Refrigerant phase change cooling type power battery thermal management test method and system

Abstract

The embodiment of the invention discloses a refrigerant phase change cooling type power battery thermal management test method and system, and the method comprises the steps: obtaining an actual refrigerating capacity in a test process, and determining a superheat degree set value of a test system through employing the actual refrigerating capacity and an expression corresponding to a pre-obtained minimum stable superheat degree; and the control stability of the test system is determined by using the current superheat degree and the superheat degree set value, and then the opening degree of the electronic expansion valve is adjusted based on the control stability, so that the adjustment of the superheat degree in the test system is realized. The problem that in the prior art, refrigerant phase change cooling type power battery thermal management test equipment does not consider the minimum stable superheat degree or only depends on an empirical formula to determine the minimum stable superheat degree is solved. And system parameter oscillation or compressor liquid impact caused by deviation between the superheat degree set value and the optimal superheat degree set value required by the power battery to be tested in the test process are solved.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the technical field of testing, in particular to a refrigerant phase change cooling type power battery thermal management test method and system. BACKGROUND

[0002] The refrigerant phase change cooling type power battery thermal management test equipment, also known as refrigerant phase change heat transfer test bench, is a core equipment for testing the performance and environmental reliability of the power battery using the refrigerant phase change heat transfer technology. The main function of the refrigerant phase change cooling type power battery thermal management test equipment is to accurately simulate various working conditions such as the environmental temperature and the charging and discharging current that the battery may encounter in actual use, to control the refrigerant parameters according to the preset boundary conditions and thermal management scheme, and to quantitatively evaluate the safety, durability and performance stability of the battery.

[0003] In the current refrigerant phase change cooling type power battery thermal management test, the refrigerant superheat degree at the outlet of the refrigerant phase change plate is one of the core control indicators. Reducing the refrigerant superheat degree at the outlet of the refrigerant phase change plate can lengthen the two-phase heat exchange zone of the refrigerant phase change plate, increase the evaporation pressure and evaporation temperature, greatly improve the energy efficiency ratio of the thermal management system, and improve the refrigeration efficiency. Therefore, in the refrigerant phase change cooling type power battery thermal management test, it is usually necessary to set the target value of the superheat degree in a lower range (0-7℃). However, when the refrigerant superheat degree at the outlet of the refrigerant phase change plate is lower than a certain value (usually 7℃), serious system oscillation or compressor liquid knock problems will occur.

[0004] In addition, the traditional refrigerant phase change cooling type power battery thermal management test equipment does not have a minimum stable superheat degree prompting function, which causes users to often set a too low superheat degree set value when testing the battery performance using the equipment, resulting in system parameter oscillation or compressor liquid knock problems. SUMMARY

[0005] The embodiment of the present application provides a refrigerant phase change cooling type power battery thermal management test method and system, which solves the technical problem of system parameter oscillation or compressor liquid knock caused by too low superheat degree set value in the test process due to the fact that the refrigerant phase change cooling type power battery thermal management test equipment in the prior art does not consider the minimum stable superheat degree.

[0006] The embodiment of the present application provides a refrigerant phase change cooling type power battery thermal management test method. The refrigerant phase change cooling type power battery thermal management test system includes a low-pressure side unit, a high-pressure side unit and a control unit. The control unit is electrically connected with the low-pressure side unit and the high-pressure side unit. The low-pressure side unit includes a test branch connected with a refrigerant phase change plate evaporator and a power battery to be tested, and an identification branch provided with a simulated load heater, an electric heating device and an adjustable power supply. The test branch is connected in parallel with the identification branch. The high-pressure side unit includes an electronic expansion valve. The test method is applied to the control unit.

[0007] The test method comprises:

[0008] The test branch is connected, the identification branch is disconnected, the refrigerant flow of the test system is controlled based on a preset sampling interval, and the thermal management test of the to-be-tested power battery is started.

[0009] During the test, the pre-valve parameter of the electronic expansion valve and the inlet and outlet parameters of the refrigerant phase change plate evaporator are obtained.

[0010] The actual refrigeration capacity of the test branch is calculated using the pre-valve parameter and the inlet and outlet parameters.

[0011] The actual refrigeration capacity and the expression corresponding to the minimum stable superheat degree are used to determine the superheat degree set value of the test system, wherein the expression corresponding to the minimum stable superheat degree is obtained by simulating the thermal management test through the identification branch.

[0012] The control stability of the test system is determined using the current superheat degree and the superheat degree set value.

[0013] The opening of the electronic expansion valve is adjusted based on the control stability to adjust the superheat degree of the test system.

[0014] Further, the determination method of the expression corresponding to the minimum stable superheat degree comprises:

[0015] The identification branch is connected and the test branch is turned off, the refrigerant flow of the test system is controlled using the electronic expansion valve based on a preset sampling interval, and the simulation thermal management test is performed using the identification branch.

[0016] During the simulation, the first set superheat degree is reduced to the second set superheat degree at a set step, and the superheat degree response at the outlet of the simulation load heater is monitored in real time. When the oscillation amplitude exceeds the set error value, the current superheat degree is increased by 0.1℃, which is the minimum stable superheat degree under the current refrigeration capacity, and the actual refrigeration capacity under the corresponding superheat degree is calculated.

[0017] The above process of simulating the thermal management test using the identification branch is repeated within the rated refrigeration capacity range of the test system until a set number of parameter groups of actual refrigeration capacity and corresponding minimum stable superheat degree are obtained.

[0018] The expression corresponding to the minimum stable superheat degree is fitted based on the obtained set number of parameter groups.

[0019] Further, the expression corresponding to the minimum stable superheat degree is fitted based on the obtained set number of parameter groups.

[0020] Based on the obtained set of parameters, a quadratic polynomial is fitted to the actual cooling capacity: Q e1 =a*MSS1 2 +b*MSS1+c, where Q e1 To identify the actual cooling capacity when the branch is working, MSS1 is the minimum stable superheat when the branch is working, and a, b, and c are all quadratic polynomial coefficients.

[0021] Converting the quadratic polynomial of the actual cooling capacity into its inverse function yields the expression for the minimum stable superheat:

[0022]

[0023] Furthermore, determining the control stability of the test system using the current superheat and the superheat setpoint includes:

[0024] Compare the current superheat with the superheat set value;

[0025] If the current superheat is greater than or equal to the superheat set value, the control stability flag displays 0, indicating good control stability.

[0026] If the current superheat is less than the superheat set value, the control stability flag displays 1, and the test system provides a prompt that the superheat is lower than the minimum temperature superheat.

[0027] This invention also provides a refrigerant phase change cooling power battery thermal management test system, including a control unit using the refrigerant phase change cooling power battery thermal management test method described in any of the above embodiments, and further including a low-pressure side unit and a high-pressure side unit;

[0028] The control unit is electrically connected to the low-pressure side unit and the high-pressure side unit respectively, and the low-pressure side unit and the high-pressure side unit are connected by a refrigerant pipe;

[0029] The low-pressure side unit includes a test branch connected to a refrigerant phase change plate evaporator and the power battery under test, and an identification branch equipped with a simulated load heater, an electric heating device and an adjustable power supply. The test branch is connected in parallel with the identification branch.

[0030] The high-pressure side unit includes an electronic expansion valve;

[0031] The control unit is configured to control the connection of the test branch and the disconnection of the identification branch, and to perform thermal management testing on the power battery under test by controlling the refrigerant flow using the electronic expansion valve based on a preset sampling interval.

[0032] The control unit is further configured to calculate an actual refrigerating capacity of the test branch by using the obtained pre-valve parameter of the electronic expansion valve and the inlet and outlet parameters of the refrigerant phase-change plate evaporator during the test, determine a superheat setting value of the test system based on the actual refrigerating capacity and an expression corresponding to the minimum stable superheat, determine a control stability of the test system by using a current superheat and the superheat setting value, and adjust the opening degree of the electronic expansion valve based on the control stability to achieve adjustment of the superheat of the test system, wherein the expression corresponding to the minimum stable superheat is obtained by simulating the thermal management test through the identification branch.

[0033] Further, the control unit is further configured to control the identification branch to be connected and control the test branch to be turned off, control the refrigerant flow by using the electronic expansion valve based on a preset sampling interval, and perform the simulated thermal management test through the identification branch to obtain the expression corresponding to the minimum stable superheat.

[0034] Further, the high-pressure side unit comprises a mass flow meter, a condensing system, a compressor and a gas-liquid separator connected in sequence with the electronic expansion valve.

[0035] Further, the high-pressure side unit comprises a mass flow meter, a condensing system, a compressor and a gas-liquid separator connected in sequence with the electronic expansion valve.

[0036] Further, the test branch further comprises a first electromagnetic valve and a second electromagnetic valve; the first electromagnetic valve, the refrigerant phase-change plate evaporator and the second electromagnetic valve are connected in sequence, and the to-be-tested power battery is arranged at the refrigerant phase-change plate evaporator.

[0037] The identification branch further comprises a third electromagnetic valve and a fourth electromagnetic valve; the third electromagnetic valve, the simulated load evaporator and the fourth electromagnetic valve are connected in sequence; and the electric heating device is arranged at the simulated load evaporator in series with the adjustable power supply.

[0038] Further, the low-pressure side unit further comprises a fourth pressure sensor and a second temperature sensor arranged at the inlet of the refrigerant pipeline, and a fifth pressure sensor and a third temperature sensor arranged at the outlet of the refrigerant pipeline.

[0039] Further, the low-pressure side unit further comprises a fourth pressure sensor and a second temperature sensor arranged at the inlet of the refrigerant pipeline, and a fifth pressure sensor and a third temperature sensor arranged at the outlet of the refrigerant pipeline.

[0040] The data storage unit and the display unit are electrically connected with the control unit.

[0041] The embodiment of the application discloses a kind of refrigerant phase change cooling type power battery thermal management test method and system, test method includes: control test branch communication, identification branch disconnect, based on preset sampling interval, the refrigerant flow of test system is controlled using electronic expansion valve, start to carry out thermal management test to the power battery to be tested;During testing, the pre-valve parameter of electronic expansion valve and the inlet and outlet parameter of refrigerant phase change plate evaporator are acquired;Actual refrigerating capacity of test branch is calculated using pre-valve parameter and inlet and outlet parameter;The overheat degree set value of test system is determined based on actual refrigerating capacity and the expression corresponding to minimum stable superheat degree;The control stability of test system is determined using current overheat degree and overheat degree set value;The opening of electronic expansion valve is adjusted based on control stability, to realize the adjustment of overheat degree in test system.This application obtains actual refrigerating capacity during testing, and the overheat degree set value of test system is determined using actual refrigerating capacity and the expression corresponding to minimum stable superheat degree obtained in advance, and the control stability of test system is determined using current overheat degree and overheat degree set value, solve the technical problems that refrigerant phase change cooling type power battery thermal management test equipment in prior art does not consider minimum stable superheat degree or only relies on experience formula to determine minimum stable superheat degree, there is deviation between overheat degree set value and optimal set value of required overheat degree of power battery to be tested during testing, causing system parameter oscillation or compressor liquid knock, realize real-time adjustment of system overheat degree according to minimum stable superheat degree principle during testing, and then improve the technical effect of system control stability. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 For the minimum stable superheat curve of refrigeration system;

[0043] Figure 2 It is a structure diagram of the refrigerant phase change cooling type power battery thermal management test system provided by the embodiment of the application;

[0044] Figure 3 It is a flow chart of the refrigerant phase change cooling type power battery thermal management test method provided by the embodiment of the application;

[0045] Figure 4 It is the flow chart of the determination method of the expression corresponding to minimum stable superheat degree provided by the embodiment of the application;

[0046] Figure 5 It is the MSS identification flowchart under fixed load state provided by the embodiment of the application;

[0047] Figure 6 It is the minimum stable superheat curve diagram based on quadratic polynomial fitting provided by the embodiment of the application. DETAILED DESCRIPTION

[0048] The application will be described in further detail below with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are intended to be illustrative only and not limiting of the application. In addition, it is to be understood that the drawings are not necessarily to scale and that, unless otherwise indicated, the drawings are intended to be illustrative only and not limiting of the application.

[0049] It should be noted that the terms "first", "second", and the like in the description and claims of the application and the drawings are used to distinguish different objects, and are not intended to limit a specific order. The various embodiments of the application can be executed independently, and can also be executed in combination with each other, and the embodiments of the application do not specifically limit this.

[0050] According to the minimal stable superheat (MSS) theory, the superheat range of the refrigeration system is divided into a stable section and an unstable section, as shown in Figure 1 As the heat load of the refrigerant phase change plate gradually increases, the unstable section gradually deviates to the side with a larger superheat, and when the heat load increases to a certain maximum value, the unstable section no longer lengthens and is stabilized at the maximum superheat corresponding to the heat load. Conversely, there is also a minimum load value. The existence of the maximum heat load and the minimum heat load is of great help to the stability control of the refrigeration system. If the system load is small, a certain superheat also needs to be maintained at the outlet of the refrigerant phase change plate. Based on the above theory, the embodiments of the application provide a refrigerant phase change cooling type power battery thermal management test method and system.

[0051] Figure 2 is a structural diagram of a refrigerant phase change cooling type power battery thermal management test system provided by the embodiments of the application. As shown in Figure 2 The refrigerant phase change cooling type power battery thermal management test system includes a low-pressure side unit 10, a high-pressure side unit 20, and a control unit 30, the control unit 30 is electrically connected with the low-pressure side unit 10 and the high-pressure side unit 20 respectively; the low-pressure side unit 10 includes a test branch A1 connected with a refrigerant phase change plate evaporator 11 and a power battery to be tested 12, and further includes an identification branch A2 provided with a simulated load heater 13, an electric heating device 14, and an adjustable power supply 15, the test branch A1 and the identification branch A2 are connected in parallel, and the high-pressure side unit 20 includes an electronic expansion valve EEV.

[0052] As shown in Figure 2As shown, the identification branch A2 uses the analog load heater 13 to simulate the case that the test branch A1 carries the load (i.e. the power battery 12 to be tested), and through the identification branch A2 simulation heat management test, the expression of the minimum stable overheat degree corresponding to the current refrigerant in the test system is obtained, and then the test branch A1 is used to perform heat management test on the power battery 12 to be tested, and the minimum stable overheat degree is monitored based on the expression of the minimum stable overheat degree determined in advance during the test, and the overheat degree setting value is constrained to avoid liquid impact and parameter oscillation problem under low overheat degree.

[0053] Figure 3 is a flow chart of a refrigerant phase change cooling type power battery heat management test method provided by an embodiment of the present application. The refrigerant phase change cooling type power battery heat management test method is applied to the control unit 30. As shown, Figure 3 the test method specifically includes the following steps:

[0054] S101, control the test branch A1 to be connected, and the identification branch A2 to be disconnected, based on a preset sampling interval, use the electronic expansion valve EEV to control the refrigerant flow of the test system, and start the heat management test on the power battery 12 to be tested.

[0055] Specifically, when performing the heat management test on the power battery 12 to be tested, first, the branch connected in the low-pressure side unit 10 needs to be switched to the test branch A1, and then the actual refrigeration capacity Q e1 of the test branch A1 is calculated. The preset sampling interval can be set as needed, for example, set to 1s, based on the preset sampling interval, use the electronic expansion valve-overheat single closed loop control system, use the electronic expansion valve EEV to control the refrigerant flow of the test system, and realize the heat management test on the power battery 12 to be tested.

[0056] S102, during the test process, acquire the pre-valve parameters of the electronic expansion valve EEV and the inlet and outlet parameters of the refrigerant phase change plate evaporator 11.

[0057] Specifically, the pre-valve parameters of the electronic expansion valve EEV include the pressure value collected by the first pressure sensor P1 at the inlet of the electronic expansion valve EEV and the temperature value collected by the first temperature sensor T1. The inlet and outlet parameters of the refrigerant phase change plate evaporator 11 include the pressure value collected by the fifth pressure sensor P5 at the outlet of the refrigerant phase change plate evaporator 11 when it is connected in the system, and the temperature value collected by the third temperature sensor T3 at the outlet of the refrigerant phase change plate evaporator 11, and the pressure value collected by the fourth pressure sensor P4 at the inlet of the refrigerant phase change plate evaporator 11 and the temperature value collected by the second temperature sensor T2 at the inlet of the refrigerant phase change plate evaporator 11.

[0058] S103, calculate the actual refrigeration capacity of the test branch A1 using the pre-valve parameters and the inlet and outlet parameters.

[0059] Specifically, after obtaining the pre-valve parameters and the inlet and outlet parameters, the enthalpy difference of the refrigerant at the inlet and outlet of the phase-change plate evaporator 11 is calculated based on the enthalpy at the refrigerant inlet and the enthalpy at the refrigerant outlet according to the energy conservation principle, and then the actual refrigeration capacity Q of the test branch A1 is determined according to the calculated enthalpy difference of the refrigerant. e2 .

[0060] S104, determining the superheat setting value of the test system based on the actual refrigeration capacity and the expression corresponding to the minimum stable superheat, wherein the expression corresponding to the minimum stable superheat is obtained in advance by identifying the simulation thermal management test of the branch A2.

[0061] Specifically, the expression corresponding to the minimum stable superheat is:

[0062]

[0063] wherein Q e2 is the actual refrigeration capacity when the test branch is working, MSS2 is the minimum stable superheat when the test branch is working, a, b, and c are all quadratic polynomial coefficients, and SHsv is the superheat setting value. The actual refrigeration capacity Q e2 of the test branch A1 is calculated, and the minimum stable superheat MSS2 of the test system is determined by using the above formula, and the minimum stable superheat MSS2 is determined as the superheat setting value SHsv.

[0064] S105, determining the control stability of the test system by using the current superheat and the superheat setting value.

[0065] Specifically, after the superheat setting value SHsv is determined, the control stability of the test system is determined by using the formula , wherein SHsv is the superheat setting value, MSS0 is the current superheat of the test system, and M represents the control stability. When M=0, it means that the test system is stable, and when M=1, it means that the superheat setting value of the test system is lower than the minimum stable superheat under the current load, and the test system is unstable.

[0066] S106, adjusting the opening of the electronic expansion valve based on the control stability to realize the adjustment of the superheat in the test system.

[0067] Specifically, after the control stability of the test system is determined, if the test system is in an unstable state, the opening of the electronic expansion valve EEV is adjusted to realize the adjustment of the superheat of the test system, so as to avoid the problem of system parameter oscillation or compressor liquid knock caused by too low superheat setting value.

[0068] The present application obtains the actual refrigerating capacity in the test process, and determines the superheat setting value of the test system by using the expression corresponding to the minimum stable superheat obtained in advance and the actual refrigerating capacity, and determines the control stability of the test system by using the current superheat and the superheat setting value, which solves the technical problems of the existing refrigerant phase change cooling type power battery thermal management test equipment, that is, the deviation between the superheat setting value in the test process and the optimal setting value of the required superheat of the power battery to be tested, which causes system parameter oscillation or compressor liquid knock, by not considering the minimum stable superheat or only relying on the empirical formula to determine the minimum stable superheat, realizes the technical effect of adjusting the system superheat according to the minimum stable superheat principle in the test process, and further improves the system control stability.

[0069] Figure 4 The flowchart of the determination method of the expression corresponding to the minimum stable superheat provided by the embodiment of the present application.

[0070] Optionally, as shown in Figure 4 The determination method of the expression corresponding to the minimum stable superheat specifically includes the following steps:

[0071] S401, control the connection of the identification branch A2 and the shutdown of the test branch A1, control the refrigerant flow of the test system by using the electronic expansion valve EEV based on the preset sampling interval, and perform the simulation thermal management test by using the identification branch A2.

[0072] Specifically, the control unit 30 shuts down the test branch A1 of the refrigerant phase change plate evaporator 11 of the low-pressure side unit 10 and the actual load (i.e. the above-mentioned power battery 12 to be tested), i.e. the actual load is 0, enables the identification branch A2 where the simulation load evaporator 13 is located, adjusts the electric heating device 14 by the adjustable power supply 15 to simulate the load, and fixes it at a certain power value, and performs the simulation thermal management test.

[0073] S402, in the simulation process, reduce the first set superheat to the second set superheat at a set step length, and monitor the superheat response at the outlet of the simulation load heater in real time, when the oscillation amplitude exceeds the set error value, increase the current superheat by 0.1℃, which is the minimum stable superheat under the current refrigerating capacity, and calculate the actual refrigerating capacity under the corresponding superheat.

[0074] Specifically, the electronic expansion valve-superheat single closed loop control system is adopted, the preset sampling interval is set to 1s, the superheat setting value is gradually reduced from the high superheat (i.e. the first set superheat), and the superheat response at the outlet of the simulation load heater 13 is monitored in real time, wherein the first set superheat can be set to 9℃, and the second set superheat can be set to the minimum superheat value allowed by the test system.

[0075] Specifically, the actual measurement value of the superheat degree of the test system in the refrigeration process is not necessarily constant at the set value, and there will be an oscillation around the set value, as shown in Figure 5 The MSS identification process diagram in the fixed load state is shown in FIG. 1. Assuming that the set error value of the oscillation amplitude is ±1.0℃, when the oscillation amplitude is less than the set error value, it indicates that the minimum superheat degree has not been reached, and it is still in the superheat degree stable region as shown in Figure 1 When the oscillation amplitude exceeds the set error value, it indicates that the superheat degree has entered the unstable region, that is, the critical point between the stable and unstable superheat degrees is reached. At this time, 0.1℃ is added to the current superheat degree set value, that is, the minimum stable superheat degree under the current refrigeration capacity, and the actual refrigeration capacity Q e1 under the corresponding superheat degree of the working branch A2 is calculated by using the following method.

[0076] The calculation method of the actual refrigeration capacity Q e1 of the working branch A2 includes: detecting the refrigerant mass flow rate (i.e., the flow parameter of the mass flow meter 21), the pre-valve parameter of the electronic expansion valve EEV, and the inlet and outlet parameters of the simulated load evaporator 13 in real time, wherein the inlet and outlet parameters of the simulated load evaporator 13 include the pressure value of the refrigerant outlet collected by the fifth pressure sensor P5 and the temperature value of the refrigerant outlet collected by the third temperature sensor T3 when the simulated load evaporator 13 is connected in the system, and the pressure value of the refrigerant inlet collected by the fourth pressure sensor P4 and the temperature value of the refrigerant inlet collected by the second temperature sensor T2.

[0077] After obtaining the flow parameter of the mass flow meter 21, the pre-valve parameter of the electronic expansion valve EEV, and the inlet and outlet parameters of the simulated load evaporator 13, the refrigerant enthalpy difference at the inlet and outlet of the simulated load evaporator 13 is calculated based on the energy conservation principle according to the enthalpy value at the refrigerant inlet and the enthalpy value at the refrigerant outlet, and then the actual refrigeration capacity Q e1 of the identification branch A2 is determined according to the calculated refrigerant enthalpy difference.

[0078] S403, repeat the above process of simulating heat management test by using the identification branch in the rated refrigeration capacity range of the test system until a set number of parameter groups of the actual refrigeration capacity and the corresponding minimum stable superheat degree are obtained.

[0079] S404, based on the obtained set number of parameter groups, an expression corresponding to the minimum stable superheat degree is fitted.

[0080] Specifically, the process of S401-S402 is repeatedly performed within the rated refrigerating capacity range of the test system, to obtain a plurality of different actual refrigerating capacity and corresponding minimum stable superheat degree parameter groups, and an expression of the budget minimum stable superheat degree can be fitted using the corresponding plurality of parameter groups. e1 =a*MSS1 2 +b*MSS1+c, wherein Q e1 is the actual refrigerating capacity when the identification branch is working, MSS1 is the minimum stable superheat degree when the identification branch is working, a, b, and c are all quadratic polynomial coefficients; the quadratic polynomial of the actual refrigerating capacity is converted into a corresponding inverse function to obtain an expression of the minimum stable superheat degree: wherein the fitted a, b, and c uniquely correspond to the current type of refrigerant in the current test system. After obtaining the quadratic polynomial of the actual refrigerating capacity, a minimum stable superheat degree curve can be plotted based on the quadratic polynomial fitting, as shown in Figure 6 .

[0081] On the basis of the above technical solutions, S105 specifically includes:

[0082] The current superheat degree is compared with the superheat degree set value; if the current superheat degree is greater than or equal to the superheat degree set value, the stability flag is controlled to display 0, and the stability is controlled to be good; if the current superheat degree is less than the superheat degree set value, the stability flag is controlled to display 1, and the test system gives a prompt that the superheat degree is lower than the minimum temperature superheat degree.

[0083] Specifically, the current superheat degree MSS0 of the test system when the test branch A1 is working is compared with the superheat degree set value SHsv, and there is: When M=1, the test system gives an information prompt of “the superheat degree set value is lower than the minimum stable superheat degree MSS2℃ under the current load, please check” in the display unit 60, and the value of M is recorded in real time.

[0084] In the embodiment of the present application, by providing the minimum stable superheat degree prompt function for the refrigerant phase change cooling type power battery thermal management test system, it is helpful for the test personnel to set a reasonable superheat degree set value when testing the battery performance using the equipment, to avoid various equipment abnormal problems caused by system parameter oscillation, compressor liquid knock, or invalid test results under low superheat degree state. Recording the value of M in real time not only helps the test personnel to understand the control stability of the test equipment in the whole test process, but also facilitates data tracing and analysis when the parameters are abnormal.

[0085] In summary, the test method for thermal management of the refrigerant phase change cooling type power battery provided by the embodiment of the application has the following advantages: (1) the actual refrigeration capacity is taken as the judgment criterion for MSS identification, the power of the electric heating simulation load is fixed, the control mode of adjusting the superheat degree by using the electronic expansion valve is adopted, and the actual refrigeration capacity is obtained; (2) dynamic MSS identification, the quadratic curve is fitted through experimental data, and the non-linear relationship between the actual refrigeration capacity and the superheat degree is more accurately reflected; (3) the minimum stable superheat degree indication, the superheat degree set value is constrained, the user is prompted, and the problems of liquid impact and parameter oscillation under low superheat degree are avoided.

[0086] The test method for thermal management of the refrigerant phase change cooling type power battery provided by the embodiment of the application will be specifically introduced below with a specific embodiment.

[0087] For example, the control identification branch A2 is connected and the test branch A1 is turned off, the initial superheat degree (i.e., the first set superheat degree) is set to 9℃ under the 10kW electric heating simulation load, the superheat degree set value is reduced by 1℃ as the set step, and the oscillation amplitude of the superheat degree is monitored, as shown in Figure 5 The critical MSS is determined to be 7.2℃, 6 sets of data are obtained through repeated experiments, and the fitting curve is as shown in Figure 6 .

[0088] The test branch A1 is connected and the identification branch A2 is disconnected, the superheat degree set value is 6℃, when the heat load of the refrigerant phase change plate evaporator 11 changes from 1.1kW to 5.2kW, the corresponding minimum superheat degree changes from 5.7℃ to 6.5℃, at this time, the superheat degree set value is lower than the minimum stable superheat degree corresponding to the current heat load, the test system gives the information prompt of “the superheat degree set value is lower than the minimum stable superheat degree 6.5℃ under the current load, please check”, and the value of the control stability M is recorded in real time.

[0089] The embodiment of the application also provides a test system for thermal management of a refrigerant phase change cooling type power battery, as shown in Figure 2 The test system comprises a control unit 30 using the test method for thermal management of the refrigerant phase change cooling type power battery according to any of the above embodiments, and further comprises a low-pressure side unit 10 and a high-pressure side unit 20; the control unit 30 is electrically connected with the low-pressure side unit 10 and the high-pressure side unit 20 respectively, and the low-pressure side unit 10 and the high-pressure side unit 20 are connected through a refrigerant pipeline 40.

[0090] The low-pressure side unit 10 comprises a test branch A1 connected with the refrigerant phase change plate evaporator 11 and the power battery to be tested 12, and further comprises an identification branch A2 provided with a simulation load heater 13, an electric heating device 14 and an adjustable power supply 15, and the test branch A1 is connected in parallel with the identification branch A2; the high-pressure side unit 20 comprises an electronic expansion valve EEV.

[0091] The control unit 30 is configured to control the test branch A1 to be connected, the identification branch A2 to be disconnected, control the refrigerant flow by using the electronic expansion valve EEV based on a preset sampling interval, and perform thermal management testing on the to-be-tested power battery 12.

[0092] The control unit 30 is further configured to calculate an actual refrigeration capacity of the test branch A1 by using the obtained pre-valve parameters of the electronic expansion valve EEV and the inlet and outlet parameters of the refrigerant phase change plate evaporator 11 during the testing process, determine a superheat setting value of the testing system based on an expression corresponding to the minimum stable superheat, determine the control stability of the testing system by using the current superheat and the superheat setting value, and adjust the opening degree of the electronic expansion valve EEV based on the control stability to realize the adjustment of the superheat in the testing system, wherein the expression corresponding to the minimum stable superheat is obtained by simulating the thermal management testing through the identification branch A2.

[0093] Specifically, the test branch A1 and the identification branch A2 form an evaporation system for heat exchange with the refrigerant, and through refrigerant loop switching, the identification of the minimum stable superheat curve and the variable load testing control under the actual application state of the refrigerant phase change plate can be realized.

[0094] Optionally, the control unit 30 is further configured to control the identification branch A2 to be connected and the test branch A1 to be turned off, control the refrigerant flow by using the electronic expansion valve EEV based on a preset sampling interval, and perform the simulated thermal management testing through the identification branch A2 to obtain the expression corresponding to the minimum stable superheat.

[0095] Optionally, as shown in Figure 2 The high-pressure side unit 20 includes, in sequence, a mass flow meter 21, a condensing system 22, a compressor 23, and a gas-liquid separator 24 connected with the electronic expansion valve EEV; and further includes a first pressure sensor P1 and a first temperature sensor T1 arranged at the pre-valve of the electronic expansion valve EEV, and a second pressure sensor P2 and a third pressure sensor P3 arranged at the outlet and inlet of the compressor 23.

[0096] Specifically, the mass flow meter 21 is used to measure the refrigerant mass flow under the working state of the system; the condensing system 22 is used to condense the high-temperature and high-pressure refrigerant discharged by the compressor 23; the compressor 23 is used to maintain the high and low pressures of the system during the operation of the testing system; the electronic expansion valve EEV is used as a throttling component to throttle and reduce the pressure of the refrigerant to a low-pressure state; and the gas-liquid separator 24 is used to separate the gas-liquid refrigerant to prevent the risk of liquid hammer of the compressor that may occur during the operation.

[0097] Optionally, as shown in Figure 2As shown, the test branch A1 further comprises a first electromagnetic valve V1 and a second electromagnetic valve V2; the first electromagnetic valve V1, the refrigerant phase-change plate evaporator 11, and the second electromagnetic valve V2 are sequentially connected, and the to-be-tested power battery 12 is arranged at the refrigerant phase-change plate evaporator 11.

[0098] The identification branch A2 further comprises a third electromagnetic valve V3 and a fourth electromagnetic valve V4; the third electromagnetic valve V3, the simulation load evaporator 13, and the fourth electromagnetic valve V4 are sequentially connected; the electric heating device 14 is connected in series with the adjustable power supply 15, and is arranged at the simulation load evaporator 13.

[0099] Optionally, as shown in the figure, Figure 2 As shown, the low-pressure side unit 10 further comprises a fourth pressure sensor P4 and a second temperature sensor T2 arranged at the inlet of the refrigerant pipeline 40, and a fifth pressure sensor P5 and a third temperature sensor T3 arranged at the outlet of the refrigerant pipeline 40.

[0100] Optionally, as shown in the figure, Figure 2 The system further comprises a data storage unit 50 and a display unit 60; the data storage unit 50 and the display unit 60 are electrically connected with the control unit.

[0101] Specifically, the data storage unit 50 is used for recording process parameters and results; and the display unit 60 is used for displaying relevant information in the operation and running process of the system.

[0102] The control unit in the refrigerant phase-change cooling type power battery thermal management test system provided by the embodiment of the present application uses the refrigerant phase-change cooling type power battery thermal management test method in the above embodiment, so the refrigerant phase-change cooling type power battery thermal management test system provided by the embodiment of the present application also has the beneficial effects described in the above embodiment, which will not be repeated here.

[0103] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the terms “mounting”, “connection”, and “linking” should be understood in a broad sense, for example, can be fixed connection, can be detachable connection, or integral connection; can be mechanical connection, or electrical connection; can be direct connection, or indirect connection through an intermediate medium; or internal communication of two elements. For those skilled in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0104] Finally, it should be noted that the above merely describes the preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, reconfigurations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for testing thermal management of a power battery with phase change cooling of refrigerant, characterized in that, The test system comprises a low-pressure unit, a high-pressure unit and a control unit, the control unit is electrically connected with the low-pressure unit and the high-pressure unit, the low-pressure unit comprises a test branch connected with a refrigerant phase change plate evaporator and a power battery to be tested, and an identification branch provided with an analog load heater, an electric heating device and an adjustable power supply, the test branch is connected in parallel with the identification branch, the high-pressure unit comprises an electronic expansion valve, and the test method is applied to the control unit; The test method comprises: controlling the test branch to be connected and the identification branch to be disconnected, controlling the refrigerant flow of the test system by using the electronic expansion valve based on a preset sampling interval, and starting the thermal management test on the power battery to be tested; During the test, the pre-valve parameter of the electronic expansion valve and the inlet and outlet parameters of the refrigerant phase change plate evaporator are obtained; The actual refrigerating capacity of the test branch is calculated by using the pre-valve parameter and the inlet and outlet parameters; The overheat setting value of the test system is determined based on the actual refrigerating capacity and an expression corresponding to the minimum stable overheat, wherein the expression corresponding to the minimum stable overheat is obtained through the identification branch simulation thermal management test in advance; The control stability of the test system is determined by using the current overheat and the overheat setting value; The opening degree of the electronic expansion valve is adjusted based on the control stability, so as to adjust the overheat of the test system.

2. The test method for thermal management of a power battery with a coolant phase change cooling system according to claim 1, wherein, The determination method of the expression corresponding to the minimum stable overheat comprises: controlling the identification branch to be connected and the test branch to be disconnected, controlling the refrigerant flow of the test system by using the electronic expansion valve based on a preset sampling interval, and performing the simulation thermal management test by using the identification branch; During the simulation, the overheat is reduced from a first set overheat to a second set overheat at a set step length, and the overheat response at the outlet of the analog load heater is monitored in real time, when the oscillation amplitude exceeds a set error value, the current overheat is increased by 0.1 DEG C, which is the minimum stable overheat under the current refrigerating capacity, and the actual refrigerating capacity under the corresponding overheat is calculated; The above process of simulating the thermal management test by using the identification branch is repeated within the rated refrigerating capacity range of the test system, until a set number of parameter groups of the actual refrigerating capacity and the corresponding minimum stable overheat are obtained; The expression corresponding to the minimum stable overheat is fitted based on the obtained set number of parameter groups.

3. The test method for thermal management of a power battery with a coolant phase change cooling system according to claim 2, wherein, The expression corresponding to the minimum stable overheat is fitted based on the obtained set number of parameter groups, which comprises: fitting a quadratic polynomial of actual refrigerating capacity Q e1 = a * MSS1 2 + b * MSS1 + c based on the set number of parameter groups acquired, wherein Q e1 is the actual refrigerating capacity when the branch is working, MSS1 is the minimum stable superheat degree when the branch is working, and a, b, and c are all quadratic polynomial coefficients; the actual refrigerating capacity is converted into a corresponding inverse function by using a quadratic polynomial, and the expression corresponding to the minimum stable overheat is obtained:

4. The test method for thermal management of a power battery with a coolant phase change cooling system according to claim 1, wherein, The control stability of the test system is determined by using the current overheat and the overheat setting value, which comprises: the current overheat is compared with the overheat setting value; if the current overheat is greater than or equal to the overheat setting value, the control stability is good, and the control stability flag is displayed as 0. If the current overheat degree is less than the overheat degree set value, the control stability flag displays 1, and the test system prompts that the overheat degree is lower than the minimum temperature overheat degree.

5. A thermal management test system for a coolant phase change cooling power battery, characterized in that, The control unit comprises a low-pressure side unit and a high-pressure side unit. The control unit is electrically connected to the low-pressure side unit and the high-pressure side unit, and the low-pressure side unit and the high-pressure side unit are connected through a refrigerant pipeline. The low-pressure side unit comprises a test branch connected with a refrigerant phase change plate evaporator and a power battery to be tested, and an identification branch provided with an analog load heater, an electric heating device, and an adjustable power supply, and the test branch and the identification branch are connected in parallel. The high-pressure side unit comprises an electronic expansion valve. The control unit is configured to control the test branch to be connected, the identification branch to be disconnected, control the refrigerant flow by using the electronic expansion valve based on a preset sampling interval, and perform thermal management testing on the power battery to be tested. The control unit is further configured to calculate the actual refrigerating capacity of the test branch by using the obtained pre-valve parameters of the electronic expansion valve and the inlet and outlet parameters of the refrigerant phase change plate evaporator during testing, determine the overheat degree set value of the test system based on an expression corresponding to the minimum stable overheat degree, determine the control stability of the test system by using the current overheat degree and the overheat degree set value, and adjust the opening degree of the electronic expansion valve based on the control stability to adjust the overheat degree of the test system, wherein the expression corresponding to the minimum stable overheat degree is obtained through the identification branch simulation thermal management testing in advance.

6. The refrigerant phase change cooling type power battery thermal management test system according to claim 5, wherein The control unit is further configured to control the identification branch to be connected and the test branch to be disconnected, control the refrigerant flow by using the electronic expansion valve based on a preset sampling interval, and perform simulation thermal management testing through the identification branch to obtain the expression corresponding to the minimum stable overheat degree.

7. The thermal management test system of a power battery with coolant phase change cooling according to claim 5, characterized in that, The high-pressure side unit comprises a mass flow meter, a condensing system, a compressor, and a gas-liquid separator connected in sequence with the electronic expansion valve. Further comprising a first pressure sensor and a first temperature sensor arranged before the electronic expansion valve, and a second pressure sensor and a third pressure sensor arranged at the outlet and inlet of the compressor.

8. The refrigerant phase change cooling type power battery thermal management test system according to claim 6, wherein The test branch further comprises a first electromagnetic valve and a second electromagnetic valve; the first electromagnetic valve, the refrigerant phase change plate evaporator, and the second electromagnetic valve are connected in sequence, and the power battery to be tested is arranged at the refrigerant phase change plate evaporator; The identification branch further comprises a third electromagnetic valve and a fourth electromagnetic valve; the third electromagnetic valve, the analog load evaporator, and the fourth electromagnetic valve are connected in sequence; and the electric heating device and the adjustable power supply are connected in series and arranged at the analog load evaporator.

9. The test system for thermal management of power battery with coolant phase change cooling according to claim 8, characterized in that, the low-pressure side unit further comprises a fourth pressure sensor and a second temperature sensor arranged at the inlet of the coolant pipeline, and a fifth pressure sensor and a third temperature sensor arranged at the outlet of the coolant pipeline.

10. The thermal management test system of a power battery with coolant phase change cooling according to claim 5, characterized in that, a data storage unit and a display unit are further included; the data storage unit and the display unit are electrically connected with the control unit.

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