Variable frequency compressor stop control method and system

Abstract

The present application mainly relates to the technical field of variable frequency compressor, in order to solve the problem that the over-temperature and over-flow control of variable frequency compressor is not accurate, the noise is high, the vibration is large and the compressor is easily damaged during shutdown process, the present application provides a variable frequency compressor shutdown control method and system, first, according to the actual operation condition of the variable frequency compressor, the flexible regulation and control of the running speed of the variable frequency compressor is realized through the current limiting variable speed control module and the temperature segmented control module in turn, then the stable speed control module is adopted, so that the variable frequency compressor is stably operated at the optimal shutdown speed corresponding to the best vibration performance before shutdown, finally, the fixed angle shutdown module is adopted to realize that according to the load characteristics of the variable frequency compressor, the electric angle of the permanent magnet synchronous motor of the variable frequency compressor is adjusted to be at the position of the minimum load torque in a mechanical rotation cycle during shutdown, thereby reducing the shutdown vibration of the variable frequency compressor.

Description

Technical Field

[0001] This invention relates to the field of variable frequency compressor technology, and in particular to a method and system for controlling the shutdown of a variable frequency compressor. Background Technology

[0002] Permanent magnet synchronous motors (PMSMs) combine the advantages of AC motors—simple structure, small size, no mechanical commutator, and easy maintenance—with the benefits of high torque density and reliable operation, making them widely used in refrigerator compressors. However, in actual refrigerator matching processes, the harsh operating environment and conditions of PMSMs directly impact the shutdown performance of variable frequency compressors, affecting refrigerator energy consumption and noise matching tests. Therefore, improving the shutdown performance of variable frequency compressors has become a pressing issue. Summary of the Invention

[0003] The technical problem to be solved by this invention:

[0004] This invention provides a method and system for controlling the shutdown of a variable frequency compressor, which solves the problems of inaccurate over-temperature and over-current control, high noise, large vibration, and easy damage to the compressor during the shutdown process.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] The variable frequency compressor shutdown control method includes:

[0007] Step 1: Determine if the appliance temperature T1 has reached the shutdown temperature T2; if yes, proceed to step 5; otherwise, proceed to step 2.

[0008] Step 2, Current-limiting speed control: Determine the average value of the three-phase current of the variable frequency compressor. Is it greater than or equal to the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 3; otherwise, proceed to step 4.

[0009] Step 3: Reduce the speed of the variable frequency compressor. When the speed of the variable frequency compressor drops to its minimum value, determine the average value of the three-phase current of the variable frequency compressor. Is it less than the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 1; otherwise, proceed to step 5.

[0010] Step 4, Temperature Segmentation Control: By comparing the device temperature T of the intelligent power module with its over-temperature threshold... To control the speed of the variable frequency compressor; Proceed to step 1; if Proceed to step 5;

[0011] Step 5, Speed ​​control: Adjust the speed of the variable frequency compressor to the optimal shutdown speed. When the variable frequency compressor reaches its optimal shutdown speed If the running time t is greater than the set value, proceed to step 6; wherein, the optimal stopping speed is... The rotational speed at which the vibration performance of the variable frequency compressor is optimal during stable operation;

[0012] Step 6, Fixed Angle Stop Control: Compare the electrical angle of the variable frequency compressor's permanent magnet synchronous motor. Its optimal shutdown angle ,when and When the difference reaches a set value, the variable frequency compressor is controlled to stop running; wherein, the optimal shutdown electric angle It is the electrical angle at which the load torque of a permanent magnet synchronous motor is minimized within one mechanical rotation cycle.

[0013] Furthermore, in step 4, when At that time, if The current speed of the variable frequency compressor Adjusted to , If it is a proportionality constant, proceed to step 1; if The variable frequency compressor maintains the current speed. Then proceed to step 1.

[0014] Furthermore, in step 6, controlling the variable frequency compressor to stop operation specifically includes the inverter sending a stop signal and setting the speed input signal to zero.

[0015] Based on the above method, the present invention also provides a variable frequency compressor shutdown control system.

[0016] The system includes a first sensor, a second sensor, a current-limiting speed control module, a temperature segmented control module, a speed stabilization control module, and a fixed-angle stop control module;

[0017] The first sensor is used to measure the electrical temperature T1; the control system controls the variable frequency compressor to enter current-limited speed control or constant speed control based on whether the measured temperature T1 of the first sensor reaches the shutdown temperature T2.

[0018] The current-limiting speed control module is used to compare the average three-phase current of the variable frequency compressor. Overcurrent threshold of the intelligent power module of the variable frequency compressor Based on the comparison results, the variable frequency compressor is controlled to enter temperature segment control or return to the measured electrical temperature T1;

[0019] The second sensor is used to collect the device temperature T of the intelligent power module of the variable frequency compressor;

[0020] The temperature segmentation control module is used to compare the device temperature T of the smart power module with the over-temperature threshold. Control the variable frequency compressor to enter steady speed control or return to the measured electrical temperature T1;

[0021] The speed control module is used to adjust the speed of the variable frequency compressor to the optimal shutdown speed. ;

[0022] The fixed-angle stop control module is used to control the variable frequency compressor at the optimal stop speed. After the running time t exceeds the set value, the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor is measured. In the electrical angle of the permanent magnet synchronous motor Its optimal shutdown angle When the difference reaches the set value, the variable frequency compressor is controlled to stop running.

[0023] The beneficial effects of this invention are:

[0024] The variable frequency compressor shutdown control method and system described in this invention firstly achieves flexible adjustment of the compressor's operating speed through a current-limiting speed control module and a temperature segmentation control module, based on the actual operating conditions of the variable frequency compressor. Then, a speed stabilization control module ensures the compressor operates stably at the optimal shutdown speed corresponding to the best vibration performance before shutdown. Finally, a fixed-angle shutdown control module adjusts the electrical angle of the permanent magnet synchronous motor to the position of minimum load torque within one mechanical rotation cycle when the compressor stops, based on the compressor's load characteristics, thereby reducing compressor shutdown vibration. This method not only effectively controls and intelligently protects against overcurrent and overtemperature issues in the variable frequency compressor but also precisely controls its shutdown characteristics, avoiding high noise and vibration during shutdown. It significantly reduces the risk of motor burnout and inverter component damage, improving the energy efficiency and safety of the entire refrigerator control system. It boasts advantages such as reasonable design, simple operation, high intelligence, and strong safety. Attached Figure Description

[0025] Figure 1 This is a flowchart of the variable frequency compressor shutdown control method according to an embodiment of the present invention.

[0026] Figure 2 This is a load torque diagram of the permanent magnet synchronous motor of the variable frequency compressor during one mechanical cycle. Detailed Implementation

[0027] like Figure 1 As shown, the method for stopping a variable frequency compressor in an electrical appliance, as described in this invention, specifically includes the following steps:

[0028] Step 1: Determine if the appliance temperature T1 has reached the shutdown temperature T2; if yes, proceed to step 5; otherwise, proceed to step 2.

[0029] Step 2, Current-limiting speed control: Determine the average value of the three-phase current of the variable frequency compressor. Is it greater than or equal to the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 3; otherwise, proceed to step 4.

[0030] Step 3: Reduce the speed of the variable frequency compressor. When the speed of the variable frequency compressor drops to its minimum value, determine the average value of the three-phase current of the variable frequency compressor. Is it less than the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 1; otherwise, proceed to step 5.

[0031] Step 4, Temperature Segmentation Control: By comparing the device temperature T of the intelligent power module with its over-temperature threshold... To control the speed of the variable frequency compressor; Proceed to step 1; if Proceed to step 5;

[0032] Step 5, Speed ​​control: Adjust the speed of the variable frequency compressor to the optimal shutdown speed. When the variable frequency compressor reaches its optimal shutdown speed If the running time t is greater than the set value, proceed to step 6; wherein, the optimal stopping speed is... The rotational speed at which the vibration performance of the variable frequency compressor is optimal during stable operation;

[0033] Step 6, Fixed Angle Stop Control: Compare the electrical angle of the variable frequency compressor's permanent magnet synchronous motor. Its optimal shutdown angle ,when and When the difference reaches a set value, the variable frequency compressor is controlled to stop running; wherein, the optimal shutdown electric angle It is the electrical angle at which the load torque of a permanent magnet synchronous motor is minimized within one mechanical rotation cycle.

[0034] The following embodiments use the inverter compressor shutdown control of a refrigerator as an example to introduce the inverter compressor shutdown control method of the present invention;

[0035] Example 1:

[0036] Connect the refrigerator control system to the power supply. The inverter sends a start signal to start the inverter compressor. The system uses sensors to collect the refrigerator's internal cooling or freezing temperature (T1). If the temperature T1 reaches the set shutdown standard (T2), the inverter compressor enters the speed stabilization control phase. The inverter sends an optimal shutdown speed signal, adjusting the compressor's actual speed to the speed at which its vibration performance is optimal during stable operation. The optimal speed is 1800rpm-2400rpm. If the compressor operates at its optimal speed... When the running time reaches the set time threshold, such as 5 minutes, the variable frequency compressor enters the fixed angle stop control. The MCU of the variable frequency drive collects the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor. The electrical angle of the permanent magnet synchronous motor of the variable frequency compressor The electrical angle of the permanent magnet synchronous motor is the angle between the rotor pole axis and the U-phase stator winding axis. Mechanical angle with permanent magnet synchronous motor The relationship is ,in The number of pole pairs of a permanent magnet synchronous motor is determined by controlling the electrical angle of the permanent magnet synchronous motor. To achieve the mechanical angle of a permanent magnet synchronous motor This allows for the control of the rotor position of the permanent magnet synchronous motor, such as... Figure 2 As shown, the load torque of the permanent magnet synchronous motor of the variable frequency compressor approximately follows a Gaussian distribution (normal distribution) within one mechanical rotation cycle; the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor... Optimal stopping electric angle with permanent magnet synchronous motor If a comparison is made, and If the difference between the values ​​is less than the set value, the inverter sends a stop signal, setting the speed of the variable frequency compressor to zero, and the variable frequency compressor stops running. The optimal stopping angle of the permanent magnet synchronous motor is... The electrical angle corresponding to the minimum load torque within one mechanical rotation cycle of the permanent magnet synchronous motor is selected.

[0037] Example 2:

[0038] The refrigerator control system is connected to the power supply. A start-up signal is sent via the inverter to start the inverter compressor. The system uses sensors to collect the refrigerator's internal cooling or freezing temperature (T1). If the refrigerator's cooling or freezing temperature (T1) does not reach the set shutdown temperature standard (T2), it enters current-limiting speed control mode. The inverter's MCU collects the phase currents of the three phases (U, V, W) of the inverter compressor and calculates the average value of the three phase currents. The average value of the three-phase current Overcurrent threshold of the intelligent power module (IPM) for variable frequency compressors For comparison, if the average three-phase current of the variable frequency compressor... Less than the overcurrent threshold of the smart power module The variable frequency compressor will then operate according to its current state and enter temperature segmentation control. It will collect the device temperature T of the intelligent power module of the variable frequency compressor and compare it with the over-temperature threshold of the intelligent power module. The comparison is performed, and the speed of the variable frequency compressor is adjusted based on the comparison results. Assume the current speed of the variable frequency compressor is... ,like The actual operating speed of the variable frequency compressor will be... Adjust to control speed The Where K is a proportionality constant, the preferred value of K is 75%-85%, and the system returns a judgment on whether the temperature T1 of the electrical appliance has reached the set shutdown temperature T2; if The variable frequency compressor will maintain its current operating speed. And return to determine whether the temperature T1 of the appliance has reached the set shutdown temperature T2; if Then it enters speed control mode, adjusting the speed of the variable frequency compressor to the optimal shutdown speed. The optimal stopping speed is... The optimal speed for vibration performance during stable operation of the variable frequency compressor, when the variable frequency compressor stops at its optimal shutdown speed. After the running time t exceeds the set value, the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor is measured. In the electrical angle of the permanent magnet synchronous motor Its optimal shutdown angle When the difference reaches the set value, the variable frequency compressor is controlled to stop running.

[0039] Example 3:

[0040] The refrigerator control system is connected to the power supply. A start signal is sent via the inverter to start the inverter compressor. The system uses sensors to collect the refrigerator's internal cooling or freezing temperature (T1). If the temperature (T1) does not reach the set shutdown standard (T2), current-limiting speed control is activated. The inverter's MCU collects the phase currents (U, V, W) of the inverter compressor and calculates the average value of the three-phase currents. The average value of the three-phase current Overcurrent threshold of the intelligent power module (IPM) for variable frequency compressors In comparison, the average three-phase current of the variable frequency compressor The value is greater than or equal to the overcurrent threshold of the intelligent power module. The variable frequency compressor operates according to its current state. The microcontroller (MCU) of the inverter collects the compressor's operating speed and uses a variable speed control strategy to adjust its speed. The compressor reduces its speed in increments of 300 rpm and continuously adjusts the average three-phase current of the compressor. With intelligent power module (IPM) overcurrent threshold For comparison, if the variable frequency compressor speed is reduced to its lowest level, the average three-phase current of the variable frequency compressor is... Less than the intelligent power module (IPM) overcurrent threshold If the temperature of the appliance has not reached the set shutdown temperature, the system will return to reassess whether the temperature has been reached. If not, it will enter speed control mode and adjust the speed of the inverter compressor to the optimal shutdown speed. The optimal stopping speed is... The optimal speed for vibration performance during stable operation of the variable frequency compressor, when the variable frequency compressor stops at its optimal shutdown speed. After the running time t exceeds the set value, the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor is measured. In the electrical angle of the permanent magnet synchronous motor Its optimal shutdown angle When the difference reaches the set value, the variable frequency compressor is controlled to stop running.

Claims

1. A method for controlling the shutdown of a variable frequency compressor, applied to controlling the shutdown of a variable frequency compressor in an electrical appliance, characterized in that, Includes the following steps: Step 1: Determine if the appliance temperature T1 has reached the shutdown temperature T2; if yes, proceed to step 5; otherwise, proceed to step 2. Step 2, Current-limiting speed control: Determine the average value of the three-phase current of the variable frequency compressor. Is it greater than or equal to the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 3; otherwise, proceed to step 4. Step 3: Reduce the speed of the variable frequency compressor. When the speed of the variable frequency compressor drops to its minimum value, determine the average value of the three-phase current of the variable frequency compressor. Is it less than the overcurrent threshold of the intelligent power module of the variable frequency compressor? If yes, proceed to step 1; otherwise, proceed to step 5. Step 4, Temperature Segmentation Control: By comparing the device temperature T of the intelligent power module with its over-temperature threshold... To control the speed of the variable frequency compressor; Proceed to step 1; if Proceed to step 5; Step 5, Speed ​​control: Adjust the speed of the variable frequency compressor to the optimal shutdown speed. When the variable frequency compressor reaches its optimal shutdown speed If the running time t is greater than the set value, proceed to step 6; wherein, the optimal stopping speed is... The rotational speed at which the vibration performance of the variable frequency compressor is optimal during stable operation; Step 6, Fixed Angle Stop Control: Compare the electrical angle of the variable frequency compressor's permanent magnet synchronous motor. Its optimal shutdown angle ,when and When the difference reaches a set value, the variable frequency compressor is controlled to stop running; wherein, the optimal shutdown electric angle It is the electrical angle at which the load torque of a permanent magnet synchronous motor is minimized within one mechanical rotation cycle.

2. The variable frequency compressor shutdown control method according to claim 1, characterized in that, In step 4, when At that time, if The current speed of the variable frequency compressor Adjusted to , If it is a proportionality constant, proceed to step 1; if The variable frequency compressor maintains the current speed. Then proceed to step 1.

3. The variable frequency compressor shutdown control method according to claim 1 or 2, characterized in that, In step 6, controlling the variable frequency compressor to stop operation specifically includes the inverter sending a stop signal and setting the speed input signal to zero.

4. A variable frequency compressor shutdown control system for implementing the method of any one of claims 1-3, characterized in that, It includes a first sensor, a second sensor, a current-limiting speed control module, a temperature segmentation control module, a speed stabilization control module, and a fixed-angle stop control module; The first sensor is used to measure the electrical temperature T1; the control system controls the variable frequency compressor to enter current-limited speed control or constant speed control based on whether the measured temperature T1 of the first sensor reaches the shutdown temperature T2. The current-limiting speed control module is used to compare the average three-phase current of the variable frequency compressor. Overcurrent threshold of the intelligent power module of the variable frequency compressor Based on the comparison results, the variable frequency compressor is controlled to enter temperature segment control or return to the measured electrical temperature T1; The second sensor is used to collect the device temperature T of the intelligent power module of the variable frequency compressor; The temperature segmentation control module is used to determine the device temperature T of the intelligent power module and its over-temperature threshold. The comparison results are used to control the speed of the variable frequency compressor; The speed control module is used to adjust the speed of the variable frequency compressor to the optimal shutdown speed. ; The fixed-angle stop control module is used to control the variable frequency compressor at the optimal stop speed. After the running time t exceeds the set value, the electrical angle of the permanent magnet synchronous motor of the variable frequency compressor is measured. In the electrical angle of the permanent magnet synchronous motor Its optimal shutdown angle When the difference reaches the set value, the variable frequency compressor is controlled to stop running.

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