System with water chilling unit and control method of water chilling unit

Abstract

The invention provides a control method of a water chilling unit. The water chilling unit 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 an amount of fluid provided from the condenser to the motor for cooling the motor. The control method comprises the steps that operation of the water chilling unit is controlled with the liquid level of the condenser and / or the evaporator as a control target; obtaining the temperature of the motor and the opening degree of a motor cooling control valve; and when the temperature of the motor reaches or exceeds the temperature threshold value and the motor cooling control valve is completely opened, the operation of the water chilling unit is controlled by taking the temperature of the motor as the control target. The control method can be realized only by adopting the existing design of the unit without adding extra components, so that the cost is not increased, and the operation failure rate of the unit is reduced; moreover, the temperature of the motor can be accurately controlled, a large amount of test data is not needed, the control is simple and reliable, and the operation efficiency of the unit is improved to the greatest extent.

Description

Technical Field

[0001] The present application relates to a chiller, and in particular to a system having a chiller, a control method for the chiller, and a control method for the system having the chiller. Background Art

[0002] One type of chiller is a steam compression chiller. The steam compression chiller includes a compressor, a motor, a condenser, and an evaporator. In a steam compression chiller, the motor is usually cooled by a refrigerant. The motor cooling circuit is used to circulate the refrigerant through the motor cavity to cool the motor in the motor cavity. For example, one side of the motor cooling circuit is connected to the condenser on the high-pressure side, and the other side is connected to the evaporator on the low-pressure side. Due to the pressure difference between the evaporator and the condenser, the refrigerant from the condenser side will enter the motor cavity to cool the motor, and then return to the evaporator on the low-pressure side after cooling. Summary of the invention

[0003] Motors usually need to maintain a certain temperature to ensure stable and efficient operation, and too much or too little motor cooling refrigerant (also called refrigerant) will have a significant impact on the temperature of the motor. Therefore, a control valve (for example, an electronic expansion valve) is usually installed on the motor cooling pipe to control the opening of the electronic expansion valve so that an appropriate amount of refrigerant enters the motor cavity to cool the motor, thereby ensuring that the temperature of the motor is stable within an appropriate range.

[0004] When the chiller is operating under normal conditions, in order to ensure that a certain amount of refrigerant is supplied from the condenser to the evaporator, the flow regulating valve (e.g., throttle valve) on the liquid supply pipeline between the evaporator and the condenser adopts, for example, a control method that takes the liquid level of the condenser and / or evaporator as the control target. This control method can ensure good control effects when operating under normal conditions. When the chiller is operating under normal conditions, the inlet water temperature of the condenser is usually higher than the outlet water temperature of the evaporator. When the chiller is operating under inverted conditions, the inlet water temperature of the condenser is lower than the outlet water temperature of the evaporator. This inverted condition is common in winter, when the inlet water temperature of the condenser is low, but at the same time, the outlet water temperature of the evaporator must be kept at a certain value higher than the inlet water temperature of the condenser to ensure production needs, such as data center requirements. When the chiller is operating under inverted conditions, if the flow regulating valve still adopts the conventional control method with the liquid level of the condenser and / or evaporator as the control target, the pressure difference between the condenser and the evaporator will be too small. As a result, even if the electronic expansion valve on the motor cooling pipe is fully opened (for example, the opening of the electronic expansion valve is 100%), only a small amount of refrigerant will enter the motor cavity from the condenser to cool the motor, and the refrigerant flow demand for motor cooling cannot be met.

[0005] The inventors have found that in order to meet the motor cooling and liquid supply requirements under the inverted working condition, one solution currently adopted is to add a pump (refrigerant pump) to use the pump to pump the refrigerant in the condenser into the motor cavity to meet the motor cooling requirements. Another solution currently adopted is a control solution that takes the pressure difference between the condenser and the evaporator as the control target to ensure sufficient pressure difference to supply liquid cooling to the motor.

[0006] The inventors also found that the solution of adding a pump will increase costs on the one hand, and on the other hand make the unit structure more complicated and increase the failure rate. The control scheme that uses the pressure difference between the condenser and the evaporator as the control target has the following defects: it is difficult to ensure accurate liquid supply for motor cooling because the motor temperature cannot be accurately controlled. If the throttle valve opening is too large, a small pressure difference will still lead to insufficient motor cooling liquid supply; if the throttle valve opening is too small, a large pressure difference will lead to too low evaporation pressure, increase the compressor operating power and reduce the overall operating efficiency. In addition, when establishing the relationship between the motor cooling liquid supply and the pressure difference between the condenser and the evaporator, it is often necessary to conduct a large number of tests on each compressor, which takes a long time and costs a lot of testing fees.

[0007] In order to solve the above problems, the present application provides a control method for a chiller, wherein when the motor cooling control valve (e.g., electronic expansion valve) is fully opened and the current motor temperature exceeds the motor temperature threshold, the opening control of the flow control valve on the main liquid supply pipeline of the unit will be controlled by the liquid level of the condenser and / or evaporator as the control target and will be controlled by the temperature of the motor as the control target, and for example, PID adjustment will be performed to meet the control requirements of the temperature of the motor under the reverse working condition. In addition, the present application also controls the opening control of the flow control valve by the motor temperature as the control target and the liquid level of the condenser and / or evaporator as the control target when the motor cooling control valve is fully opened and the liquid level of the condenser is lower than or equal to the condenser liquid level threshold, and / or the motor cooling control valve is fully opened and the liquid level of the evaporator is higher than or equal to the evaporator liquid level threshold. The control method of the present application does not have additional components, and can be realized by only using the existing design of the unit, without increasing costs, and reducing the failure rate of the unit operation. In addition, the control method of the present application can also realize accurate control of the temperature of the motor, does not require a large amount of test data, is simple and reliable to control, and maximizes the operation efficiency of the unit.

[0008] Specifically, according to the first aspect of the present application, the present application provides a control method for a chiller. The chiller 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 provided 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 is controlled with the liquid level of the condenser and / or the evaporator as the control target. In step S2, the temperature of the motor and the opening of the motor cooling control valve are obtained. In step S3, when the temperature of the motor reaches or exceeds the motor temperature threshold and the motor cooling control valve is fully opened, switch to controlling the operation of the chiller with the temperature of the motor as the control target.

[0009] According to the first aspect of the present application, the control method further includes the following steps S4 and S5. In step S4, when the operation of the chiller is controlled with the temperature of the motor as the control target, the opening of the motor cooling control valve and the liquid level of the condenser and / or the evaporator are obtained. In step S5, when the motor cooling control valve is fully opened and the liquid level of the condenser is lower than or equal to the condenser liquid level threshold, and / or the motor cooling control valve is fully opened and the liquid level of the evaporator is higher than or equal to the evaporator liquid level threshold, the control target is switched from the temperature of the motor as the control target to the liquid level of the condenser and / or the evaporator as the control target to control the operation of the chiller and go to step S1.

[0010] According to the first aspect of the present application, the chiller further comprises a flow control valve between the condenser and the evaporator. The opening of the flow control valve is adjusted to control the operation of the chiller with the liquid level of 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 the present application, in step S3, when controlling the operation of the chiller with the temperature of the motor 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 the present application, in step S3, when the operation of the chiller is controlled with the temperature of the motor 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 lasts for a predetermined time, the chiller is shut down.

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

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

[0015] According to the first aspect of the present application, the motor temperature offset value, the condenser liquid level offset value and the evaporator liquid level offset value are all adjustable.

[0016] According to the first aspect of the present application, the temperature of the motor includes: the temperature of the winding, rotor, bearing and / or casing of the motor.

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

[0018] According to a second aspect of the present application, the present application provides a controller for a chiller, wherein the controller comprises a processor configured to execute the aforementioned control method to control the operation of the chiller.

[0019] According to a third aspect of the present application, the present application provides an air conditioning system. The air conditioning system includes a chiller, a detection device and a controller. The detection device is configured to detect operating data of the chiller. The controller includes a processor, which is configured to execute the aforementioned control method based on the detected operating data of the chiller to control the operation of the chiller. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are not drawn to scale. In the drawings, each identical or nearly identical component represented in different figures is represented by the same reference numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

[0021] Figure 1 A block diagram structure of a system with a chiller according to the present application is shown;

[0022] Figure 2A Shows Figure 1 The overall flow chart of the control method of the chiller shown;

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

[0024] Figure 3 Shows Figure 1 The structural block diagram of the controller is shown. DETAILED DESCRIPTION

[0025] Various specific embodiments of the present application will be described below with reference to the accompanying drawings which constitute a 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 components.

[0026] Figure 1 The block diagram structure of a system 100 having a chiller 101 according to the present application is shown.

[0027] like Figure 1 As shown, the system 100 includes a chiller 101, a detection device 108 and a controller 110. The chiller 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 101 includes main liquid supply pipelines 109a, 109b, 109c, 109d and motor cooling pipelines 113a, 113b, 113c. In the main liquid supply pipelines 109a, 109b, 109c, 109d, the refrigerant flows from the outlet of the compressor 102 to the condenser 103, flows through the flow regulating valve 104 from the condenser 103, and then flows to the evaporator 105, and returns to the compressor 102 after flowing through the evaporator 105. One end of the motor cooling pipeline is connected to the condenser 103 on the high pressure side, and the other end is connected to the evaporator 105 on the low pressure side. The motor cooling control valve 106 is disposed 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 out from the condenser 103 to the motor cooling control valve 106, and reaches the motor cavity (not shown) through 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, the chiller 101 is a steam compression chiller, for example, the chiller 101 is a magnetic levitation centrifugal chiller, which is a chiller using a magnetic levitation centrifugal compressor. Figure 1 The main components of the chiller 101 are shown in FIG. The chiller 101 also includes other components ( Figure 1(not shown). For example, the chiller 101 further includes an economizer, or the condenser 103 of the chiller 101 further includes a subcooler. In one embodiment, the motor 107 is disposed in the compressor 102. In other embodiments, the motor 107 is disposed in other suitable locations. In one embodiment, the system 100 is an air conditioning system 100. In other embodiments, the system 100 is other suitable systems having a chiller.

[0029] like Figure 1 As shown, the detection device 108 is connected to the chiller 101 and is configured to detect and obtain operation data of the chiller 101 when it is in operation. The connection between the detection device 108 and the chiller 101 includes mechanical connection, electrical connection and / or communication connection, as well as direct or indirect connection, etc., so that the detection device 108 detects and obtains the operation data of the chiller 101. The detection device 108 can be a part of the chiller 101, or a device independent of the chiller 101.

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

[0031] Figure 2A Shows Figure 1 The overall flow chart of the control method 200 of the chiller 101 is shown.

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

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

[0034] In one embodiment, PID regulation is performed with the condenser liquid level setting value as the control target to control the operation of the chiller 101, so as to meet the control requirements for the condenser liquid level. For example, the condenser liquid level setting value is used as the target value of PID regulation, the flow control valve 104 is used as the actuator of PID regulation to generate the required condenser liquid level, and the condenser liquid level sensor is used as the detection mechanism of PID regulation. In other embodiments, the operation of the chiller 101 is controlled with the liquid level of the condenser 103 as the control target in other suitable ways. In one embodiment, PID regulation is performed with the evaporator liquid level setting value as the control target to control the operation of the chiller 101, so as to meet the control requirements for the evaporator liquid level. For example, the evaporator liquid level setting value is used as the target value of PID regulation, the flow control valve 104 is used as the actuator of PID regulation to generate the required evaporator liquid level, and the evaporator liquid level sensor is used as the detection mechanism of PID regulation. In other embodiments, the operation of the chiller 101 is controlled with the liquid level of the evaporator 105 as the control target in other suitable ways.

[0035] At step 206, the temperature of the motor 107 and the opening of the motor cooling control valve 106 are obtained. Then, the process proceeds to step 208 from step 206. In one embodiment, the controller 110 obtains the temperature of the motor 107 and the opening of the motor cooling control valve 106. The temperature of the motor 107 includes the temperature of the winding, rotor, bearing and / or housing of the motor 107. The temperature of the motor 107 also includes the temperature of other suitable components of the motor 107, which is used to indicate the temperature of the motor 107. In one embodiment, the controller 110 estimates the temperature of the motor 107 by the operating parameters of the chiller 101. For example, the temperature of the winding of the motor 107 is used as the temperature of the motor 107. The temperature of the housing of the motor 107 is detected by a housing temperature sensor, and the controller 110 obtains the temperature of the housing of the motor 107 from the housing temperature sensor, and obtains the temperature of the winding of the motor 107 based on the temperature of the housing (for example, by a temperature model). In one embodiment, the temperature of the motor 107 is detected by a motor temperature sensor (not shown), and the controller 110 obtains the detected temperature of the motor 107 from the motor temperature sensor. For example, the temperature of the motor 107 is the temperature of the winding of the motor 107. The temperature of the winding of the motor 107 is detected by one or more motor winding temperature sensors. The motor winding temperature sensor is disposed at one or both ends of the stator of the motor 107. In other embodiments, the temperature of the motor 107 is obtained by other suitable means. In one embodiment, the opening of the motor cooling control valve 106 is detected by a magnetoelectric sensor (not shown), and the controller 110 obtains the detected opening of the motor cooling control valve 106 from the magnetoelectric sensor. For example, the magnetoelectric sensor is disposed in the motor cooling control valve 106 or outside the motor cooling control valve 106. In other embodiments, the opening of the motor cooling control valve 106 is obtained by other suitable means.

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

[0037] At step 208, when the temperature of the motor 107 reaches or exceeds the motor temperature threshold and the motor cooling control valve 106 is fully opened, the process proceeds from step 208 to step 210, otherwise the process proceeds from step 208 to step 204 and continues to control the operation of the chiller 101 with the liquid level of the condenser 103 and / or the evaporator 105 as the control target. At step 210, the process switches from controlling the operation of the chiller 101 with the liquid level of the condenser 103 and / or the evaporator 105 as the control target to controlling the operation of the chiller 101 with the temperature of the motor 107 as the control target. 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 reaches or exceeds the motor temperature threshold and the motor cooling control valve 106 is fully opened, the controller 110 enters a new control mode, that is, the operation of the chiller 101 is controlled by taking the temperature of the motor 107 as the control target. When the controller 110 determines that the condition that the temperature of the motor 107 reaches or exceeds the motor temperature threshold and the motor cooling control valve 106 is fully opened is not met, the controller 110 maintains the original control mode of the chiller, that is, continues to control the operation of the chiller 101 by taking the liquid level of the condenser 103 and / or the evaporator 105 as the control target.

[0039] The temperature of the motor 107 reaches or exceeds the motor temperature threshold and the motor cooling control valve 106 is fully opened, indicating that the motor cooling control valve 106 is fully opened and cannot meet the cooling demand of the motor 107. The reason for this situation may be that the pressure difference between the condenser 103 and the evaporator 105 is small, so that the refrigerant in the condenser 103 cannot or less flows to the motor cavity through the motor cooling pipeline 113a, 113b, 113c to cool the motor 107, thereby failing to meet the cooling demand of the motor 107. Based on this situation, the present application switches the original control mode of the chiller 101 with the liquid level of the condenser 103 and / or the evaporator 105 as the control target (see step 204) to a new control mode with the temperature of the motor 107 as the control target (see step 210). The above situation may occur when the chiller 101 is operated under the reverse working condition, that is, the motor cooling control valve 106 is fully opened and cannot meet the cooling demand of the motor 107. The above situation may also occur when the chiller 101 is operated under other working conditions.

[0040] In one embodiment, when the operation of the chiller 101 is controlled with the temperature of the motor 107 as the control target, the controller 110 generates an opening control signal of the motor cooling control valve 106 based on the temperature of the motor 107 detected by the motor temperature sensor (not shown) to control the opening of the motor cooling control valve 106, thereby changing the pressure difference between the condenser 103 and the evaporator 105, and correspondingly causing the refrigerant to flow from the condenser 103 through the motor cooling pipeline to the motor cavity to cool the motor 107 to meet the cooling demand of the motor 107. In one embodiment, PID regulation is performed with the motor temperature setting value as the control target to control the operation of the chiller 101, thereby meeting the control requirements for the temperature of the motor 107. For example, the motor temperature setting value is used as the target value of the PID regulation, the flow control valve 104 is used as the actuator of the PID regulation to generate the required motor temperature, and the motor temperature sensor is used as the detection mechanism of the PID regulation. In 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 the motor 107 is controlled to meet the requirements in other suitable ways.

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

[0042] At step 214, it is determined whether the obtained opening of the motor cooling control valve 106 reaches 100% (i.e., whether the motor cooling control valve 106 is fully opened) 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 obtained opening 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 obtained opening of the motor cooling control valve 106 and the liquid level 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 setting value and the condenser liquid level offset value. For example, the operator inputs the condenser liquid level setting value and the condenser liquid level offset value into the controller 110, so that the controller 110 obtains the condenser liquid level threshold value based on the sum of the condenser liquid level setting value and the condenser liquid level offset value, and compares the obtained liquid level of the condenser 103 with the condenser liquid level threshold value to determine whether the liquid level of the condenser 103 is lower than or equal to the condenser liquid level threshold value. For example, the condenser liquid level offset value is +10%. The condenser liquid level offset value can also be other suitable values. In one embodiment, the evaporator liquid level threshold value is the sum of the evaporator liquid level setting value and the evaporator liquid level offset value. For example, the operator inputs the evaporator liquid level setting value and the evaporator liquid level offset value into the controller 110, so that the controller 110 obtains the evaporator liquid level threshold value based on the sum of the evaporator liquid level setting value and the evaporator liquid level offset value, and compares the obtained liquid level of the evaporator 105 with the evaporator liquid level threshold value to determine whether the liquid level of the evaporator 105 is higher than or equal to the evaporator liquid level threshold value. The evaporator level offset value may also be other suitable values. According to the actual situation, such as the actual structure of the chiller, the condenser level setting value, the condenser level offset value, the evaporator level setting value and the evaporator level offset value may be set (adjusted) to suitable values.

[0043] At step 214, when the motor cooling control valve 106 is fully opened 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 opened and the liquid level of 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 to control the operation of the chiller 101 with the temperature of the motor 107 as the control target. At step 216, it is determined whether the chiller 101 needs to be shut down. When the chiller 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 of the chiller 101 is terminated. When the chiller 101 does not need to be shut down, the process proceeds from step 216 to step 204, and the operation of the chiller 101 is controlled by switching from the temperature of the motor 107 as the control target to the liquid level of the condenser 103 and / or the evaporator 105 as the control target. In one embodiment, the controller 110 executes the above steps 214-218.

[0044] When the chiller 101 is operating under the control of taking 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, so as to meet the normal liquid supply required for motor cooling, the chiller 101 can be switched to the original control mode taking the liquid level of the condenser 103 and / or the evaporator 105 as the control target. However, the inventors have discovered that when the operation of the chiller 101 is controlled with the temperature of the motor 107 as the control target, due to the reduction in the opening of the flow regulating valve 104, the liquid level of the condenser 103 will generally be maintained at a relatively high height (for example, more than 90% of the maximum condenser liquid level set by the condenser liquid level sensor). In the original control mode of the chiller 101, for example, when the liquid level of the condenser 103 and / or the evaporator 105 is used as the control target, the liquid level setting value of the condenser 103 is, for example, 50% of the maximum condenser liquid level set by the condenser liquid level sensor, that is, the liquid level of the condenser 103 is approximately maintained at 50% of the set maximum condenser liquid level. If the control mode is switched from one in which the temperature of the motor 107 is used as the control target (for example, at this time the liquid level of the condenser 103 is maintained at more than 90% of the set maximum liquid level of the condenser) to one in which the liquid level of the condenser 103 and / or the evaporator 105 is used as the control target (for example, at this time the liquid level of the condenser 103 is roughly maintained at more than 50% of the set maximum liquid level of the condenser), the liquid level of the condenser 103 will fluctuate greatly, causing unstable operation of the chiller 101.

[0045] Therefore, in order to ensure that when the flow regulating valve 104 switches between the control of the chiller 101 with the temperature of the motor 107 as the control target (or called "reverse control") and the original control, the liquid level of the condenser 103 will not fluctuate greatly and cause unstable operation of the chiller 101, when the motor cooling control valve 106 is fully opened and the liquid level of the condenser 103 is lower than or equal to the condenser liquid level threshold, the application switches from controlling the operation of the chiller 101 with the temperature of the motor 107 as the control target to the original control of the chiller 101, for example, controlling the operation of the chiller 101 with the liquid level of the condenser 103 and / or the evaporator 105 as the control target. The present application does not switch back to the original control of the chiller 101 immediately when the temperature of the motor 107 reaches the required temperature, but switches back to the original control of the chiller 101 when the liquid level of the condenser 103 is further lower than or equal to the required liquid level (at this time the temperature of the motor 107 has reached the required temperature), thereby ensuring that the liquid level of the condenser 103 will not fluctuate greatly after the switch, and ensuring the stable operation of the chiller 101. The reasons for the reduction in the liquid level of the condenser 103 include: when the pressure difference between the condenser 103 and the evaporator 105 increases under the operating condition of the chiller 101 due to changes in external operating conditions, on the one hand, the increased pressure difference will drive more refrigerant from the condenser 103 to the evaporator 105, thereby causing the liquid level of the condenser 103 to drop; on the other hand, the increase in the pressure difference leads to an increase in the motor cooling liquid supply. At this time, the PID adjustment based on the temperature setting value will increase the opening of the flow control valve 104 to reduce the pressure difference, thereby further allowing more refrigerant to enter the evaporator 105 from the condenser 103.

[0046] In the chiller, 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 when the liquid level in the condenser 103 is low, the liquid level in the evaporator 105 is correspondingly high. Therefore, in another embodiment, in the control mode with the temperature of the motor 107 as the control target, the present application further switches back to the original control of the chiller 101 when the liquid level of the evaporator 105 is higher than or equal to the required liquid level (at this time, the temperature of the motor 107 has reached the required temperature), which can also ensure that the liquid levels of the condenser 103 and the evaporator 105 will not fluctuate greatly after the switch, and ensure the stable operation of the chiller 101.

[0047] Figure 2B Shows Figure 2A FIG. 2 is a flow chart of an embodiment of step 210 in the control method 200 shown in FIG. Figure 2A As shown, at step 210 , the operation of the chiller 101 is controlled by switching from taking the liquid level of the condenser 103 as the control target to taking the temperature of the motor 107 as the control target.

[0048] like Figure 2B As shown by Figure 2A Step 208 Go 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 101 with the temperature of the motor 107 as the control target. In other embodiments, the operation of the chiller 101 is controlled with the temperature of the motor 107 as the control target in other suitable ways. Then, step 222 is transferred to step 224. In one embodiment, when the operation of the chiller 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 generates 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 reducing the opening of the flow regulating valve 104. Therefore, the pressure difference between the condenser 103 and the evaporator 105 increases, so that more refrigerant reaches the motor cavity from the condenser 103 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 (refrigerant)) and the outlet water temperature in the evaporator 105. Then, step 224 is transferred 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 the detected. In addition, the controller 110 obtains the pressure of the refrigerant in the evaporator 105 detected from the pressure sensor, obtains the saturation temperature (i.e., evaporation temperature) of the refrigerant based on the pressure of the refrigerant, and obtains the outlet water temperature of the evaporator 105 detected from the outlet water temperature sensor, and compares the obtained evaporation temperature with the 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] At step 226, it is determined whether 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. 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 is transferred from step 226 to step 227. Figure 2A Step 218 is used to terminate the execution of the control method 200 of the chiller 101, otherwise the execution is transferred from step 226 to Figure 2AStep 212. In one embodiment, the controller 110 performs the above step 226. In one embodiment, the operator inputs the heat exchange temperature difference threshold and the predetermined time into the controller 110. The controller 110 compares the obtained 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 obtains the duration of the 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 reaches the predetermined time.

[0051] In one embodiment, when the chiller 101 is operating under the reverse working condition, it is necessary to increase the heat exchange temperature difference of the evaporator 105 to achieve the purpose of increasing the pressure difference between the condenser 103 and the evaporator 105. The inventor found that due to the limitations of the adjustment capacity of the flow control valve 104, the heat exchange temperature difference of the evaporator 105 should not be increased 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 101 shuts down and prompts (or warns) that the heat exchange temperature difference of the evaporator 105 is too large, thereby protecting the chiller 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 ) includes the above-mentioned motor temperature sensor, casing temperature sensor, motor winding temperature sensor, magnetoelectric sensor, condenser liquid level sensor, evaporator liquid level sensor, pressure sensor, water outlet temperature sensor, etc.

[0053] Figure 3 Shows Figure 1 The structural block diagram of the controller 110 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, the memory 303, the input interface 304, and the 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 the processing of data. 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] The input interface 304 is configured to receive the acquired operation data of the chiller 101 from the detection device 108 through the connection line 112. The input interface 304 is also configured to convert the received data into data recognizable by the processor 302, and output the data to the processor 302. For example, the detection device 108 includes a motor temperature sensor for detecting the temperature of the motor 107, a shell temperature sensor for detecting the temperature of the shell of the motor 107, a motor winding temperature sensor for detecting the temperature of the winding of the motor 107, a magnetoelectric sensor for detecting the opening of the motor cooling control valve 106, a condenser liquid level sensor for detecting the liquid level of the condenser 103, an evaporator liquid level sensor for detecting the liquid level of the evaporator 105, a pressure sensor for detecting the pressure of the refrigerant in the evaporator 105, a water outlet temperature sensor for detecting the outlet water temperature of the evaporator 105, and the like. The input interface 304 receives data of the above parameters when the chiller 101 is running from the detection device 108 , converts the data into data recognizable by the processor 302 , and outputs the data to the processor 302 .

[0056] The processor 302 is configured to process (e.g., calculate) the received data to generate a control signal. In one embodiment, the processor 302 generates an opening control signal of the flow control valve 104 to control the opening of the flow control valve 104, and also generates an opening control signal of the motor cooling control valve 106 to control the opening of the motor cooling control valve 106. For example, the 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] The output interface 305 is configured to receive a control signal from the processor 302, convert the control signal into a signal suitable for the chiller 101, and send the control signal to the chiller 101 to control the operation of the chiller 101. In one embodiment, the output interface 305 sends an opening control signal of the flow regulating valve 104 and / or the motor cooling control valve 106 to the chiller 101 through the connecting line 111 to control the opening of the flow regulating valve 104 and / or the motor cooling control valve 106, thereby controlling the operation of the chiller 101.

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

[0059] 1. This application uses the flow control valve to directly control the motor temperature, which can greatly reduce the cost of the whole machine, simplify the system structure of the unit, and reduce the failure rate;

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

[0061] 3. The present application does not require a large number of tests to be performed on each compressor to establish the relationship between the motor cooling liquid supply and the pressure difference between the condenser and the evaporator, which can save a lot of testing time and testing costs.

[0062] All features disclosed in this specification (including any attached claims, abstracts and drawings) and / or all steps of any method or process disclosed in this specification can be combined in any suitable combination, except for at least some mutually exclusive combinations of such features and / or steps. The application is not limited to the specific order of steps described in the specification, but includes other suitable order of steps for implementing the application.

[0063] Although the present application has been described in conjunction with the examples of the embodiments summarized above, various alternatives, modifications, changes, improvements and / or substantially equivalent solutions, whether known or currently or foreseeable in the near future, may be apparent to those skilled in the art. In addition, the technical effects and / or technical problems described in this specification are exemplary rather than restrictive; so the disclosure in this specification may be used to solve other technical problems and have other technical effects and / or may solve other technical problems. Therefore, the examples of the embodiments of the present application as stated above are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit or scope of the present application. Therefore, the present application is intended to include all known or earlier developed alternatives, modifications, changes, improvements and / or substantially equivalent solutions.

Claims

1. A control method (200) for a chiller, the chiller (101) comprising 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), the motor cooling control valve (106) being configured to control the amount of fluid provided from the condenser (103) to the motor (107) for cooling the motor (107), the control method (200) comprising: S1: controlling the operation of the chiller (101) with the liquid level of the condenser (103) and / or the evaporator (105) as a control target; S2: Acquiring 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 opened, switching to control the operation of the chiller (101) with the temperature of the motor (107) as the control target.

2. The control method (200) for a chiller according to claim 1, the control method (200) further comprising: S4: when controlling the operation of the chiller (101) with the temperature of the motor (107) as a control target, obtaining the opening of the motor cooling control valve (106) and the liquid level of the condenser (103) and / or the evaporator (105); S5: When the motor cooling control valve (106) is fully opened and the liquid level of the condenser (103) is lower than or equal to the condenser liquid level threshold, and / or when the motor cooling control valve (106) is fully opened and the liquid level of the evaporator (105) is higher than or equal to the evaporator liquid level threshold, the operation of the chiller (101) is controlled by switching from taking the temperature of the motor (107) as the control target to taking the liquid level of the condenser (103) and / or the evaporator (105) as the control target and proceeding to step S1.

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

4. The control method (200) for a chiller according to claim 3, wherein: In step S3, when the operation of the chiller (101) is controlled 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 according to claim 1, wherein: In step S3, when the operation of the chiller (101) is controlled with the temperature of the motor (107) as a control target: Obtaining the heat exchange temperature difference of the evaporator (105); When the heat exchange temperature difference of the evaporator (105) reaches or exceeds a heat exchange temperature difference threshold and lasts for a predetermined time, the chiller (101) is shut down.

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

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

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

9. The control method (200) for a chiller according to claim 1, wherein the temperature of the motor (107) comprises: The temperature of the windings, rotor, bearings and / or casing of the motor (107).

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

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

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

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