening degree of a main valve and the opening degree of a bypass valve, so that the split coefficient alpha under each working condition is equal to the optimal split coefficient alpha opt under the variable load working condition, thereby solving the low-efficiency power generation problem caused by using a constant design optimal split coefficient during unit variable load operation.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new cycle system control technology, in particular to a supercritical carbon dioxide cycle optimal split ratio control system and method. BACKGROUND

[0002] In the field of supercritical carbon dioxide cycle power generation, split recompression technology is one of the key means to improve the power generation efficiency of the system, and the core is to accurately regulate the split ratio to adjust the matching relationship between turbine work and compressor power consumption. The split ratio is defined as the ratio of bypass flow to total main cycle flow. The change of the split ratio will directly affect the power generation efficiency of the system. In the system design stage, the optimal split ratio is aimed to be found to maximize the design power generation efficiency of the unit.

[0003] The specific value of the optimal split ratio depends on multiple key parameters of the unit, such as main gas pressure, main gas temperature, turbine efficiency, compressor efficiency, etc. In the process of dynamic change of unit load, the optimal split ratio value under each specific working condition will also be adjusted accordingly, rather than simply fixed as the optimal value under the design condition. When the unit deviates from the design point operation, fixing the split ratio will destroy the thermodynamic coupling balance of the turbine and compressor system, resulting in the dual adverse effects of decreased turbine work and increased compressor power consumption. Therefore, in order to ensure that the system can maintain high efficiency operation under different working conditions, dynamic split ratio regulation strategy needs to be implemented. SUMMARY

[0004] The present application provides a supercritical carbon dioxide cycle optimal split ratio control system and method to solve the problem of low efficiency power generation caused by using constant design optimal split ratio during unit variable load operation.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] A supercritical carbon dioxide cycle optimal split ratio control system, comprising a split ratio control module, a flow control module and a split recompression cycle system.

[0007] In the split recompression cycle system, the hot side outlet of the low temperature recuperator is connected with the inlet of the main path valve and the inlet of the bypass valve; the outlet of the main path valve is connected with the inlet of the pre-cooler, the outlet of the pre-cooler is connected with the inlet of the pressure stabilizing tank, the outlet of the pressure stabilizing tank is connected with the inlet of the main compressor, the outlet of the main compressor is connected with the cold side inlet of the low temperature recuperator, the cold side outlet of the low temperature recuperator is connected with the cold side inlet of the high temperature recuperator; the outlet of the bypass valve is connected with the inlet of the bypass flow meter, the outlet of the bypass flow meter is connected with the inlet of the recompression compressor, the outlet of the recompression compressor is connected with the cold side inlet of the high temperature recuperator; the cold side outlet of the high temperature recuperator is connected with the cold side inlet of the intermediate heat exchanger; the cold side outlet of the intermediate heat exchanger is connected with the inlet of the turbine, the outlet of the turbine is connected with the inlet of the main cycle flow meter, the outlet of the main cycle flow meter is connected with the hot side inlet of the high temperature recuperator, and the hot side outlet of the high temperature recuperator is connected with the hot side inlet of the low temperature recuperator.

[0008] In the flow control module, the input signal is the flow detected by the main cycle flow meter, and the speed signal is output to the turbine, the main compressor and the recompression compressor; in the split coefficient control module, the input signal is the flow detected by the main cycle flow meter and the bypass flow meter, and the opening signal is output to the main path valve and the bypass valve.

[0009] The further improvement of the present application is that the turbine, the main compressor and the recompression compressor are coaxially arranged.

[0010] The further improvement of the present application is that the speed of the turbine, the main compressor and the recompression compressor is equal.

[0011] The further improvement of the present application is that in the flow control module, the speed RS is set as the control quantity, and the total flow m of the closed system is set as the controlled quantity.

[0012] The further improvement of the present application is that the measuring point of the speed RS is arranged on the coaxial system of the turbine, the main compressor and the recompression compressor.

[0013] The further improvement of the present application is that the measuring point of the total flow m of the closed system is the main cycle flow meter, and the main cycle flow meter is arranged between the outlet of the turbine and the hot side inlet of the high temperature recuperator.

[0014] The further improvement of the present application is 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, the opening of the bypass valve is set as the direct control quantity, the opening of the main path valve is set as the indirect control quantity, and the split coefficient α is set as the controlled quantity.

[0015] The further improvement of the present application is 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 flow meter, and the bypass flow meter is arranged between the outlet of the bypass valve and the inlet of the recompression compressor.

[0016] The further improvement of the present application is that the calculated value of the split ratio α is the ratio of the flow monitoring value of the bypass flow meter to the flow monitoring value of the main circulation flow meter.

[0017] A supercritical carbon dioxide cycle optimal split ratio control method, which is based on a supercritical carbon dioxide cycle optimal split ratio control system, comprises the following steps of:

[0018] The opening degrees of the main path valve and the bypass valve always satisfy the constraint that the opening degrees of the main path valve and the bypass valve are both greater than 0% and less than or equal to 100%;

[0019] Under the conditions that the rotating speed RS is 100%, 95%, 90%, 85%, 80%, 75% and 70% of the rated rotating speed, the load that can be output at the working condition point and the corresponding optimal split ratio α opt are calculated.

[0020] Based on the optimal split ratio α opt corresponding to each working condition point, a function α opt of the optimal split ratio α opt varying with the rotating speed RS is fitted.

[0021] The function is input into a split ratio control module as a judgment criterion to carry out optimal split ratio α opt tracking control.

[0022] During the variable load operation of the unit, after receiving the feedback signal of the real-time split ratio α, the split ratio control module determines the difference between the actual split ratio α and the optimal split ratio α opt corresponding to the current rotating speed RS by calculating the optimal split ratio α opt in real time, and continuously adjusts the opening degrees of the main path valve and the bypass valve, so as to ensure that the split ratio α is equal to the optimal split ratio α opt under the variable load working condition.

[0023] When α>α opt , the opening degree of the bypass valve is increased and the opening degree of the main path valve is decreased until α=α opt .

[0024] When α<α opt , the opening degree of the bypass valve is decreased and the opening degree of the main path valve is increased until α=α opt .

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

[0026] The application provides a supercritical carbon dioxide cycle optimal split coefficient control system and method, which integrates an optimal split coefficient tracking mode in a split coefficient control module, ensures that the system can automatically adjust the opening degrees of a main valve and a bypass valve under various variable load conditions to match the optimal split coefficient for operation, thereby solving the problem of poor dynamic performance of a fixed split ratio system when a unit deviates from a design point for operation, effectively avoiding the compressor surge problem that may be caused in a 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 DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

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

[0029] Explanation of reference signs:

[0030] 1-compressor, 2-low temperature regenerator, 3-high temperature regenerator, 4-intermediate heat exchanger, 5-turbine, 6-recompression machine, 7-precooler, 8-pressure stabilizing tank, 9-generator, F1-main cycle flow meter, F2-bypass flow meter, V1-main valve, V2-bypass valve, CM-m-flow control module, CM-α-split coefficient control module. DETAILED DESCRIPTION

[0031] In the following, 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 application. Therefore, the drawings and description are considered to be exemplary in nature rather than limiting.

[0032] In the description of the application, it should be understood that the orientation or positional relationship indicated by terms such as "central", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0033] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can include one or more of the features explicitly or implicitly. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0034] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection, or communication; it can be direct connection, or indirect connection through intermediate medium, or internal communication of two elements or interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0035] In the present application, unless otherwise explicitly specified and limited, "on" or "under" of the first feature to the second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, "on", "above" and "above" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. "Below", "below" and "below" of the first feature to the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

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

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

[0038] The accompanying drawings illustrate various structural schematic diagrams according to embodiments disclosed in this invention. These drawings are not to scale, and some details have been enlarged for clarity, and some details may have been omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate from reality due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed.

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

[0040] Example 1

[0041] like Figure 1 As shown, the present invention provides an optimal split coefficient control system for supercritical carbon dioxide cycle, comprising: 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 speed of turbine 5, main compressor 1 and recompressor 6 by monitoring the flow rate of the main circulation flow meter F1.

[0043] The flow splitting coefficient control module CM-α controls the opening degree of the main circulation valve V1 and the bypass valve V2 by monitoring the flow rate of the main circulation flow meter F1 and the flow rate of the bypass flow meter.

[0044] The bypass valve V2 is connected with the inlet of the bypass flowmeter F2, the outlet of the bypass flowmeter F2 is connected with the inlet of the re-compressor 6, the outlet of the re-compressor 6 is connected with the cold side inlet of the high temperature regenerator 3. The cold side outlet of the high temperature regenerator 3 is connected with the cold side inlet of the intermediate heat exchanger 4. The cold side outlet of the intermediate heat exchanger 4 is connected with the inlet of the turbine 5, the outlet of the turbine 5 is connected with the inlet of the main cycle flowmeter F1, the outlet of the main cycle flowmeter F1 is connected with the hot side inlet of the high temperature regenerator 3, the hot side outlet of the high temperature regenerator 3 is connected with the hot side inlet of the low temperature regenerator 2, the hot side outlet of the low temperature regenerator 2 is connected with the inlet of the main valve V1, the outlet of the main valve V1 is connected with the inlet of the pre-cooler 7, the outlet of the pre-cooler 7 is connected with the inlet of the pressure stabilizer 8, the outlet of the pressure stabilizer 8 is connected with the inlet of the main compressor 1, the outlet of the main compressor 1 is connected with the cold side inlet of the low temperature regenerator 2.

[0045] The rotating speed of the turbine 5, the main compressor 1 and the re-compressor 6 is always equal.

[0046] The working process and principle of the application is as follows:

[0047] One part of the low pressure fluid at the cold side outlet of the low temperature regenerator 2 enters the re-compressor 6 to be compressed to a high pressure and low temperature state after the flow is controlled by the bypass valve V2 and measured by the bypass flowmeter F2, and the other part enters the pre-cooler 7 to be cooled to a temperature near the supercritical state point after the flow is controlled by the main valve V1, then enters the pressure stabilizer 8 to stabilize the pressure fluctuation, and then enters the main compressor 1 to be compressed to a high pressure and low temperature fluid, and then enters the cold side of the low temperature regenerator 2 to be heated and warmed up, and then the two high pressure fluids at the cold side outlet of the low temperature regenerator 2 enter the cold side of the high temperature regenerator 3 and the cold side of the intermediate heat exchanger 4 in turn to be heated, and then enter the turbine 5 to be adiabatically expanded to do work and be converted to a low pressure and high temperature fluid. The fluid passes through the main cycle flowmeter F1 to measure the flow, and then passes through the hot side of the high temperature regenerator 3 and the hot side of the low temperature regenerator 2 in turn to be cooled and warmed up, and then enters the next cycle.

[0048] The working medium is adiabatically expanded in the turbine 5 to drive the blades to rotate, the rotating movement of the turbine 5 drives the generator 9 to generate electric energy through a mechanical transmission device, realizes the conversion of heat energy to electric energy, and drags the main compressor 1 and the re-compressor 6 to rotate, reduces the mechanical energy loss when the turbine and the compressor are arranged in separate shafts.

[0049] During the variable load process, the flow control module CM-m controls the rotation speed of the turbine 5, the main compressor 1 and the re-compressor 6 by monitoring the flow size of the main circulation flowmeter F1. If the monitored main circulation flow becomes larger, the rotation speed of the turbine 5, the main compressor 1 and the re-compressor 6 is increased; if the monitored main circulation flow becomes smaller, the rotation speed of the turbine 5, the main compressor 1 and the re-compressor 6 is decreased.

[0050] During the variable load process, the split ratio control module CM-α controls the opening size of the main path valve V1 and the bypass valve V2 by monitoring the flow size of the main circulation flowmeter F1 and the bypass flowmeter, and calculating the split ratio α according to the ratio of the two, and comparing the size between the calculated split ratio α and the set value. If the calculated split ratio α is smaller than the set value, the opening of the main path valve V1 is decreased and the opening of the bypass valve V2 is increased; if the calculated split ratio α is larger than the set value, the opening of the main path valve V1 is increased and the opening of the bypass valve V2 is decreased.

[0051] Embodiment 2

[0052] The application provides a supercritical carbon dioxide cycle optimal split ratio control method, which comprises the following steps:

[0053] The opening of the main path valve and the bypass valve always satisfies the constraint that the opening of the main path valve V1 and the opening of the bypass valve V2 are both greater than 0% and less than or equal to 100%; under the working conditions that the rotation speed RS is 100%, 95%, 90%, 85%, 80%, 75% and 70% of the rated rotation speed, the output load and the corresponding optimal split ratio α of the working point are calculated opt .

[0054] The matching relationship between the split ratio α and the rotation speed RS is adjusted to maximize the power generation efficiency. The rotation speed is fixed at 95% of the rated rotation speed RS d , the split ratio α is set to linearly decrease from 0.5 to 0.2, and the change trend of the power generation efficiency is obtained. The optimal split ratio value corresponding to the highest power generation efficiency under the rotation speed (i.e. 95% of the rated rotation speed) is identified.

[0055] Subsequently, the rotation speed is sequentially decreased to 90%, 85%, 80%, 75% and 70% of the rated rotation speed, and the above process is repeated at each rotation speed to find and determine the optimal split ratio value under the rotation speed.

[0056] Based on the distribution of the optimal split ratio values under each rotation speed, a function α opt =f(RS) is fitted with the rotation speed as the independent variable and the optimal split ratio as the dependent variable. The function is input as an input signal into the split ratio control module CM-α.

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

[0058] During the load change process of the unit, after receiving the feedback signal of the real-time shunt coefficient α, the shunt coefficient control module CM-α calculates the optimal shunt coefficient value α corresponding to the current speed RS opt , compares the size of α and α opt , and adjusts the opening of the main valve V1 and the opening of the bypass valve V2.

[0059] When α < α opt , the opening of the bypass valve V2 is increased and the opening of the main valve V1 is decreased, so that the bypass flow is increased and the main flow is decreased, thereby increasing the real-time shunt coefficient α to equal α opt .

[0060] When α > α opt , the opening of the bypass valve V2 is decreased and the opening of the main valve V1 is increased, so that the bypass flow is decreased and the main flow is increased, thereby decreasing the real-time shunt coefficient α to equal α opt .

[0061] During the whole 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 condition process, and the working state of the re-compressor gradually deviates from the surge line, which can ensure the safe and stable operation of the unit.

[0062] Example 3

[0063] This embodiment takes a 1MW supercritical carbon dioxide shunt re-compression cycle power generation system as the implementation object, and the system design parameters are: rated speed RS d = 44000 rpm, and design optimal shunt coefficient α d = 0.33.

[0064] Comparative example: fixed shunt coefficient control method

[0065] During the whole load change process, the set speed is linearly reduced according to RS = RS d × (1-1.22t), where t is the time variable, unit: second. The control module CM-α adopts a fixed parameter strategy, and the shunt coefficient set value is locked as α d = 0.33. During the load change process, the shunt coefficient calculation value α increases, in order to resist this trend and maintain the shunt coefficient value as α dInvariable, the shunt coefficient control module CM-α gradually increases the main valve V1 opening degree, and simultaneously reduces the bypass valve V2 opening degree. With the further reduction of the rotating speed RS, the main valve V1 opening degree reaches 100% and remains invariable, and the bypass valve V2 opening degree continues to reduce. Since the volume flow of the working medium through the re-compressor 6 reduces more quickly, this makes the actual working state of the re-compressor 6 closer to the surge line. Since the real-time shunt coefficient is constant as the design working condition value α d During the load change process, the main gas pressure, the main gas temperature, the turbine efficiency, and the compressor efficiency change, so that the power generation efficiency of the unit does not match the optimal value of the current working condition. The real-time monitoring data shows that the time-averaged power generation efficiency of the unit is 18.72%.

[0066] The present application is an optimal shunt coefficient control method:

[0067] During the entire variable load process, the set rotating speed is linearly reduced according to RS=RS d ×(1-1.22t), where t is a time variable, and the unit is second. The control module CM-α uses the optimal shunt coefficient strategy, and calculates the α opt value corresponding to the current rotating speed RS in real time through the cubic spline interpolation algorithm, as shown in Table 1. During the variable load process, after receiving the feedback signal of the shunt coefficient calculation value α, the control module CM-α continuously adjusts the opening degrees of the main valve V1 and the bypass valve V2 by calculating the difference between the current shunt coefficient α and α opt , so as to ensure that α is equal to α opt under each working condition. 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 shunt coefficient control mode. Therefore, in the actual variable load process, it is recommended that the unit uses the optimal shunt coefficient method to operate.

[0068] Table 1

[0069] RS opt ]]> ​ 30800 0.37491 33000 0.35399 35200 0.33994 37400 0.32531 39600 0.31287 41800 0.31367

[0070] The basic principles and main features of the present application and the advantages of the present application are shown and described above. It is obvious for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present application is defined by the appended claims rather than the above description, and therefore all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0071] Furthermore, it should be understood that although the specification is described in terms of embodiments, each of which contains only one independent technical solution, the specification is described in this way only for the sake of clarity, and the skilled person should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that the skilled person can understand. The above is only to illustrate the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made on the basis of the technical solutions according to the technical idea of the present application falls within the protection scope of the claims of the present application.

Claims

1. A method for controlling the optimal split coefficient in a supercritical carbon dioxide cycle, characterized in that, This method is based on an optimal split coefficient control system for supercritical carbon dioxide cycle, which includes a split coefficient control module (CM-α), a flow control module (CM-m), and a split recompression cycle system; In the split recompression cycle system, the hot-side outlet of the low-temperature regenerator (2) is connected to the inlet of the main valve (V1) and simultaneously to 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 tank (8), the outlet of the pressure 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), and 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 flow meter (F2) is connected to the inlet of the recompressor (6), and 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), and the outlet of the turbine (5) is connected to the inlet of the main circulation flow meter (F1); the outlet of the main circulation flow meter (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 rate detected by the main circulation flow meter (F1), and the output speed signal is sent to the turbine (5), the main compressor (1) and the re-compressor (6); in the flow split coefficient control module (CM-α), the input signal is the flow rate detected by the main circulation flow meter (F1) and the bypass flow meter (F2), and the output opening signal is sent to the main valve (V1) and the bypass valve (V2); In the flow control module (CM-m), the rotational speed RS is set as the control variable, and the total flow rate m of the closed system is set as the controlled variable. The measuring point for the total flow m of the closed system is the main circulation flow meter (F1); the main circulation flow meter (F1) is located between the outlet of the turbine (5) and the hot side inlet of the high-temperature regenerator (3); In the diversion coefficient control module (CM-α), the bypass valve (V2) is set as the direct control device, and the main valve (V1) is set as the reverse linkage control device. The opening degree of the bypass valve (V2) is the direct control quantity, the opening degree of the main valve (V1) is the indirect control quantity, and the diversion coefficient α is the controlled quantity. The main valve (V1) is located between the hot side outlet of the low-temperature regenerator (2) and the inlet of the precooler (7); the bypass valve (V2) is located between the hot side outlet of the low-temperature regenerator (2) and the inlet of the bypass flow meter (F2); the bypass flow meter (F2) is located between the outlet of the bypass valve (V2) and the inlet of the recompressor (6); The flow splitting coefficient α is calculated as the ratio of the flow rate monitored by the bypass flow meter (F2) to the flow rate monitored by the main circulation flow meter (F1). The method includes: The opening degrees of the main valve and bypass valve are set to always meet the following constraints: the opening degree of both the main valve (V1) and the bypass valve (V2) must be greater than 0% and less than or equal to 100%. Calculate the load that can be output at each operating point and the corresponding optimal flow splitting coefficient α under the operating conditions where the speed RS is 100%, 95%, 90%, 85%, 80%, 75%, and 70% of the rated speed. opt ; Power generation efficiency is maximized by adjusting the matching relationship between the current splitting coefficient α and the rotational speed RS; the rotational speed is fixed at its rated speed RS. d The current splitting coefficient α is set to decrease linearly from 0.5 to 0.2 at 95% of the rated speed to obtain the trend of power generation efficiency; the optimal current splitting coefficient value corresponding to the highest power generation efficiency at 95% of the rated speed is identified. Subsequently, the speed was reduced to 90%, 85%, 80%, 75% and 70% of the rated speed in sequence, and the above process was repeated at each speed to find and determine the optimal flow splitting coefficient value at that speed. Based on the optimal diversion coefficient α corresponding to each operating point opt Fit the optimal split coefficient α opt α, a function of rotational speed RS opt = f (RS); This function is input as the judgment criterion into the flow diversion coefficient control module (CM-α) to carry out the optimal flow diversion coefficient α under varying loads. opt Tracking and control; During unit operation under varying loads, the shunt coefficient control module (CM-α), upon receiving the feedback signal of the real-time shunt coefficient α, calculates the optimal shunt coefficient α corresponding to the current speed RS in real time. opt Determine the actual diversion coefficients α and α opt The difference is used to continuously adjust the opening of the main valve (V1) and the bypass valve (V2) to ensure that the flow diversion coefficient α is equal to the optimal flow diversion coefficient α under varying load conditions in all operating conditions. opt ; When α > α opt At this time, increase the opening of the bypass valve (V2) and decrease the opening of the main valve (V1) until α = α opt ; When α < α opt At this time, decrease the opening of the bypass valve (V2) and increase the opening of the main valve (V1) until α = α opt .

2. The method for controlling the optimal split coefficient of a supercritical carbon dioxide cycle according to claim 1, characterized in that, The turbine (5), main compressor (1) and recompressor (6) are arranged coaxially.

3. The method for controlling the optimal split coefficient of a supercritical carbon dioxide cycle according to claim 1, characterized in that, The turbine (5), main compressor (1) and recompressor (6) operate at the same speed.

4. The method for controlling the optimal split coefficient of a supercritical carbon dioxide cycle according to claim 1, characterized in that, The speed RS measuring points are arranged on the coaxial system of the turbine, main compressor and re-compressor.

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