A supercritical carbon dioxide cycle load following control system and method

Abstract

The present invention discloses a supercritical carbon dioxide cycle load following control system and method, which relates to the technical field of power cycles and includes: a main compressor; a recompressor; a CO2 storage tank; a primary heater; a secondary heater; a generator; a high-pressure turbine; a low-pressure turbine; a high-temperature recuperator; a low-temperature recuperator; a CO2 exhaust valve; a CO2 inlet valve; and a turbine inlet valve. In the present invention, the carbon dioxide injection position is arranged at the outlet position of the high-pressure cylinder, which improves the system load increase rate; a new load following control strategy that combines valve control and inventory control to achieve fast variable load and efficient wide load is adopted, that is, the turbine inlet valve is used as a means for fast variable load and the opening of the turbine inlet valve is regarded as a signal for evaluating whether the power generation power of the generator matches the grid load; the need for frequency modulation and load following is quickly met by adjusting the opening of the turbine inlet valve; and the thermal efficiency of the cycle is maintained at a high value within a wide load range through inventory master control.

Description

Technical Field

[0001] The present invention relates to the technical field of power circulation, and in particular to a supercritical carbon dioxide circulation load following control system and a control method thereof. Background Art

[0002] With the rapid development of the global economy, the demand for electricity is growing, the consumption of fossil energy continues to increase, and energy shortage and environmental pollution have become two major problems that need to be solved in today's society. Developing efficient, clean and economical power generation technology is the core goal pursued by the power industry, and seeking advanced power cycles is an important direction to achieve this goal. The supercritical carbon dioxide Brayton cycle is a power cycle that can achieve efficient heat-to-work conversion. It uses supercritical carbon dioxide as a working fluid and has the characteristics of simple system, compact structure, environmental friendliness, high thermal efficiency and good economy. The typical supercritical carbon dioxide Brayton cycle system is the supercritical carbon dioxide simple recompression cycle (SCBC), which mainly includes compressors, heaters, turbines, coolers, regenerators and other equipment. The supercritical carbon dioxide system needs to meet various load requirements and cope with the influence of heat source changes. Therefore, its dynamic performance and control strategy are critical to ensure that the system can quickly and efficiently follow the load. The load following control strategy of the supercritical carbon dioxide simple recompression cycle (SCBC) can be divided into four categories: valve control, heat source control, inventory control and impeller machinery speed control.

[0003] Inventory control is a control strategy that achieves load following by changing the inventory of working fluid in the system, thereby changing the circulation flow of the system and then changing the circulation power generation. This control strategy can be combined with heat source control to ensure a higher average heat absorption temperature during variable load. Therefore, inventory control can maintain a higher cycle thermal efficiency within a wide load range; at the same time, a well-designed inventory control strategy can achieve a wide load adjustment range; however, both the regenerator and the precooler have large volume inertia, so the load following performance of inventory control is poor. Figure 3 Two types of storage tank layouts are shown. Most scholars in the literature use layout 1, and a few use layout 2. In layout 1, the volume of the storage tank is usually fixed. According to the needs of load changes, the CO2 working fluid is injected into the storage tank at the outlet of the compressor or injected into the system from the inlet of the precooler. The internal pressure of the storage tank is between the highest and lowest pressures of the cycle, and the flow rate injected into and out of the system can be controlled by adjusting the opening of the inlet and outlet regulating valves of the storage tank. In layout 2, it is generally believed that the volume of storage tank 1 and storage tank 2 is unlimited. The compressor is used to inject CO2 into the system and the regulating valve is used to discharge CO2 from the system, thereby achieving the purpose of raising and lowering the load of the power system.

[0004] The valve control strategies are mainly divided into two categories: the turbine inlet throttle valve and the bypass valve. Adjusting the valve opening can directly change the turbine inlet air volume, thereby changing the work done by the turbine. Therefore, it has good load following characteristics. However, reducing the valve opening will increase the throttling loss, resulting in a decrease in the cycle thermal efficiency of the system. Due to the large throttling loss in valve control, it is generally only suitable for load regulation in a relatively narrow range. Figure 4 The layout positions of the valves in the supercritical carbon dioxide recompression cycle are given. To give full play to the good load response characteristics of valve control, the valves are usually arranged at positions closer to the power conversion equipment in the process flow, such as V3 and V4.

[0005] The principles, advantages and disadvantages of the existing load following control strategies for the supercritical carbon dioxide simple recompression cycle (SCBC) are shown in the following table.

[0006] Table 1 Comparison of different load following control strategies

[0007]

[0008] Inventory control can ensure that the supercritical carbon dioxide simple recompression cycle (SCBC) maintains a high cycle thermal efficiency within a wide load range. However, the system has a large volume inertia, resulting in poor load following characteristics of the power conversion system. Valve (bypass valve or throttle valve) control can directly change the flow rate and pressure of the cycle, so it has a fast response speed for various cycle layouts. However, due to the throttling loss of the valve, the cycle efficiency at low loads is relatively low.

[0009] In summary, there are mainly three problems with the conventional load following control strategies:

[0010] (1) The conventional load following control strategies are only the single load following control strategies introduced above, and each control strategy has corresponding disadvantages, which will lead to the problem that it is difficult to combine fast variable load and high efficiency within a wide load range for the supercritical carbon dioxide system;

[0011] (2) Some scholars have also integrated multiple control strategies to achieve the purpose of complementary advantages. The main integration method is to couple valve control and inventory control. However, since the response time difference between inventory control and valve control is an order of magnitude, directly switching from valve control to inventory control during the load reduction process of the power conversion system will cause a peak in the system power generation, reducing the load following characteristics of the system;

[0012] (3) Integrating valve control with conventional inventory control can achieve stable load reduction of the system. However, for the load increase process with a relatively fast ramp rate, it will be difficult for the rapid increase in the valve opening to compensate for the increase in the grid load, and the response time of the inventory control system is relatively long. Therefore, through the integration method of conventional inventory control and valve control, it is difficult for the power generation system to follow the rapid load increase process of the grid.

[0013] In summary, the existing control strategies are difficult to balance rapid response, wide load range, and high thermal efficiency. Currently, there is an urgent need for a control strategy that can simultaneously achieve rapid and efficient load following of SCBC within a wide load range. Summary of the Invention

[0014] The present invention proposes a load following control system and its control method for a supercritical carbon dioxide cycle, specifically proposing a new form of inventory tank layout, which can significantly improve the load increase rate of the supercritical carbon dioxide system; by complementing the advantages of inventory control and valve control, the problem that it is difficult to combine rapid load change and high efficiency within a wide load range in a supercritical carbon dioxide power generation system is solved.

[0015] The present invention provides a load following control system for a supercritical carbon dioxide cycle, including:

[0016] A main compressor, with a pre-cooler at its inlet;

[0017] A CO2 storage tank, whose inlet is connected to the outlet of the main compressor, and a CO 2 exhaust valve is provided at its inlet, and a CO 2 inlet valve is provided at its outlet;

[0018] A generator, on the turbine shaft connected to its output shaft, there are a high-pressure turbine and a low-pressure turbine, and a turbine inlet valve is provided at the inlet of the high-pressure turbine;

[0019] A regenerative assembly, its first inlet is connected to the outlet of the low-pressure turbine, and its first outlet is connected to the pre-cooler at the inlet of the main compressor; the outlet of the main compressor is divided into two paths and then respectively connected to the CO2 storage tank and the second inlet of the regenerative assembly;

[0020] A heater, its outlet is respectively connected to the high-pressure turbine and the low-pressure turbine, the outlet of the CO2 storage tank and the outlet of the high-pressure turbine converge and then are connected to the inlet of the heater, and the second outlet of the regenerative assembly is connected to the heater;

[0021] Wherein, according to the change of the grid load, the opening degree of the turbine inlet valve is adjusted to realize the adjustment of the generator speed, and by adjusting the CO 2 exhaust valve and CO 2 inlet valve at the inlet and outlet of the CO2 storage tank, the opening degree adjustment of the turbine inlet valve is realized.

[0022] Further, the regenerative assembly includes:

[0023] A high-temperature regenerator, its first inlet is connected to the outlet of the low-pressure turbine;

[0024] A low-temperature recuperator, whose first inlet is connected to the first outlet of a high-temperature recuperator, and whose first outlet is connected to a pre-cooler at the inlet of a main compressor; the outlet of the main compressor is divided into two paths and is respectively connected to a CO2 storage tank and the second inlet of the low-temperature recuperator, the second outlet of the low-temperature recuperator is connected to the second inlet of the high-temperature recuperator, and the second outlet of the high-temperature recuperator is connected to a heater;

[0025] Further, the heater includes:

[0026] A primary heater, whose inlet is connected to the second outlet of the high-temperature recuperator, and whose outlet is connected to the inlet of a high-pressure turbine;

[0027] A secondary heater, the outlet of the CO2 storage tank and the outlet of the high-pressure turbine converge and are connected to the inlet of the secondary heater, and the outlet of the secondary heater is connected to the inlet of a low-pressure turbine;

[0028] Further, the pipeline where the 2 exhaust valve is located is connected to the outlet end of the high-pressure turbine and the inlet end of the secondary heater through a three-way valve; the pipeline where the 2 inlet valve is located is connected to the outlet end of the main compressor and the second inlet end of the cold side of the low-temperature recuperator through a three-way valve.

[0029] Further, it further includes a recompressor, the first outlet of the low-temperature recuperator is divided into two paths and is respectively connected to the pre-cooler at the inlet of the main compressor and the inlet of the recompressor through a three-way valve; the outlet of the recompressor and the second outlet of the low-temperature recuperator converge and are connected to the second inlet of the high-temperature recuperator through a three-way valve.

[0030] Further, it further includes a power grid load feedforward signal acquisition module, which is used to provide power grid load information;

[0031] Control the opening degree of the turbine inlet valve according to the power grid load information provided by the power grid load feedforward signal acquisition module.

[0032] Further, it further includes a check valve, which is arranged at the outlet end of the CO2 storage tank.

[0033] The present invention also provides a control method for a supercritical carbon dioxide cycle load following control system, including the following steps:

[0034] When the power grid load decreases, the generator speed will increase, then reduce the opening degree of the turbine inlet valve, so that the inlet pressure of the high-pressure turbine decreases, then the power generation of the high-pressure turbine decreases, the output torque of the high-pressure turbine decreases, and the generator speed decreases;

[0035] When the grid load increases, the rotational speed of the generator decreases. Then, the opening degree of the turbine inlet valve is increased, so that the inlet pressure of the high-pressure turbine increases. As a result, the power generation of the high-pressure turbine increases, the output torque of the high-pressure turbine increases, and the rotational speed of the generator increases.

[0036] Furthermore, it also includes setting a reasonable value for the opening degree of the turbine inlet valve, and this reasonable value is less than 100%;

[0037] When the actual opening degree of the turbine inlet valve is less than the reasonable value, open the CO 2 exhaust valve and close the CO 2 inlet valve. Then, the CO 2 inventory in the system decreases, and the CO 2 circulation flow rate in the system decreases. As a result, the power generation of the high-pressure turbine decreases, achieving an increase in the opening degree of the high-pressure turbine;

[0038] When the actual opening degree of the turbine inlet valve is greater than the reasonable value, close the CO 2 exhaust valve and open the CO 2 inlet valve. Then, the CO 2 inventory in the system increases, and the CO 2 circulation flow rate in the system increases. As a result, the power generation of the high-pressure turbine increases, achieving a decrease in the opening degree of the high-pressure turbine.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The present invention proposes a new form of inventory tank arrangement for the variable load process of the ultra-supercritical system, specifically a supercritical carbon dioxide cycle load-following control system. It arranges the carbon dioxide injection position at the outlet of the high-pressure cylinder, which can significantly improve the load increase rate of the supercritical carbon dioxide cycle system.

[0041] The present invention combines valve control and inventory control skillfully to achieve a new load-following control strategy with fast variable load and high efficiency in a wide load range. That is, the turbine inlet valve is used as a means for fast variable load, and the valve opening degree of the turbine inlet valve is regarded as a signal to evaluate whether the power generation power of the power conversion system matches the grid load.

[0042] The present invention quickly meets the needs of frequency modulation and load following by auxiliary valve control, that is, adjusting the opening degree of the turbine inlet valve; and ensures that the thermal efficiency of the cycle remains at a high value within a wide load range through main inventory control. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation to the present invention. In the drawings:

[0044] Figure 1It is the process flow diagram of a supercritical carbon dioxide cycle load following control system proposed by the present invention;

[0045] Figure 2 It is the combined control strategy of valve control and inventory control for a supercritical carbon dioxide cycle load following control system proposed by the present invention;

[0046] Figure 3 It is the layout form of the inventory tank of the supercritical carbon dioxide recompression cycle proposed in the background art of the present invention;

[0047] Figure 4 It is the arrangement position of the valve of the supercritical carbon dioxide recompression cycle proposed in the background art of the present invention. Description of the Drawings:

[0049] 1 - Main compressor; 2 - CO2 storage tank; 3 - Generator; 4 - High - pressure turbine; 5 - Low - pressure turbine; 6 - Pre - cooler; 7 - High - temperature recuperator; 8 - Low - temperature recuperator; 9 - First - stage heater; 10 - Second - stage heater; 11 - Re - compressor. Detailed Embodiments

[0050] Next, in combination with the drawings in the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments.

[0051] Embodiment 1

[0052] As Figure 1 shown, a supercritical carbon dioxide cycle load following control system provided by the present invention includes a main compressor 1 with a pre - cooler 6 at its inlet; a CO2 storage tank 2 whose inlet is connected to the outlet of the main compressor 1 and has a CO 2 exhaust valve at its inlet and a CO 2 inlet valve at its outlet; a generator 3 with a high - pressure turbine 4 and a low - pressure turbine 5 on the turbine shaft connected to its output shaft, and a turbine inlet valve at the inlet of the high - pressure turbine 4; a heat - recovery assembly whose first inlet is connected to the outlet of the low - pressure turbine 5 and whose first outlet is connected to the pre - cooler 6 at the inlet of the main compressor 1; the outlet of the main compressor 1 is divided into two paths and is respectively connected to the CO2 storage tank 2 and the second inlet of the heat - recovery assembly; a heater whose outlet is respectively connected to the high - pressure turbine 4 and the low - pressure turbine 5, the outlet of the CO2 storage tank 2 and the outlet of the high - pressure turbine 4 converge and are connected to the inlet of the heater, and the second outlet of the heat - recovery assembly is connected to the heater;

[0053] Among them, according to the change of the grid load, the opening of the turbine inlet valve is adjusted to realize the adjustment of the speed of the generator 3, and by adjusting the CO 2 exhaust valve and the CO 2An intake valve is used to adjust the opening degree of the turbine intake valve.

[0054] During the actual operation process, when the grid load decreases and the power generation of the generator 3 needs to be reduced, the opening degree of the turbine intake valve is directly reduced to quickly achieve the matching between the grid load and the system power. In addition, to reduce the throttling loss caused by the small opening degree of the turbine intake valve, the CO 2 working medium is gradually discharged from the system through inventory control, and the heating opening degree of the turbine intake valve is readjusted to a reasonable value. When the grid load increases and the power generation of the generator 3 needs to be increased, especially when the grid load climbs relatively fast, it is difficult to achieve the power matching between the grid and the system only by increasing the opening degree of the turbine intake valve. And through Figure 3 In Layout 1 where the carbon dioxide intake valve is arranged at the inlet of the precooler 6, and in Layout 2 where the carbon dioxide intake valve is arranged at the outlet of the main compressor 1, it is also difficult to achieve a rapid load increase of the power conversion system, which will cause the turbine and the generator 3 to stall. Therefore, the carbon dioxide storage tank intake valve needs to be arranged at a more appropriate position, that is, the CO 2 intake valve is arranged at the outlet of the high-pressure turbine 4. This position has a suitable pressure and is closer to the turbine of the generator 3 in the system process flow, which is convenient for achieving a rapid load increase of the entire system.

[0055] To achieve the change of the system's power generation load by adjusting the carbon dioxide flow rate of the system, a carbon dioxide storage tank is added in the present invention. By adjusting the opening degrees of the CO 2 inlet and exhaust valves, the CO 2 working medium is introduced into and discharged from the system. The position where the CO 2 working medium flows out of the system is selected at a position where the pressure is as high as possible and the temperature is as low as possible, that is, the outlet of the main compressor 1. The position where the CO 2 is introduced into the system is selected at a position where the pressure is as low as possible and is as close as possible to the power conversion equipment, that is, the outlet of the high-pressure turbine 4. Among them, the position where the CO 2 is introduced into the system is related to the specific form of the system. If the system is a multi-stage turbine, this position is mainly selected at the outlets of each stage of the turbine.

[0056] CO 2 The position where the CO

[0057] CO 2 flows out of the system can be selected at a position far from the power conversion equipment. When the system's power generation is greater than the grid load, the load following can be quickly achieved by reducing the opening degree of the turbine intake valve, so that the turbine speed will not soar. 2to increase the power generation of the system in the form of

[0058] while when the position of the point where CO 2 is incorporated into the system is far from the power conversion device, there is a certain lag in the increase of the system power generation, and the rotational speed of the turbine will gradually decrease and then the turbine stall problem will occur. Therefore, it is necessary to select the position of the point where CO 2 is incorporated into the system at a position closer to the power conversion device.

[0059] As Figure 1 shown, the regenerative component in the present invention includes:

[0060] A high-temperature regenerator 7, whose first inlet is communicated with the outlet of the low-pressure turbine 5;

[0061] A low-temperature regenerator 8, whose first inlet is communicated with the first outlet of the high-temperature regenerator 7, and whose first outlet is communicated with the pre-cooler 6 at the inlet of the main compressor 1; the outlet of the main compressor 1 is divided into two paths and then respectively communicated with the CO2 storage tank 2 and the second inlet of the low-temperature regenerator 8, the second outlet of the low-temperature regenerator 8 is communicated with the second inlet of the high-temperature regenerator 7, and the second outlet of the high-temperature regenerator 7 is communicated with the heater;

[0062] As Figure 1 shown, the heater in the present invention includes:

[0063] A primary heater 9, whose inlet is communicated with the second outlet of the high-temperature regenerator 7, and whose outlet is communicated with the inlet of the high-pressure turbine 4;

[0064] A secondary heater 10, the outlet of the CO2 storage tank 2 and the outlet of the high-pressure turbine 4 converge and then are communicated with the inlet of the secondary heater 10, and the outlet of the secondary heater 10 is communicated with the inlet of the low-pressure turbine 5;

[0065] As Figure 1 shown, the pipeline where the CO 2 exhaust valve is located is communicated with the outlet end of the high-pressure turbine 4 and the inlet end of the secondary heater through a three-way valve; the pipeline where the CO 2 inlet valve is located is communicated with the outlet end of the main compressor 1 and the second inlet end of the cold side of the low-temperature regenerator 8 through a three-way valve.

[0066] As Figure 1 shown, the present invention further includes a recompressor 11, the first outlet of the low-temperature regenerator 8 is divided into two paths and then respectively communicated with the pre-cooler 6 at the inlet of the main compressor 1 and the inlet of the recompressor 11 through a three-way valve; the outlet of the recompressor 11 and the second outlet of the low-temperature regenerator 8 converge and then are communicated with the second inlet of the high-temperature regenerator 7 through a three-way valve.

[0067] As Figure 2As shown in the figure, the present invention further includes a grid load feedforward signal acquisition module, which is used to provide grid load information; and control the opening degree of the turbine inlet valve according to the grid load information provided by the grid load feedforward signal acquisition module.

[0068] In the present invention, the grid signal is introduced as a feedforward signal into the load following control strategy, avoiding the defect of inevitable hysteresis existing in the feedback control system alone.

[0069] As Figure 1 shown in the figure, the present invention further includes a check valve, which is arranged at the outlet end of the CO2 storage tank 2 to prevent the CO in the system 2 from flowing back to the CO2 storage tank 2 in the reverse direction.

[0070] During operation, the CO2 working medium first does work in the high-pressure turbine 4, then enters the secondary heater 10 for heating, then enters the low-pressure turbine 5 for doing work, and the exhausted gas after doing work enters the high-temperature recuperator 7 to release heat, and then enters the low-temperature recuperator 8 to further release heat. After the heat release is completed, the carbon dioxide working medium is divided into two fluid streams. One of them enters the pre-cooler 6 to further release heat, then enters the main compressor 1 for heating, and then enters the low-temperature recuperator 8 to absorb heat. The other fluid stream is compressed by the recompressor 11 and then merges with the previous fluid stream into one fluid stream, and then enters the high-temperature recuperator 7 to further absorb heat, and then enters the primary heater 9 for further heating and enters the high-pressure turbine 4 to complete the entire cycle.

[0071] Embodiment 2

[0072] The present invention also provides a control method for a supercritical carbon dioxide cycle load following control system, including the following steps:

[0073] When the grid load decreases, the speed of the generator 3 will increase, then reduce the opening degree of the turbine inlet valve, so that the inlet pressure of the high-pressure turbine 4 decreases, then the power generation of the high-pressure turbine 4 decreases, the output torque of the high-pressure turbine 4 decreases, and the speed of the generator 3 decreases;

[0074] When the grid load increases, the speed of the generator 3 will decrease, then increase the opening degree of the turbine inlet valve, so that the inlet pressure of the high-pressure turbine 4 increases, then the power generation of the high-pressure turbine 4 increases, the output torque of the high-pressure turbine 4 increases, and the speed of the generator 3 increases.

[0075] As Figure 2 shown in the figure, the present invention further includes setting a reasonable value for the opening degree of the turbine inlet valve, and this reasonable value is less than 100%;

[0076] When the actual opening degree of the turbine inlet valve is less than the reasonable value, open the CO 2 exhaust valve and close the CO 2 inlet valve, then the CO 2 inventory in the system decreases, and the CO 2When the circulation flow rate decreases, the power generation of the high-pressure turbine 4 decreases, and the opening degree of the high-pressure turbine 4 increases;

[0077] When the actual opening of the turbine inlet valve is greater than the reasonable value, close the CO 2 Exhaust valve and open CO 2 Inlet valve, the system's CO 2 The inventory increases, and the system's CO 2 As the circulation flow increases, the power generation of the high-pressure turbine 4 increases, and the opening of the high-pressure turbine 4 decreases.

[0078] During the actual operation of the system, the opening of the turbine inlet valve is controlled near a reasonable value in order to prevent the valve from being set to a smaller opening when the system is in a steady state, resulting in a significant increase in valve throttling losses. However, the valve opening does not need to be completely controlled at the target value, and a certain valve opening range is allowed. Firstly, the throttling loss at the valve does not change much when the valve opening fluctuates around the target value. Secondly, to completely control the valve opening at the target value, the CO2 inlet and exhaust valves need to be frequently actuated, which is not conducive to the stable operation of the system nor to the long-term operation of the valve.

[0079] The specific implementation modes of the present invention are described below in conjunction with specific embodiments.

[0080] like Figure 1-2 As shown, a joint control strategy that cleverly combines valve control and inventory control is provided in the present invention. The cleverness lies in that the present invention uses the turbine intake valve as a means of rapid load change and regards the opening of the turbine intake valve as a signal for evaluating whether the power generation of the generator 3 matches the grid load, and integrates valve control and inventory control with the opening of the turbine intake valve as a signal.

[0081] To meet the requirement of 50Hz power generation frequency, the target value of the rotation speed of generator 3 is set to 3000rpm, then:

[0082] When the speed of the generator 3 is greater than 3000rpm, the opening of the turbine intake valve is reduced, so that the turbine intake pressure is reduced, the power generation of the turbine is reduced, and the output torque of the turbine is reduced, so that the speed of the generator 3 is reduced;

[0083] On the contrary, increasing the opening of the turbine intake valve increases the speed of the generator 3.

[0084] In order to reduce the throttling loss caused by the small opening of the turbine intake valve, a reasonable value of the turbine intake valve opening is set. In order to ensure that the valve opening has an adjustable margin up and down, the reasonable value of the valve opening is set to be less than 100%.

[0085] When the actual opening of the adjusted turbine intake valve is less than the set value, the carbon dioxide exhaust valve is opened and the intake valve is closed at the same time, thereby reducing the CO2 The inventory level is reduced, thereby decreasing the circulating flow rate of the system, resulting in a decrease in the power generation of the turbine. As a result, the opening degree of the turbine inlet valve increases until the opening degree of the turbine inlet valve reaches the set value;

[0086] Conversely, open the carbon dioxide inlet valve and close the exhaust valve simultaneously to make the opening degree of the turbine inlet valve reach the target value.

[0087] To further improve the load following characteristics of the combined control strategy, a grid load feedforward signal is introduced in the control of the turbine inlet valve; and to prevent the frequent switching of the carbon dioxide inlet valve and the exhaust valve of the system, a dead zone of the opening degree is added after the valve opening degree deviation signal.

[0088] Finally, it should be noted that: the above disclosure is only a specific embodiment of the present invention. However, the embodiments of the present invention are not limited thereto, and any changes that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A supercritical carbon dioxide cycle load following control system, characterized in that, it includes: A main compressor (1) with a pre-cooler (6) at its inlet; CO2 storage tank (2), whose inlet is connected to the outlet of the main compressor (1), and a CO 2 exhaust valve is provided at its inlet, and a CO 2 inlet valve is provided at its outlet; A generator (3), on the turbine shaft connected to its output shaft, there are a high-pressure turbine (4) and a low-pressure turbine (5), and a turbine inlet valve is provided at the inlet of the high-pressure turbine (4); A regenerative component, its first inlet is connected to the outlet of the low-pressure turbine (5), and its first outlet is connected to the pre-cooler (6) at the inlet of the main compressor (1); the outlet of the main compressor (1) is divided into two paths and then respectively connected to the CO2 storage tank (2) and the second inlet of the regenerative component; A heater, its outlet is respectively connected to the high-pressure turbine (4) and the low-pressure turbine (5), the outlet of the CO2 storage tank (2) and the outlet of the high-pressure turbine (4) converge and then are connected to the inlet of the heater, and the second outlet of the regenerative component is connected to the heater; Among them, according to the change of the power grid load, the opening degree of the turbine inlet valve is adjusted to realize the adjustment of the rotational speed of the generator (3), and the opening degree of the turbine inlet valve is realized by adjusting the CO 2 exhaust valve and the CO 2 inlet valve at the inlet and outlet of the CO2 storage tank (2).

2. The supercritical carbon dioxide cycle load following control system according to claim 1, characterized in that: The regenerative component includes: A high-temperature regenerator (7), its first inlet is connected to the outlet of the low-pressure turbine (5); A low-temperature regenerator (8), its first inlet is connected to the first outlet of the high-temperature regenerator (7), and its first outlet is connected to the pre-cooler (6) at the inlet of the main compressor (1); the outlet of the main compressor (1) is divided into two paths and then respectively connected to the CO2 storage tank (2) and the second inlet of the low-temperature regenerator (8), the second outlet of the low-temperature regenerator (8) is connected to the second inlet of the high-temperature regenerator (7), and the second outlet of the high-temperature regenerator (7) is connected to the heater.

3. The supercritical carbon dioxide cycle load following control system according to claim 2, characterized in that: The heater includes: A primary heater (9), its inlet is connected to the second outlet of the high-temperature regenerator (7), and its outlet is connected to the inlet of the high-pressure turbine (4); A secondary heater (10), the outlet of the CO2 storage tank (2) and the outlet of the high-pressure turbine (4) converge and then are connected to the inlet of the secondary heater (10), and the outlet of the secondary heater (10) is connected to the inlet of the low-pressure turbine (5).

4. The supercritical carbon dioxide cycle load following control system according to claim 3, characterized in that: The CO 2 The pipeline where the exhaust valve is located is connected to the outlet end of the high-pressure turbine (4) and the inlet end of the secondary heater through a three-way valve; the CO 2 The pipeline where the intake valve is located is connected to the outlet end of the main compressor (1) and the second inlet end on the cold side of the low-temperature recuperator (8) through a three-way valve.

5. The supercritical carbon dioxide cycle load following control system according to claim 2, characterized in that: It further includes a recompressor (11), the first outlet of the low-temperature regenerator (8) is divided into two paths and then respectively connected to the pre-cooler (6) at the inlet of the main compressor (1) and the inlet of the recompressor (11) through a three-way valve; the outlet of the recompressor (11) and the second outlet of the low-temperature regenerator (8) converge and then are connected to the second inlet of the high-temperature regenerator (7) through a three-way valve.

6. The supercritical carbon dioxide cycle load following control system according to claim 4, characterized in that: It further includes a grid load feedforward signal acquisition module, which is used to provide grid load information; Control the opening of the turbine inlet valve according to the grid load information provided by the grid load feedforward signal acquisition module.

7. A supercritical carbon dioxide cycle load following control system according to claim 1, characterized in that: it further includes a check valve provided at the outlet end of the CO2 storage tank (2).

8. A control method for a supercritical carbon dioxide cycle load following control system according to any one of claims 1-7, characterized in that: it includes the following steps: When the grid load decreases, the speed of the generator (3) will increase, then the opening degree of the turbine inlet valve is reduced, so that the inlet pressure of the high-pressure turbine (4) is reduced, then the power generation of the high-pressure turbine (4) is reduced, the output torque of the high-pressure turbine (4) is reduced, and the speed of the generator (3) is reduced; When the grid load increases, the speed of the generator (3) will decrease, then the opening degree of the turbine inlet valve is increased, so that the inlet pressure of the high-pressure turbine (4) is increased, then the power generation of the high-pressure turbine (4) is increased, the output torque of the high-pressure turbine (4) is increased, and the speed of the generator (3) is increased.

9. A control method for a supercritical carbon dioxide cycle load following control system according to claim 8, characterized in that: it further includes setting a reasonable value for the opening degree of the turbine inlet valve, and the reasonable value is less than 100%. When the actual opening degree of the turbine inlet valve is less than the reasonable value, open the CO 2 exhaust valve and close the CO 2 inlet valve, then the CO 2 inventory in the system decreases, and the CO 2 circulation flow rate in the system decreases, so the power generation of the high-pressure turbine (4) decreases, and the opening degree of the high-pressure turbine (4) increases; When the actual opening degree of the turbine inlet valve is greater than the reasonable value, close the CO 2 exhaust valve, and open the CO 2 inlet valve, then the CO 2 inventory of the system increases, and the CO 2 circulation flow rate of the system increases, then the power generation of the high-pressure turbine (4) increases, and the opening degree of the high-pressure turbine (4) is reduced.

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