Refrigeration energy-saving method of vehicle-mounted refrigerator

Abstract

The invention relates to the field of cold-chain logistics refrigeration, discloses a refrigeration energy-saving method for a vehicle-mounted refrigerator, and aims to solve the problems that an existing vehicle-mounted refrigerator is high in energy consumption and lagged in temperature control response in the cold-chain transportation process. According to the method, the compartment temperature T is collected in real time through the frequency larger than or equal to 1 Hz, a dynamic double-threshold setting strategy is combined, the refrigeration starting and stopping threshold value is dynamically adjusted according to the compartment temperature change, and precise regulation and control of the refrigeration process are achieved. Compared with a traditional fixed threshold value control mode, the method can effectively reduce the operation energy consumption of the refrigerator, improve the temperature control stability and prolong the service life of the refrigerator, and is suitable for vehicle-mounted refrigerator systems in various cold chain transportation scenes.

Description

Technical Field

[0001] This invention relates to the field of cold chain logistics refrigeration technology, and specifically to a refrigeration energy-saving method for a vehicle-mounted refrigeration unit. Background Technology

[0002] In the cold chain logistics sector, onboard refrigeration units are core equipment for maintaining the temperature stability of transport compartments, especially for temperature-sensitive goods such as fresh food, pharmaceuticals, and chemical reagents. Their temperature control performance directly determines the quality and safety of transportation. Currently, most mainstream onboard refrigeration units adopt a "start-stop" control strategy. Their operating mechanism relies on real-time monitoring by high-precision temperature sensors: when the sensor detects that the compartment temperature reaches the upper limit of a preset threshold, the refrigeration compressor immediately stops running; after the temperature gradually rises and exceeds the lower limit of the set threshold, the system restarts the refrigeration unit. This control method is simple in structure and low in cost, and has been widely used for a long time.

[0003] While variable frequency drive (VFD) technology is quite mature in the residential and commercial air conditioning sectors, achieving smooth temperature regulation and significant energy savings, its design and optimization are based on a relatively stable indoor environment. Directly transplanting it to the vehicle-mounted cold chain transportation scenario presents several adaptation challenges. Vehicles face complex and ever-changing external environments during operation, including frequent starts and stops, changes in road gradients, fluctuations in external temperature, and cold air loss due to door opening and closing, all of which demand dynamic response capabilities from the temperature control system. More importantly, due to the inherent heat dissipation inertia of the refrigeration unit, when the temperature reaches the set shut-off point, the compressor's refrigeration cycle does not immediately stop; some residual cold air continues to be released, causing the interior temperature to drop excessively, even below the permissible lower limit. During shutdown, due to factors such as cargo heat capacity, external heat conduction, and air convection, temperature recovery is often slow, resulting in a delayed refrigeration unit restart. This mechanism causes the actual interior temperature to fluctuate significantly and frequently around the set value, often reaching ±2℃ or even higher, making it difficult to meet the high-precision constant temperature transportation requirements within ±℃C for goods such as vaccines, high-end reagents, and precision chemicals.

[0004] Furthermore, frequent start-stop operations lead to significant energy waste and equipment wear. Each restart requires the compressor to accelerate from a standstill to its rated speed, and the motor draws 5-7 times the current during smooth operation, causing a surge in energy loss. Statistics show that the extra energy consumption during start-stop can account for more than 30% of the total system energy consumption, reducing the vehicle's range and placing higher demands on the battery capacity of new energy cold chain transport vehicles. Simultaneously, the compressor, drive motor, and electromagnetic clutch are subjected to significant current surges and mechanical stress during each start-stop cycle, accelerating bearing wear, winding aging, and valve fatigue, resulting in a 30% to 40% reduction in the average lifespan of core components. This not only increases the frequency of routine equipment maintenance and parts replacement but also increases the risk of cargo damage during transport due to refrigeration unit failure, negatively impacting both the reliability and economy of the entire cold chain. Summary of the Invention

[0005] The present invention aims to provide a cooling and energy-saving method for vehicle-mounted refrigeration units, in order to solve the problems of large temperature fluctuations, excessive energy consumption and short equipment life caused by the start-stop control of existing vehicle-mounted refrigeration units.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a refrigeration energy-saving method for an on-board refrigeration unit, comprising the following steps: In the real-time data acquisition step, the real-time temperature T of the compartment is periodically sampled by a temperature sensor, with the sampling frequency set to 1-5Hz; Calculate temperature error and rate of change: First, calculate the temperature error e = T - T_set, where T_set is the set target temperature; when e > 0, it indicates that cooling is required; when e ≤ 0, it indicates that the temperature is within the target range or too low. In the dynamic threshold setting step, the thresholds for cooling start and stop are dynamically adjusted based on the temperature error e and the rate of change v; cooling is started when e > e_dynamic and v > v_threshold, where e_dynamic is adaptively calculated based on historical temperature fluctuations and v_threshold is set based on changes in ambient temperature. In the parameter adaptive mechanism step, the control parameters of the refrigeration unit are adaptively adjusted based on the temperature error e and the rate of change v.

[0007] The principles and advantages of this solution are as follows: In practical applications, this method accurately acquires the dynamic changes in the cabinet temperature at a frequency of 1~5 Hz through a real-time data acquisition step. Combined with the temperature change rate processed by moving average filtering (window length of 2~5 seconds), it provides reliable status input for subsequent control. The dynamic threshold setting step is based on the linear correction relationship between the root mean square value (RMS) of the temperature error over the past 12 hours and the current ambient temperature, adaptively adjusting the cooling start-stop conditions, effectively avoiding misjudgments caused by environmental fluctuations in traditional fixed thresholds. The parameter adaptive mechanism finely adjusts the compressor operating frequency (20%~95% of rated frequency) and condenser fan speed (low / medium / high speed) according to the combination of temperature error and its rate of change, achieving on-demand cooling supply. The energy consumption optimization feedback step evaluates the ratio of energy consumption to the time it takes for the temperature to reach the target every hour. If this value exceeds the historical average by 15%, the threshold correction coefficient and the minimum compressor operating frequency are iteratively optimized to continuously improve energy efficiency. Compared with traditional start-stop control, this method effectively suppresses excessive temperature drop and restart lag caused by residual cooling. By employing dynamic threshold and rate-of-change feedforward control, the temperature fluctuation range is compressed from the traditional ±2℃~±4℃ to ±0.5℃, meeting the high-precision temperature control requirements of fresh food, pharmaceuticals, and other products, and conforming to industry standards. Simultaneously, the number of compressor start-stop cycles is reduced by more than 30%, avoiding losses caused by starting current surges, and improving energy efficiency by 20%~25%.

[0008] Preferably, as an improvement, in the calculation of temperature error and rate of change, the rate of temperature change v = dT / dt is calculated, and a moving average filter is used to eliminate noise, with the window length set to 2-5 seconds; when v < 0, it indicates that the temperature is decreasing, where the larger |v| is, the faster the temperature decreases.

[0009] Preferably, as an improvement, in the dynamic threshold setting step, the adaptive calculation method of e_dynamic is as follows: take the root mean square value of the body temperature error in the past 12 hours multiplied by 0.4 as the initial reference value, and then combine it with the current ambient temperature T_env for linear correction. The correction formula is e_dynamic = initial reference value × (1 + 0.02 × (T_env - 25℃)), where T_env is the real-time outside temperature of the vehicle collected by the ambient temperature sensor.

[0010] Preferably, as an improvement, the adjustment rules for the control parameters in the parameter adaptive mechanism step are as follows: when the temperature error e ≥ 1.5 × e_dynamic and the rate of change v ≥ v_threshold, the compressor operating frequency is adjusted to 85%-95% of the rated frequency, and the condenser fan speed is set to the highest level; when 0.5 × e_dynamic ≤ e < 1.5 × e_dynamic and v < 0, the compressor operating frequency is reduced to 40%-60% of the rated frequency, and the condenser fan speed is switched to the medium level; when e < 0.5 × e_dynamic, the compressor operating frequency is maintained at 20%-30% of the rated frequency, and the condenser fan speed is maintained at the low level.

[0011] Preferably, as an improvement, it also includes an energy consumption optimization feedback step, which calculates the ratio of the cumulative energy consumption of the refrigeration unit to the time when the temperature of the compartment reaches the standard every hour. If the ratio is higher than 15% of the historical average, the correction coefficient of the dynamic threshold e_dynamic is reduced by 5% in the next cycle, and the minimum operating frequency of the compressor is reduced by 5%.

[0012] Preferably, as an improvement, the ambient temperature sensor is installed inside the front grille of the vehicle, the sampling frequency is the same as that of the body temperature sensor, the collected data is also processed by moving average filtering, and the window length is the same as the window length used to calculate the body temperature change rate.

[0013] Preferably, as an improvement, when the vehicle is traveling at high speed (vehicle speed ≥ 60km / h), the condenser fan speed is increased by one level from the original level, using the airflow generated by the vehicle to enhance the heat dissipation effect and reduce the compressor load.

[0014] Preferably, as an improvement, in the temperature error and rate of change calculation step, when v<0, it indicates that the temperature of the compartment is decreasing, and the larger |v| is, the faster the temperature decreases; when e>0, refrigeration regulation needs to be started, and when e≤0, the current state is maintained or refrigeration is stopped. Preferably, as an improvement, in the dynamic threshold setting step, the adaptive calculation method of e_dynamic is as follows: take the root mean square value of the body temperature error in the past 12 hours multiplied by 0.4 as the initial reference value, and perform linear correction in combination with the current ambient temperature T_env. The correction formula is e_dynamic = initial reference value × (1 + 0.02 × (T_env - 25℃)), where T_env is the real-time ambient temperature outside the vehicle. Preferably, as an improvement, in the parameter adaptive adjustment step, the control parameter adjustment rule is as follows: when e ≥ 1.5 × e_dynamic and v ≥ v_threshold, the compressor operating frequency is adjusted to 85%-95% of the rated frequency, and the condenser fan speed is set to the highest level; when 0.5 × e_dynamic ≤ e < 1.5 × e_dynamic and v < 0, the compressor frequency is reduced to 40%-60% of the rated frequency, and the fan speed is switched to the medium level; when e < 0.5 × e_dynamic, the compressor frequency is maintained at 20%-30% of the rated frequency, and the fan speed is maintained at the low level. Detailed Implementation

[0015] The following detailed description illustrates the specific implementation method: The specific implementation steps are as follows: A vehicle-mounted refrigeration energy-saving method includes the following steps: During the real-time data acquisition phase, the real-time temperature T of multiple measuring points inside the chamber is periodically sampled at a frequency of 1~5Hz using a high-precision digital temperature sensor and transmitted to the central controller for unified processing. Calculate temperature error and rate of change: The system calculates the temperature error e = T - T_set (where T_set is the target temperature set by the user) in real time. When e > 0, it indicates that cooling needs to be started. When e ≤ 0, it indicates that the temperature has reached or fallen below the set value. At the same time, the system calculates the rate of change of temperature v = dT / dt based on continuous sampling values ​​to determine the dynamic trend of temperature. During the dynamic threshold setting phase, the system dynamically adjusts the cooling start / stop threshold based on the real-time temperature error e and the rate of change v: cooling is activated when e > e_dynamic and v > v_threshold. e_dynamic is adaptively calculated based on the statistical characteristics of the temperature error over the past 12 hours, while v_threshold is set in segments based on the real-time collected ambient temperature outside the vehicle to improve adaptability to operating conditions. In the parameter adaptive mechanism stage, based on the real-time values ​​and trends of temperature error e and rate of change v, the key control parameters of the refrigeration unit are adaptively adjusted, including the compressor operating frequency and the condenser fan speed, to achieve dynamic energy matching.

[0016] This method captures the temperature gradient distribution and dynamic changes within the enclosure in real time through high-frequency sampling of 1-5Hz. Combined with the temperature change rate after being filtered by a moving average over a 2-5 second time window, it effectively suppresses measurement noise and provides reliable input for control decisions. The dynamic threshold e_dynamic is iteratively adjusted based on the linear correction relationship between the root mean square (RMS) value of the temperature error over the past 12 hours and the ambient temperature T_env. Specifically, it is calculated as: e_dynamic = RMS(e_hist) × 0.4 × [1 + 0.02 × (T_env - 25)], where RMS(e_hist) is the root mean square value of the historical error, and T_env is the real-time outside temperature. This design significantly improves the system's robustness to ambient temperature fluctuations, avoiding frequent false starts and stops caused by traditional fixed threshold control under diurnal temperature variations or regional climate changes.

[0017] The parameter adaptive mechanism divides the control process into multiple operating ranges based on the magnitude and direction of e and v, and accordingly finely adjusts the compressor frequency (continuously adjustable within 20%~95% of the rated value) and condenser fan speed (adjustable in low, medium, and high settings) to achieve precise matching between cooling output and load demand. During the energy consumption optimization feedback phase, the system evaluates the ratio η = E / t of the actual energy consumption E to the time t it takes for the temperature to reach the target every hour. If η exceeds 15% of the average value over the past 24 hours, it automatically iteratively optimizes the correction coefficient of e_dynamic and the minimum operating frequency limit of the compressor, gradually improving the energy efficiency ratio.

[0018] Compared to traditional start-stop control methods, this method effectively suppresses temperature overshoot and restart lag caused by residual cooling after shutdown by introducing rate-of-change feedforward and dynamic threshold setting. Practical applications show that this method can reduce internal temperature fluctuations from ±2℃~±4℃ under traditional control to within ±0.5℃, making it particularly suitable for transporting temperature-sensitive high-value goods such as fresh food and pharmaceuticals. Simultaneously, the number of compressor start-stop cycles is reduced by more than 30%, avoiding current surges and mechanical wear caused by frequent starts, and improving the overall energy efficiency of the system by 20%~25%.

[0019] The temperature change rate v is calculated by the difference between adjacent sampled values ​​and then filtered by a 2-5 second moving average to suppress noise: v < 0 indicates that the temperature is in the process of decreasing, and the larger the |v|, the faster the cooling rate. v_threshold is set in segments according to T_env: it is set to 0.3°C / min when T_env < 20°C, 0.5°C / min between 20°C and 35°C, and increased to 0.7°C / min when T_env > 35°C to cope with high temperature and high load conditions.

[0020] The parameter adjustment rules are based on a comparison between the current temperature error e and the dynamic error threshold e_dynamic, as well as the state of variable v. The specific rules are as follows: - When e is greater than or equal to 1.5 times e_dynamic and v reaches or exceeds the threshold v_threshold, the compressor frequency is adjusted to 85% to 95% and the fan is set to the highest speed to achieve rapid cooling. - When e is between 0.5 times e_dynamic and 1.5 times e_dynamic, and v is less than 0, the compressor frequency is adjusted to 40% to 60%, and the fan is set to medium speed to balance energy consumption and cooling effect. - When e is less than 0.5 times e_dynamic, the compressor frequency is adjusted to 20% to 30%, and the fan is set to low speed to maintain a stable low temperature. The energy consumption optimization feedback mechanism calculates the ratio of energy consumption to the time the temperature meets the target every hour, and this ratio is used to evaluate the system's energy efficiency. If the ratio is higher than 15% of the historical average, the correction coefficient of e_dynamic will be reduced by 5% in the next control cycle, and the minimum operating frequency of the compressor will also be reduced by 5%, thereby optimizing the overall energy consumption performance. An ambient temperature sensor is installed inside the vehicle's front grille to accurately measure the external ambient temperature. Its sampling frequency is consistent with that of the sensors inside the compartment, and all collected data undergoes a moving average filter with the same window size to ensure data smoothness and reliability, and reduce noise interference. When the vehicle speed reaches or exceeds 60km / h, the system will automatically increase the condenser fan speed by one level, using the airflow generated during driving to enhance the heat dissipation effect, improve cooling efficiency, and meet the heat dissipation requirements under high-speed driving conditions. The core innovation of this solution lies in proactively reducing the compressor's operating speed before the temperature approaches the set value, allowing the temperature curve to smoothly approach the target value. Once the target is reached, dynamic adjustments to low-speed operation maintain temperature stability. Unlike the fixed-parameter PID control commonly used in household air conditioners, this solution employs ΔT_high as a dynamic threshold, combined with a feedforward compensation mechanism, effectively addressing the control challenges posed by heat dissipation inertia in vehicle environments. While household air conditioner algorithms typically shut down completely when the error e is zero, this solution maintains the compressor's minimum operating frequency f_min greater than zero even when the error e is less than or equal to ΔT_low. This prevents temperature rebound due to cold chain heat leakage, ensuring the accuracy and continuity of temperature control.

[0021] ADTRF algorithm flow (setting the target temperature T_set, e.g., -2℃): 1. Real-time data acquisition: ≥1Hz sampling chamber temperature T 2. Calculation error: e = T - T_set (e > 0 requires cooling, e ≤ 0 meets the standard) 3. Calculate the rate of change: v = dT / dt (after a 2-5 second sliding filter). When v < 0, the larger |v| is, the faster the cooling rate. 4. Dynamic dual threshold setting: ΔT_high = 0.5 × |v| + 1.0 ΔT_low = 0.2 × |v| + 0.2 (Example: When |v|=0.5℃ / min, ΔT_high=1.25℃, ΔT_low=0.3℃) Variable frequency control logic: - Rapid cooling zone (e>ΔT_high): Compressor f_max is running - Smooth approach region (ΔT_low) <e≤ΔT_high): Frequency f = linear interpolation dynamic adjustment Where f_min is the minimum sustaining frequency (e.g., 15Hz) to ensure basic cooling capacity.

[0022] Feedforward compensation: When v < -0.3℃ / min, f × attenuation factor α = 1 - (|v| - 0.3) / 1.0 (α ∈ [0.7, 1.0]) - Stable maintenance region (e≤ΔT_low): When e > 0: f = f_min + 5 × e When e≤0: f=f_min×(1+0.1×|e|) Parameter Adaptation: Threshold parameters are optimized every 5 minutes based on historical data. k_high is increased when the standard deviation of temperature fluctuation is >0.8℃, and k_low is decreased when it is <0.3℃. Parameter reset is triggered by GPS and door signals to adapt to sudden environmental changes.

[0023] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention. In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for energy-saving refrigeration of an on-board refrigeration unit, characterized in that, Includes the following steps: In the real-time data acquisition step, the real-time temperature T of the compartment is periodically sampled by a temperature sensor, with the sampling frequency set to 1-5Hz; Calculate temperature error and rate of change: First, calculate the temperature error e = T - T_set, where T_set is the set target temperature; when e > 0, it indicates that cooling is required; when e ≤ 0, it indicates that the temperature is within the target range or too low. In the dynamic threshold setting step, the thresholds for cooling start and stop are dynamically adjusted based on the temperature error e and the rate of change v; cooling is started when e > e_dynamic and v > v_threshold, where e_dynamic is adaptively calculated based on historical temperature fluctuations and v_threshold is set based on changes in ambient temperature. In the parameter adaptive mechanism step, the control parameters of the refrigeration unit are adaptively adjusted based on the temperature error e and the rate of change v.

2. The energy-saving refrigeration method for a vehicle-mounted refrigeration unit according to claim 1, characterized in that: In the calculation of temperature error and rate of change, the rate of temperature change v = dT / dt is calculated, and a moving average filter is used to eliminate noise. The window length is set to 2-5 seconds. When v < 0, it indicates that the temperature is decreasing. The larger |v| is, the faster the temperature decreases.

3. The energy-saving refrigeration method for a vehicle-mounted refrigeration unit according to claim 1, characterized in that: In the dynamic threshold setting step, the adaptive calculation method of e_dynamic is as follows: take the root mean square value of the body temperature error in the past 12 hours, multiply it by 0.4 as the initial reference value, and then combine it with the current ambient temperature T_env for linear correction. The correction formula is e_dynamic = initial reference value × (1 + 0.02 × (T_env - 25℃)), where T_env is the real-time outside temperature of the vehicle collected by the ambient temperature sensor.

4. The energy-saving refrigeration method for a vehicle-mounted refrigeration unit according to claim 1, characterized in that: In the parameter adaptive mechanism step, the adjustment rules for the control parameters are as follows: when the temperature error e ≥ 1.5 × e_dynamic and the rate of change v ≥ v_threshold, the compressor operating frequency is adjusted to 85%-95% of the rated frequency, and the condenser fan speed is set to the highest level; when 0.5 × e_dynamic ≤ e < 1.5 × e_dynamic and v < 0, the compressor operating frequency is reduced to 40%-60% of the rated frequency, and the condenser fan speed is switched to the medium level; when e < 0.5 × e_dynamic, the compressor operating frequency is maintained at 20%-30% of the rated frequency, and the condenser fan speed is maintained at the low level.

5. The energy-saving refrigeration method for an on-board refrigeration unit according to claim 1, characterized in that: It also includes an energy consumption optimization feedback step, which calculates the ratio of the cumulative energy consumption of the refrigeration unit to the time it takes for the temperature of the compartment to reach the standard every hour. If the ratio is higher than 15% of the historical average, the correction coefficient of the dynamic threshold e_dynamic will be reduced by 5% in the next cycle, and the minimum operating frequency of the compressor will be reduced by 5%.

6. The energy-saving refrigeration method for a vehicle-mounted refrigeration unit according to claim 3, characterized in that: The ambient temperature sensor is installed inside the front grille of the vehicle. Its sampling frequency is the same as that of the body temperature sensor. The collected data is also processed by moving average filtering. The window length is the same as that used to calculate the body temperature change rate.

7. The energy-saving refrigeration method for a vehicle-mounted refrigeration unit according to claim 4, characterized in that: When the vehicle is traveling at high speed (≥60km / h), the condenser fan speed is increased by one level from the original setting to enhance the heat dissipation effect by utilizing the airflow generated by the vehicle's movement, thereby reducing the compressor load.

8. The energy-saving method for vehicle-mounted refrigeration according to claim 1, characterized in that: In the temperature error and rate of change calculation steps, when v < 0, it indicates that the temperature of the compartment is decreasing, and the larger |v| is, the faster the temperature decreases; when e > 0, refrigeration regulation needs to be started, and when e ≤ 0, the current state is maintained or refrigeration is stopped. The vehicle-mounted refrigeration energy-saving method according to claim 1 is characterized in that: In the dynamic threshold setting step, the adaptive calculation method of e_dynamic is as follows: take the root mean square value of the body temperature error in the past 12 hours, multiply it by 0.4 as the initial reference value, and perform linear correction in combination with the current ambient temperature T_env. The correction formula is e_dynamic = initial reference value × (1 + 0.02 × (T_env - 25℃)), where T_env is the real-time ambient temperature outside the vehicle. The vehicle-mounted refrigeration energy-saving method according to claim 1 is characterized in that: In the parameter adaptive adjustment step, the control parameter adjustment rules are as follows: when e ≥ 1.5 × e_dynamic and v ≥ v_threshold, the compressor operating frequency is adjusted to 85%-95% of the rated frequency, and the condenser fan speed is set to the highest level; when 0.5 × e_dynamic ≤ e < 1.5 × e_dynamic and v < 0, the compressor frequency is reduced to 40%-60% of the rated frequency, and the fan speed is switched to the medium level; when e < 0.5 × e_dynamic, the compressor frequency is maintained at 20%-30% of the rated frequency, and the fan speed is maintained at the low level.

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