A segmented control method and device for an electric compressor based on a CO2 heat pump system

Abstract

This invention discloses a segmented control method and device for an electric compressor based on a CO2 heat pump system. The method includes: PID control of the compressor speed, using the difference between the target temperature and the actual temperature as input and the compressor speed control quantity as output; real-time acquisition of the difference between the target temperature and the actual temperature for segmented control: in the rapid adjustment phase, the three PID parameters are set relatively large; in the slow adjustment phase, the three PID parameters are set relatively small; in the stable phase, the three PID parameters are set to fixed values; after the actual temperature first reaches the target temperature, the integral and derivative coefficients are adjusted according to the temperature overshoot; finally, the electric compressor of the CO2 heat pump system is controlled according to the compressor speed control quantity. This invention can effectively reduce system overshoot in actual control, enabling the actual temperature to quickly stabilize around the target temperature ±1 degree, and enabling rapid stabilization of the air conditioning vent temperature, improving driving reliability and comfort.

Description

Technical Field

[0001] This invention belongs to the field of compressor control technology, specifically relating to a segmented control method and device for an electric compressor based on a CO2 heat pump system. Background Technology

[0002] Most electric vehicle thermal management systems employ heat pump systems, while the electric compressor plays a crucial role in the overall vehicle control, affecting the safety of the entire electric drive system. Meanwhile, the air conditioning system, responsible for regulating the interior temperature, is also directly related to user comfort.

[0003] In the PID control of compressor speed in a CO2 heat pump system, the temperature response of the system is relatively lagging behind the adjustment speed. This can lead to a situation where the compressor reaches a certain speed, which can actually meet the system requirements. However, due to the slow temperature response, the compressor is still adjusting during the system response process, resulting in a large overshoot in the system. This causes the actual temperature stabilization time of the system to be too long, which is reflected in a larger perceived temperature difference at the air outlet, leading to poor comfort. Summary of the Invention

[0004] The purpose of this invention is to provide a segmented control method and device for an electric compressor based on a CO2 heat pump system, which solves the problem of temperature control overshoot in a CO2 heat pump system that prevents it from stabilizing quickly.

[0005] The technical solution of the present invention is as follows:

[0006] A segmented control method for an electric compressor based on a CO2 heat pump system includes:

[0007] The compressor speed PID control takes the difference between the target temperature and the actual temperature as input and the compressor speed control quantity as output;

[0008] The difference between the target temperature and the actual temperature is acquired in real time for segmented control.

[0009] If the absolute value of the difference exceeds the preset temperature threshold, the CO2 heat pump system enters the rapid adjustment phase; during the rapid adjustment phase, the P, I, and D parameters are set relatively high.

[0010] If the absolute value of the difference does not exceed the preset temperature threshold, the CO2 heat pump system enters the slow adjustment phase; during the slow adjustment phase, the P, I, and D parameters are set relatively low.

[0011] If the absolute value of the difference stabilizes within a first specific range, the CO2 heat pump system enters the stable phase; during the stable phase, the three parameters P, I, and D are set to fixed values, namely K p5 K I5 With KD5 ;

[0012] After the actual temperature reaches the target temperature for the first time, adjust the integral and derivative coefficients according to the temperature overshoot:

[0013] If the temperature overshoot exceeds the preset overshoot threshold, the CO2 heat pump system will experience significant oscillations. The integral and derivative coefficients are set to max(K) and max(K) respectively. I5 K I51 ) and max(K D5 K D51 );

[0014] If the temperature overshoot does not exceed the preset overshoot threshold, the CO2 heat pump system will experience less oscillation and tend to stabilize. The integral and derivative coefficients are set to min(K) respectively. I5 K I53 ) and min(K D5 K D53 );

[0015] If the temperature overshoot stabilizes within the second specific range, the CO2 heat pump system is stable. The integral and derivative coefficients are set to min(K) respectively. I5 K I55 ) and min(K D5 K D55 );

[0016] Among them, K I55 K I53 With K I51 Set the integral coefficient value and K I55 Less than K I53 Less than K I51 K is less than the integral coefficient of the slow adjustment phase. D55 K D53 With K D51 The set value for the differential coefficients and K D55 Less than K D53 Less than K D51 Less than the differential coefficient of the slow adjustment phase;

[0017] The electric compressor of the CO2 heat pump system is controlled based on the compressor speed control value.

[0018] Furthermore, in the rapid adjustment phase and the slow adjustment phase, different P, I, and D parameters are set according to different temperature differences. The larger the temperature difference, the larger the corresponding P, I, and D parameters.

[0019] Furthermore, the first specific range is within 1 degree.

[0020] Furthermore, K p5 K I5 With K D5 All are zero.

[0021] Furthermore, when the CO2 heat pump system experiences large oscillations or small oscillations and tends to be stable, different integral coefficient and derivative coefficient settings are set according to different temperature overshoot amounts. The larger the temperature overshoot amount, the larger the corresponding integral coefficient and derivative coefficient settings.

[0022] Furthermore, the second specific range is within 1 degree.

[0023] A segmented control device for an electric compressor based on a CO2 heat pump system, wherein the device employs any one of the above-described segmented control methods for an electric compressor based on a CO2 heat pump system.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] This invention provides a segmented control method and device for an electric compressor based on a CO2 heat pump system. In actual control, it can effectively reduce system overshoot, quickly stabilize the actual temperature at around ±1 degree of the target temperature, and quickly stabilize the air outlet temperature of the air conditioner, thereby improving driving reliability and comfort. Attached Figure Description

[0026] Figure 1 This is a block diagram of the segmented control method for an electric compressor based on a CO2 heat pump system according to the present invention. Detailed Implementation

[0027] 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. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The compressor of a CO2 heat pump system uses PID control to keep the actual temperature within ±1 degree of the target temperature. However, actual testing revealed a large overshoot after the system response, resulting in significant temperature fluctuations and a long system stabilization time. To reduce overshoot and enable rapid system stabilization, this invention proposes a segmented control method and device for the electric compressor of a CO2 heat pump system. This method effectively reduces system overshoot in actual control, quickly stabilizing the actual temperature to around ±1 degree of the target temperature, and rapidly stabilizing the air conditioning vent temperature, thereby improving driving reliability and comfort.

[0029] To reduce system overshoot to a certain extent, this invention provides a segmented control method for an electric compressor based on a CO2 heat pump system. In the actual PID control of the compressor, a variable parameter adjustment method is used, such as... Figure 1As shown, the specific method is as follows:

[0030] 1. The compressor speed PID control uses the difference between the target temperature and the actual temperature as input and the compressor speed control quantity as output.

[0031] 2. The temperature difference between the target temperature and the actual temperature is first input to the PID parameter selector to select appropriate PID control parameters; the internal parameters of the PID parameter selector are as follows:

[0032] During the system response phase, the temperature difference should reasonably consider the actual system temperature difference and adjustment requirements, and the specific temperature difference values ​​in Table 1, T1-T, should be set accordingly. n It should cover the temperature difference distribution of the adjusted operating conditions. The three parameters P, I, and D should be set relatively large when the temperature difference is large, and the system enters the rapid adjustment stage; when the temperature difference is small, the parameter settings should be relatively small, and the system enters the slow adjustment stage; when the temperature difference is stable within ±1 degree or ±2 degrees for a period of time, the parameters should be set to fixed values, and even the system PID can stop adjusting.

[0033] Table 1 Internal Parameters of the PID Parameter Selector

[0034]

[0035] In the table, the left side represents the heating condition, and the right side represents the cooling condition. On the left, the temperature difference is positive from the rapid adjustment phase to the stable phase; on the right, the temperature difference is negative from the rapid adjustment phase to the stable phase. When the absolute value of the temperature difference exceeds the preset temperature threshold, for example, above 5 degrees Celsius, the P, I, and D parameters are set relatively high, and the system enters the rapid adjustment phase. Once the absolute value of the temperature difference falls below 5 degrees Celsius, the system enters the slow adjustment phase, and the P, I, and D parameters are set relatively low. When the absolute value of the temperature difference stabilizes within 1 degree Celsius, that is, when the difference between the target temperature and the actual temperature remains within ±1 degree Celsius for a period of time, it indicates that the system has entered the stable phase. In the stable phase, the P, I, and D parameters are set to fixed values, each set to K. p5 K I5 With K D5 Even PID can stop adjustment, i.e., K p5 K I5 With K D5 All values ​​are set to zero. The rapid adjustment and slow adjustment phases can be configured with different P, I, and D parameters based on varying temperature differences; the larger the temperature difference, the larger the corresponding P, I, and D parameters.

[0036] It should be noted that the steady-state phase has higher priority than the slow-adjustment phase. That is, even if the absolute value of the temperature difference in the steady-state phase also meets the conditions for the slow-adjustment phase, the PID parameters set in the steady-state phase should be used first.

[0037] 3. The system response time was optimized using the above PID parameters. To ensure rapid system stabilization, after the system response first reaches the target temperature, the integral and derivative coefficients were adjusted based on the overshoot using a lookup table. As shown in Table 2, when the system overshoot is too large, the system enters a period of significant oscillation, so the integral and derivative coefficients are increased; when the oscillation is small and the system tends to stabilize, the integral and derivative coefficients are decreased. The specific coefficient selection is handled as follows:

[0038] During periods of significant system oscillation, the temperature difference T 51 : max(K I5 K I51 ),max(K D5 K D51 )

[0039] During periods of significant system oscillation, the temperature difference T 52 : max(K I5 K I52 ),max(K D5 K D52 )

[0040] The system oscillations are stabilizing, and the temperature difference T 53 min(K) I5 K I53 ),min(K D5 K D53 )

[0041] The system oscillations are stabilizing, and the temperature difference T 54 min(K) I5 K I54 ),min(K D5 K D54 )

[0042] The system has stabilized, temperature difference T 55 min(K) I5 K I55 ),min(K D5 K D55 )

[0043] Table 2. Lookup table for integral and differential coefficients

[0044]

[0045] After the actual temperature reaches the target temperature for the first time, the integral and derivative coefficients are first looked up in Table 2. If the temperature overshoot exceeds the preset overshoot threshold, such as 3 degrees, it is considered a large oscillation. Then, based on the overshoot temperature difference, the corresponding integral and derivative coefficients are looked up in Table 2, and compared with the integral and derivative coefficients in the steady-state phase to determine the final integral and derivative coefficients. The larger the temperature overshoot, the larger the corresponding integral coefficient setting value and derivative coefficient setting value. In Table 2, K... I55K I53 With K I51 Set the integral coefficient value and K I55 Less than K I53 Less than K I51 K is less than the integral coefficient of the slow adjustment phase. D55 K D53 With K D51 The set value for the differential coefficients and K D55 Less than K D53 Less than K D51 It is less than the differential coefficient of the slow adjustment phase.

[0046] If the temperature overshoot remains within 1 degree for a period of time, the CO2 heat pump system is considered stable.

[0047] It should be noted that system stability has a higher priority than the relatively small and stable oscillation of CO2 heat pump systems. For systems with large oscillations or those that are trending towards stability, different integral and derivative coefficients can be set according to different temperature differences.

[0048] Steps 2 and 3 are used in combination. Step 2 enables the system to respond quickly, while step 3 focuses on adjusting the integral and derivative components, with the proportional component as a secondary component, to make the system quickly and stably stable.

[0049] Typically, a CO2 heat pump system first enters a rapid adjustment phase, then a slow adjustment phase, then the actual temperature reaches the target temperature for the first time, and finally enters a stable phase.

[0050] The present invention also provides a segmented control device for an electric compressor based on a CO2 heat pump system, wherein the device adopts the segmented control method for an electric compressor based on a CO2 heat pump system described in any one of the above.

[0051] The actual verification results of this invention are as follows:

[0052] The response time and settling time for each operating condition before using this method are shown in Table 1.

[0053] Table 1 Response time and stabilization time for each operating condition

[0054]

[0055] After using this method:

[0056] In operating condition 1, the actual water temperature response speed is maintained within 2 minutes, and the deviation after stabilization is within ±1℃.

[0057] In operating condition 2, the water temperature response speed is maintained within 2 minutes, and the maximum deviation after stabilization is within ±1℃.

[0058] In operating condition 3, the water temperature response speed is maintained within 2 minutes, and the maximum deviation after stabilization is within ±1℃.

[0059] As can be seen from the above, the system overshoot and settling time have been significantly improved.

[0060] In summary, the segmented control method and device for an electric compressor based on a CO2 heat pump system of the present invention aims to solve the problem of the system's inability to quickly stabilize due to overshoot in the actual control of the CO2 heat pump system compressor. It is highly practical, has good control effect, and the compressor control can meet the comfort requirements of the air conditioning temperature in the passenger cabin.

[0061] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0062] Those skilled in the art will readily understand that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A segmented control method for an electric compressor based on a CO2 heat pump system, characterized in that, include: The compressor speed PID control takes the difference between the target temperature and the actual temperature as input and the compressor speed control quantity as output; The difference between the target temperature and the actual temperature is acquired in real time for segmented control. If the absolute value of the difference exceeds the preset temperature threshold, the CO2 heat pump system enters the rapid adjustment phase; during the rapid adjustment phase, the P, I, and D parameters are set relatively high. If the absolute value of the difference does not exceed the preset temperature threshold, the CO2 heat pump system enters the slow adjustment phase; during the slow adjustment phase, the P, I, and D parameters are set relatively low. If the absolute value of the difference value is stabilized in the first specific range, the CO2 heat pump system enters a stable stage; in the stable stage, the P, I and D three parameters are set to fixed values, respectively K p5 , K I5 and K D5 ; After the actual temperature reaches the target temperature for the first time, adjust the integral and derivative coefficients according to the temperature overshoot: If the temperature overshoot exceeds the preset overshoot threshold, the CO2 heat pump system has a larger oscillation, and the integral and differential coefficients are set as max(K I5 , K I51 ) and max(K D5 , K D51 ), respectively. If the temperature overshoot does not exceed the preset overshoot threshold, the CO2 heat pump system will experience less oscillation and tend to stabilize. The integral and derivative coefficients are set to min(K) respectively. I5 K I53 ) and min(K D5 K D53 ); If the temperature overshoot stabilizes within the second specific range, the CO2 heat pump system is stable. The integral and derivative coefficients are set to min(K) respectively. I5 K I55 ) and min(K D5 K D55 ); Among them, K I55 K I53 With K I51 Set the integral coefficient value and K I55 Less than K I53 Less than K I51 K is less than the integral coefficient of the slow adjustment phase. D55 K D53 With K D51 The set value for the differential coefficients and K D55 Less than K D53 Less than K D51 Less than the differential coefficient of the slow adjustment phase; The electric compressor of the CO2 heat pump system is controlled based on the compressor speed control value.

2. The segmented control method for an electric compressor based on a CO2 heat pump system according to claim 1, characterized in that, During the rapid adjustment phase and the slow adjustment phase, different P, I, and D parameters are set according to different temperature differences. The larger the temperature difference, the larger the corresponding P, I, and D parameters.

3. The segmented control method for an electric compressor based on a CO2 heat pump system according to claim 1, characterized in that, The first specific range is within 1 degree.

4. The segmented control method for an electric compressor based on a CO2 heat pump system according to claim 1, characterized in that, K p5 K I5 With K D5 All are zero.

5. The segmented control method for an electric compressor based on a CO2 heat pump system according to claim 1, characterized in that, When the CO2 heat pump system experiences large fluctuations or small fluctuations and tends to be stable, different integral coefficient and derivative coefficient settings are set according to different temperature overshoot amounts. The larger the temperature overshoot, the larger the corresponding integral coefficient and derivative coefficient settings.

6. The segmented control method for an electric compressor based on a CO2 heat pump system according to claim 1, characterized in that, The second specific range is within 1 degree.

7. A segmented control device for an electric compressor based on a CO2 heat pump system, characterized in that, The device employs the segmented control method for an electric compressor based on a CO2 heat pump system as described in any one of claims 1 to 6.

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