Electric vehicle air conditioner control method

Abstract

The application discloses an electric vehicle air conditioner control method, and the main design concept of the application is that after the variable frequency air conditioner compressor of the electric vehicle is allowed to start, an initial compressor rotating speed value is given, and an actual evaporation temperature is collected in real time to judge the temperature change trend; according to the difference between the actual evaporation temperature and the target evaporation temperature and the temperature change trend, the compressor capacity is compensated and controlled in a given compensation period. The application makes the rotating speed of the compressor more reasonable, prevents the compressor from frequently starting and stopping, and makes the compressor play the optimal performance, so that the precision of the temperature control in the vehicle, the comfort of the passengers and the system energy efficiency ratio are improved, the consumption of the air conditioner for the electric energy of the whole vehicle is effectively reduced, and the cruising range of the whole vehicle can be improved.

Description

Technical Field

[0001] This invention relates to the field of vehicle air conditioning technology, and more particularly to a method for controlling the air conditioning of an electric vehicle. Background Technology

[0002] Currently, electric vehicles are a significant trend in automotive development. To achieve the industrialization and marketization of electric vehicles, they must not only possess sufficient power like traditional gasoline-powered vehicles but also provide a comfortable driving and riding environment. Therefore, electric vehicles must be equipped with efficient air conditioning systems. Compared to the air conditioning systems of ordinary gasoline-powered vehicles, electric vehicle air conditioning systems cannot use a traditional engine-driven compressor to meet the cooling needs of the system, nor can they utilize the waste heat of a traditional engine as a heat source for the heating function. Therefore, the key changes in the components of electric vehicle air conditioning systems mainly involve replacing the traditional engine-driven compressor with an electric motor-driven compressor, and using a high-pressure PTC (Power Transmission Control Unit) to achieve the heating function.

[0003] In the current solution, the air conditioning system can meet basic needs in terms of cooling and heating, and the control logic is relatively simple. However, there is also the problem of wasting battery power due to the inefficiency of cooling and heating. Therefore, it is necessary to consider optimizing the air conditioning control strategy to reduce the power consumption of the air conditioning system, reduce the loss of battery power, and improve the vehicle's range.

[0004] Specifically, electric vehicle air conditioning systems use electric compressors and high-pressure PTCs to meet the cooling and heating needs of the air conditioning system. However, in the current solution, if the compressor speed is too high or too low, it will seriously affect the cooling capacity, resulting in an unstable and energy-inefficient system.

[0005] For example, the air conditioning system temperature is adjusted via a temperature knob, which controls the outlet air temperature. This is divided into cooling and heating zones, assuming 29 levels in total (blue and red). The blue level represents the cooling zone (levels 1-14), and the red level represents the heating zone (levels 15-29). Levels 1-14 are applied to the set evaporation temperature, and the compressor speed operates between 2000 and 4000 rpm. The compressor operates at a fixed speed corresponding to the set temperature. When the evaporation temperature protection is reached, the protection program is activated: the evaporator temperature drops below 0°C, the A / C is turned off, and the compressor stops working. When the evaporation temperature rises to 4°C, the compressor speed resumes at the set speed. Levels 15-29 are applied to the PTC settings; for example, levels 15-19 correspond to PTC1, levels 20-24 to PTC2, and levels 25-29 to PTC3. Under these conditions, the current electric vehicle air conditioning control strategy will encounter at least the following three problems:

[0006] The air conditioner controller controls the compressor speed according to the user's set temperature requirements. The compressor is adjusted and controlled in three levels between 2000 and 4000 rpm, which is equivalent to controlling the compressor's displacement in three levels. The compressor only works at a fixed displacement in the three set levels. If the compressor either works or stops, or the speed is either too high or too low, it will seriously affect the cooling capacity of the air conditioning system, making the air conditioning system unstable and the energy consumption unstable.

[0007] Furthermore, the air conditioning system operates directly at the compressor speed set according to the user's temperature setting. Lacking target temperature control and the assistance of an air outlet temperature sensor, the compressor only stops when the system protection is activated. This results in the compressor speed being either too high or too low, leading to poor passenger comfort. The air conditioning compressor only accepts start and stop signals to achieve constant speed operation. Because it operates at a single speed for extended periods, even under low heat load conditions (i.e., low cooling capacity), the compressor maintains a high speed, wasting cooling capacity and power, thus impacting the vehicle's battery life and range.

[0008] Furthermore, the air conditioning controller controls the PTC setting according to the user's set temperature requirements. The PTC requires the temperature to be below 110℃ to activate. When the PTC temperature sensor temperature rises to 100℃, the PTC operation is required to be cut off; when the PTC temperature sensor temperature drops to 85℃, the PTC operation is required to be activated, restoring the previously set setting.

[0009] To address the aforementioned issues, the conventional solution currently used in air conditioning systems is to add outlet temperature sensors. These sensors control the compressor speed or PTC setting based on the outlet temperature data. However, outlet temperature sensors are expensive. To ensure accurate and comfortable temperature control, at least four surface air outlet temperature sensors and six foot air outlet temperature sensors are required, which significantly increases the overall system development cost. Summary of the Invention

[0010] In view of the above, the present invention aims to provide an electric vehicle air conditioning control method to reduce the impact on the vehicle's driving range and reduce energy waste when the air conditioning is on, in response to the complex and ever-changing operating conditions of the vehicle.

[0011] The technical solution adopted in this invention is as follows:

[0012] This invention provides a method for controlling the air conditioning of an electric vehicle, comprising:

[0013] After detecting that the AC mode of the air conditioner has been activated, determine whether to start the compressor based on preset conditions;

[0014] When the compressor is allowed to start, the initial compressor speed is set according to the outside temperature, corresponding to the current outside temperature.

[0015] Based on the first difference between the current actual evaporation temperature and the target evaporation temperature, the different stages corresponding to the temperature environment inside the vehicle are determined; wherein, the target evaporation temperature has a preset correspondence with each level of the air conditioning cooling mode;

[0016] At different stages, the compressor speed is compensated based on the second difference between two actual evaporation temperatures collected sequentially over a preset time period, and the compressor speed is controlled to remain within a preset speed range.

[0017] In at least one of the possible implementations, the second difference is equal to the actual evaporation temperature collected at the previous moment of the time period minus the actual evaporation temperature at the current moment.

[0018] In at least one of the possible implementations, the timing of the time period begins upon receiving the compressor speed signal.

[0019] In at least one of the possible implementations, the first difference and the second difference each comprise multiple temperature ranges.

[0020] In at least one possible implementation, the compensation compressor speed includes: increasing, decreasing, or maintaining the compressor speed based on the speed change value calibrated for each temperature range corresponding to the second difference.

[0021] In at least one of the possible implementations, the preset conditions include whether the following conditions are met simultaneously: the blower is turned on, the outside temperature is ≥0℃, the current actual evaporation temperature is ≥ the preset evaporation protection temperature, the high voltage is powered on, the air conditioning system pressure meets the predetermined pressure protection strategy, and the VCU sends a condenser fan start signal.

[0022] In at least one possible implementation, the control method further includes one or more of the following compressor protection strategies:

[0023] When the compressor's discharge temperature is greater than or equal to the preset discharge temperature threshold, the compressor is disabled from operating, and when the compressor's discharge temperature drops below the preset enable temperature, the compressor is allowed to operate.

[0024] When the outside temperature is ≤ the preset sub-zero temperature, the compressor is disabled; when the outside temperature is between the sub-zero temperature and 0°C, the air conditioner is turned off in AC mode.

[0025] When a preset power limit message is received, the compressor speed is limited to a preset protection speed.

[0026] In at least one possible implementation, the control method further includes heating control logic:

[0027] The PTC will be activated when the following conditions are met simultaneously: the blower is turned on, the PTC temperature switch is closed, the PTC temperature is lower than the preset high limit, and the high voltage is powered on.

[0028] After the PTC is turned on, when the PTC temperature rises to the preset high limit and remains there for the set duration, the PTC operation is cut off.

[0029] After the PTC is disconnected, it is triggered to restart when the PTC temperature drops to the preset restart value; and,

[0030] When a PTC temperature sensor failure is detected, PTC operation is disabled.

[0031] In at least one possible implementation, the heating control logic further includes one or more of the following PTC protection strategies:

[0032] When the airflow is at level 1 or when a preset power limit message is received, the PTC is restricted to operate only at the preset PTC level 1.

[0033] When the airflow is at level 2 to 3, the PTC is limited to operate within the preset PTC level 2.

[0034] When the airflow is at level 4 to 7 and the PTC temperature is ≥ the first preset temperature, the PTC will gradually decrease in level, and the hysteresis range will be set to a predetermined value.

[0035] When the airflow is greater than or equal to level 8 and the PTC temperature is greater than or equal to the second preset temperature, the PTC will gradually decrease in speed, and the hysteresis range will be set to a predetermined value.

[0036] When the airflow changes from OFF to ON, the PTC is delayed in activation; and...

[0037] When the PTC is triggered to shut down, the blower is controlled to shut down with a delay.

[0038] In at least one possible implementation, the PTC protection strategy further includes:

[0039] When the airflow is at level 2 or 3 and the PTC temperature is ≥ the first preset temperature, the PTC is restricted to operate only at the preset PTC level 1, and the hysteresis range is set to a predetermined value.

[0040] The main design concept of this invention is that, after the variable frequency air conditioning compressor of an electric vehicle is allowed to start, an initial compressor speed value is given, and the actual evaporation temperature is collected in real time to determine the temperature change trend. Based on the difference between the actual evaporation temperature and the target evaporation temperature and the temperature change trend, the compressor capacity is compensated and controlled within a predetermined compensation period. This invention makes the compressor speed more reasonable, prevents frequent start-stop of the compressor, and allows the compressor to perform at its optimal level. This improves the accuracy of in-vehicle temperature control, passenger comfort, and system energy efficiency ratio, while effectively reducing the air conditioning's energy consumption and thus improving the vehicle's range.

[0041] Furthermore, the cooling fan can be turned on in advance to protect the compressor through a preset mechanism between the VCU and the air conditioning controller;

[0042] Furthermore, this invention also helps to improve the energy-saving effect of electric vehicle air conditioning systems by optimizing the PTC control strategy. Attached Figure Description

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings, wherein:

[0044] Figure 1 A flowchart of an electric vehicle air conditioning control method provided in an embodiment of the present invention. Detailed Implementation

[0045] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0046] This invention proposes an embodiment of an electric vehicle air conditioning control method, specifically, as follows: Figure 1 As shown, it includes:

[0047] Step S1: After detecting that the AC mode of the air conditioner is activated, determine whether to start the compressor based on preset conditions;

[0048] Step S2: When the compressor is allowed to start, set the initial compressor speed corresponding to the current outside temperature based on the outside temperature.

[0049] Step S3: Based on the first difference between the current actual evaporation temperature and the target evaporation temperature, determine the different stages corresponding to the temperature environment inside the vehicle; wherein, the target evaporation temperature has a preset correspondence with each level of the air conditioning cooling mode;

[0050] Step S4: At different stages, based on the second difference between two actual evaporation temperatures collected sequentially over a preset time period, the compressor speed is compensated, and the compressor speed is controlled to remain within a preset speed range (e.g., 1000-4000 rpm).

[0051] Specifically, the second difference is equal to the actual evaporation temperature collected before the time period minus the actual evaporation temperature at the current moment.

[0052] Furthermore, the first difference and the second difference each encompass multiple temperature ranges.

[0053] Therefore, the compensation compressor speed includes: increasing, decreasing, or maintaining the compressor speed according to the speed change value calibrated for each temperature range corresponding to the second difference.

[0054] Furthermore, the timing of the time period begins upon receiving the compressor speed signal.

[0055] Based on the aforementioned embodiments, the logic of the refrigeration section is as follows:

[0056] The target evaporation temperature for each preset cooling mode can be found in the table below:

[0057] gear 1 2～3 4～5 6～7 8～9 10～11 12～13 14 Target Evaporation 2℃ 3℃ 4℃ 5℃ 6℃ 7℃ 8℃ 9℃

[0058] The initial compressor speed (Ns) can be determined based on the outside temperature (Tamb) using the following table as a reference:

[0059] Tamb (°C) Ns (rpm) Tamb (°C) Ns (rpm) ≥40 4000 25 2000 35 3000 20 1500 30 2500 ≤15 1000

[0060] The corresponding relationships for compressor speed variable frequency control can be found in the table below:

[0061]

[0062] In the table, △T1 = current actual evaporation temperature - target evaporation temperature; △T2 = the actual evaporation temperature collected last time (e.g., 10 seconds ago) - current actual evaporation temperature; and △T1 and △T2 are positive and negative (not absolute values).

[0063] Due to the cost pressure of adding an air outlet temperature sensor to the air conditioning system, this invention calibrates the speed change value, compensation time period, etc. in the above strategy through a large number of environmental chamber simulation tests. In some embodiments, it is preferred to confirm that a 10-second acquisition period is more suitable as the compensation period for the difference in actual evaporation temperature, and the compensation speed can be between 50 and 400 revolutions per minute.

[0064] Regarding the aforementioned preset conditions, these include whether the following conditions are met simultaneously: the blower is on, the outside temperature is ≥0℃, the current actual evaporation temperature is ≥ the preset evaporation protection temperature (e.g., 4℃), the high voltage is powered on, the pressure meets the predetermined pressure protection strategy (e.g., 0.35MPa~2.86MPa), and the VCU sends a condenser fan start signal (FANPWMState, which is provided that the AC is valid and the air conditioner is in non-heating mode or in defrosting mode, and the air conditioner controller requests the VCU to turn on the cooling fan).

[0065] Building upon the preceding text, the control method further includes heating control logic:

[0066] The PTC will be activated when the following conditions are met simultaneously: the blower is turned on, the PTC temperature switch is closed, the PTC temperature is lower than the preset high limit (e.g., 85°C), and the high voltage is powered on.

[0067] After the PTC is turned on, when the PTC temperature rises to the preset high limit and remains there for a set duration (e.g., 5 seconds), the PTC operation is cut off.

[0068] After the PTC is disconnected, it will restart when the PTC temperature drops to the preset restart value (75°C); and,

[0069] When a PTC temperature sensor failure is detected (such as a short circuit or open circuit fault), PTC operation is disabled.

[0070] Furthermore, the heating control logic also includes a PTC protection strategy:

[0071] When the airflow is at level 1 or when a preset power limit message is received (such as 0x258 sending a 1.5KW signal), the PTC is limited to operate only at the preset PTC level 1.

[0072] When the airflow is at level 2 to 3, the PTC status is limited to operate within the preset PTC level 2.

[0073] When the airflow is at level 4 to 7 and the PTC temperature is ≥ the first preset temperature (e.g., 60℃), the PTC will gradually decrease in level, and the hysteresis range will be set to a predetermined value (e.g., 5℃).

[0074] When the airflow is at level 8 or 9 and the PTC temperature is ≥ the second preset temperature (e.g., 65℃), the PTC will gradually decrease in level, and the hysteresis range will be set to a predetermined value (e.g., 5℃).

[0075] When the airflow changes from OFF to ON, the PTC (Power Control Center) is activated with a delay (e.g., a 3-second delay after receiving the PTC activation command); and...

[0076] When the PTC shutdown is triggered, the blower is controlled to shut down with a delay (e.g., the blower is shut down 3 seconds after the PTC shutdown command is issued).

[0077] Based on the above concept, the PTC protection strategy also includes:

[0078] When the airflow is at level 2 or 3 and the PTC temperature is ≥ the first preset temperature, the PTC is restricted to operate only at the preset PTC level 1, and the hysteresis range is set to a predetermined value (e.g., 5℃).

[0079] Understandably, for PTC control in heating mode, it is also preferable to use an environmental chamber for simulation calibration and to use temperature sensors arranged on the PTC surface to confirm its operating level.

[0080] Finally, it can be added that the present invention also includes the following protection strategies for the compressor:

[0081] (1) When the compressor's discharge temperature is ≥ the preset discharge temperature threshold (e.g., 110℃), the compressor is disabled from running, and when the compressor's discharge temperature drops below the preset enable temperature (e.g., 105℃), the compressor is allowed to run; and if the set hysteresis range is met, the compressor's previous state is maintained.

[0082] (2) When the outside temperature is ≤ the preset zero low temperature (-2℃), the compressor is disabled; when the outside temperature is between the zero low temperature and 0℃, the air conditioner is turned off in AC mode first.

[0083] (3) When a preset power limit message is received (e.g., 0x258 sends a 1.5KW signal), the compressor speed is limited to a preset protection speed (e.g., 1800rpm).

[0084] In summary, the main design concept of this invention is that after the variable frequency air conditioning compressor of an electric vehicle is allowed to start, an initial compressor speed value is given, and the actual evaporation temperature is collected in real time to determine the temperature change trend. Based on the difference between the actual evaporation temperature and the target evaporation temperature and the temperature change trend, the compressor capacity is compensated and controlled within a predetermined compensation period. This invention makes the compressor speed more reasonable, prevents frequent start-stop of the compressor, and allows the compressor to perform at its optimal level. This improves the accuracy of in-vehicle temperature control, passenger comfort, and system energy efficiency ratio, while effectively reducing the air conditioning's energy consumption and thus improving the vehicle's range.

[0085] In this embodiment of the invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent the existence of A alone, A and B simultaneously, or B alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, at least one of a, b, and c can represent: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, and c can be single or multiple.

[0086] The above description of the structure, features, and effects of the present invention is based on the embodiments shown in the figures. However, the above are only preferred embodiments of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred methods can be reasonably combined and matched by those skilled in the art to form a variety of equivalent solutions without departing from or changing the design concept and technical effects of the present invention. Therefore, the present invention is not limited to the scope of implementation shown in the figures. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments, that do not exceed the spirit covered by the specification and figures, should be within the protection scope of the present invention.

Claims

1. A method for controlling the air conditioning of an electric vehicle, characterized in that, include: After detecting that the AC mode of the air conditioner is activated, the system determines whether to start the compressor based on preset conditions. These preset conditions include whether the following conditions are met simultaneously: the blower is on, the outside temperature is ≥0℃, the current actual evaporation temperature is ≥ the preset evaporation protection temperature, the high voltage is powered on, the pressure meets the predetermined pressure protection strategy, and the VCU sends a condenser fan start signal. The prerequisite for the condenser fan start signal is that the AC is valid and the air conditioner is in non-heating mode or in defrosting mode. The air conditioner controller requests the VCU to start the cooling fan. When the compressor is allowed to start, the initial compressor speed is set according to the outside temperature, corresponding to the current outside temperature. Based on the first difference between the current actual evaporation temperature and the target evaporation temperature, the different stages corresponding to the temperature environment inside the vehicle are determined; wherein, the target evaporation temperature has a preset correspondence with each level of the air conditioning cooling mode; At different stages, the compressor speed is compensated based on the second difference between two actual evaporation temperatures collected sequentially over a preset time period, and the compressor speed is controlled to remain within a preset speed range. The electric vehicle air conditioning control method also includes one or more of the following PTC protection strategies: When the airflow is at level 1 or when a preset power limit message is received, the PTC is restricted to operate only at the preset PTC level 1. When the airflow is at level 2 to 3, the PTC is limited to operate within the preset PTC level 2. When the airflow is at level 4 to 7 and the PTC temperature is ≥ the first preset temperature, the PTC will gradually decrease in level, and the hysteresis range will be set to a predetermined value. When the airflow is greater than or equal to level 8 and the PTC temperature is greater than or equal to the second preset temperature, the PTC will gradually decrease in speed, and the hysteresis range will be set to a predetermined value. When the airflow changes from OFF to ON, the PTC is delayed in activation; and... When the PTC shutdown is triggered, the blower is controlled to shut down with a delay. Furthermore, the air conditioning control method also includes a compressor protection strategy: When the compressor's discharge temperature is greater than or equal to the preset discharge temperature threshold, the compressor is disabled from operating, and when the compressor's discharge temperature drops below the preset enable temperature, the compressor is allowed to operate; and if the set hysteresis range is met, the compressor remains in its previous state. When the outside temperature is ≤ the preset sub-zero temperature, the compressor is disabled; when the outside temperature is between the sub-zero temperature and 0°C, the air conditioner is turned off in AC mode first. When a preset power limit message is received, the compressor speed is limited to a preset protection speed.

2. The electric vehicle air conditioning control method according to claim 1, characterized in that, The second difference = the actual evaporation temperature collected at the previous moment of the time period - the actual evaporation temperature at the current moment.

3. The electric vehicle air conditioning control method according to claim 2, characterized in that, The timing of the time period begins upon receiving the compressor speed signal.

4. The electric vehicle air conditioning control method according to claim 1, characterized in that, The first difference and the second difference each encompass multiple temperature ranges.

5. The electric vehicle air conditioning control method according to claim 4, characterized in that, The compensation compressor speed includes: increasing, decreasing, or maintaining the compressor speed according to the speed change value calibrated for each temperature range corresponding to the second difference.

6. The electric vehicle air conditioning control method according to any one of claims 1 to 5, characterized in that, The control method also includes heating control logic: The PTC will be activated when the following conditions are met simultaneously: the blower is turned on, the PTC temperature switch is closed, the PTC temperature is lower than the preset high limit, and the high voltage is powered on. After the PTC is turned on, when the PTC temperature rises to the preset high limit and remains there for the set duration, the PTC operation is cut off. After the PTC is disconnected, it will restart when the PTC temperature drops to the preset restart value. as well as, When a PTC temperature sensor failure is detected, PTC operation is disabled.

7. The electric vehicle air conditioning control method according to claim 1, characterized in that, The PTC protection strategy also includes: When the airflow is at level 2 or 3 and the PTC temperature is ≥ the first preset temperature, the PTC is restricted to operate only at the preset PTC level 1, and the hysteresis range is set to a predetermined value.

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