An electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm

Abstract

The present application relates to the technical field of compressor protection, and belongs to an electric vehicle air conditioner compressor protection method based on an exhaust temperature estimation algorithm, wherein the exhaust temperature estimation method does not need to install an exhaust temperature sensor, realizes monitoring of the compressor exhaust temperature, and avoids the function of damaging the compressor due to excessively high exhaust temperature. For a vehicle model equipped with an engine, the influence of engine heat production on the increase of compressor suction temperature is estimated by the engine water temperature, and the accuracy of exhaust temperature estimation is improved. When the exhaust temperature is excessively high, the compressor speed is controlled in stages, and with the increase of the exhaust temperature, the logic of prohibiting the speed rise, forcibly reducing the speed, and forcibly stopping is respectively executed. When the limitation is exited, the speed recovery logic is executed, the speed rise rate of the compressor is limited, and it is ensured that the compressor can stably operate near the boundary speed without triggering the protection, which fully releases the compressor performance, and at the same time avoids the fluctuation of the system. The features and advantages of the present application will be described in detail in combination with the embodiments and the drawings.

Description

Technical Field

[0001] This invention relates to the field of compressor protection technology, specifically a method for protecting electric vehicle air conditioning compressors based on an exhaust temperature estimation algorithm. Background Technology

[0002] The electric air conditioning compressor is a core component of the thermal management system in new energy vehicles. Because these systems often operate under complex and demanding conditions, the compressor's reliability faces significant challenges. One common problem is excessively high compressor discharge temperature, which can easily damage the compressor. Therefore, appropriate measures must be taken to prevent the compressor from operating when the discharge temperature exceeds its design limit.

[0003] In existing technologies, a temperature sensor is typically installed on the compressor's exhaust pipe. The controller collects the exhaust temperature, and when the exhaust temperature exceeds the design limit, the compressor is shut down to protect it. Since exhaust temperature is not used in other control logic of the thermal management system, this sensor is rarely used, only under certain harsh operating conditions when the exhaust temperature is too high, especially for non-heat pump systems commonly used in range-extended vehicles. The extremely limited use of exhaust temperature sensors in this type of system leads to increased costs and wasted resources. Some models omit the exhaust temperature sensor to save costs, failing to protect against excessively high compressor exhaust temperatures. Furthermore, existing technologies typically shut down the compressor when the exhaust temperature is too high, resuming operation only after the exhaust temperature decreases, which can easily cause system oscillations. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for protecting the air conditioning compressor of an electric vehicle based on an exhaust temperature estimation algorithm.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a protection method for an electric vehicle air conditioning compressor based on an exhaust temperature estimation algorithm. The method steps are as follows:

[0007] S1. Obtain isentropic efficiency Map data through compressor bench tests;

[0008] S2. Based on the experimental data obtained in S1, a polynomial fitting formula with isentropic efficiency is constructed using a linear regression algorithm.

[0009] S3. The thermal management controller collects the intake pressure, intake temperature and exhaust pressure data of the vehicle compressor in real time, and performs filtering and correction.

[0010] S4. Based on the isentropic efficiency fitting formula obtained in S2, and combined with the data obtained in S3, calculate the isentropic efficiency under the current operating condition, and convert the data to further calculate the current compressor exhaust temperature value.

[0011] S5. Based on the relationship between the current compressor discharge temperature calculated in S4 and the preset level threshold, execute the graded protection control logic:

[0012] Graded limitation of compressor speed;

[0013] When the speed recovery logic is triggered, the speed increase rate is limited.

[0014] Preferably, the construction process in step S2 is as follows:

[0015] S21. Based on the three basic independent variables: compressor suction pressure Ps, compressor discharge pressure Pd, and compressor speed RS, construct the independent variables used for linear regression, and perform normalization to obtain the input table of isentropic efficiency formula fitting data.

[0016] S22. Based on the input data obtained in step S21, perform linear regression using the least squares method to obtain the polynomial fitting calculation formula for isentropic efficiency.

[0017] Preferably, the correction in step S3 includes:

[0018] Compensate for pressure drop in exhaust pressure;

[0019] Temperature rise compensation is applied to the intake air temperature;

[0020] For models without an engine, the temperature rise compensation is set to zero. For models with an engine, the temperature rise compensation is obtained from the compressor suction temperature rise compensation table.

[0021] Preferably, the exhaust temperature calculation step in step S4 is as follows:

[0022] S41. Standardize the compressor data to obtain standardized values;

[0023] S42. Based on the normalized data obtained in S41, calculate the compressor's isentropic efficiency according to the polynomial fitting formula obtained in S22.

[0024] S43. Based on the normalized data obtained in S41, the enthalpy and entropy values ​​of the compressor intake, the exhaust temperature and exhaust enthalpy values ​​of the compressor isentropically compressed exhaust are obtained from the gaseous refrigerant enthalpy table and the gaseous refrigerant entropy table.

[0025] S44. Based on the isentropic efficiency obtained in S42, the current compressor discharge enthalpy is calculated according to the variable operating condition enthalpy correction formula.

[0026] S45. Based on the normalized data obtained in S41 and the current compressor exhaust enthalpy obtained in S44, the current compressor exhaust temperature is obtained by combining the first-order low-pass filtering algorithm.

[0027] Preferably, in step S4, when the system has no superheat, the current compressor discharge temperature is replaced with the default value.

[0028] Preferably, in step S5, the hierarchical protection logic includes:

[0029] Set the exhaust temperature limit level: Calculate the exhaust temperature limit level based on the compressor exhaust temperature limit and the current compressor exhaust temperature value in step S4;

[0030] The current compressor discharge temperature value is compared with the level threshold. When the current compressor discharge temperature value Td exceeds the level threshold, the restriction level is increased to the restriction level corresponding to the level threshold. When the current compressor discharge temperature value Td is lower than the initial restriction level threshold, the restriction level is reduced to the initial restriction level.

[0031] Preferably, in step S5, the speed recovery logic is as follows:

[0032] Control the compressor speed according to the calculated limit level;

[0033] When the current compressor discharge temperature is too high, triggering the compressor speed reduction or shutdown limiting logic, wait for the compressor discharge temperature limit level to drop to the initial limit level, and then start executing the compressor speed recovery logic.

[0034] Preferably, when executing the compressor speed recovery logic, the rate of increase of the compressor target speed is limited, and the specific limitation logic is as follows:

[0035] When executing the compressor speed recovery logic, it first checks whether the exit conditions of the recovery logic are met. If condition 1, condition 2, or condition 3 is met, the recovery logic exits and normal control logic is executed. The specific conditions are as follows:

[0036] Condition 1: The increase in the target compressor speed within 10 seconds is less than 100 rpm.

[0037] Condition 2: The compressor reaches its maximum speed for 10 seconds.

[0038] Condition 3: The duration of executing the speed recovery logic exceeds 60 seconds.

[0039] Preferably, the speed recovery logic adopts a segmented rate limiting formula:

[0040] When the rotational speed is <4000 rpm: the rate of increase is ≤500 rpm / s;

[0041] When the rotational speed is 4000-6000 rpm: the rate of increase is ≤150 rpm / s;

[0042] When the rotational speed is >6000 rpm: the rate of increase is ≤50 rpm / s.

[0043] Compared with the prior art, the present invention provides a protection method for electric vehicle air conditioning compressor based on exhaust temperature estimation algorithm, which has the following beneficial effects:

[0044] 1. By using the exhaust temperature estimation method, the exhaust temperature sensor can be eliminated, thus enabling the monitoring of the compressor's exhaust temperature and preventing damage to the compressor due to excessively high exhaust temperature.

[0045] 2. For models equipped with engines, the impact of engine heat generation on the increase of compressor intake temperature is estimated by estimating engine coolant temperature, thereby improving the accuracy of exhaust temperature estimation.

[0046] 3. When the exhaust temperature is too high, the compressor speed is controlled in stages. As the exhaust temperature increases, logic is executed to prohibit speed increase, force speed reduction, and force shutdown respectively. When the restriction is lifted, speed recovery logic is executed to limit the rate of compressor speed increase, ensuring that the compressor can operate smoothly near the boundary speed that does not trigger protection, thus fully releasing the compressor performance while avoiding system fluctuations. The features and advantages of this invention will be described in detail through embodiments and accompanying drawings. Attached Figure Description

[0047] Figure 1 This is a flowchart of a method for protecting an electric vehicle air conditioning compressor based on an exhaust temperature estimation algorithm, according to the present invention.

[0048] Figure 2 Flowchart of compressor exhaust temperature protection in this invention;

[0049] Figure 3 This is the logic diagram for the compressor exhaust temperature limit level jump in this invention;

[0050] Figure 4 This is an example diagram of the data input table format for fitting the isentropic efficiency formula of this invention. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0052] See Figures 1-2 A protection method for an electric vehicle air conditioning compressor based on an exhaust temperature estimation algorithm is described below:

[0053] S1. Obtain isentropic efficiency Map data through compressor bench tests;

[0054] S2. Based on the experimental data obtained in S1, a polynomial fitting formula with isentropic efficiency is constructed using a linear regression algorithm.

[0055] S3. The thermal management controller collects the intake pressure, intake temperature and exhaust pressure data of the vehicle compressor in real time, and performs filtering and correction.

[0056] S4. Based on the isentropic efficiency fitting formula obtained in S2, and combined with the data obtained in S3, calculate the isentropic efficiency under the current operating condition, and convert the data to further calculate the current compressor exhaust temperature value.

[0057] S5. Based on the relationship between the current compressor discharge temperature calculated in S4 and the preset level threshold, execute the graded protection control logic: graded limit on compressor speed; when the speed recovery logic is triggered, limit the speed increase rate.

[0058] Steps S1 to S2 are the process of obtaining the compressor isentropic efficiency fitting formula, which is processed offline and does not need to be implemented in the thermal management control software.

[0059] In a specific embodiment, the specific content of step S1 is as follows:

[0060] 1.1 Compressor bench tests were conducted according to the operating conditions listed in Table 1 (compressor operation map test conditions). Suction temperature and pressure sensors and discharge temperature and pressure sensors were arranged on the test bench. The test condition was that the suction superheat was fixed at 10℃. Different suction pressures Ps, discharge pressures Pd, and compressor speeds RS were set in turn to obtain the discharge temperature Td after the compressor had been running stably for 3 minutes under each operating condition.

[0061] Table 1 Compressor Operation Map Test Conditions Table

[0062]

[0063] 1.2 The isentropic efficiency eff_is for each test condition is calculated, and the isentropic efficiency Map data of the compressor is obtained. The specific algorithm is as follows:

[0064] 1.2.1 Based on the suction temperature Ts and suction pressure Ps, the suction enthalpy Hs under this operating condition is obtained using refrigerant property calculation software;

[0065] 1.2.2, Based on the exhaust temperature Td and exhaust pressure Pd, the actual exhaust enthalpy Hd under this operating condition is obtained using refrigerant property calculation software;

[0066] 1.2.3 Based on the suction temperature Ts and suction pressure Ps, the actual suction entropy Ss under this operating condition is obtained using refrigerant property calculation software;

[0067] 1.2.4, Under this operating condition, the exhaust entropy of isentropic compression is Sd_is = Ss;

[0068] 1.2.5 Based on the exhaust entropy Sd_is from isentropic compression and the actual exhaust pressure Pd, the exhaust enthalpy Hd_is at isentropic compression to Pd under this operating condition is obtained using refrigerant property calculation software;

[0069] 1.2.6 Calculate the isentropic efficiency under this operating condition. The formula is: Isentropic efficiency eff_is = (Hd_is - Hs) / (Hd - Hs);

[0070] Specifically, the construction process in step S2 is as follows:

[0071] S21. Based on the three basic independent variables: compressor suction pressure Ps, compressor discharge pressure Pd, and compressor speed RS, construct the independent variables used for linear regression, and perform normalization to obtain the input table of isentropic efficiency formula fitting data.

[0072] S22. Based on the input data obtained in step S21, perform linear regression using the least squares method to obtain the polynomial fitting calculation formula for isentropic efficiency.

[0073] In a specific embodiment, the specific content of step S2 is as follows:

[0074] 2.1 Based on three basic independent variables: compressor suction pressure Ps, compressor discharge pressure Pd, and compressor speed RS, the independent variables used for linear regression are constructed and normalized. The normalization process includes...

[0075] 2.1.1, Normalization process yields intermediate variables:

[0076] Rs_Nrm = RS / 10000,

[0077] Pd_Nrm = Pd / 28,

[0078] Ps_Nrm = Ps / 8,

[0079] Perr_Nrm = (Pd - Ps) / 28

[0080] 2.1.2 Construct the independent variables and calculate their values ​​for each experimental condition to obtain... Figure 4 The input data for the linear regression algorithm shown (format example; actual data is obtained from bench tests) includes:

[0081] Independent variable:

[0082] Rs_Nrm,

[0083] Pd_Nrm,

[0084] Rs_Nrm2 = Rs_Nrm^2,

[0085] Rs_Nrm3 = Rs_Nrm^3,

[0086] RsPd = Rs_Nrm Pd_Nrm,

[0087] Pd2Ps = Pd_Nrm^2 Ps,

[0088] RsOverPs = Rs_Nrm / Ps_Nrm,

[0089] RsSquareOverPd = Rs_Nrm^2 / Pd_Nrm,

[0090] RsSquareOverPs = Rs_Nrm^2 / Ps_Nrm,

[0091] RsSquareOverPdPs = Rs_Nrm^2 / ( Pd_Nrm Ps_Nr),

[0092] Rs2Perr = Rs_Nrm^2 Perr_Nrm,

[0093] RsOverPr = Rs_Nrm / ( Pd_Nrm / Ps_Nrm),

[0094] Rs2OverPerr = Rs_Nrm^2 / Perr_Nrm,

[0095] Dependent variable: eff_is

[0096] 2.2 Based on the input data obtained in step 2.1.2, linear regression is performed using the least squares method to obtain the polynomial fitting formula for isentropic efficiency:

[0097]

[0098] Wherein, K0~K13 are polynomial coefficients, obtained by linear regression based on specific compressor bench test data.

[0099] Steps S3 to S4 are the algorithms for estimating the compressor exhaust temperature, which need to be implemented in the thermal management control software.

[0100] Specifically, the correction in step S3 includes:

[0101] Compensate for pressure drop in exhaust pressure;

[0102] Temperature rise compensation is applied to the intake air temperature;

[0103] For models without an engine, the temperature rise compensation is set to zero. For models with an engine, the temperature rise compensation is obtained from the compressor suction temperature rise compensation table.

[0104] In a specific embodiment, step S3 is described as follows:

[0105] 3.1 The controller acquires the value of the compressor suction pressure sensor and obtains the filtered suction pressure Ps after passing through a first-order low-pass filter.

[0106] 3.2 The controller acquires the value of the compressor exhaust pressure sensor and obtains the filtered raw exhaust pressure value Pd_raw after passing through a first-order low-pass filter.

[0107] As a further improvement of the present invention, the exhaust pressure obtained in step 3.2 is further corrected by compensating for the pressure drop in the pipeline from the compressor exhaust port to the location of the exhaust pressure sensor, resulting in an exhaust pressure correction value Pd. The specific logic is as follows:

[0108] 3.2.1 Based on the compressor speed RS and the filtered suction pressure Ps, refer to Table 2 (compressor exhaust pressure drop compensation table) to obtain the pressure drop compensation amount Pd_ofst. Table 2 is a two-dimensional nonlinear table and needs to be calibrated.

[0109] Table 2 Compressor Discharge Pressure Drop Compensation Table

[0110]

[0111] 3.2.2, the corrected compressor discharge pressure Pd = Pd_raw + Pd_ofst is obtained.

[0112] 3.3 The controller acquires the value of the compressor suction temperature sensor and obtains the filtered raw suction temperature value Ts_raw after passing through a first-order low-pass filter.

[0113] As a further improvement of the present invention, the original intake temperature value Ts_raw obtained in step 3.3 is further corrected by compensating for the temperature rise in the pipeline from the location of the intake temperature sensor to the compressor inlet, resulting in a corrected intake temperature value Ts. The specific logic is as follows.

[0114] 3.3.1 For models without an engine (pure electric), the temperature rise compensation Ts_ofst = 0. For models with an engine (range-extended or hybrid), the suction temperature rise compensation Ts_ofst is obtained by referring to Table 3 (compressor suction temperature rise compensation table) based on the engine coolant temperature. Table 3 is a one-dimensional non-linear table and needs to be calibrated.

[0115] Table 3 Compressor Suction Temperature Rise Compensation Table

[0116]

[0117] 3.3.2, the corrected compressor suction temperature Ts = Ts_raw + Ts_ofst is obtained.

[0118] At this point, the corrected intake pressure Ps, intake temperature Ts, and exhaust pressure Pd are obtained. Next, the isentropic efficiency eff_is of the compressor needs to be calculated using the fitting formula obtained in step 2.2, and the exhaust temperature Td needs to be calculated further.

[0119] Specifically, in step S4, the exhaust temperature calculation step is as follows:

[0120] S41. Standardize the compressor data to obtain standardized values;

[0121] S42. Based on the normalized data obtained in S41, calculate the compressor's isentropic efficiency according to the polynomial fitting formula obtained in S22.

[0122] S43. Based on the normalized data obtained in S41, the enthalpy and entropy values ​​of the compressor intake, the exhaust temperature and exhaust enthalpy values ​​of the compressor isentropically compressed exhaust are obtained from the gaseous refrigerant enthalpy table and the gaseous refrigerant entropy table.

[0123] S44. Based on the isentropic efficiency obtained in S42, the current compressor discharge enthalpy is calculated according to the variable operating condition enthalpy correction formula.

[0124] S45. Based on the normalized data obtained in S41 and the current compressor exhaust enthalpy obtained in S44, the current compressor exhaust temperature is obtained by combining the first-order low-pass filtering algorithm.

[0125] Specifically, in step S4, when the system has no superheat, the current compressor discharge temperature is replaced by the default value.

[0126] In a specific embodiment, step S4 is as follows:

[0127] 4.1 The actual compressor speed RS is normalized to obtain the normalized speed Rs_Nrm = RS / 10000.

[0128] 4.2 The compensated exhaust pressure Pd is normalized to obtain the normalized exhaust pressure Pd_Nrm = Pd / 28.

[0129] 4.3. The compensated inspiratory pressure Ps is normalized to obtain the normalized inspiratory pressure Ps_Nrm = Ps / 8.

[0130] 4.4, the normalized pressure difference Perr_Nrm = (Pd - Ps) / 28 is calculated.

[0131] 4.5 Calculate the isentropic efficiency eff_is of the compressor using the fitting formula obtained in step 2.2.

[0132] Table 4 Enthalpy Values ​​of Gaseous Refrigerants

[0133]

[0134] Table 5 Entropy Values ​​of Gaseous Refrigerants

[0135]

[0136] 4.6. Based on the filtered suction pressure Ps and the corrected suction temperature Ts, refer to Table 4 (Enthalpy Table of Gaseous Refrigerant) to obtain the enthalpy Hs of the compressor suction.

[0137] 4.7. Based on the filtered suction pressure Ps and the corrected suction temperature Ts, refer to Table 5 (Gaseous Refrigerant Entropy Table) to obtain the compressor suction entropy value Ss.

[0138] 4.8. Based on the corrected exhaust pressure Pd and the intake entropy value Ss, the exhaust temperature value Td_is for isentropic compression of the compressor is obtained by referring to Table 5.

[0139] 4.9. Based on the corrected exhaust pressure Pd and the exhaust temperature value Td_is under isentropic compression, the exhaust enthalpy value Hd_is under isentropic compression is obtained by looking up Table 4.

[0140] 4.10. Based on the isentropic efficiency eff_is obtained in step 4.5, calculate the compressor exhaust enthalpy Hd. The calculation formula is Hd = Hs + (Hd_is - Hs) / eff_is.

[0141] 4.11 Calculate the compressor discharge temperature Td. The calculation method is to look up Table 4 based on the corrected compressor discharge pressure Pd and the compressor discharge enthalpy Hd to obtain the compressor discharge temperature Td_raw.

[0142] As a further improvement of the present invention, the exhaust temperature Td_raw obtained in step 4.11 is filtered to obtain the filtered compressor exhaust temperature Td, as detailed below:

[0143] 4.11.1 The filtering uses a first-order low-pass filter algorithm, and its calculation formula is Td(k) = (1-r). Td(k-1) + r Td_raw(k). Where r is the filter coefficient, which needs to be calibrated. Td(k) represents Td in the kth calculation cycle.

[0144] As a further improvement of the present invention, when the system has no superheat, considering that the refrigerant state at the compressor intake cannot be calculated, and therefore the exhaust temperature cannot be accurately calculated, and that a high exhaust temperature will not occur when the intake superheat is low, to avoid calculation errors causing false system protection, the compressor exhaust temperature uses a default value instead in the low intake superheat condition. The specific logic includes:

[0145] 4.11.2 If the compressor suction superheat SH_s < 3℃, then set Td = 50℃.

[0146] Specifically, in step S5, the hierarchical protection logic includes:

[0147] Set the exhaust temperature limit level: Calculate the exhaust temperature limit level based on the compressor exhaust temperature limit and the current compressor exhaust temperature value in step S4;

[0148] The current compressor discharge temperature value is compared with the level threshold. When the current compressor discharge temperature value Td exceeds the level threshold, the restriction level is increased to the restriction level corresponding to the level threshold. When the current compressor discharge temperature value Td is lower than the initial restriction level threshold, the restriction level is reduced to the initial restriction level.

[0149] Specifically, in step S5, the speed recovery logic is as follows:

[0150] Control the compressor speed according to the calculated limit level;

[0151] When the current compressor discharge temperature is too high, triggering the compressor speed reduction or shutdown limiting logic, wait for the compressor discharge temperature limit level to drop to the initial limit level, and then start executing the compressor speed recovery logic.

[0152] Specifically, when executing the compressor speed recovery logic, the rate of increase of the compressor target speed is limited, and the specific limiting logic is as follows:

[0153] When executing the compressor speed recovery logic, it first checks whether the exit conditions of the recovery logic are met. If condition 1, condition 2, or condition 3 is met, the recovery logic exits and normal control logic is executed. The specific conditions are as follows:

[0154] Condition 1: The increase in the target compressor speed within 10 seconds is less than 100 rpm.

[0155] Condition 2: The compressor reaches its maximum speed for 10 seconds.

[0156] Condition 3: The duration of executing the speed recovery logic exceeds 60 seconds.

[0157] Specifically, the speed recovery logic adopts a segmented rate limiting formula:

[0158] When the rotational speed is <4000 rpm: the rate of increase is ≤500 rpm / s;

[0159] When the rotational speed is 4000-6000 rpm: the rate of increase is ≤150 rpm / s;

[0160] When the rotational speed is >6000 rpm: the rate of increase is ≤50 rpm / s.

[0161] When the calculated exhaust temperature Td is too high, the compressor exhaust protection logic in step 5 is triggered.

[0162] The execution logic of step 5 is as follows: Figure 2 As shown, the specific content is as follows:

[0163] 5.1 Based on the compressor discharge temperature Td and the compressor discharge temperature upper limit T_lmt obtained in step 4, calculate the discharge temperature limit level (LimitLevel).

[0164] As a further improvement of the present invention, graded protection is provided for compressor exhaust, such as... Figure 3 As shown, the protection level is calculated based on the exhaust temperature Td and the upper limit of the exhaust temperature T_lmt. The specific method is as follows:

[0165] 5.1.1, The initial restriction level is Level 0.

[0166] 5.1.2 If the current restriction level is Level 0, and Td > T1, the restriction level is raised to Level 1.

[0167] 5.1.3 If the current restriction level is Level 1, and Td > T2, the restriction level is raised to Level 2.

[0168] 5.1.4, If the current limit level is Level2, when Td > T3, the limit level is increased to Level3.

[0169] 5.1.5, If the current limit level is not Level0, then when Td < T0, the limit level is decreased to Level0.

[0170] Where T3 = T_lmt, T2 = T_lmt – dT1, T1 = T_lmt – dT2, T0 = T_lmt - dT3,

[0171] dT3 > dT2 > dT1 > 0, and all can be calibrated.

[0172] 5.2, Control the compressor speed according to the calculated limit level. The specific content includes:

[0173] 5.2.1, If the limit level is Level0, the speed of the compressor is not restricted and is controlled according to normal requirements.

[0174] 5.2.2, If the limit level is Level1, the increase in the compressor speed is prohibited. That is, if it is required to increase the compressor speed, the speed should be controlled to maintain the current value. If it is required to decrease the compressor speed, the speed should be controlled to decrease according to the requirement.

[0175] 5.2.2, If the limit level is Level2, the compressor speed should be controlled to decrease at a rate of k1 (Td – T0) + k0 revolutions per second, where k0 and k1 are parameters of the decrease rate and can be calibrated.

[0176] 5.2.3, If the limit level is Level3, the compressor speed should be controlled to decrease at a relatively large rate of K3 rpm / s, and K3 can be calibrated. When the speed drops to the minimum speed allowed by the compressor, or after the limit level remains at Level3 for 10 s, the compressor is shut down.

[0177] 5.3, When the compressor exhaust temperature is too high and triggers the limit logic for reducing the compressor speed or shutting down, wait until the compressor exhaust temperature limit level drops to Level0, and then start to execute the compressor speed recovery logic.

[0178] As a further improvement of the present invention, when entering the compressor speed recovery logic, the rising rate of the compressor target speed is restricted. The specific method is as follows.

[0179] When the target speed is lower than 4000 rpm, the rising rate of the compressor speed cannot exceed 500 rpm per second.

[0180] When the target speed is higher than 4000 rpm but lower than 6000 rpm, the rate of increase of the compressor speed must not exceed 150 rpm per second.

[0181] When the target speed is higher than 6000 rpm, the rate of increase of the compressor speed must not exceed 50 rpm per second.

[0182] The speed threshold and speed increase rate in step 5.3 are both calibrable quantities.

[0183] 5.4 When executing the compressor speed recovery logic, it first checks whether the exit conditions of the recovery logic are met. If condition 1, condition 2, or condition 3 is met, the recovery logic exits and the normal control logic is executed. The specific conditions are as follows:

[0184] Condition 1: The increase in the target compressor speed within 10 seconds is less than 100 rpm.

[0185] Condition 2: The compressor reaches its maximum speed for 10 seconds, or...

[0186] Condition 3: The duration of executing the speed recovery logic exceeds 60 seconds.

[0187] The time and rotation speed thresholds in step 5.4 are both calibrable quantities.

[0188] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm, characterized in that: The method steps are as follows: S1, obtain isentropic efficiency Map data through compressor bench test; S2, based on the experimental data obtained in S1, construct a polynomial fitting formula of isentropic efficiency by linear regression algorithm; The construction process in step S2 is as follows: S21, according to three basic independent variables: compressor suction pressure Ps, compressor discharge pressure Pd and compressor speed RS, construct the independent variables used for linear regression, and obtain the isentropic efficiency formula fitting data input table after normalization processing; S22, according to the input data obtained in step S21, use least squares method for linear regression to obtain the polynomial fitting calculation formula of isentropic efficiency; S3, the thermal management controller collects the suction pressure, suction temperature and discharge pressure data values of the vehicle compressor in real time, and performs filtering and correction; The correction in step S3 includes: Pressure drop compensation is performed on the discharge pressure; Temperature rise compensation is performed on the suction temperature; Wherein for the vehicle model without engine configuration, the temperature rise compensation amount is set to zero, and for the vehicle model with engine configuration, the suction temperature rise compensation amount is obtained according to the engine water temperature and the compressor suction temperature rise compensation table; S4, based on the isentropic efficiency fitting formula obtained in S2, combined with the data obtained in S3, calculate the isentropic efficiency of the current working condition, and further calculate the current compressor discharge temperature value; S5, according to the size relationship between the current compressor discharge temperature calculated in S4 and the preset level threshold, execute the grading protection control logic: Grading limit compressor speed; Limit the speed rising rate when triggering the speed recovery logic.

2. The electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm according to claim 1, characterized in that: In step S4, the discharge temperature calculation step is as follows: S41, normalize the compressor data to obtain normalized values; S42, based on the normalized data obtained in S41, calculate the isentropic efficiency of the compressor according to the polynomial fitting calculation formula obtained in S22; S43, based on the normalized data obtained in S41, obtain the enthalpy and entropy values of the compressor suction, the discharge temperature value and the discharge enthalpy value of the isentropic compression discharge according to the gaseous refrigerant enthalpy table and the gaseous refrigerant entropy table; S44, based on the isentropic efficiency obtained in S42, calculate the current compressor discharge enthalpy value according to the variable working condition enthalpy correction formula; S45, based on the normalized data obtained in S41 and the current compressor discharge enthalpy value obtained in S44, combined with the first-order low-pass filter algorithm, obtain the current compressor discharge temperature.

3. The electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm according to claim 1, characterized in that: In step S4, When the system has no overheating degree, the current compressor discharge temperature is replaced by the default value.

4. The electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm according to claim 1, characterized in that: In step S5, the grading protection logic includes: Set the exhaust temperature limit level: calculate the exhaust temperature limit level according to the upper limit of the compressor discharge temperature and the current compressor discharge temperature value in step S4; Compare the current compressor discharge temperature value with the level threshold, when the current compressor discharge temperature value exceeds the level threshold, the limit level is increased to the limit level corresponding to the level threshold; when the current compressor discharge temperature value is lower than the starting limit level threshold, the limit level is reduced to the starting limit level.

5. An electric vehicle air conditioner compressor protection method based on exhaust gas temperature estimation algorithm according to claim 4, characterized in that: The step S5 is specifically as follows: When the current compressor discharge temperature is too high, triggering the compressor speed reduction or shutdown limit logic, waiting for the compressor discharge temperature limit level to be reduced to the starting limit level, and starting to execute the compressor speed recovery logic.

6. An electric vehicle air conditioner compressor protection method based on exhaust gas temperature estimation algorithm according to claim 5, characterized in that: When executing the compressor speed recovery logic, the rising rate of the compressor target speed is limited, and the specific limit logic is as follows: When executing the compressor speed recovery logic, it is started to judge whether the exit condition of the recovery logic is met, such as condition 1 or condition 2 or condition 3 is met, then the recovery logic is exited, and the normal control logic is executed, and the specific conditions are as follows: Condition 1: the increase amount of the compressor target speed within 10s < 100rpm, Condition 2: the compressor reaches the upper limit of the speed for 10s, Condition 3: the duration of executing the speed recovery logic exceeds 60s.

7. The electric vehicle air conditioner compressor protection method based on exhaust temperature estimation algorithm according to claim 5, characterized in that: The speed recovery logic adopts a segmented rate limit formula: When the speed <4000rpm: the rising rate ≤500rpm / s; When the speed 4000-6000rpm: the rising rate ≤150rpm / s; When the speed >6000rpm: the rising rate ≤50rpm / s.

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