System with water chiller and control method of water chiller

Abstract

The application provides a control method of a water chiller. The water chiller comprises a condenser, an evaporator, a compressor, a motor and a motor cooling control valve. The motor is configured to drive the compressor, and the motor cooling control valve is configured to control the amount of fluid provided from the condenser to the motor for cooling the motor. The control method comprises: controlling the operation of the water chiller with the liquid level of the condenser and / or the evaporator as a control target; obtaining the temperature of the motor and the opening of the motor cooling control valve; and switching to control the operation of the water chiller with the temperature of the motor as a control target when the temperature of the motor reaches or exceeds a temperature threshold and the motor cooling control valve is fully opened. The control method does not increase additional components, but only uses the existing design of the unit to achieve, without increasing the cost, reducing the unit operation failure rate; and also can realize accurate control of the temperature of the motor, without a large amount of test data, simple and reliable control and maximum improvement of the unit operation efficiency.

Description

Technical Field

[0001] This application relates to chiller units, and more particularly to systems having chiller units, control methods for chiller units, and control methods for systems having chiller units. Background Technology

[0002] One type of chiller is a vapor compression chiller. A vapor compression chiller includes a compressor, a motor, a condenser, and an evaporator. In a vapor compression chiller, the motor is typically cooled by refrigerant. Motor cooling lines circulate refrigerant through the motor cavity to cool the motor inside. For example, one side of the motor cooling lines connects to the high-pressure side condenser, and the other side connects to the low-pressure side evaporator. Driven by the pressure difference between the evaporator and condenser, refrigerant from the condenser side enters the motor cavity to cool the motor, and then returns to the low-pressure side evaporator. Summary of the Invention

[0003] Motors typically need to maintain a certain temperature to ensure stable and efficient operation. Too much or too little refrigerant (also known as coolant) can significantly affect the motor's temperature. Therefore, a control valve (e.g., an electronic expansion valve) is usually installed on the motor's cooling pipes. By controlling the opening of the electronic expansion valve, an appropriate amount of refrigerant enters the motor cavity to cool the motor and ensure its temperature remains stable within a suitable range.

[0004] When a chiller unit operates under normal conditions, to ensure a certain refrigerant supply from the condenser to the evaporator, the flow control valve (e.g., a throttle valve) on the liquid supply line between the evaporator and condenser employs a control method that uses the liquid level in the condenser and / or evaporator as the control target. This control method ensures good control performance under normal operating conditions. Under normal operating conditions, the condenser inlet water temperature is typically higher than the evaporator outlet water temperature. However, when the chiller unit operates under reverse conditions, the condenser inlet water temperature is lower than the evaporator outlet water temperature. This reverse operating condition is common in winter, when the condenser inlet water temperature is low, but the evaporator outlet water temperature must be maintained at a value higher than the condenser inlet water temperature to meet production requirements; this is often seen in data centers. When the chiller unit is operating in reverse mode, if the flow control valve still uses the conventional control method that uses the liquid level of the condenser and / or evaporator as the control target, a small amount of refrigerant will enter the motor cavity from the condenser to cool the motor because the pressure difference between the condenser and the evaporator is too small. This will result in only a small amount of refrigerant entering the motor cavity to cool the motor, even if the electronic expansion valve on the motor cooling pipe is fully open (e.g., the electronic expansion valve is 100% open). This still cannot meet the refrigerant flow requirements for motor cooling.

[0005] The inventors discovered that, to meet the motor's cooling liquid supply requirements under reverse operating conditions, one current solution is to add a pump (refrigerant pump) to pump the refrigerant from the condenser into the motor cavity to meet the motor's cooling needs. Another current solution is a control scheme that uses the pressure difference between the condenser and evaporator as the control objective to ensure sufficient pressure difference for motor cooling.

[0006] The inventors also discovered that adding a pump increases costs and complicates the unit structure, leading to a higher failure rate. The control scheme using the pressure difference between the condenser and evaporator as the control target has the following drawbacks: It is difficult to accurately control the motor temperature, making it hard to guarantee accurate cooling fluid supply to the motor. If the throttle valve opening is too large, even a small pressure difference will still result in insufficient cooling fluid supply to the motor; conversely, if the throttle valve opening is too small, an excessively large pressure difference will lead to low evaporation pressure, increasing compressor operating power and reducing overall machine efficiency. Furthermore, establishing the correlation between motor cooling fluid supply and the pressure difference between the condenser and evaporator often requires extensive testing for each compressor, which is time-consuming and costly.

[0007] To address the aforementioned problems, this application provides a control method for a chiller unit. When the motor cooling control valve (e.g., an electronic expansion valve) is fully open and the current motor temperature exceeds a certain threshold, the opening control of the flow regulating valve located on the unit's main liquid supply line shifts from targeting the condenser and / or evaporator liquid level to targeting the motor temperature. This is achieved, for example, through PID control to meet the motor temperature control requirements under reverse operating conditions. Furthermore, when the motor cooling control valve is fully open and the condenser liquid level is below or equal to a certain threshold, and / or when the motor cooling control valve is fully open and the evaporator liquid level is above or equal to a certain threshold, the opening control of the flow regulating valve shifts from targeting the motor temperature to targeting the condenser and / or evaporator liquid level. This control method requires no additional components and can be implemented using the existing unit design, without increasing costs and reducing the unit's failure rate. Moreover, this control method enables precise control of the motor temperature without requiring extensive test data, offering simple and reliable control while maximizing unit operating efficiency.

[0008] Specifically, according to a first aspect of this application, this application provides a control method for a chiller unit. The chiller unit includes a condenser, an evaporator, a compressor, a motor, and a motor cooling control valve. The motor is configured to drive the compressor. The motor cooling control valve is configured to control the amount of fluid supplied from the condenser to the motor for cooling the motor. The control method includes the following steps S1-S3. In step S1, the operation of the chiller unit is controlled with the liquid level of the condenser and / or evaporator as the control target. In step S2, the temperature of the motor and the opening degree of the motor cooling control valve are acquired. In step S3, when the temperature of the motor reaches or exceeds a motor temperature threshold and the motor cooling control valve is fully open, the operation of the chiller unit is switched to be controlled with the motor temperature as the control target.

[0009] According to the first aspect of this application, the control method further includes steps S4 and S5. In step S4, when the chiller unit is operated with the motor temperature as the control target, the opening degree of the motor cooling control valve and the liquid level of the condenser and / or evaporator are acquired. In step S5, when the motor cooling control valve is fully open and the liquid level of the condenser is lower than or equal to the condenser liquid level threshold, and / or when the motor cooling control valve is fully open and the liquid level of the evaporator is higher than or equal to the evaporator liquid level threshold, the operation of the chiller unit is switched from being controlled with the motor temperature as the control target to being controlled with the liquid level of the condenser and / or evaporator as the control target, and the process returns to step S1.

[0010] According to a first aspect of this application, the chiller unit also includes a flow regulating valve located between the condenser and the evaporator. The opening of the flow regulating valve is adjusted to control the operation of the chiller unit with the liquid level in the condenser and / or the evaporator as the control target, or with the temperature of the motor as the control target.

[0011] According to the first aspect of this application, in step S3, when the chiller unit is operated with the motor temperature as the control target, the motor cooling control valve is kept fully open and the opening of the flow regulating valve is reduced.

[0012] According to the first aspect of this application, in step S3, when the chiller unit is controlled to operate with the motor temperature as the control target: the heat exchange temperature difference of the evaporator is obtained; and when the heat exchange temperature difference of the evaporator reaches or exceeds the heat exchange temperature difference threshold and continues for a predetermined time, the chiller unit is shut down.

[0013] According to a first aspect of this application, the motor temperature threshold is the sum of the motor temperature setpoint and the motor temperature offset. The condenser liquid level threshold is the sum of the condenser liquid level setpoint and the condenser liquid level offset. The evaporator liquid level threshold is the sum of the evaporator liquid level setpoint and the evaporator liquid level offset.

[0014] According to the first aspect of this application, controlling the operation of a chiller unit with the motor temperature as the control target includes: performing PID regulation with the motor temperature setpoint as the control target to control the operation of the chiller unit. Controlling the operation of a chiller unit with the condenser and / or evaporator liquid level as the control target includes: performing PID regulation with the condenser liquid level setpoint as the control target or performing PID regulation with the evaporator liquid level setpoint as the control target to control the operation of the chiller unit.

[0015] According to the first aspect of this application, the motor temperature bias, the condenser liquid level bias, and the evaporator liquid level bias can all be adjusted.

[0016] According to the first aspect of this application, the temperature of the motor includes the temperature of the motor windings, rotor, bearings, or housing.

[0017] According to the first aspect of this application, the motor temperature is obtained by estimating the motor temperature based on the operating data of the chiller unit; or by obtaining the motor temperature through a motor temperature sensor. The condenser level and / or evaporator level are obtained by estimating the condenser level and / or evaporator level based on the operating data of the chiller unit; or by obtaining the condenser level through a condenser level sensor and / or the evaporator level through an evaporator level sensor.

[0018] According to a second aspect of this application, this application provides a controller for a chiller unit. The controller includes a processor configured to execute the aforementioned control method to control the operation of the chiller unit.

[0019] According to a third aspect of this application, an air conditioning system is provided. The air conditioning system includes a chiller unit, a detection device, and a controller. The detection device is configured to detect operating data of the chiller unit. The controller includes a processor configured to execute the aforementioned control method to control the operation of the chiller unit based on the detected operating data of the chiller unit. Attached Figure Description

[0020] The accompanying drawings are not to scale. In the drawings, each identical or nearly identical component shown in different figures is indicated by the same reference numerals. For clarity, not every component may be labeled in every drawing. In the drawings:

[0021] Figure 1 A block diagram of a system with a chiller unit according to this application is shown;

[0022] Figure 2A It shows Figure 1 The flowchart shown is the overall control method of the chiller unit.

[0023] Figure 2BIt shows Figure 2A A flowchart of an embodiment of step 210 in the control method shown; and

[0024] Figure 3 It shows Figure 1 The block diagram of the controller is shown. Detailed Implementation

[0025] Various specific embodiments of this application will now be described with reference to the accompanying drawings, which form part of this specification. It should be understood that, where possible, the same or similar reference numerals used in this application refer to the same parts.

[0026] Figure 1 A block diagram of a system 100 having a chiller unit 101 according to this application is shown.

[0027] like Figure 1 As shown, system 100 includes a chiller unit 101, a detection device 108, and a controller 110. The chiller unit 101 includes a compressor 102, a condenser 103, a flow regulating valve 104, an evaporator 105, a motor cooling control valve 106, and a motor 107. The chiller unit 101 includes main liquid supply lines 109a, 109b, 109c, and 109d, and motor cooling lines 113a, 113b, and 113c. In the main liquid supply lines 109a, 109b, 109c, and 109d, refrigerant flows from the outlet of compressor 102 to condenser 103, then through flow regulating valve 104, and then to evaporator 105. After passing through evaporator 105, it returns to compressor 102. One end of the motor cooling line is connected to the high-pressure side of condenser 103, and the other end is connected to the low-pressure side of evaporator 105. The motor cooling control valve 106 is installed in the motor cooling pipeline. In the motor cooling pipelines 113a, 113b, and 113c, driven by the pressure difference between the condenser 103 and the evaporator 105 (the pressure in the condenser 103 is higher than the pressure in the evaporator 105), the refrigerant flows from the condenser 103 to the motor cooling control valve 106, and then reaches the motor cavity (not shown) via the motor cooling control valve 106 to cool the motor. After the refrigerant flows through the motor cavity to cool the motor, it reaches the evaporator 105.

[0028] In one embodiment, chiller unit 101 is a vapor compression chiller unit. For example, chiller unit 101 is a magnetic levitation centrifugal chiller unit, which is a chiller unit that uses a magnetic levitation centrifugal compressor. Figure 1 The diagram shows the main components of chiller unit 101, which also includes other components ( Figure 1(Not shown). For example, chiller 101 may also include an economizer, or the condenser 103 of chiller 101 may also include a subcooler. In one embodiment, motor 107 is disposed within compressor 102. In other embodiments, motor 107 is disposed in other suitable locations. In one embodiment, system 100 is air conditioning system 100. In other embodiments, system 100 is other suitable systems with chillers.

[0029] like Figure 1 As shown, the detection device 108 is connected to the chiller unit 101 and configured to detect and acquire operating data during the operation of the chiller unit 101. The connection between the detection device 108 and the chiller unit 101 includes mechanical, electrical, and / or communication connections, as well as direct or indirect connections, for the detection device 108 to detect and acquire the operating data of the chiller unit 101. The detection device 108 can be part of the chiller unit 101 or a device independent of the chiller unit 101.

[0030] The detection device 108 is also connected to the controller 110 (e.g., via connection line 112) and configured to send the acquired operating data of the chiller unit 101 to the controller 110, for example, via connection line 112. The connection between the detection device 108 and the controller 110 includes a communication connection. The controller 110 generates a control signal based on the operating data of the chiller unit 101 received from the detection device 108 and outputs the control signal (e.g., via connection line 111) to the chiller unit 101 to control its operation. For example, the controller 110 generates an opening control signal for the flow regulating valve 104 based on the operating data of the chiller unit 101 received from the detection device 108 to control the opening degree of the flow regulating valve 104. The controller 110 also generates a control signal based on the operating data of the chiller unit 101 received from the detection device 108, and generates an opening control signal for the motor cooling control valve 106 to control the opening of the motor cooling control valve 106.

[0031] Figure 2A It shows Figure 1 The flowchart of the control method 200 for the chiller unit 101 is shown.

[0032] like Figure 2A As shown, the control method 200 of the chiller unit 101 starts at step 202 and then proceeds to step 204.

[0033] At step 204, the operation of the chiller unit 101 is controlled with the liquid level of condenser 103 and / or evaporator 105 as the control target. Then, the process proceeds from step 204 to step 206. In one embodiment, the controller 110 controls the chiller unit 101 to operate under the required conditions with the liquid level of condenser 103 and / or evaporator 105 as the control target. For example, when the liquid level of condenser 103 is the control target, the controller 110 generates an opening control signal for the flow regulating valve 104 based on the liquid level of condenser 103 detected by a condenser level sensor (not shown), thereby controlling the opening of the flow regulating valve 104. The controller 110 can also estimate the liquid level of condenser 103 based on operating data of the chiller unit 101, such as the subcooling of condenser 103, and then generate an opening control signal for the flow regulating valve 104 based on the estimated liquid level of condenser 103, thereby controlling the opening of the flow regulating valve 104. When the liquid level of evaporator 105 is the control target, controller 110 generates an opening control signal for flow regulating valve 104 based on the liquid level of evaporator 105 detected by evaporator liquid level sensor (not shown), thereby controlling the opening degree of flow regulating valve 104. Controller 110 can also estimate the liquid level of evaporator 105 based on operating data of chiller unit 101, such as suction superheat and / or discharge superheat of compressor 102, and then generate an opening control signal for flow regulating valve 104 based on the estimated liquid level of evaporator 105, thereby controlling the opening degree of flow regulating valve 104.

[0034] In one embodiment, PID control is performed using the condenser level setpoint as the control target to control the operation of chiller unit 101, thereby meeting the control requirements for the condenser level. For example, the condenser level setpoint is used as the target value for PID control, the flow control valve 104 is used as the actuator for PID control to generate the desired condenser level, and the condenser level sensor is used as the detection mechanism for PID control. In other embodiments, the operation of chiller unit 101 is controlled using the condenser level 103 as the control target through other suitable methods. In one embodiment, PID control is performed using the evaporator level setpoint as the control target to control the operation of chiller unit 101, thereby meeting the control requirements for the evaporator level. For example, the evaporator level setpoint is used as the target value for PID control, the flow control valve 104 is used as the actuator for PID control to generate the desired evaporator level, and the evaporator level sensor is used as the detection mechanism for PID control. In other embodiments, the operation of chiller unit 101 is controlled using the evaporator level 105 as the control target through other suitable methods.

[0035] At step 206, the temperature of motor 107 and the opening degree of motor cooling control valve 106 are acquired. Then, the process proceeds from step 206 to step 208. In one embodiment, controller 110 acquires the temperature of motor 107 and the opening degree of motor cooling control valve 106. The temperature of motor 107 includes the temperature of the windings, rotor, bearings, or housing of motor 107. The temperature of motor 107 also includes the temperature of other suitable components of motor 107 used to indicate the temperature of motor 107. In one embodiment, controller 110 estimates the temperature of motor 107 using operating parameters of chiller unit 101. For example, the temperature of the windings of motor 107 is used as the temperature of motor 107. The temperature of the housing of motor 107 is detected by a housing temperature sensor, controller 110 acquires the temperature of the housing of motor 107 from the housing temperature sensor, and acquires the temperature of the windings of motor 107 based on that housing temperature (e.g., by a temperature model). In one embodiment, the temperature of motor 107 is detected by a motor temperature sensor (not shown), and controller 110 acquires the detected temperature of motor 107 from that motor temperature sensor. For example, the temperature of motor 107 is the temperature of the windings of motor 107. The temperature of the windings of motor 107 is detected by one or more motor winding temperature sensors. These motor winding temperature sensors are located at one or both ends of the stator of motor 107. In other embodiments, the temperature of motor 107 is obtained by other suitable methods. In one embodiment, the opening degree of motor cooling control valve 106 is detected by a magnetoelectric sensor (not shown), and the controller 110 obtains the detected opening degree of motor cooling control valve 106 from the magnetoelectric sensor. For example, the magnetoelectric sensor is located in or outside the motor cooling control valve 106. In other embodiments, the opening degree of motor cooling control valve 106 is obtained by other suitable methods.

[0036] At step 208, it is determined whether the acquired temperature of motor 107 reaches or exceeds a motor temperature threshold and whether the opening degree of motor cooling control valve 106 reaches 100% (i.e., whether motor cooling control valve 106 is fully open). In one embodiment, controller 110 determines whether the acquired temperature of motor 107 reaches or exceeds a motor temperature threshold and whether the opening degree of motor cooling control valve 106 reaches 100% based on the acquired temperature of motor 107 and the opening degree of motor cooling control valve 106. In one embodiment, the motor temperature threshold is the sum of a motor temperature setpoint and a motor temperature bias value. For example, the operator inputs the motor temperature setpoint and the motor temperature bias value to controller 110, so controller 110 obtains the motor temperature threshold based on the sum of the motor temperature setpoint and the motor temperature bias value, and compares the acquired temperature of motor 107 with the motor temperature threshold to determine whether the temperature of motor 107 reaches or exceeds the motor temperature threshold. Depending on the actual situation, such as the actual structure of the chiller unit, the motor temperature setpoint and the motor temperature bias value can be set (adjusted) to appropriate values. In one embodiment, the temperature of motor 107 is the temperature of the windings of motor 107, the motor temperature threshold is the motor winding temperature threshold, and the motor temperature bias value is the motor winding temperature bias value. For example, the motor winding temperature bias value is +10°C. The motor winding temperature bias value can also be other suitable values.

[0037] At step 208, if the temperature of motor 107 reaches or exceeds the motor temperature threshold and motor cooling control valve 106 is fully open, the process proceeds from step 208 to step 210; otherwise, it proceeds from step 208 to step 204 to continue controlling the operation of chiller unit 101 based on the liquid level of condenser 103 and / or evaporator 105. At step 210, the control target changes from the liquid level of condenser 103 and / or evaporator 105 to the temperature of motor 107. Then, the process proceeds from step 210 to step 212.

[0038] In one embodiment, when the controller 110 determines that the temperature of the motor 107 has reached or exceeded the motor temperature threshold and the motor cooling control valve 106 is fully open, it enters a new control mode, that is, controlling the operation of the chiller unit 101 with the temperature of the motor 107 as the control target. When the controller 110 determines that the conditions of the motor 107 temperature reaching or exceeding the motor temperature threshold and the motor cooling control valve 106 being fully open are not met, it maintains the original control mode of the chiller unit, that is, continues to control the operation of the chiller unit 101 with the liquid level of the condenser 103 and / or the evaporator 105 as the control target.

[0039] When the temperature of motor 107 reaches or exceeds the motor temperature threshold and motor cooling control valve 106 is fully open, it indicates that even with motor cooling control valve 106 fully open, the cooling demand of motor 107 cannot be met. This situation may be caused by a small pressure difference between condenser 103 and evaporator 105, resulting in insufficient or minimal refrigerant flow from condenser 103 to the motor cavity via motor cooling pipes 113a, 113b, and 113c to cool motor 107, thus failing to meet the cooling demand of motor 107. Based on this situation, this application switches the original control method of chiller unit 101, which uses the liquid level of condenser 103 and / or evaporator 105 as the control target (see step 204), to a new control method that uses the temperature of motor 107 as the control target (see step 210). The above situation may occur when chiller unit 101 is operating in reverse condition, meaning that even with motor cooling control valve 106 fully open, the cooling demand of motor 107 cannot be met. The above situation may also occur when chiller unit 101 is operating under other conditions.

[0040] In one embodiment, when the chiller unit 101 is operated with the temperature of motor 107 as the control target, the controller 110 generates an opening control signal for the motor cooling control valve 106 based on the temperature of motor 107 detected by a motor temperature sensor (not shown). This controls the opening of the motor cooling control valve 106, thereby changing the pressure difference between the condenser 103 and the evaporator 105. Consequently, refrigerant flows from the condenser 103 through the motor cooling pipe to the motor cavity to cool the motor 107, thus meeting the cooling requirements of the motor 107. In another embodiment, PID control is performed with the motor temperature setpoint as the control target to control the operation of the chiller unit 101, thereby meeting the temperature control requirements of the motor 107. For example, the motor temperature setpoint is used as the target value for PID control, the flow control valve 104 is used as the actuator for PID control to generate the required motor temperature, and the motor temperature sensor is used as the detection mechanism for PID control. In yet another embodiment, the motor cooling control valve 106 is kept fully open to control only the opening of the flow control valve 104. This control method can simply and effectively control the temperature of the motor 107 to meet the requirements. In other embodiments, the temperature of motor 107 is controlled to meet the requirements by other suitable means.

[0041] At step 212, the opening degree of the motor cooling control valve 106 and the liquid level of the condenser 103 and / or evaporator 105 are acquired. Then, the process proceeds from step 212 to step 214. In one embodiment, the controller 110 acquires the opening degree of the motor cooling control valve 106 and the liquid level of the condenser 103 and / or evaporator 105. In one embodiment, the liquid level of the condenser 103 is detected by a condenser level sensor (not shown), and the controller 110 acquires the detected liquid level of the condenser 103 from the condenser level sensor. For example, the condenser level sensor is located inside and / or outside the condenser 103. In one embodiment, the controller 110 acquires operating parameters of the chiller unit 101, such as the subcooling degree of the condenser 103, and estimates the liquid level of the condenser 103 based on these operating parameters. In other embodiments, the liquid level of the condenser 103 is acquired by other suitable methods. In one embodiment, the liquid level of evaporator 105 is detected by an evaporator level sensor (not shown), and controller 110 obtains the detected liquid level of evaporator 105 from the evaporator level sensor. For example, the evaporator level sensor is located inside and / or outside the evaporator 105. In one embodiment, controller 110 obtains operating parameters of chiller unit 101, such as suction superheat and / or discharge superheat of compressor 102, and estimates the liquid level of evaporator 105 based on these operating parameters. In other embodiments, the liquid level of evaporator 105 is obtained by other suitable methods.

[0042] In step 214, it is determined whether the acquired opening degree of the motor cooling control valve 106 reaches 100% (i.e., whether the motor cooling control valve 106 is fully open) and whether the liquid level of the condenser 103 is lower than or equal to the condenser liquid level threshold, and / or it is determined whether the acquired opening degree of the motor cooling control valve 106 reaches 100% and whether the liquid level of the evaporator 105 is higher than or equal to the evaporator liquid level threshold. In one embodiment, the controller 110 performs the above determination based on the acquired opening degree of the motor cooling control valve 106 and the liquid levels of the condenser 103 and / or the evaporator 105. In one embodiment, the condenser liquid level threshold is the sum of the condenser liquid level setpoint and the condenser liquid level bias value. For example, the operator inputs the condenser level setpoint and condenser level bias value to the controller 110. The controller 110 then obtains the condenser level threshold based on the sum of the condenser level setpoint and the condenser level bias value, and compares the obtained condenser level 103 with the condenser level threshold to determine whether the condenser level 103 is lower than or equal to the condenser level threshold. For example, the condenser level bias value is +10%. The condenser level bias value can also be other suitable values. In one embodiment, the evaporator level threshold is the sum of the evaporator level setpoint and the evaporator level bias value. For example, the operator inputs the evaporator level setpoint and the evaporator level bias value to the controller 110. The controller 110 then obtains the evaporator level threshold based on the sum of the evaporator level setpoint and the evaporator level bias value, and compares the obtained evaporator level 105 with the evaporator level threshold to determine whether the evaporator level 105 is higher than or equal to the evaporator level threshold. The evaporator level offset can also be set to other suitable values. Depending on the actual situation, such as the actual structure of the chiller unit, the condenser level setpoint, condenser level offset, evaporator level setpoint, and evaporator level offset can be set (adjusted) to suitable values.

[0043] At step 214, if the motor cooling control valve 106 is fully open and the liquid level in the condenser 103 is lower than or equal to the condenser liquid level threshold, and / or the motor cooling control valve 106 is fully open and the liquid level in the evaporator 105 is higher than or equal to the evaporator liquid level threshold, the process proceeds from step 214 to step 216; otherwise, the process proceeds from step 214 to step 210 to continue controlling the operation of the chiller unit 101 with the temperature of the motor 107 as the control target. At step 216, it is determined whether the chiller unit 101 needs to be shut down. If the chiller unit 101 needs to be shut down, the process proceeds from step 216 to step 218. At step 218, the execution of the control method 200 for the chiller unit 101 ends. When the chiller unit 101 does not need to be shut down, the process transitions from step 216 to step 204, switching from controlling the operation of the chiller unit 101 based on the temperature of the motor 107 to controlling the operation based on the liquid level of the condenser 103 and / or the evaporator 105. In one embodiment, the controller 110 executes steps 214-218 as described above.

[0044] When the chiller unit 101 is operating under control with the temperature of the motor 107 as the control target, for example, by reducing the opening of the flow regulating valve 104 to increase the pressure difference between the evaporator 105 and the condenser 103, thereby ensuring the normal liquid supply required for motor cooling, the chiller unit 101 can be switched back to its original control mode with the liquid level of the condenser 103 and / or evaporator 105 as the control target. However, the inventors discovered that when the chiller unit 101 is controlled with the temperature of motor 107 as the control target, the liquid level of condenser 103 is usually maintained at a high level (e.g., more than 90% of the highest liquid level of condenser set by the condenser liquid level sensor) due to the reduced opening of flow regulating valve 104. In the original control mode of chiller unit 101, for example, when the liquid level of condenser 103 and / or evaporator 105 is the control target, the liquid level set value of condenser 103 is, for example, 50% of the highest liquid level of condenser set by the condenser liquid level sensor, that is, the liquid level of condenser 103 is maintained at approximately 50% of the set highest liquid level of condenser. If the control mode that controls the temperature of motor 107 (for example, the liquid level of condenser 103 is maintained at more than 90% of the set maximum liquid level of condenser) is switched to the control mode that controls the liquid level of condenser 103 and / or evaporator 105 (for example, the liquid level of condenser 103 is maintained at approximately more than 50% of the set maximum liquid level of condenser), the liquid level of condenser 103 will fluctuate significantly, causing the chiller unit 101 to operate unstablely.

[0045] Therefore, in order to ensure that the liquid level of the condenser 103 does not fluctuate significantly and cause instability in the operation of the chiller 101 when the flow regulating valve 104 switches between the control of the chiller unit 101 with the temperature of the motor 107 as the control target (or "reverse control") and the original control, this application switches the operation of the chiller unit 101 from the control with the temperature of the motor 107 as the control target to the original control of the chiller unit 101 when the motor cooling control valve 106 is fully open and the liquid level of the condenser 103 is lower than or equal to the condenser liquid level threshold. For example, the operation of the chiller unit 101 is controlled with the liquid level of the condenser 103 and / or the evaporator 105 as the control target. This application does not immediately switch back to the original control of the chiller unit 101 when the temperature of the motor 107 reaches the required temperature. Instead, it switches back to the original control of the chiller unit 101 only when the liquid level of the condenser 103 is lower than or equal to the required liquid level (at which point the temperature of the motor 107 has reached the required temperature). This ensures that the liquid level of the condenser 103 will not fluctuate significantly after the switch and ensures the stable operation of the chiller unit 101. The reasons for the decrease in the liquid level of condenser 103 include: when the pressure difference between condenser 103 and evaporator 105 increases due to changes in external operating conditions, the increased pressure difference will drive more refrigerant from condenser 103 into evaporator 105, thus causing the liquid level of condenser 103 to drop; on the other hand, the increase in pressure difference will lead to an increase in the amount of cooling liquid supplied to the motor. At this time, the PID control based on the temperature setpoint will increase the opening of the flow control valve 104 to reduce the pressure difference, thereby further allowing more refrigerant to enter evaporator 105 from condenser 103.

[0046] In the chiller unit, the refrigerant circulates in the condenser 103 and the evaporator 105. When the liquid level in the condenser 103 is high, the liquid level in the evaporator 105 is correspondingly low, and vice versa. Therefore, in another embodiment, in the control mode with the temperature of the motor 107 as the control target, this application further switches back to the original control of the chiller unit 101 only when the liquid level in the evaporator 105 is higher than or equal to the required liquid level (at which point the temperature of the motor 107 has reached the required temperature). This also ensures that the liquid levels in the condenser 103 and the evaporator 105 do not fluctuate significantly after the switch, and ensures the stable operation of the chiller unit 101.

[0047] Figure 2B It shows Figure 2A A flowchart of an embodiment of step 210 in the control method 200 shown. (See attached flowchart.) Figure 2A As shown, in step 210, the operation of the chiller unit 101 is switched from being controlled by the liquid level of the condenser 103 to being controlled by the temperature of the motor 107.

[0048] like Figure 2B As shown, by Figure 2A Step 208 Proceed to Figure 2B Step 222. At step 222, the motor cooling control valve 106 is kept fully open and the opening of the flow regulating valve 104 is reduced to control the operation of the chiller unit 101 with the temperature of the motor 107 as the control target. In other embodiments, the operation of the chiller unit 101 is controlled with the temperature of the motor 107 as the control target in other suitable ways. Then, the process proceeds from step 222 to step 224. In one embodiment, when the chiller unit 101 is controlled with the temperature of the motor 107 as the control target, the controller 110 generates a control signal to keep the motor cooling control valve 106 fully open and a control signal to reduce the opening of the flow regulating valve 104, thereby controlling the motor cooling control valve 106 to be fully open and the opening of the flow regulating valve 104 to be reduced. Therefore, the pressure difference between the condenser 103 and the evaporator 105 increases, so that more refrigerant from the condenser 103 reaches the motor cavity via the motor cooling control valve 106 to cool the motor 107, thereby meeting the liquid supply required for motor cooling.

[0049] At step 224, the heat exchange temperature difference of the evaporator 105 is obtained. The heat exchange temperature difference of the evaporator 105 refers to the temperature difference between the evaporation temperature (i.e., the saturation temperature of the refrigerant) in the evaporator 105 and the outlet water temperature. Then, the process proceeds from step 224 to step 226. In one embodiment, the pressure of the refrigerant in the evaporator 105 is detected by a pressure sensor, and the outlet water temperature of the evaporator 105 is detected by an outlet water temperature sensor. Based on this detection, the controller 110 obtains the detected refrigerant pressure in the evaporator 105 from the pressure sensor, obtains the refrigerant saturation temperature (i.e., the evaporation temperature) based on the refrigerant pressure, and obtains the detected outlet water temperature of the evaporator 105 from the outlet water temperature sensor, and compares the obtained evaporation temperature and outlet water temperature to obtain the heat exchange temperature difference of the evaporator 105. In other embodiments, the heat exchange temperature difference of the evaporator 105 is obtained by other suitable methods.

[0050] In step 226, it is determined whether the obtained heat exchange temperature difference of the evaporator 105 reaches or exceeds the heat exchange temperature difference threshold and is maintained for a predetermined time. When the heat exchange temperature difference of the evaporator 105 reaches or exceeds the heat exchange temperature difference threshold and is maintained for a predetermined time, the process transitions from step 226 to... Figure 2A Step 218 terminates the execution of control method 200 for chiller unit 101; otherwise, proceed to step 226. Figure 2AStep 212. In one embodiment, the controller 110 performs step 226 described above. In one embodiment, the operator inputs a heat exchange temperature difference threshold and a predetermined time to the controller 110. The controller 110 compares the acquired heat exchange temperature difference of the evaporator 105 with the heat exchange temperature difference threshold to determine whether the heat exchange temperature difference of the evaporator 105 reaches or exceeds the heat exchange temperature difference threshold. The controller 110 also acquires the duration of this state when the heat exchange temperature difference of the evaporator 105 reaches or exceeds the heat exchange temperature difference threshold, and compares the duration with the predetermined time to determine whether the duration has reached the predetermined time.

[0051] In one embodiment, when the chiller unit 101 operates under reverse conditions, it is necessary to increase the heat exchange temperature difference of the evaporator 105 to increase the pressure difference between the condenser 103 and the evaporator 105. The inventors discovered that due to limitations such as the regulating capacity of the flow control valve 104, the heat exchange temperature difference of the evaporator 105 should not increase indefinitely. Therefore, it is necessary to set an upper limit value for the heat exchange temperature difference of the evaporator 105, such as a heat exchange temperature difference threshold. In one embodiment, when the heat exchange temperature difference of the evaporator 105 is greater than or equal to 15°C and lasts for 5 minutes, the chiller unit 101 shuts down and indicates (or warns) that the heat exchange temperature difference of the evaporator 105 is too large, thereby protecting the chiller unit 101 from damage. In other embodiments, the heat exchange temperature difference threshold and the predetermined time can be adjusted (set) to other suitable values ​​according to actual conditions.

[0052] Detection device 108 (see) Figure 1 This includes the aforementioned motor temperature sensor, housing temperature sensor, motor winding temperature sensor, magnetoelectric sensor, condenser level sensor, evaporator level sensor, pressure sensor, outlet water temperature sensor, etc.

[0053] Figure 3 It shows Figure 1 The block diagram of controller 110 shown is shown.

[0054] like Figure 3 As shown, the controller 110 includes a bus 301, a processor 302, a memory 303, an input interface 304, and an output interface 305. The processor 302, memory 303, input interface 304, and output interface 305 are connected to the bus 301. The processor 302 can read a program (or instruction) from the memory 303 and execute the program (or instruction) to perform data processing. The processor 302 can also write data or a program (or instruction) into the memory 303. The memory 303 can store programs (instructions) or data. By executing the instructions in the memory 303, the processor 302 can control the memory 303, the input interface 304, and the output interface 305.

[0055] Input interface 304 is configured to receive operating data of the chiller unit 101 acquired from detection device 108 via connection line 112. Input interface 304 is also configured to convert the received data into data recognizable by processor 302 and output the data to processor 302. For example, detection device 108 includes a motor temperature sensor for detecting the temperature of motor 107, a housing temperature sensor for detecting the temperature of the housing of motor 107, a motor winding temperature sensor for detecting the temperature of the windings of motor 107, a magnetoelectric sensor for detecting the opening degree of motor cooling control valve 106, a condenser level sensor for detecting the liquid level of condenser 103, an evaporator level sensor for detecting the liquid level of evaporator 105, a pressure sensor for detecting the pressure of refrigerant in evaporator 105, an outlet water temperature sensor for detecting the outlet water temperature of evaporator 105, etc. The input interface 304 receives data of the above parameters from the detection device 108 when the chiller unit 101 is running, converts these data into data that can be recognized by the processor 302, and outputs these data to the processor 302.

[0056] Processor 302 is configured to process (e.g., compute) the received data to generate control signals. In one embodiment, processor 302 generates an opening control signal for flow regulating valve 104 to control the opening of flow regulating valve 104, and also generates an opening control signal for motor cooling control valve 106 to control the opening of motor cooling control valve 106. For example, processor 302 executes... Figure 2A and Figure 2B The steps in the method shown, such as steps 204, 208, 210, 214, 222, and 226, are used to generate corresponding control signals.

[0057] Output interface 305 is configured to receive control signals from processor 302, convert the control signals into signals suitable for chiller unit 101, and send control signals to chiller unit 101 to control the operation of chiller unit 101. In one embodiment, output interface 305 sends opening control signals of flow regulating valve 104 and / or motor cooling control valve 106 to chiller unit 101 via connection line 111 to control the opening degree of flow regulating valve 104 and / or motor cooling control valve 106, thereby controlling the operation of chiller unit 101.

[0058] This application has at least the following beneficial effects:

[0059] 1. This application uses the motor temperature as the control target directly through the flow regulating valve, which can greatly reduce the overall cost, simplify the unit system structure, and reduce the failure rate;

[0060] 2. This application uses the motor temperature as the control target directly through the flow regulating valve, which can greatly improve the accuracy of motor temperature control, improve the heat exchange efficiency of the evaporator, and improve the unit efficiency;

[0061] 3. This application does not require extensive testing for each compressor to establish the relationship between the motor cooling fluid supply and the pressure difference between the condenser and evaporator, which can save a lot of testing time and testing costs.

[0062] All features and / or steps of any method or process so disclosed in this specification (including any appended claims, abstract, and drawings) can be combined in any suitable combination, except for at least some mutually exclusive combinations of such features and / or steps. This application is not limited to the specific sequence of steps described in the specification, but includes other suitable sequences of steps for carrying out this application.

[0063] Although this application has been described with reference to examples of the embodiments outlined above, various alternatives, modifications, variations, improvements, and / or substantially equivalents, whether known or currently or soon to be foreseen, will likely be apparent to those skilled in the art. Furthermore, the technical effects and / or technical problems described herein are exemplary and not limiting; therefore, the disclosures herein may be used to solve other technical problems and have other technical effects and / or can solve other technical problems. Thus, the examples of embodiments of this application as set forth above are intended to be illustrative and not limiting. Various changes can be made without departing from the spirit or scope of this application. Therefore, this application is intended to include all known or previously developed alternatives, modifications, variations, improvements, and / or substantially equivalents.

Claims

1. A control method (200) for a chiller unit (101) including a condenser (103), an evaporator (105), a compressor (102), a motor (107), and a motor cooling control valve (106), the motor (107) being configured to drive the compressor (102), and the motor cooling control valve (106) being configured to control the amount of fluid supplied from the condenser (103) to the motor (107) for cooling the motor (107), the control method (200) comprising: S1: Control the operation of the chiller unit (101) with the liquid level of the condenser (103) and / or the evaporator (105) as the control target; S2: Obtain the temperature of the motor (107) and the opening degree of the motor cooling control valve (106); S3: When the temperature of the motor (107) reaches or exceeds the motor temperature threshold and the motor cooling control valve (106) is fully open, switch to controlling the operation of the chiller unit (101) with the temperature of the motor (107) as the control target.

2. The control method (200) for a chiller unit according to claim 1, wherein the control method (200) further comprises: S4: When the chiller unit (101) is controlled with the temperature of the motor (107) as the control target, the opening degree of the motor cooling control valve (106) and the liquid level of the condenser (103) and / or the evaporator (105) are obtained. S5: When the motor cooling control valve (106) is fully open and the liquid level of the condenser (103) is lower than or equal to the condenser liquid level threshold, and / or the motor cooling control valve (106) is fully open and the liquid level of the evaporator (105) is higher than or equal to the evaporator liquid level threshold, the operation of the chiller unit (101) is switched from being controlled by the temperature of the motor (107) to being controlled by the liquid level of the condenser (103) and / or the evaporator (105), and the process returns to step S1.

3. The control method (200) for a chiller unit according to claim 1, wherein the chiller unit (101) further includes a flow regulating valve (104) located between the condenser (103) and the evaporator (105), wherein, The operation of the chiller unit (101) is controlled by adjusting the opening of the flow regulating valve (104) with the liquid level of the condenser (103) and / or the evaporator (105) as the control target or with the temperature of the motor (107) as the control target.

4. The control method (200) for a chiller unit according to claim 3, wherein, In step S3, when the chiller unit (101) is controlled to operate with the temperature of the motor (107) as the control target, the motor cooling control valve (106) is kept fully open and the opening of the flow regulating valve (104) is reduced.

5. The control method (200) for a chiller unit according to claim 1, wherein, In step S3, when the chiller unit (101) is operated with the temperature of the motor (107) as the control target: Obtain the heat exchange temperature difference of the evaporator (105); When the heat exchange temperature difference of the evaporator (105) reaches or exceeds the heat exchange temperature difference threshold and continues for a predetermined time, the chiller unit (101) is shut down.

6. The control method (200) for a chiller unit according to claim 2, wherein, The motor temperature threshold is the sum of the motor temperature setpoint and the motor temperature offset. The condenser liquid level threshold is the sum of the condenser liquid level set value and the condenser liquid level offset value; The evaporator liquid level threshold is the sum of the evaporator liquid level setpoint and the evaporator liquid level offset.

7. The control method (200) for a chiller unit according to claim 6, wherein, Controlling the operation of the chiller unit (101) with the temperature of the motor (107) as the control target includes: performing PID regulation with the set value of the motor temperature as the control target to control the operation of the chiller unit (101); Controlling the operation of the chiller unit (101) with the liquid level of the condenser (103) and / or the evaporator (105) as the control target includes: performing PID regulation with the liquid level setpoint of the condenser as the control target or performing PID regulation with the liquid level setpoint of the evaporator as the control target to control the operation of the chiller unit (101).

8. The control method (200) for a chiller unit according to claim 6, wherein, The motor temperature bias value, the condenser liquid level bias value, and the evaporator liquid level bias value are all adjustable.

9. The control method (200) for a chiller unit according to claim 1, wherein the temperature of the motor (107) includes: The temperature of the windings, rotor, bearings or housing of the motor (107).

10. The control method (200) for a chiller unit according to claim 2, wherein, The temperature of the motor (107) is obtained by estimating the temperature of the motor (107) based on the operating data of the chiller unit (101); or by obtaining the temperature of the motor (107) through a motor temperature sensor. The liquid level of the condenser (103) and / or the liquid level of the evaporator (105) are obtained by: estimating the liquid level of the condenser (103) and / or the liquid level of the evaporator (105) based on the operating data of the chiller unit (101); or obtaining the liquid level of the condenser (103) by means of a condenser liquid level sensor and / or obtaining the liquid level of the evaporator (105) by means of an evaporator liquid level sensor.

11. A controller (110) for a chiller unit, the controller (110) comprising: A processor (302) configured to execute the control method (200) of any one of claims 1-10 to control the operation of the chiller unit (101).

12. An air conditioning system (100), the air conditioning system (100) comprising: Chiller unit (101); A detection device (108) configured to detect the operating data of the chiller unit (101); and The controller (110) includes a processor (302) configured to execute the control method (200) of any one of claims 1-10 to control the operation of the chiller (101) based on detected operating data of the chiller unit (101).

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