Energy storage thermal management system and control method thereof

Abstract

The present invention discloses an energy storage thermal management system, which adopts a centrifugal compressor for refrigeration cycle, and is provided with a guide vane with adjustable opening at the inlet of the centrifugal compressor. By jointly adjusting the opening of the guide vane and the rotation speed of the centrifugal compressor, the surge margin of the centrifugal compressor can be significantly increased, and the energy efficiency of the energy storage thermal management system under all working conditions can be significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of thermal management technology, and in particular to an energy storage thermal management system and a control method thereof. Background Art

[0002] Thermal management refers to the management and control of the temperature of the total system, discrete components or their environment, with the purpose of maintaining the normal operation of each component or improving its performance or life. At present, thermal management is usually required in fields such as electrochemical energy storage, and thermal management has a significant impact on the performance, life and safety of the energy storage system. Since the liquid-cooled thermal management system has a strong heat exchange capacity and the temperature difference of the battery cell can be within 3°C, liquid cooling can significantly increase the life of the energy storage system compared to the air-cooled system. In view of this, liquid cooling systems are currently mostly used in the energy storage field.

[0003] The cooling capacity required by the energy storage liquid cooling system is usually 100kW or less. This kind of small cooling capacity refrigeration cycle mostly uses traditional scroll or rotor compressors. At present, in some thermal management systems, in order to save the return oil pipeline and improve the reliability of the compressor and the system, centrifugal compressors are also used instead of scroll compressors. The centrifugal compressor is equipped with an air-floating bearing. When it is working, the rotating shaft does not contact the bearing, but relies on the air film to suspend the motor rotor, which can increase the bearing life by at least 1 times; at the same time, the size and weight of the centrifugal compressor based on the high-speed permanent magnet synchronous motor will be about 50% and 90% smaller than the scroll compressor, respectively.

[0004] However, centrifugal compressors usually have surge protection, that is, under a certain exhaust pressure, the minimum flow rate by adjusting the speed alone will be limited by the surge line. This means that under a certain ambient temperature, the minimum cooling capacity of the centrifugal compressor will be constrained, which is not conducive to improving the partial load energy efficiency of the energy storage power station. Summary of the invention

[0005] In view of some or all of the problems in the prior art and in order to increase the surge margin of a centrifugal compressor, the first aspect of the present invention provides an energy storage thermal management system, which adopts a centrifugal compressor for a refrigeration cycle, wherein a guide vane is arranged at the inlet of the centrifugal compressor, and the opening of the guide vane is adjustable.

[0006] Furthermore, the guide vane comprises:

[0007] a plurality of blades, wherein the plurality of blades are evenly distributed around the circumference of the rotating shaft of the centrifugal compressor; and

[0008] An actuator shaft is arranged along the central axis of the blade and is perpendicular to the rotating shaft of the centrifugal compressor. Under the control of a driving mechanism, the actuator shaft drives the blade to rotate to adjust the opening of the guide vane, thereby adjusting the flow entering the centrifugal compressor.

[0009] Furthermore, the centrifugal compressor includes multiple stages, and guide vanes are provided at the air inlet of each stage.

[0010] Based on the energy storage thermal management system as described above, the second aspect of the present invention provides a control method for the energy storage thermal management system, which improves the energy efficiency of the energy storage thermal management system under all working conditions by jointly adjusting the opening of the guide vane and the speed of the centrifugal compressor. The control method includes:

[0011] The surge lines of centrifugal compressors at different speeds are obtained by fitting;

[0012] Control the guide vanes to fully open and determine whether the current cooling capacity reaches the target cooling capacity:

[0013] If the current cooling capacity is greater than the target cooling capacity, the speed is reduced according to the first preset step length. If the target cooling capacity is still not reached when the speed touches the variable frequency surge line, the guide vane opening is reduced according to the second preset step length, and the speed is adjusted at the same time until the target cooling capacity is reached; and

[0014] If the current cooling capacity is less than the target cooling capacity, the opening of the guide vane is increased according to the third preset step size. If the target cooling capacity is still not reached when the guide vane is fully opened, the speed is increased according to the fourth preset step size until the target cooling capacity is reached.

[0015] Furthermore, the surge line is fitted according to the following formula:

[0016] Pr=Prmin-(Prmax-Prmin) / (e^a-1)+ (Prmax-Prmin) / (e^a-1)*e^b;

[0017] in,

[0018] Pr is the pressure ratio, Prmin is the minimum pressure ratio, Prmax is the maximum pressure ratio, and Prmin=Prmin_d*(Spd_a / Spd_d)^(SF_spd*c*Prmin / Prmax), Prmax=Prmax_d*(Spd_a / Spd_d)^(SF_spd*c), where Spd_d is the design speed, Spd_a is the actual speed, Prmin_d is the minimum pressure ratio of the design speed, Prmax_d is the maximum pressure ratio of the design speed, SF_spd is the speed line shape factor, and when Spd_a>Spd_d, c=Spd_d / Spd_a, when Spd_a<Spd_d, c=Spd_a / Spd_d;

[0019] a=SF*(IGVmax-IGVmin), where IGVmax is the maximum opening of the guide vane, IGVmin is the minimum opening of the guide vane, and SF is a shape factor used to control the shape of the surge line. The smaller its absolute value is, the more conservative the surge line is; and

[0020] b=SF*(IGV-IGVmin), where IGV is the current opening of the guide vane.

[0021] Furthermore, the second preset step size is equal to the third preset step size, and its value is 1%; and / or

[0022] The first preset step size is equal to the fourth preset step size, and its value is 0.5%.

[0023] Furthermore, judging in real time whether the current cooling capacity reaches the target cooling capacity includes:

[0024] Real-time measurement of condensing temperature and return water temperature;

[0025] Calculate the difference between the condensation temperature and the ambient temperature, and compare it with the first preset value:

[0026] If the difference is less than the first preset value, the target cooling capacity is not reached; and

[0027] If the difference is greater than or equal to the first preset value, the difference between the return water temperature and the target value is calculated and compared with the second preset value:

[0028] If the difference between the return water temperature and the target value is greater than a second preset value, the target cooling capacity is not achieved; and

[0029] If the difference between the return water temperature and the target value is less than or equal to the second preset value, then when the current temperature maintenance time is recorded, if it is greater than or equal to the preset time, the target cooling capacity is reached, otherwise the target cooling capacity is not reached.

[0030] Furthermore, the control method further includes:

[0031] Before the speed reaches the frequency conversion surge line, if the difference between the condensing temperature and the ambient temperature is less than the first preset value and the cooling capacity has not reached the target cooling capacity, the throttling device is closed while the speed is reduced until the target cooling capacity is reached.

[0032] Furthermore, the speed reaching the frequency conversion surge line includes:

[0033] The number of surges occurring within the specified time period is greater than a first preset surge number value.

[0034] Furthermore, the control method further includes:

[0035] When the guide vanes are closed, if the difference between the condensing temperature and the ambient temperature is less than a first preset value and the cooling capacity has not reached the target cooling capacity, the rotation speed is increased while the guide vanes are closed until the target cooling capacity is reached.

[0036] Furthermore, the control method further includes:

[0037] If the number of surges occurring within the specified time period is greater than a second preset number of surges, the centrifugal compressor is controlled to shut down.

[0038] Furthermore, the control method further includes:

[0039] When two stages of guide vanes are included, the opening of the second stage guide vanes is interpolated piecewise according to the opening of the first stage guide vanes.

[0040] The present invention provides an energy storage thermal management system and a control method thereof. A guide vane with adjustable opening is arranged at the inlet of a centrifugal compressor. By jointly adjusting the opening of the guide vane and the rotational speed of the centrifugal compressor, the surge margin of the centrifugal compressor can be significantly increased. Under a certain ambient temperature, the energy storage thermal management system can operate at a smaller cooling capacity, thereby significantly improving the energy efficiency of the energy storage thermal management system under all working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] To further illustrate the above and other advantages and features of various embodiments of the present invention, a more specific description of various embodiments of the present invention will be presented with reference to the accompanying drawings. It will be understood that these drawings only depict typical embodiments of the present invention and are therefore not to be considered as limiting the scope thereof. In the accompanying drawings, for clarity, identical or corresponding parts will be represented by identical or similar reference numerals.

[0042] Figure 1 A schematic diagram showing the structure of an energy storage thermal management system according to an embodiment of the present invention;

[0043] Figure 2 A schematic diagram showing the structure of a guide vane according to an embodiment of the present invention;

[0044] Figure 3 A schematic diagram of a centrifugal compressor unloading line according to an embodiment of the present invention is shown;

[0045] Figure 4 A schematic flow chart showing a control method of an energy storage thermal management system according to an embodiment of the present invention;

[0046] Figure 5 A schematic diagram showing the relationship between the shape factor SF and the surge line shape according to an embodiment of the present invention;

[0047] Figure 6 A schematic diagram showing surge lines at different speeds according to an embodiment of the present invention; and

[0048] Figure 7 A schematic diagram showing the relationship between the opening degrees of two-stage guide vanes according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0049] In the following description, the present invention is described with reference to various embodiments. However, those skilled in the art will recognize that various embodiments can be implemented without one or more specific details or with other replacement and / or additional methods, materials or components. In other cases, well-known structures, materials or operations are not shown or described in detail to avoid blurring the inventive point of the present invention. Similarly, for the purpose of explanation, specific quantities, materials and configurations are set forth to provide a comprehensive understanding of embodiments of the present invention. However, the present invention is not limited to these specific details. In addition, it should be understood that the various embodiments shown in the drawings are illustrative representations and are not necessarily drawn in correct proportions.

[0050] In this specification, reference to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. The phrase "in one embodiment" appearing in various places in this specification does not necessarily all refer to the same embodiment.

[0051] In the embodiment of the present invention, the term "surge line" refers to the line connecting the surge points of different guide vane openings. A point located on the "variable frequency surge line" means that the compressor can no longer be unloaded by reducing the speed. A point located on the "closed guide vane surge line" means that the point is the minimum cooling point that the compressor can achieve under the corresponding pressure ratio.

[0052] Since centrifugal compressors have surge protection, that is, under a certain exhaust pressure, the minimum flow rate that only relies on adjusting the speed will be limited by the surge line, which means that under a certain ambient temperature, the minimum cooling capacity of the compressor is constrained, which is not conducive to improving the partial load energy efficiency of energy storage power stations. In response to this problem, the present invention provides an energy storage thermal management system and a control method thereof, in which a guide vane with adjustable opening is provided at the inlet of the centrifugal compressor, and the surge margin of the centrifugal compressor can be significantly increased by jointly adjusting the opening of the guide vane and the speed of the centrifugal compressor.

[0053] The scheme of the present invention is further described below in conjunction with the accompanying drawings of the embodiments.

[0054] Figure 1 FIG. 1 is a schematic diagram showing the structure of an energy storage thermal management system according to an embodiment of the present invention. Figure 1 As shown, an energy storage thermal management system includes a refrigeration cycle module 001, an intermediate heat exchanger 002, and a coolant circulation module 003. The refrigeration cycle module 001 is used for the circulation of refrigerant, and heat is taken away by the phase change of the refrigerant, thereby cooling the coolant. The coolant circulation module 003 is used for the circulation of coolant to cool or heat the energy storage device. The refrigeration cycle module 001 and the coolant circulation module 003 are coupled through the intermediate heat exchanger 002.

[0055] like Figure 1 As shown, the core component of the refrigeration module 001 is a centrifugal compressor 011, preferably an air-floating centrifugal compressor. The air inlet of the centrifugal compressor 011 is connected to the intermediate heat exchanger 002, and the high-temperature low-pressure refrigerant that has completed heat exchange with the coolant in the intermediate heat exchanger enters the centrifugal compressor 011 for compression to form a refrigerant in the first state.

[0056] In order to increase the surge margin of the centrifugal compressor, in one embodiment of the present invention, guide vanes are provided at the air inlet of the centrifugal compressor 011, wherein the opening of the guide vanes is adjustable. Figure 2 FIG. 2 is a schematic diagram showing the structure of a guide vane according to an embodiment of the present invention. Figure 2 As shown, in one embodiment of the present invention, the guide vane includes a plurality of blades 201, and the plurality of blades are evenly distributed around the rotating shaft of the centrifugal compressor. By controlling the rotation of the blades around the axis, the opening of the guide vane can be controlled, thereby adjusting the flow entering the centrifugal compressor. In one embodiment of the present invention, the axis of the blade is perpendicular to the rotating shaft of the centrifugal compressor. Figure 2 As shown, in one embodiment of the present invention, an actuator shaft 202 is provided at the center axis of each blade, and the actuator shaft 202 is perpendicular to the rotating shaft of the centrifugal compressor. Under the control of a driving mechanism such as a driving motor, the actuator shaft drives the blade to rotate to adjust the opening of the guide vane, thereby adjusting the flow entering the centrifugal compressor to increase or decrease the cooling capacity. In one embodiment of the present invention, when the centrifugal compressor is multi-stage, guide vanes can be provided at each stage of the air inlet, that is, the refrigeration module can include multiple stages of guide vanes.

[0057] like Figure 1As shown, the refrigeration cycle module 001 also includes a condenser 012 and a throttling device 013. The inlet of the condenser 012 is connected to the exhaust port of the centrifugal compressor 011, which is used to cool the refrigerant in the first state to obtain the refrigerant in the second state. The temperature of the refrigerant in the second state is lower than that of the refrigerant in the first state, but the pressure is basically unchanged. In one embodiment of the present invention, in order to improve the refrigeration efficiency, a fan 014 is also provided at the fin of the condenser 012. The fan 014 introduces normal temperature air into the fin of the condenser 012, so that the heat of the high-temperature refrigerant inside the condenser 012 is heat-exchanged with the air, thereby achieving the purpose of condensation. The throttling device 013 is connected to the outlet of the condenser 012 to throttle the refrigerant in the second state. The throttled refrigerant expands rapidly to form a third state. The pressure of the refrigerant in the third state is lower than that of the refrigerant in the second state, but the temperature is basically unchanged. The refrigerant in the third state enters the intermediate heat exchanger to exchange heat with the coolant. In the embodiment of the present invention, the throttling device refers to a device or element used to reduce the gas pressure to achieve the purpose of evaporation, for example, it may be: an expansion valve, a capillary tube, a throttling tube, etc.

[0058] In order to calculate the system refrigeration demand and then control the working state of each device or module, and protect the system operation, in one embodiment of the present invention, a temperature sensor T and a pressure sensor P are also provided in the refrigeration module 001. As shown in the figure, the temperature sensor T and the pressure sensor P can be provided at the first outlet of the intermediate heat exchanger and / or the exhaust port of the centrifugal compressor, for example.

[0059] The intermediate heat exchanger includes two inlets and two outlets, thereby forming a refrigerant pipeline and a coolant pipeline. Among them, the inlet and outlet of the refrigerant pipeline are recorded as the first inlet and the first outlet, the first inlet is connected to the throttling device 013, and the first outlet is connected to the air inlet of the centrifugal compressor 011. The inlet and outlet of the coolant pipeline are recorded as the second inlet and the second outlet, which are respectively connected to the inlet and outlet of the pipeline in the coolant circulation module. The coolant pipeline is arranged around the refrigerant pipeline so that the coolant and the refrigerant can exchange heat. In one embodiment of the present invention, an evaporator is used as the intermediate heat exchanger.

[0060] As shown in the figure, in one embodiment of the present invention, the cooling module 003 includes a water pump 031 and a PTC heater 032. The water pump 031 is used to provide power for the coolant circulation. The water pump 031 is connected to the second inlet of the intermediate heat exchanger through a water pipe to send the coolant into the intermediate heat exchanger. After transferring the heat to the refrigerant, the coolant reaches the energy storage device through the pipeline, and the heat generated by the energy storage device, such as the battery cell of the energy storage battery, is transferred to the coolant. The heated coolant returns to the water pump again to circulate. The PTC heater 032 is used to provide heat for the energy storage device, such as the battery cell. In one embodiment of the present invention, in order to improve the heat exchange efficiency, in the intermediate heat exchanger, the coolant inflow direction and the refrigerant inflow direction are exactly opposite. For example, the first inlet and the second outlet of the intermediate heat exchanger can be set on the first side of the intermediate heat exchanger, and the second inlet and the first outlet can be set on the second side of the intermediate heat exchanger relative to the first side.

[0061] The energy storage thermal management system in the embodiment of the present invention adopts an air-cooled condenser. When the cooling demand of the energy storage power station decreases and the cooling capacity needs to be reduced accordingly, since the ambient temperature remains unchanged, the unloading line of the centrifugal compressor is as follows: Figure 3 As shown in , the pressure ratio remains unchanged, only the flow rate decreases. Figure 3 As shown, at rated cooling capacity, the centrifugal compressor operates at point P1, and its flow pressure ratio to speed ratio is (m1, pr, N1). When the cooling capacity decreases, the centrifugal compressor unloads along the unloading line and first reaches point P2 (m2, pr, N2). During the process from P1 to P2, the guide vane remains fully open, but the speed is reduced from N1 to N2. Point P2 is already located on the variable frequency surge line and cannot be further unloaded by reducing the speed. In one embodiment of the present invention, m2 is equal to about 70% of m1, that is, the cooling capacity can be reduced to about 70% of the rated value only by variable frequency. In order to further reduce the cooling capacity, the guide vane opening needs to be closed from point P2, and finally reaches point P3 (m3, pr, N2). During this process, the speed remains unchanged at N2, and only the guide vane opening is closed. In one embodiment of the present invention, m3 is equal to about 40% of m1, that is, the rated cooling capacity can be reduced to about 40% by adjusting the guide vane opening only. Point P3 is located on the surge line of the guide vane closing, that is, point P3 is the minimum cooling capacity point that the centrifugal compressor can achieve under the pressure ratio pr.

[0062] Based on this, Figure 4 A schematic flow chart showing a control method of an energy storage thermal management system according to an embodiment of the present invention is shown. Figure 4 As shown, the control method includes:

[0063] First, in step 401, a surge line is fitted. The surge lines of the centrifugal compressor at different speeds are fitted. Before the real-time cooling capacity control strategy is implemented, the map of the centrifugal compressor needs to be calibrated experimentally. Each speed line will have surge points with different guide vane openings. To improve efficiency, only limited data points are usually measured. Based on the priority data points, in one embodiment of the present invention, the surge line is fitted using the following functional relationship:

[0064] Pr=Prmin-(Prmax-Prmin) / (e^a-1)+ (Prmax-Prmin) / (e^a-1)*e^b;

[0065] in,

[0066] Pr is the pressure ratio, Prmin is the minimum pressure ratio, Prmax is the maximum pressure ratio, and Prmin=Prmin_d*(Spd_a / Spd_d)^(SF_spd*c*Prmin / Prmax), Prmax=Prmax_d*(Spd_a / Spd_d)^(SF_spd*c), wherein Spd_d is the design speed, Spd_a is the actual speed, Prmin_d is the minimum pressure ratio of the design speed, Prmax_d is the maximum pressure ratio of the design speed, SF_spd is the speed line shape factor, in one embodiment of the present invention, its value is 2, and when Spd_a>Spd_d, c=Spd_d / Spd_a, when Spd_a<Spd_d, c=Spd_a / Spd_d, Figure 6 A schematic diagram of surge lines at different speeds, 100%, 90%, and 110%, of an embodiment of the present invention is shown;

[0067] a=SF*(IGVmax-IGVmin), where IGVmax is the maximum opening of the guide vane, IGVmin is the minimum opening of the guide vane, and SF is a shape factor used to control the shape of the surge line. The smaller its absolute value, the more conservative the surge line. Figure 5 A schematic diagram showing the relationship between the shape factor SF and the surge line shape according to an embodiment of the present invention is shown as follows: Figure 5 As shown, when SF=-0.01, the surge line is conservative, when SF=-0.02, the surge line is moderate, and when SF=-0.04, the surge line is aggressive; and

[0068] b=SF*(IGV-IGVmin), where IGV is the current opening of the guide vane;

[0069] Next, in step 402, the system is initialized. After the surge line is fitted, the cooling capacity can be adjusted. In the initial state, that is, when the system is just started, the guide vanes are controlled to be fully open;

[0070] Next, in step 403, the current cooling capacity is monitored in real time and it is determined whether the target cooling capacity is reached. After the energy storage thermal management system starts working, it is monitored in real time and it is determined whether the current cooling capacity reaches the target cooling capacity. In one embodiment of the present invention, the current cooling capacity is determined by real-time monitoring of the condensing temperature and the cooling water return temperature. Specifically, it includes:

[0071] Real-time measurement of condensing temperature and return water temperature;

[0072] Calculate the difference between the condensation temperature and the ambient temperature, and compare it with the first preset value:

[0073] If the difference is less than the first preset value, the target cooling capacity is not reached; and

[0074] If the difference is greater than or equal to the first preset value, the difference between the return water temperature and the target value is calculated and compared with the second preset value:

[0075] If the difference between the return water temperature and the target value is greater than a second preset value, the target cooling capacity is not achieved; and

[0076] If the difference between the return water temperature and the target value is less than or equal to the second preset value, then when the current temperature maintenance time is recorded, if it is greater than or equal to the preset time, the target cooling capacity is reached, otherwise the target cooling capacity is not reached.

[0077] In one embodiment of the present invention, the first preset value is 7°C, the second preset value is 1.5°C, and the preset duration is 15 minutes. When the condensing temperature minus the ambient temperature is ≥ 7°C, if the deviation between the measured return water temperature and the target value is stable within 1.5°C and the temperature is maintained for 15 minutes, it is considered that the target cooling capacity is achieved. According to the monitoring results, if the cooling capacity needs to be reduced, step 441 is entered; if the cooling capacity needs to be increased, step 451 is entered;

[0078] In step 441, the speed is reduced. When the cooling capacity needs to be reduced, the speed is reduced according to the first preset step size, and at the same time, the current cooling capacity is monitored in real time according to the method described above to see whether it reaches the target cooling capacity. In one embodiment of the present invention, the first preset step size is a step size of 0.5% of the design speed. In one embodiment of the present invention, if the difference between the condensing temperature and the ambient temperature is lower than the first preset value, the target cooling capacity is still not reached, the throttling device can be closed to make the difference between the condensing temperature and the ambient temperature rise to above the first preset value, and then the speed is reduced and the throttling device is closed until the target cooling capacity is reached. In the process of reducing the speed, as the speed gradually decreases, the variable frequency surge line will be touched, and step 442 will be entered at this time. In one embodiment of the present invention, when the number of surges occurring within a specified time period is greater than the first preset surge number value, it is considered that the surge line is touched, wherein whether surge occurs is determined based on the current percentage fluctuation. In one embodiment of the present invention, a current percentage fluctuation of ≥10% is considered to be a surge. For example, if the current percentage is 50% in the first second without any operation, and the current percentage is 65% in the second second, and the current percentage fluctuation is 15%, it is considered that a surge has occurred. In another embodiment of the present invention, if two surges occur within 4 minutes, it is considered to have touched the surge line.

[0079] In step 442, the guide vane opening and the speed are adjusted jointly. When the surge line is touched, if the cooling capacity still needs to be further reduced, the guide vane opening needs to be reduced according to the second preset step size. In one embodiment of the present invention, the second preset step size is 1% opening. When the guide vane is closed, the pressure ratio will decrease. When the difference between the condensing temperature and the ambient temperature is lower than the first preset value, the target cooling capacity has not been reached. It is necessary to further increase the speed to return the condensing temperature to the ambient temperature + 7°C or above. Then the guide vane and the speed are adjusted jointly to maintain the difference between the condensing temperature and the ambient temperature above the first preset value until the target cooling capacity is reached. When the cooling capacity continues to decrease, the guide vane closing surge line will be touched, and the minimum cooling capacity has been reached. In order to protect the centrifugal compressor, in one embodiment of the present invention, in the process of reducing the cooling capacity, if the number of surges within a specified time period is greater than the second preset surge number value, the compressor shutdown protection will be triggered. For example, if 4 surges occur within 8 minutes, the centrifugal compressor is controlled to shut down;

[0080] In step 451, the guide vane opening is increased. When the cooling capacity needs to be increased, the guide vane opening is increased according to the third preset step length, and at the same time, the current cooling capacity is monitored in real time according to the method described above to see whether it reaches the target cooling capacity. In one embodiment of the present invention, the third preset step length is 1% opening. If the target cooling capacity is still not reached when the guide vane is fully opened, proceed to step 452;

[0081] In step 452, the rotation speed is increased. If the target cooling capacity is still not reached when the guide vanes are fully opened, the rotation speed is increased according to a fourth preset step length until the target cooling capacity is reached. In one embodiment of the present invention, the fourth preset step length is a step length of 0.5% of the design rotation speed.

[0082] As mentioned above, in other embodiments of the present invention, if the centrifugal compressor is multi-stage, guide vanes may be provided at the air inlet of each stage. Taking a two-stage centrifugal compressor as an example, when guide vanes are provided at the air inlet of both stages, it is necessary to calibrate the surge lines of the two-stage guide vanes respectively, and perform parameter fitting according to the method described above, and two-stage linkage is required when adjusting the guide vane opening, and the opening of the second-stage guide vane is a function of the opening of the first stage, as shown in FIG. Figure 7 The opening relationship shown is piecewise interpolated.

[0083] The present invention provides an energy storage thermal management system and a control method thereof. A guide vane with adjustable opening is arranged at the inlet of a centrifugal compressor. By jointly adjusting the opening of the guide vane and the rotational speed of the centrifugal compressor, the surge margin of the centrifugal compressor can be significantly increased. Under a certain ambient temperature, the energy storage thermal management system can operate at a smaller cooling capacity, thereby significantly improving the energy efficiency of the energy storage thermal management system under all working conditions.

[0084] Although various embodiments of the present invention are described above, it should be understood that they are presented as examples only and not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made thereto without departing from the spirit and scope of the present invention. Therefore, the breadth and scope of the present invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should only be defined according to the attached claims and their equivalents.

Claims

1. A control method for an energy storage thermal management system, characterized in that: The energy storage thermal management system includes a centrifugal compressor and a guide vane, wherein the centrifugal compressor is configured to perform a refrigeration cycle, the guide vane is arranged at the inlet of the centrifugal compressor, wherein the opening of the guide vane is adjustable, and the guide vane includes a plurality of blades and an actuator shaft, wherein the plurality of blades are evenly distributed around the rotating shaft of the centrifugal compressor, the actuator shaft is arranged along the central axis of the blade and is perpendicular to the rotating shaft of the centrifugal compressor, the actuator shaft is configured to drive the blade to rotate under the control of a driving mechanism to adjust the opening of the guide vane, thereby adjusting the flow entering the centrifugal compressor, and the control method includes the steps of: The surge line of the centrifugal compressor at different speeds is obtained by fitting, wherein the surge line is obtained by fitting according to the following formula: Pr=Prmin-(Prmax-Prmin) / (e^a-1)+(Prmax-Prmin) / (e^a-1)*e^b, where Pr is the pressure ratio, Prmin is the minimum pressure ratio, Prmax is the maximum pressure ratio, and Prmin=Prmin_d*(Spd_a / Spd_d)^(SF_spd*c*Prmin / Prmax), Prmax=Prmax_d*(Spd_a / Spd_d)^(SF_spd*c), where Spd_d is the design speed, Spd_a is the actual speed, and Prmin_d is the design speed minimum pressure ratio, Prmax_d is the maximum pressure ratio of the design speed, SF_spd is the speed line shape factor, and when Spd_a>Spd_d, c=Spd_d / Spd_a, when Spd_a<Spd_d, c=Spd_a / Spd_d, a=SF*(IGVmax-IGVmin), where IGVmax is the maximum opening of the guide vane, IGVmin is the minimum opening of the guide vane, SF is the shape factor, SF is used to control the surge line shape, the smaller its absolute value, the more conservative the surge line, b=SF*(IGV-IGVmin), where IGV is the current opening of the guide vane; Control the guide vanes to be fully open and determine in real time whether the current cooling capacity reaches the target cooling capacity: If the current cooling capacity is greater than the target cooling capacity, the speed is reduced according to the first preset step length. If the target cooling capacity is still not reached when the speed touches the frequency conversion surge line, the guide vane opening is reduced according to the second preset step length, and the speed is adjusted at the same time until the target cooling capacity is reached; as well as If the current cooling capacity is less than the target cooling capacity, increase the opening of the guide vane according to the third preset step length; if the target cooling capacity is still not reached when the guide vane is fully opened, increase the speed according to the fourth preset step length until the target cooling capacity is reached; and Before the speed reaches the frequency conversion surge line, if the difference between the condensing temperature and the ambient temperature is less than the first preset value and the cooling capacity does not reach the target cooling capacity, the throttling device is closed while the speed is reduced until the target cooling capacity is reached; The real-time judgment of whether the current cooling capacity reaches the target cooling capacity includes: Real-time measurement of condensing temperature and return water temperature; Calculate the difference between the condensing temperature and the ambient temperature, and compare it with the first preset value: If the difference is less than the first preset value, the target cooling capacity is not reached; and If the difference is greater than or equal to the first preset value, the difference between the return water temperature and the target value is calculated and compared with the second preset value: If the difference between the return water temperature and the target value is greater than a second preset value, the target cooling capacity is not achieved; and If the difference between the return water temperature and the target value is less than or equal to the second preset value, then when the current temperature maintenance time is recorded, if it is greater than or equal to the preset time, the target cooling capacity is reached, otherwise the target cooling capacity is not reached.

2. The control method according to claim 1, characterized in that: The second preset step size is equal to the third preset step size and is set to 1%; and / or The first preset step size is equal to the fourth preset step size, and its value is 0.5%.

3. The control method according to claim 1, characterized in that: The speed reaching the frequency conversion surge line includes: The number of surges occurring within the specified time period is greater than a first preset surge number value.

4. The control method according to claim 1, characterized in that: Also includes the steps: When the guide vanes are closed, if the difference between the condensing temperature and the ambient temperature is less than a first preset value and the cooling capacity has not reached the target cooling capacity, the rotation speed is increased while the guide vanes are closed until the target cooling capacity is reached.

5. The control method according to claim 1, characterized in that: Also includes the steps: If the number of surges occurring within the specified time period is greater than a second preset surge number value, the centrifugal compressor is controlled to shut down.

6. The control method according to claim 1, characterized in that: The centrifugal compressor includes multiple stages, and guide vanes are provided at the air inlet of each stage. When two stages of guide vanes are included, the opening of the second stage guide vanes is interpolated in sections according to the opening of the first stage guide vanes.

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