Star-delta switching duration control method, device, compressor and chiller

Abstract

The present invention discloses a star-delta switching duration control method, device, compressor and chiller. The method comprises: obtaining the last shutdown reason of the chiller and the current temperature parameter of the chiller before the chiller is started; and controlling the star-delta switching duration of the compressor when the chiller is started this time according to the shutdown reason and the temperature parameter. The present invention can reduce the secondary switching current when the compressor is started under load, avoid the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, and extend the life of the contactor.

Description

Technical Field

[0001] The present invention relates to the technical field of heat exchange equipment, and in particular to a star-delta switching duration control method, device, compressor and chiller. Background Art

[0002] Star-delta starting is one of the commonly used starting methods for motors. Since its cost is lower than that of soft starters and the starting current can be much lower than direct starting, star-delta is often used as the starting method for compressors in chillers.

[0003] The star-delta switching time of traditional chillers is a fixed value. However, if the switching time is set too short, it will easily cause a short circuit during the star-delta switching and burn out the contactor contacts. If the switching time is set too long, the secondary switching current will increase. Especially in actual engineering use, the compressor of the chiller often starts under load. If the star-delta switching time is not adjusted according to the actual operating conditions, the secondary switching current will increase, which will cause the circuit breaker to trip or even burn out the contactor contacts, shortening the contactor life.

[0004] Currently, no effective solution has been proposed to the problem that the star-delta switching time of the compressor of the chiller in the prior art cannot be adjusted according to the actual operating conditions, which leads to an increase in the secondary switching current when the compressor is started under load and shortens the life of the contactor. Summary of the invention

[0005] In an embodiment of the present invention, a problem is provided in that the star-delta switching duration of a compressor of a chiller cannot be adjusted according to actual operating conditions, thereby causing an increase in secondary switching current when the compressor is started under load and shortening the life of the contactor.

[0006] In order to solve the above technical problems, the present invention provides a star-delta switching duration control method, the method comprising:

[0007] Before the chiller is started, obtain the last shutdown reason of the chiller and the current temperature parameters of the chiller;

[0008] The star-delta switching duration of the compressor during the current startup of the chiller is controlled according to the shutdown reason and the temperature parameter.

[0009] Further, according to the shutdown reason and the temperature parameter, the star-delta switching duration of the compressor during the current startup of the chiller is controlled, including:

[0010] Determine whether the chiller was shut down abnormally or normally last time;

[0011] If the chiller was shut down abnormally last time, the star-delta switching time of the compressor when the chiller is started this time is controlled to be the minimum switching time;

[0012] If the chiller was shut down normally last time, the star-delta switching time of the compressor when the chiller is started this time is adjusted according to the temperature parameter.

[0013] Furthermore, the temperature parameters include cooling water temperature and freezing water temperature, and adjusting the star-delta switching time of the compressor when the chiller is started this time according to the temperature parameters includes:

[0014] Determine the current chilled water temperature and cooling water temperature of the chiller;

[0015] Determining whether the chilled water temperature and the cooling water temperature meet preset conditions;

[0016] If yes, the star-delta switching duration of the compressor during the current startup of the chiller is calculated according to the chilled water temperature and the cooling water temperature.

[0017] Furthermore, the preset condition is:

[0018] The chilled water temperature is greater than a first temperature threshold, or the cooling water temperature is greater than a second temperature threshold.

[0019] Further, when calculating the star-delta switching duration of the compressor when the chiller is started this time according to the chilled water temperature and the cooling water temperature, it is implemented according to the following formula:

[0020]

[0021] Wherein, t is the duration of the star-delta switching, t is less than the maximum switching duration, C is the proportional coefficient, T 冷冻 is the current chilled water temperature of the chiller, T 冷却 is the current cooling water temperature of the chiller, Max(T 冷冻 , T 冷却 ) is the maximum value of the freezing water temperature and the cooling water temperature, t min The minimum switching time.

[0022] Furthermore, after determining whether the chilled water temperature and the cooling water temperature meet a preset condition, the method further includes:

[0023] If not, the star-delta switching time of the compressor during the start-up of the chiller is controlled to be the maximum switching time.

[0024] The present invention also provides a star-delta switching duration control device, the device comprising:

[0025] The acquisition module is used to obtain the last shutdown reason of the chiller and the current temperature parameters of the chiller before the chiller is started;

[0026] The control module is used to control the star-delta switching duration of the compressor when the chiller is started this time according to the shutdown reason and the temperature parameter.

[0027] The present invention also provides a compressor, comprising the above-mentioned star-delta switching duration control device.

[0028] The present invention also provides a water chiller, comprising the above compressor.

[0029] The present invention also provides a computer-readable storage medium on which a computer program is stored, and when the program is executed by a processor, the above-mentioned star-delta switching duration control method is implemented.

[0030] By applying the technical solution of the present invention, the reason for the last shutdown of the chiller and the current temperature parameters of the chiller are obtained before the chiller is started, and the star-delta switching duration of the compressor when the chiller is started this time is controlled according to the reason for the last shutdown of the chiller and the current temperature parameters of the chiller. When the compressor is started under load, the secondary switching current can be reduced, avoiding the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, thereby extending the life of the contactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the state switching of each contactor of the compressor;

[0032] Figure 2 is a flow chart of a method for controlling the duration of a star-delta switching according to an embodiment of the present invention;

[0033] Figure 3 is a flow chart of a method for controlling the duration of star-delta switching according to another embodiment of the present invention;

[0034] Figure 4 4 is a structural block diagram of a device for controlling star-delta switching duration according to an embodiment of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0037] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0038] It should be understood that, although the terms first, second, etc. may be used to describe temperature thresholds in embodiments of the present invention, these temperature thresholds should not be limited to these terms. These terms are only used to distinguish different temperature thresholds. For example, without departing from the scope of embodiments of the present invention, the first temperature threshold may also be referred to as the second temperature threshold, and similarly, the second temperature threshold may also be referred to as the first temperature threshold.

[0039] As used herein, the words "if" and "if" may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0040] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0041] The optional embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0042] Example 1

[0043] Figure 1 The schematic diagram of the state switching of each contactor of the compressor is as follows: Figure 1As shown in the figure, the whole process of star-delta starting is: first, the main AC contactor and the star contactor are controlled to be simultaneously closed, and after a period of time, the star contactor is controlled to be disconnected, and after a period of time, the delta contactor is controlled to be closed. The time from the moment the star contactor is disconnected to the moment the delta contactor is closed is the star-delta switching time t of the compressor. The above star-delta switching time t is in the interval [t min , t max ], the upper limit value t max and the lower limit t min Determined by the parameters of the contactor, t is generally in the range of 10ms to 300ms. The star-delta switching time of traditional chillers is a fixed value. However, if the switching time is set too short, it is easy to cause a short-term short circuit during the star-delta switching, burning the contactor contacts; if the switching time is set too long, it will increase the secondary switching current. Especially in actual engineering use, the compressor of the chiller often starts with load. If the star-delta switching time is not adjusted according to the actual operating conditions, the secondary switching current will increase, which will cause the circuit breaker to trip, or even burn the contactor contacts, shortening the contactor life.

[0044] In order to solve the above problem, this embodiment provides a star-delta switching duration control method. Figure 2 : is a flow chart of a method for controlling the duration of a star-delta switching according to an embodiment of the present invention. Figure 2 As shown, the method includes:

[0045] S101, before the chiller is started, the last shutdown reason of the chiller and the current temperature parameters of the chiller are obtained.

[0046] Among them, the shutdown reasons of the chiller include normal shutdown and abnormal shutdown. Abnormal shutdown refers to shutdown caused by failure, emergency shutdown or power outage, while normal shutdown refers to shutdown caused by receiving a shutdown command.

[0047] S102, controlling the star-delta switching duration of the compressor when the chiller is started this time according to the last shutdown reason of the chiller and the current temperature parameters of the chiller.

[0048] The shutdown reason of the chiller and the current temperature parameters of the chiller can both reflect whether the chiller is started with load this time. Therefore, according to the shutdown reason of the chiller and the current temperature parameters of the chiller, the star-delta switching time can be adjusted for the situation of starting with load.

[0049] The star-delta switching duration control method of the present embodiment obtains the last shutdown reason of the chiller and the current temperature parameters of the chiller before the chiller is started, and controls the star-delta switching duration of the compressor when the chiller is started this time according to the last shutdown reason of the chiller and the current temperature parameters of the chiller. When the compressor is started under load, the secondary switching current can be reduced to avoid the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, thereby extending the life of the contactor.

[0050] As mentioned above, the shutdown reason of the chiller can reflect whether the chiller is started under load this time. Specifically, if the chiller was shut down due to a fault, emergency shutdown or power outage last time, then there was no unloading during shutdown. There will be a problem of the compressor starting under load during this startup, and there is a risk of increased secondary switching current. In order to reduce the secondary switching current, the star-delta switching duration of the compressor when the chiller is started this time is controlled according to the shutdown reason and the temperature parameters, including: determining whether the chiller was shut down abnormally or normally last time; if the chiller was shut down abnormally last time, controlling the star-delta switching duration of the compressor when the chiller is started this time to the minimum switching duration, so as to minimize the secondary switching current; if the chiller was shut down normally last time, the star-delta switching duration of the compressor when the chiller is started this time should continue to be adjusted according to the current temperature parameters of the chiller.

[0051] The above temperature parameters include cooling water temperature and freezing water temperature. If the cooling water temperature and freezing water temperature of the chiller are high when it is started, the compressor will be loaded when the chiller is started. Therefore, the star-delta switching time of the compressor when the chiller is started is adjusted according to the current temperature parameters of the chiller, including: determining the current freezing water temperature and cooling water temperature of the chiller; judging whether the above freezing water temperature and the above cooling water temperature meet the preset conditions; if so, calculating the star-delta switching time of the compressor when the chiller is started according to the above freezing water temperature and the above cooling water temperature. The above preset conditions are: the freezing water temperature is greater than the first temperature threshold, or the cooling water temperature is greater than the second temperature threshold.

[0052] In actual application, the higher the cooling water temperature or the chilled water temperature is, the heavier the load is when the compressor is started with load, and the shorter the star-delta switching time needs to be adjusted to ensure that the secondary switching current is reduced to the greatest extent. In order to accurately adjust the star-delta switching time, the star-delta switching time of the compressor at the start of the chiller is calculated according to the above-mentioned chilled water temperature and the above-mentioned cooling water temperature, and it is implemented according to the following formula:

[0053]

[0054] Among them, t is the star-delta switching time, C is the proportional coefficient, C is a positive value, which is related to the change of the starting current of the compressor itself caused by the influence of water temperature. It can be obtained through experimental testing, T 冷冻 is the current chilled water temperature of the chiller, T 冷却 is the current cooling water temperature of the chiller, Max(T 冷冻 , T 冷却 ) is the maximum value of the chilled water temperature and the cooling water temperature, t min is the minimum switching time. It should be noted that t cannot exceed the maximum switching time t max .

[0055] If the chiller did not shut down abnormally last time, and the cooling water temperature and the chilled water temperature were not too high when the chiller was started this time, the surface compressor would not start under load. Therefore, there is no risk of excessive secondary switching current during star-delta switching. Therefore, the star-delta switching time can be maintained at the maximum switching time. Therefore, after determining whether the chilled water temperature and the cooling water temperature meet the preset conditions, the above method also includes: if the chilled water temperature and the cooling water temperature do not meet the above preset conditions, in order to protect the contactor, the star-delta switching time of the compressor when the chiller is started this time is controlled to be the maximum switching time.

[0056] Figure 3 FIG. 1 is a flow chart of a method for controlling the duration of a star-delta switching according to another embodiment of the present invention. Figure 3 As shown, the method comprises the following preferred steps:

[0057] S1, the chiller receives the start-up command.

[0058] S2, determine whether the chiller was shut down normally last time, if not, execute step S3, if yes, execute step S4.

[0059] S3, let the star-delta switching time t = t min .

[0060] If the last shutdown was caused by a fault, emergency stop or power failure, the chiller was not shut down without unloading, which means that the compressor will be started with load this time. In order to reduce the secondary switching current, the star-delta switching time t is shortened to the minimum switching time t during the start control of the unit. min .

[0061] S4, determine whether the current cooling water temperature and freezing water temperature of the chiller meet the preset conditions, if yes, execute step S5, if not, execute step S6.

[0062] The above preset conditions are: the temperature of the chilled water is greater than the first temperature threshold, or the temperature of the cooling water is greater than the second temperature threshold.

[0063] S5, let the star-delta switching time t = t max When the above two judgment conditions are not met when the unit is started, it means that the current of the compressor is small. In order to protect the contactor, the start-up control of the chiller is to extend the star-delta switching time t to the maximum switching time t max .

[0064] S6, the duration of the star-delta switching

[0065] If the cooling water temperature and chilled water temperature of the chiller are too high, the compressor will start with load when the unit starts. The star-delta switching time needs to be adjusted according to the cooling water temperature and chilled water temperature to reduce the secondary switching current. C is a preset proportional coefficient, which is related to the change in starting current of the compressor caused by the water temperature. 冷冻 is the current chilled water temperature of the chiller, T 冷却 is the current cooling water temperature of the chiller, Max(T 冷冻 , T 冷却 ) is the maximum value of the chilled water temperature and the cooling water temperature. In addition, the value of t cannot exceed the maximum switching time t max .

[0066] S7, controls the chiller to start up and executes star-delta switching.

[0067] Example 2

[0068] This embodiment provides a star-delta switching duration control device. Figure 4 : is a structural block diagram of a star-delta switching duration control device according to an embodiment of the present invention. Figure 4 As shown, the device comprises:

[0069] The acquisition module 10 is used to acquire the last shutdown reason of the chiller and the current temperature parameters of the chiller before the chiller is started.

[0070] Among them, the shutdown reasons of the chiller include normal shutdown and abnormal shutdown. Abnormal shutdown refers to shutdown caused by failure, emergency shutdown or power outage, while normal shutdown refers to shutdown caused by receiving a shutdown command.

[0071] The control module 20 is used to control the star-delta switching time of the compressor when the chiller is started this time according to the last shutdown reason of the chiller and the current temperature parameters of the chiller.

[0072] The shutdown reason of the chiller and the current temperature parameters of the chiller can both reflect whether the chiller is started with load this time. Therefore, according to the shutdown reason of the chiller and the current temperature parameters of the chiller, the star-delta switching time can be adjusted for the situation of starting with load.

[0073] The star-delta switching duration control device of the present embodiment obtains the last shutdown reason of the chiller and the current temperature parameters of the chiller before the chiller is started through the acquisition module 10, and controls the star-delta switching duration of the compressor when the chiller is started this time according to the last shutdown reason of the chiller and the current temperature parameters of the chiller through the control module 20. When the compressor is started under load, the secondary switching current can be reduced to avoid the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, thereby extending the life of the contactor.

[0074] As mentioned above, the shutdown reason of the chiller can reflect whether the chiller is started under load this time. Specifically, if the chiller was shut down due to a fault, emergency shutdown or power outage last time, then there was no unloading during the shutdown. There will be a problem of the compressor starting under load during this startup, and there is a risk of increased secondary switching current. In order to reduce the secondary switching current, the control module 20 is specifically used to: determine whether the chiller was shut down abnormally or normally last time; if the chiller was shut down abnormally last time, then control the star-delta switching time of the compressor when the chiller is started this time to the minimum switching time, so as to minimize the secondary switching current; if the chiller was shut down normally last time, then the star-delta switching time of the compressor when the chiller is started this time should continue to be adjusted according to the current temperature parameters of the chiller.

[0075] The above temperature parameters include cooling water temperature and freezing water temperature. If the cooling water temperature and freezing water temperature of the chiller are high when the chiller is started, the compressor will be loaded when the chiller is started. Therefore, the control module 20 is also used to: determine the current freezing water temperature and cooling water temperature of the chiller; determine whether the freezing water temperature and cooling water temperature meet the preset conditions; if so, calculate the star-delta switching time of the compressor when the chiller is started this time according to the freezing water temperature and cooling water temperature. The above preset conditions are: the freezing water temperature is greater than the first temperature threshold, or the cooling water temperature is greater than the second temperature threshold.

[0076] In order to accurately adjust the star-delta switching time, the star-delta switching time of the compressor when the chiller is started this time is calculated according to the above-mentioned chilled water temperature and the above-mentioned cooling water temperature, and it is implemented according to the following formula:

[0077]

[0078] Among them, t is the star-delta switching time, C is the proportional coefficient, which is related to the change in starting current caused by the water temperature of the compressor itself, T 冷冻 is the current chilled water temperature of the chiller, T 冷却 is the current cooling water temperature of the chiller, t min is the minimum switching time, Max(T 冷冻 , T 冷却 ) is the maximum value of the chilled water temperature and the cooling water temperature. The maximum value of t cannot exceed the maximum switching time t max .

[0079] If the chiller did not shut down abnormally last time, and the cooling water temperature and the chilled water temperature are not too high when the chiller is started this time, the surface compressor will not start under load. Therefore, there is no risk of excessive secondary switching current during star-delta switching. Therefore, the star-delta switching time can be maintained at the maximum switching time. Therefore, the above-mentioned control module 20 is also used for: when the chilled water temperature and the cooling water temperature do not meet the above-mentioned preset conditions, in order to protect the contactor, the star-delta switching time of the compressor when the chiller is started this time is controlled to be the maximum switching time.

[0080] Example 3

[0081] The present embodiment provides a compressor, including the star-delta switching time control device of the above embodiment, which is used to reduce the secondary switching current when the compressor is started under load, avoid the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, and extend the life of the contactor.

[0082] Example 4

[0083] This embodiment provides a chiller, including the compressor of the above embodiment, which is used to reduce the secondary switching current when the compressor is started under load, avoid the problem of circuit breaker tripping or even burning of contactor contacts caused by the increase of secondary switching current, and extend the life of the contactor.

[0084] Example 5

[0085] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the above-mentioned star-delta switching duration control method is implemented.

[0086] The device embodiments described above are merely illustrative, wherein the modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, i.e., they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0087] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the duration of star-delta switching, characterized in that: The method comprises: Before the chiller is started, obtain the last shutdown reason of the chiller and the current temperature parameters of the chiller; The star-delta switching duration of the compressor when the chiller is started this time is controlled according to the shutdown reason and the temperature parameters; including: judging whether the chiller was shut down abnormally or normally last time; if the chiller was shut down abnormally last time, controlling the star-delta switching duration of the compressor when the chiller is started this time to be the minimum switching duration; if the chiller was shut down normally last time, adjusting the star-delta switching duration of the compressor when the chiller is started this time according to the temperature parameters.

2. The method according to claim 1, characterized in that The temperature parameters include cooling water temperature and freezing water temperature. Adjusting the star-delta switching time of the compressor when the chiller is started this time according to the temperature parameters includes: Determine the current chilled water temperature and cooling water temperature of the chiller; Determining whether the chilled water temperature and the cooling water temperature meet preset conditions; If yes, the star-delta switching duration of the compressor during the current startup of the chiller is calculated according to the chilled water temperature and the cooling water temperature.

3. The method according to claim 2, characterized in that The preset conditions are: The chilled water temperature is greater than a first temperature threshold, or the cooling water temperature is greater than a second temperature threshold.

4. The method according to claim 2, characterized in that: When calculating the star-delta switching time of the compressor when the chiller is started this time according to the chilled water temperature and the cooling water temperature, it is achieved according to the following formula: Wherein, t is the duration of the star-delta switching, t is less than the maximum switching duration, C is the proportional coefficient, T 冷冻 is the current chilled water temperature of the chiller, T 冷却 is the current cooling water temperature of the chiller, Max(T 冷冻 , T 冷却 ) is the maximum value of the freezing water temperature and the cooling water temperature, t min The minimum switching time.

5. The method according to claim 2, characterized in that: After determining whether the chilled water temperature and the cooling water temperature meet a preset condition, the method further includes: If not, the star-delta switching time of the compressor during the start-up of the chiller is controlled to be the maximum switching time.

6. A star-delta switching duration control device, characterized in that: The device comprises: The acquisition module is used to obtain the last shutdown reason of the chiller and the current temperature parameters of the chiller before the chiller is started; A control module is used to control the star-delta switching duration of the compressor when the chiller is started this time according to the shutdown reason and the temperature parameters. The control module is specifically used to: determine whether the chiller was shut down abnormally or normally last time; if the chiller was shut down abnormally last time, control the star-delta switching duration of the compressor when the chiller is started this time to be the minimum switching duration; if the chiller was shut down normally last time, continue to adjust the star-delta switching duration of the compressor when the chiller is started this time according to the current temperature parameters of the chiller.

7. A compressor, characterized in that: It includes the star-delta switching duration control device as described in claim 6.

8. A chiller, characterized in that: Comprising the compressor as claimed in claim 7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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