A screw water chiller and a control method and device thereof

Abstract

The application discloses a screw water chiller, a control method and device thereof, and belongs to the technical field of air conditioning. The screw water chiller comprises at least a compressor, a frequency converter and a variable valve. The control method of the screw water chiller comprises the following steps: obtaining a target water temperature, a current water temperature and a current water temperature change rate of the screw water chiller; determining a unit adjustment value according to the target water temperature, the current water temperature and the current water temperature change rate; judging whether the unit adjustment value is within a preset adjustment range; and if not, adjusting the opening degree of the variable valve and the frequency of the frequency converter according to the unit adjustment value. The technical scheme can realize efficient and accurate water temperature adjustment and improve energy efficiency.

Description

Technical Field

[0001] This invention relates to control technology for water chillers, and more particularly to a screw chiller and its control method and apparatus. Background Technology

[0002] When a conventional fixed-frequency screw chiller unit is started in a star-delta configuration, the unit load is adjusted by the solenoid valve built into the compressor, which can be either stepped or stepless. However, stepped adjustment results in unstable water temperature, while stepless adjustment cannot precisely control the specific position of the compressor slider, thus failing to accurately control the unit load and achieve precise water temperature control. Summary of the Invention

[0003] This invention provides a screw chiller unit and its control method and device to achieve efficient and precise water temperature regulation.

[0004] In a first aspect, the present invention provides a control method for a screw chiller unit, the screw chiller unit comprising at least a compressor, a frequency converter, and an adjustable valve, the control method for the screw chiller unit comprising:

[0005] Obtain the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit;

[0006] The unit adjustment value is determined based on the target water temperature, the current water temperature, and the rate of change of the current water temperature;

[0007] Determine whether the unit's adjustment value is within the preset adjustment range;

[0008] If not, adjust the opening of the control valve and the frequency of the inverter according to the unit's adjustment value.

[0009] Optionally, the unit adjustment value is determined based on the target water temperature, the current water temperature, and the rate of change of the current water temperature, including:

[0010] Based on the target water temperature, the current water temperature, and the rate of change of the current water temperature, the unit adjustment value is determined using a PID control algorithm.

[0011] Optionally, the adjustable valve includes n levels of adjustable opening; the frequency converter includes m levels of adjustable frequency; the opening value of the n levels of adjustable opening increases progressively; the frequency value of the m levels of adjustable frequency increases progressively; wherein, n and m are both positive integers greater than or equal to 2, and m is greater than n.

[0012] Optionally, adjusting the opening of the control valve and the frequency of the frequency converter according to the unit's adjustment value includes:

[0013] When the unit adjustment value is less than the lower limit of the preset adjustment range, determine whether the current frequency of the inverter is the m-th level adjustment frequency;

[0014] If not, control the energy regulating valve to maintain its current opening, adjust the current frequency of the inverter to the next level of regulation frequency, and return to the step of obtaining the target water temperature, current water temperature and current water temperature change rate of the screw chiller unit;

[0015] If so, the control valve is adjusted to the next level of opening below the current opening, and the current frequency of the inverter is adjusted to the first level of adjustment frequency. Then, the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0016] Optionally, controlling the adjustable valve to maintain its current opening and adjusting the current frequency of the frequency converter to the next adjustable frequency includes:

[0017] The control valve is kept at its current opening, and the current frequency of the inverter is adjusted to the next level of adjustment frequency at a first preset rate.

[0018] Controlling the adjustable valve to adjust to the next level of opening from the current opening, and adjusting the current frequency of the frequency converter to the first-level adjustment frequency, includes:

[0019] The control valve is adjusted to the next level of opening of the current opening, and the current frequency of the inverter is adjusted to the first level of adjustment frequency at a second preset rate;

[0020] The second preset rate is greater than the first preset rate.

[0021] Optionally, adjusting the opening of the control valve and the frequency of the frequency converter according to the unit's adjustment value includes:

[0022] When the unit adjustment value is greater than the upper limit of the preset adjustment range, it is determined whether the current frequency of the frequency converter is the first-level adjustment frequency;

[0023] If not, control the energy regulating valve to maintain its current opening, adjust the current frequency of the inverter to the next higher level of regulation frequency, and return to the step of obtaining the target water temperature, current water temperature and current water temperature change rate of the screw chiller unit.

[0024] If so, the control valve is adjusted to the next higher level of opening, and the current frequency of the inverter is adjusted to the m-th level adjustment frequency. Then, the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0025] Optionally, controlling the adjustable valve to maintain its current opening and adjusting the current frequency of the frequency converter to the next higher adjustment frequency includes:

[0026] The control valve is kept at its current opening, and the current frequency of the inverter is adjusted to the next higher adjustment frequency at a third preset rate.

[0027] Controlling the adjustable valve to adjust to the next higher opening degree and adjusting the current frequency of the frequency converter to the m-th adjustment frequency includes:

[0028] Control the adjustable valve to adjust to the next higher level of opening of the current opening, and adjust the current frequency of the inverter to the m-th level of adjustment frequency at a fourth preset rate;

[0029] The fourth preset rate is greater than the third preset rate.

[0030] Optional, also includes:

[0031] If the unit adjustment value is within the preset adjustment range, then the energy regulating valve is controlled to maintain its current opening, and the frequency converter is controlled to maintain its current frequency.

[0032] Secondly, the present invention provides a control device for a screw chiller unit, the screw chiller unit including at least a compressor, a frequency converter, and an adjustable valve, the control device for the screw chiller unit comprising:

[0033] The temperature acquisition module is used to acquire the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0034] The adjustment value determination module is used to determine the unit adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature;

[0035] The adjustment value judgment module is used to determine whether the unit adjustment value is within the preset adjustment range;

[0036] The opening frequency adjustment module is used to adjust the opening of the energy regulating valve and the frequency of the frequency converter according to the unit adjustment value when the unit adjustment value is not within the preset adjustment range.

[0037] Thirdly, the present invention provides a screw chiller unit, comprising: a compressor, a frequency converter, an adjustable valve, and a controller;

[0038] The controller is used to execute the control method for the screw chiller unit described in the first aspect of the present invention.

[0039] The technical solution of this invention determines the unit adjustment value based on the acquired target water temperature, current water temperature, and current water temperature change rate. If the unit adjustment value is within the preset adjustment range, the energy regulating valve is controlled to maintain its current opening, and the frequency converter is controlled to maintain its current frequency. If the unit adjustment value is not within the preset adjustment range, the opening of the energy regulating valve and the frequency of the frequency converter are adjusted according to the unit adjustment value, so that the current water temperature of the unit after adjustment is basically consistent with and stable with the target water temperature, thereby achieving efficient and precise water temperature regulation and improving energy efficiency. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of a screw chiller unit provided in an embodiment of the present invention;

[0041] Figure 2 A flowchart of a control method for a screw chiller unit provided in Embodiment 2 of the present invention;

[0042] Figure 3 A flowchart of a control method for a screw chiller unit provided in Embodiment 3 of the present invention;

[0043] Figure 4 A flowchart of a control method for a screw chiller unit provided in Embodiment 4 of the present invention;

[0044] Figure 5 This is a schematic diagram of the control device for a screw chiller unit provided in Embodiment 5 of the present invention. Detailed Implementation

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0046] Example 1

[0047] Figure 1 A schematic diagram of a screw chiller unit provided in an embodiment of the present invention includes: a compressor 11, an adjustable valve 12, a frequency converter 13, and a controller 14.

[0048] The compressor 11 draws in low-temperature, low-pressure refrigerant gas. An internal motor drives a compression unit to compress the refrigerant gas, discharging high-temperature, high-pressure refrigerant liquid, thus providing power for the refrigeration cycle and achieving a compression-condensation-expansion-evaporation refrigeration cycle. The compressor 11 can be a screw compressor, etc. An adjustable valve 12 is connected to the compressor 11 to regulate the intake air volume, thereby controlling the cooling capacity of the compressor 11. A frequency converter 13 is connected to the controller 14 and the compressor 11, receiving signals from the controller 14 and adjusting the frequency of the compressor 11 according to the control signals.

[0049] The controller provided in this embodiment of the invention is used to execute the control method of the screw chiller provided in any embodiment of the invention. It controls the frequency converter to change the operating frequency of the compressor and controls the opening degree of the adjustable valve to control the operating state of the compressor. It has the same beneficial effect as the method, that is, by controlling the operating frequency of the compressor and controlling the opening degree of the adjustable valve, the current water temperature of the screw chiller is made to be basically consistent with the target water temperature.

[0050] Example 2

[0051] Figure 2 This is a flowchart illustrating a control method for a screw chiller unit according to Embodiment 2 of the present invention. This method is applicable to situations where the chilled water temperature in a screw chiller unit is controlled. The method can be executed by the control device of the screw chiller unit provided in this embodiment of the invention. This control device is implemented in hardware and / or software and can be integrated into the controller of the screw chiller unit. The screw chiller unit includes at least a compressor, a frequency converter, and a variable valve. Figure 2 As shown, the control method for screw chiller units includes:

[0052] S101. Obtain the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0053] The target water temperature can be a user-defined value or a value automatically determined by the screw chiller based on the current room temperature. The current water temperature is the actual water temperature under the current operating conditions of the screw chiller. The current water temperature change rate is the rate at which the actual water temperature changes under the current operating conditions of the screw chiller. A large current water temperature change rate indicates a large and unstable temperature fluctuation; a small current water temperature change rate indicates a small and stable temperature change.

[0054] S102. Determine the unit adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature.

[0055] The unit's regulation value is determined by the target water temperature, the current water temperature, and the rate of change of the current water temperature. In other words, the unit's regulation value is related to the target water temperature, the current water temperature, and the rate of change of the current water temperature.

[0056] Specifically, if the difference between the current water temperature and the target water temperature is large, then the current water temperature and the target water temperature have a large difference; if the difference between the current water temperature and the target water temperature is small, then the current water temperature and the target water temperature have a small difference.

[0057] In an optional embodiment, the unit adjustment value is determined based on the target water temperature, the current water temperature, and the rate of change of the current water temperature. Specifically, based on the target water temperature, the current water temperature, and the rate of change of the current water temperature, the unit adjustment value is determined using a PID control algorithm. That is, the acquired target water temperature, current water temperature, and rate of change of the current water temperature are fed back to the PID control algorithm, and the unit adjustment value is determined according to the specific PID control algorithm, so that the screw chiller unit can be adjusted accordingly in subsequent operations. It is understood that the PID control algorithm can be specifically designed according to actual needs, and this embodiment of the invention does not impose specific limitations on it.

[0058] S103. Determine whether the unit adjustment value is within the preset adjustment range; if yes, proceed to S105; if no, proceed to S104.

[0059] The preset adjustment range can be set according to actual needs, and the embodiments of the present invention do not impose specific limitations on it.

[0060] S104. Adjust the opening degree of the control valve and the frequency of the frequency converter according to the unit's adjustment value.

[0061] S105 controls the energy regulating valve to maintain its current opening degree and controls the frequency converter to maintain its current frequency.

[0062] Specifically, if the unit's adjustment value is within the preset adjustment range, it indicates that the current water temperature is basically consistent with the target water temperature and is stable. At this time, the control valve maintains its current opening, and the frequency converter maintains its current frequency. If the unit's adjustment value is not within the preset adjustment range, it indicates that the current water temperature differs significantly from the target water temperature and / or the current water temperature fluctuates significantly and is unstable. At this time, the opening of the control valve and the frequency of the frequency converter are adjusted according to the unit's adjustment value to make the adjusted water temperature basically consistent with the target water temperature, and stable without fluctuation or with small fluctuations within a certain range.

[0063] The technical solution of this invention determines the unit adjustment value based on the acquired target water temperature, current water temperature, and current water temperature change rate. If the unit adjustment value is within a preset adjustment range, the energy regulating valve is controlled to maintain its current opening, and the frequency converter is controlled to maintain its current frequency. If the unit adjustment value is not within the preset adjustment range, the opening of the energy regulating valve and the frequency of the frequency converter are adjusted according to the unit adjustment value, so that the current water temperature of the unit after adjustment is basically consistent with and stable with the target water temperature, thereby achieving efficient and precise water temperature regulation and improving energy efficiency.

[0064] Example 3

[0065] Based on the above embodiments, Figure 3 This is a flowchart of a control method for a screw chiller unit according to Embodiment 3 of the present invention. This embodiment describes the adjustment of the opening degree of the control valve and the frequency of the frequency converter based on the unit's adjustment value. Figure 3 As shown, the control method for screw chiller units includes:

[0066] S201. Obtain the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0067] S202. Determine the unit adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature.

[0068] S203. Determine whether the unit's adjustment value is within the preset adjustment range; if not, proceed to S204.

[0069] S204. When the unit's adjustment value is less than the lower limit of the preset adjustment range, determine whether the current frequency of the frequency converter is the m-th level adjustment frequency; if not, execute S205; if yes, execute S206.

[0070] Optionally, the adjustable valve may include n levels of adjustable opening; the opening values ​​of the n levels of adjustable opening increase progressively; that is, the opening value of the nth level is greater than the opening value of the (n-1)th level, the opening value of the (n-1)th level is greater than the opening value of the (n-2)th level, ..., the opening value of the 2nd level is greater than the opening value of the 1st level. Correspondingly, the frequency converter may include m levels of adjustable frequency; the frequency values ​​of the m levels of adjustable frequency increase progressively, that is, the mth level adjustable frequency > the (m-1)th level adjustable frequency > ... > the 1st level adjustable frequency; where n and m are both positive integers greater than or equal to 2, and m is greater than n.

[0071] For example, such as Figure 1As shown, taking an example with n=4, m=21, and the opening values ​​of the 1st, 2nd, 3rd, and 4th adjustment levels being 25%, 50%, 75%, and 100% respectively, and the adjustment frequencies of the 1st, 2nd, ..., and 21st levels being 30Hz, 31Hz, ..., and 50Hz respectively, the adjustable valve 12 includes 4 adjustment opening levels, and the frequency converter 13 includes 21 adjustment frequencies. The opening values ​​of the 4th adjustment level increase progressively, i.e., the opening value of the 4th adjustment level is greater than that of the 3rd adjustment level, the opening value of the 3rd adjustment level is greater than that of the 2nd adjustment level, and the opening value of the 2nd adjustment level is greater than that of the 1st adjustment level. Correspondingly, the frequency values ​​of the 21st adjustment levels increase sequentially, i.e., the 21st adjustment frequency > the 20th adjustment frequency > ... > the 1st adjustment frequency.

[0072] It is understood that the above example only illustrates the case where n=4, m=21, and the opening values ​​of the 1st, 2nd, 3rd and 4th adjustment levels are 25%, 50%, 75% and 100% respectively, and the adjustment frequencies of the 1st, 2nd, ... and 21st levels are 30, 31, ... and 50 respectively. The opening value of each level in the n-level adjustment and the adjustment frequency of each level in the m-level adjustment can be set according to actual needs, and the embodiments of the present invention do not impose specific limitations on this.

[0073] S205: Control the control valve to maintain its current opening, adjust the current frequency of the frequency converter to the next level of adjustment frequency, and return to execute S201.

[0074] Specifically, when the unit's adjustment value is less than the lower limit of the preset adjustment range, if the inverter's current frequency is not the m-th level adjustment frequency, it indicates that the inverter's current frequency is less than the m-th level adjustment frequency, and loading is required to make the current water temperature basically consistent with and stable with the target water temperature. At this time, the control valve is kept at its current opening, and the inverter's current frequency is adjusted to the next level adjustment frequency. The process then returns to the steps of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit. If the adjusted unit's adjustment value is still less than the lower limit of the preset adjustment range and the inverter's current frequency is still not the m-th level adjustment frequency, the control valve is again kept at its current opening, and the inverter's current frequency is adjusted to the next level adjustment frequency until the unit's adjustment value is within the preset adjustment range. Specifically, when controlling the control valve to maintain its current opening and adjusting the inverter's current frequency to the next level adjustment frequency, the control valve can be kept at its current opening, and the inverter's current frequency can be adjusted to the next level adjustment frequency at a first preset rate. The first preset rate can be set according to actual needs, and the embodiments of the present invention do not impose specific limitations.

[0075] S206: Control the adjustable valve to adjust to the next level of opening of the current opening, adjust the current frequency of the frequency converter to the first level of adjustment frequency, and return to execute S201.

[0076] Specifically, when the unit's adjustment value is less than the lower limit of the preset adjustment range, if the inverter's current frequency is the m-th level adjustment frequency, it indicates that the inverter's current frequency is the m-th level adjustment frequency. At this time, the control valve is adjusted to the next level of opening, and the inverter's current frequency is adjusted to the first level adjustment frequency. The process then returns to the steps of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit until the unit's adjustment value is within the preset adjustment range. Specifically, when the control valve is adjusted to the next level of opening and the inverter's current frequency is adjusted to the first level adjustment frequency, the inverter's current frequency can be adjusted to the first level adjustment frequency at a second preset rate.

[0077] In an optional embodiment, the second preset rate may be greater than the first preset rate.

[0078] Specifically, the inverter's current frequency is adjusted to the next lower regulation frequency at a first preset rate. Since the current frequency and the next lower regulation frequency are relatively close, the adjustment can be achieved quickly even at a small first preset rate. The inverter's current frequency is then adjusted to the first regulation frequency at a second preset rate. Since the current frequency may differ significantly from the first regulation frequency, a larger second preset rate is needed to adjust the inverter's current frequency to the first regulation frequency as quickly as possible.

[0079] In the technical solution of this invention embodiment, when the unit adjustment value is less than the lower limit of the preset adjustment range, if the current frequency of the frequency converter is not the m-th level adjustment frequency, the control valve is kept at its current opening, the current frequency of the frequency converter is adjusted to the next level adjustment frequency, and the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit; if the current frequency of the frequency converter is the m-th level adjustment frequency, the control valve is adjusted to the next level opening, the current frequency of the frequency converter is adjusted to the first level adjustment frequency, and the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit until the unit adjustment value is within the preset adjustment range.

[0080] Example 4

[0081] Based on the above embodiments, Figure 4This is a flowchart illustrating a control method for a screw chiller unit according to Embodiment 4 of the present invention. This embodiment describes the adjustment of the opening degree of the control valve and the frequency of the frequency converter based on the unit's adjustment values. Figure 4 As shown, the control method for screw chiller units includes:

[0082] S301. Obtain the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

[0083] S302. Determine the unit's adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature.

[0084] S303. Determine whether the unit's adjustment value is within the preset adjustment range; if not, proceed to S304.

[0085] S304. When the unit's adjustment value is greater than the upper limit of the preset adjustment range, determine whether the current frequency of the frequency converter is the first-level adjustment frequency; if not, execute S305; if yes, execute S306.

[0086] S305: Control the control valve to maintain its current opening, adjust the current frequency of the frequency converter to the previous level of adjustment frequency, and return to execute S301.

[0087] Specifically, when the unit's adjustment value exceeds the upper limit of the preset adjustment range, it indicates that the inverter needs to reduce its load to ensure that the current water temperature is basically consistent with and stable against the target water temperature. If the inverter's current frequency is not the first-level adjustment frequency, the control valve is kept at its current opening, and the inverter's current frequency is adjusted to the next higher adjustment frequency. The process then returns to obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit. If the adjusted unit's adjustment value is still greater than the upper limit of the preset adjustment range and the inverter's current frequency is still not the first-level adjustment frequency, the control valve is again kept at its current opening, and the inverter's current frequency is adjusted to the next higher adjustment frequency until the unit's adjustment value is within the preset adjustment range. When controlling the control valve to keep its current opening and adjusting the inverter's current frequency to the next higher adjustment frequency, a third preset rate can be used to adjust the inverter's current frequency to the next higher adjustment frequency. This third preset rate can be set according to actual needs, and this embodiment of the invention does not impose specific limitations.

[0088] S306: Control the adjustable valve to adjust to the next higher level of opening, adjust the current frequency of the inverter to the m-th level of adjustment frequency, and return to execute S301.

[0089] Specifically, when the unit's adjustment value exceeds the upper limit of the preset adjustment range, it indicates that the inverter needs to reduce its load to ensure that the current water temperature is basically consistent with and stable against the target water temperature. If the inverter's current frequency is the first-level adjustment frequency, the control valve is adjusted to the next higher level of opening, and the inverter's current frequency is adjusted to the m-th level adjustment frequency. The process then returns to the steps of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit until the unit's adjustment value is within the preset adjustment range. Specifically, when the control valve is adjusted to the next higher level of opening, and the inverter's current frequency is adjusted to the m-th level adjustment frequency, the fourth preset rate can be used to adjust the inverter's current frequency to the m-th level adjustment frequency. This fourth preset rate can be set according to actual needs, and this embodiment of the invention does not impose specific limitations.

[0090] In an optional embodiment, the fourth preset rate is greater than the third preset rate.

[0091] Specifically, the inverter's current frequency is adjusted to the next higher regulation frequency at the third preset rate. Since the current frequency is relatively close to the previous regulation frequency, this adjustment can be achieved quickly even at a low third preset rate. The inverter's current frequency is then adjusted to the m-th regulation frequency at the fourth preset rate. Since the current frequency may differ significantly from the m-th regulation frequency, a higher fourth preset rate is needed to adjust the inverter's current frequency to the m-th regulation frequency as quickly as possible.

[0092] In the technical solution of this invention embodiment, when the unit adjustment value is greater than the upper limit of the preset adjustment range, if the current frequency of the frequency converter is not the first-level adjustment frequency, the control valve is kept at its current opening, the current frequency of the frequency converter is adjusted to the next higher level adjustment frequency, and the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit; if the current frequency of the frequency converter is the first-level adjustment frequency, the control valve is adjusted to the next higher level opening, the current frequency of the frequency converter is adjusted to the m-th level adjustment frequency, and the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit until the unit adjustment value is within the preset adjustment range.

[0093] Example 5

[0094] This invention provides a control device for a screw chiller unit, used to control the operation of the screw chiller unit. The screw chiller unit includes at least a compressor, a frequency converter, and a variable valve. This control device can execute the control method for the screw chiller unit provided in this invention. The control device can be implemented in hardware and / or software, and can be integrated into the controller of the screw chiller unit provided in this invention. Figure 5 This is a schematic diagram of the control device for a screw chiller unit provided in Embodiment 5 of the present invention, as shown below. Figure 5 As shown, the control device for the screw chiller unit includes:

[0095] Temperature acquisition module 21 is used to acquire the target water temperature, current water temperature and current water temperature change rate of the screw chiller unit.

[0096] The adjustment value determination module 22 is used to determine the unit adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature.

[0097] The adjustment value judgment module 23 is used to determine whether the unit adjustment value is within the preset adjustment range.

[0098] The opening frequency adjustment module 24 is used to adjust the opening of the control valve and the frequency of the frequency converter according to the unit adjustment value when the unit adjustment value is not within the preset adjustment range.

[0099] The control device for the screw chiller unit provided in this embodiment of the invention is used to execute the control method for the screw chiller unit provided in any embodiment of the invention, and has the same beneficial effects as the method, which will not be repeated here.

[0100] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A control method for a screw chiller unit, characterized in that, The screw chiller unit includes at least a compressor, a frequency converter, and an adjustable valve. The adjustable valve has n levels of adjustable opening degree; the frequency converter has m levels of adjustable frequency; the opening degree values ​​of the n levels of adjustable opening degree increase progressively; the frequency values ​​of the m levels of adjustable frequency increase sequentially; wherein n and m are both positive integers greater than or equal to 2, and m is greater than n; the control method of the screw chiller unit includes: Obtain the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit; The unit adjustment value is determined based on the target water temperature, the current water temperature, and the rate of change of the current water temperature; Determine whether the unit's adjustment value is within the preset adjustment range; If not, adjust the opening of the control valve and the frequency of the inverter according to the unit adjustment value; Adjusting the opening degree of the energy regulating valve and the frequency of the frequency converter according to the unit's regulation value includes: When the unit adjustment value is less than the lower limit of the preset adjustment range, determine whether the current frequency of the inverter is the m-th level adjustment frequency; If not, control the energy regulating valve to maintain its current opening, adjust the current frequency of the inverter to the next level of regulation frequency, and return to the step of obtaining the target water temperature, current water temperature and current water temperature change rate of the screw chiller unit; If so, the control valve is adjusted to the next level of opening below the current opening, and the current frequency of the inverter is adjusted to the first level of adjustment frequency. Then, the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

2. The control method for a screw chiller unit according to claim 1, characterized in that, Based on the target water temperature, the current water temperature, and the rate of change of the current water temperature, the unit adjustment values ​​are determined, including: Based on the target water temperature, the current water temperature, and the rate of change of the current water temperature, the unit adjustment value is determined using a PID control algorithm.

3. The control method for a screw chiller unit according to claim 1, characterized in that, Controlling the adjustable valve to maintain its current opening and adjusting the current frequency of the frequency converter to the next adjustable frequency includes: The control valve is kept at its current opening, and the current frequency of the inverter is adjusted to the next level of adjustment frequency at a first preset rate. Controlling the adjustable valve to adjust to the next level of opening from the current opening, and adjusting the current frequency of the frequency converter to the first-level adjustment frequency, includes: The control valve is adjusted to the next level of opening of the current opening, and the current frequency of the inverter is adjusted to the first level of adjustment frequency at a second preset rate; The second preset rate is greater than the first preset rate.

4. The control method for a screw chiller unit according to claim 1, characterized in that, Adjusting the opening degree of the energy regulating valve and the frequency of the frequency converter according to the unit's regulation value includes: When the unit adjustment value is greater than the upper limit of the preset adjustment range, it is determined whether the current frequency of the frequency converter is the first-level adjustment frequency; If not, control the energy regulating valve to maintain its current opening, adjust the current frequency of the inverter to the next higher level of regulation frequency, and return to the step of obtaining the target water temperature, current water temperature and current water temperature change rate of the screw chiller unit. If so, the control valve is adjusted to the next higher level of opening, and the current frequency of the inverter is adjusted to the m-th level adjustment frequency. Then, the process returns to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit.

5. The control method for a screw chiller unit according to claim 4, characterized in that, Controlling the adjustable valve to maintain its current opening and adjusting the current frequency of the frequency converter to the next higher adjustment frequency includes: The control valve is kept at its current opening, and the current frequency of the inverter is adjusted to the next higher adjustment frequency at a third preset rate. Controlling the adjustable valve to adjust to the next higher opening degree and adjusting the current frequency of the frequency converter to the m-th adjustment frequency includes: Control the adjustable valve to adjust to the next higher level of opening of the current opening, and adjust the current frequency of the inverter to the m-th level of adjustment frequency at a fourth preset rate; The fourth preset rate is greater than the third preset rate.

6. The control method for a screw chiller unit according to claim 1, characterized in that, Also includes: If the unit adjustment value is within the preset adjustment range, then the energy regulating valve is controlled to maintain its current opening, and the frequency converter is controlled to maintain its current frequency.

7. A control device for a screw chiller unit, characterized in that, The screw chiller unit includes at least a compressor, a frequency converter, and an adjustable valve. The adjustable valve has n levels of adjustable opening degree; the frequency converter has m levels of adjustable frequency; the opening degree values ​​of the n levels of adjustable opening degree increase progressively; the frequency values ​​of the m levels of adjustable frequency increase sequentially; wherein n and m are both positive integers greater than or equal to 2, and m is greater than n; the control device of the screw chiller unit includes: The temperature acquisition module is used to acquire the target water temperature, current water temperature, and current water temperature change rate of the screw chiller unit. The adjustment value determination module is used to determine the unit adjustment value based on the target water temperature, the current water temperature, and the rate of change of the current water temperature; The adjustment value judgment module is used to determine whether the unit adjustment value is within the preset adjustment range; The frequency adjustment module is used to adjust the opening degree of the adjustable valve and the frequency of the inverter according to the unit adjustment value when the unit adjustment value is not within the preset adjustment range. Adjusting the opening degree of the adjustable valve and the frequency of the inverter according to the unit adjustment value includes: when the unit adjustment value is less than the lower limit of the preset adjustment range, determining whether the current frequency of the inverter is the m-th level adjustment frequency; if not, controlling the adjustable valve to maintain its current opening degree, adjusting the current frequency of the inverter to the next level adjustment frequency, and returning to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller; if yes, controlling the adjustable valve to adjust to the next level opening degree, adjusting the current frequency of the inverter to the first level adjustment frequency, and returning to the step of obtaining the target water temperature, current water temperature, and current water temperature change rate of the screw chiller.

8. A screw chiller unit, characterized in that, include: Compressors, frequency converters, energy-regulating valves, and controllers; The controller is used to execute the control method of the screw chiller unit according to any one of claims 1-6.

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