CN113639520A - Control method of multi-system water chilling unit - Google Patents
Control method of multi-system water chilling unit Download PDFInfo
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- CN113639520A CN113639520A CN202110832764.7A CN202110832764A CN113639520A CN 113639520 A CN113639520 A CN 113639520A CN 202110832764 A CN202110832764 A CN 202110832764A CN 113639520 A CN113639520 A CN 113639520A
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 228
- 238000000034 method Methods 0.000 title claims abstract description 40
- 239000003507 refrigerant Substances 0.000 claims abstract description 203
- 230000003247 decreasing effect Effects 0.000 description 4
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D29/00—Arrangement or mounting of control or safety devices
- F25D29/005—Mounting of control devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D17/00—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces
- F25D17/02—Arrangements for circulating cooling fluids; Arrangements for circulating gas, e.g. air, within refrigerated spaces for circulating liquids, e.g. brine
Abstract
The invention belongs to the technical field of heat exchange, and particularly provides a control method of a multi-system water chilling unit. The problem of current multisystem water chilling unit increase and decrease system quantity's control mode is not good and influence unit operating efficiency easily is solved. Therefore, the control method can selectively increase the opening number of the refrigerant systems according to the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of all the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system and/or according to the running load of the compressors of the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system under the conditions that at least one refrigerant system which is not opened exists in the multi-system water chiller, the refrigerant system which is not opened does not have faults and the current shutdown time is longer than or equal to a first preset time, so that the opening number of the refrigerant systems can be accurately matched with different working conditions and heat exchange requirements, and the multi-system water chiller can effectively and stably run all the time.
Description
Technical Field
The invention belongs to the technical field of heat exchange, and particularly provides a control method of a multi-system water chilling unit.
Background
For the multi-system water chilling unit, the number of the correspondingly started systems is different according to different heat exchange requirements, so that the multi-system water chilling unit can stably and efficiently operate by means of increasing and decreasing the number of the systems according to different working conditions, and therefore how to determine the number of the started systems is crucial to control of the multi-system water chilling unit. Generally, the requirement of increasing or decreasing the number of systems occurs when the following three conditions occur in a multi-system water chiller: 1. in the early stage, only part of systems are started due to faults, and the requirement for increasing the systems can be met after the faults are eliminated; 2. after the number of the systems is reduced, the temperature of the chilled water rises, and the demand for increasing the systems is met; 3. the need to reduce the system occurs when the actual chilled exit (inlet) water temperature is less than the set chilled exit (inlet) water temperature. Therefore, the multi-system water chilling unit can be ensured to freely switch modes in the operation process only by the corresponding control logic, so that the number of the systems is correspondingly increased or reduced, and the operation efficiency of the multi-system water chilling unit is effectively ensured. Most of the existing multi-system water chilling units judge the increase and decrease requirements of the system by the experience of technicians, and correspondingly increase or decrease the number of the systems by a manual control mode; or, some multi-system water chilling units start to use control logic for automatically increasing and decreasing the number of the systems, but the existing control logic is too simple, so that the problem that the operation of the units is unstable or even the abnormal shutdown of the water chilling units is caused easily, and further the user experience is seriously influenced.
Disclosure of Invention
The invention aims to solve the technical problem that the operation efficiency of the multi-system water chilling unit is easily influenced due to the fact that the control mode of increasing and decreasing the number of systems of the existing multi-system water chilling unit is not good.
The invention provides a control method of a multi-system water chilling unit, wherein the multi-system water chilling unit comprises a plurality of refrigerant systems which are arranged in parallel and a chilled water supply system which can exchange heat with the refrigerant systems, and the control method comprises the following steps:
under the condition that at least one refrigerant system which is not started exists in the multi-system water chilling unit, the refrigerant system which is not started has no fault, and the shutdown time is longer than or equal to a first preset time, acquiring the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of compressors of all refrigerant systems which are in a starting state and the outlet water temperature of the chilled water supply system;
selectively increasing the opening number of the refrigerant systems according to the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system; and/or
Under the condition that at least one refrigerant system which is not started exists in the multi-system water chilling unit, the refrigerant system which is not started has no fault, and the shutdown time is longer than or equal to the first preset time, the running load of the compressors of all the refrigerant systems which are in a starting state and the outlet water temperature of the chilled water supply system are obtained;
and selectively increasing the opening number of the refrigerant systems according to the running loads of the compressors of the refrigerant systems in the opening states and the outlet water temperature of the chilled water supply system.
In a preferred embodiment of the above control method, the step of selectively increasing the number of refrigerant systems that are turned on according to the actual rotational speeds, the surge rotational speed, and the stall rotational speed of the compressors of all the refrigerant systems that are turned on, and the outlet water temperature of the chilled water supply system includes:
calculating the ratio of the difference value between the actual rotating speed and the surging rotating speed to the difference value between the locked-rotor rotating speed and the surging rotating speed;
if the ratio is continuously greater than or equal to a preset ratio for a second preset time period, and the outlet water temperature is continuously greater than or equal to a first preset outlet water temperature for a third preset time period, increasing the starting number of the refrigerant systems;
the first preset outlet water temperature is greater than the target outlet water temperature.
In a preferred technical solution of the above control method, the preset ratio is equal to a full load preset value of a compressor of the refrigerant system multiplied by an operation load of the compressor of the refrigerant system.
In a preferred embodiment of the above control method, the step of selectively increasing the number of the refrigerant systems that are turned on according to the operating loads of the compressors of all the refrigerant systems that are turned on and the outlet water temperature of the chilled water supply system includes:
if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a fourth preset time length, and the water outlet temperature is continuously greater than or equal to a second preset water outlet temperature for a fifth preset time length, increasing the starting number of the refrigerant systems;
and the second preset outlet water temperature is greater than the target outlet water temperature.
In a preferred embodiment of the above control method, the step of selectively increasing the number of the refrigerant systems that are turned on according to the operating loads of the compressors of all the refrigerant systems that are turned on and the outlet water temperature of the chilled water supply system further includes:
if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a sixth preset time length, and the effluent temperature is continuously greater than or equal to the target effluent temperature for a fifth preset time length, increasing the starting number of the refrigerant systems;
and the sixth preset time length is greater than the fourth preset time length.
In a preferred embodiment of the above control method, the step of increasing the number of the refrigerant systems to be turned on further includes:
and determining the increasing quantity of the refrigerant systems according to the total quantity of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature.
In a preferred technical scheme of the control method, the step of determining the increased number of the refrigerant systems according to the total number of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature specifically comprises the following steps:
and the increased number of the refrigerant systems is equal to the total number of the refrigerant systems divided by the standard condition temperature difference preset value and then multiplied by the calculation result of the difference value between the outlet water temperature and the target outlet water temperature, and the calculation result is rounded.
In a preferred embodiment of the above control method, the control method further includes:
under the condition that the number of the refrigerant systems in the starting state is more than or equal to two, acquiring the outlet water temperature of the chilled water supply system and the operation loads of the compressors of all the refrigerant systems in the starting state;
and selectively reducing the number of the refrigerant systems in the starting state according to the outlet water temperature of the chilled water supply system and/or the running load of the compressors of all the refrigerant systems in the starting state.
In a preferred embodiment of the above control method, the step of selectively reducing the number of the refrigerant systems in an on state according to a discharge water temperature of the chilled water supply system and/or an operation load of compressors of all the refrigerant systems in an on state includes:
if the outlet water temperature is continuously lower than a third preset outlet water temperature for a seventh preset time, reducing the number of the refrigerant systems in an opening state;
and the third preset outlet water temperature is lower than the target outlet water temperature.
In a preferred embodiment of the above control method, the step of selectively reducing the number of the refrigerant systems in the on state according to the outlet water temperature of the chilled water supply system and/or the operation loads of the compressors of all the refrigerant systems in the on state further includes:
if the outlet water temperature is continuously lower than the target outlet water temperature for the seventh preset time period and the duration that the operation load of the compressors of all the refrigerant systems in the opening state is smaller than or equal to the low-efficiency load preset value is reached for the eighth preset time period, reducing the number of the refrigerant systems in the opening state;
wherein the eighth preset duration is greater than the seventh preset duration.
Under the condition of adopting the preferred technical scheme, the invention can selectively increase the opening number of the refrigerant systems according to the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of all the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system under the conditions that at least one refrigerant system which is not opened exists in the multi-system water chilling unit, the refrigerant system which is not opened has no fault and the shutdown time is longer than or equal to a first preset time, and/or selectively increase the opening number of the refrigerant systems according to the operating load of the compressors of all the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system, so that the opening number of the refrigerant systems can be accurately matched with different working conditions and heat exchange requirements, thereby effectively ensuring that the multi-system water chilling unit can be always in a stable and efficient operating state, thereby effectively improving the user experience.
Drawings
Preferred embodiments of the present invention are described below with reference to the accompanying drawings, in which:
FIG. 1 is a flow chart of the main steps of the control method of the present invention;
FIG. 2 is a flow chart of the specific steps of the increase system number portion of the preferred embodiment of the control method of the present invention;
fig. 3 is a flowchart showing the detailed steps of the system number reducing portion of the preferred embodiment of the control method of the present invention.
Detailed Description
Preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only for explaining the technical principle of the present invention, and are not intended to limit the scope of the present invention. And can be adjusted as needed by those skilled in the art to suit particular applications. For example, the invention does not limit the specific structure and the specific number of the systems of the multi-system water chilling unit, and technicians can set the water chilling unit according to actual use requirements. Such changes in the specific structure and quantities may be made without departing from the basic principles of the invention and are intended to be within the scope of the invention.
It should be noted that in the description of the preferred embodiment, the terms of direction or positional relationship indicated by the terms "inside", "outside", and the like are based on the directions or positional relationships shown in the drawings, which are only for convenience of description, and do not indicate or imply that the device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus should not be construed as limiting the present invention. Furthermore, in the description of the present invention, unless explicitly specified or limited otherwise, the term "connected" is to be understood broadly, for example, as electrical or mechanical connections; either directly or indirectly through intervening media, or through the communication between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Further, it should be noted that in the description of the present invention, although the steps of the control method of the present invention are described in a specific order in the present application, the order is not limited, and those skilled in the art may perform the steps in a different order without departing from the basic principle of the present invention.
The multi-system water chilling unit comprises a plurality of refrigerant systems which are arranged in parallel and a chilled water supply system which can exchange heat with the refrigerant systems, the refrigerating capacity of the multi-system water chilling unit can be changed by changing the starting number of the refrigerant systems, the refrigerant systems can exchange heat with the chilled water supply system so as to reduce the temperature of water in the chilled water supply system, and then the space needing to be refrigerated can be cooled through the chilled water supply system. It should be noted that the present invention does not limit the specific structures of the multi-system water chiller, the refrigerant system, and the chilled water supply system, and the technicians can set the configuration by themselves according to the actual use requirements.
In addition, the multi-system water chilling unit further comprises a controller, and the controller can control the running state of the multi-system water chilling unit, for example, the opening and closing state of the refrigerant system is controlled to control the total opening number of the refrigerant system. It can be understood by those skilled in the art that the present invention does not limit the specific structure and model of the controller, and the controller may be the original controller of the multi-system water chilling unit, or may be a controller separately configured to execute the control method of the present invention, and the structure and model of the controller may be set by a technician according to actual use requirements.
Referring first to fig. 1, a flow chart of main steps of the control method of the present invention is shown. As shown in fig. 1, based on the multi-system water chilling unit described in the above embodiment, the control method of the present invention mainly includes the following steps:
s1: at least one refrigerant system which is not started exists in the multi-system water chilling unit, and the refrigerant system which is not started has no fault and the shutdown time is longer than or equal to a first preset time;
s2: acquiring the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of all the refrigerant systems in the starting state and the outlet water temperature of the chilled water supply system;
s3: selectively increasing the opening number of the refrigerant systems according to the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of all the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system;
s4: acquiring the operation loads of compressors of all refrigerant systems in an opening state and the outlet water temperature of a chilled water supply system;
s5: and selectively increasing the opening number of the refrigerant systems according to the operation loads of the compressors of all the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system.
Firstly, in step S1, before determining to increase the number of systems, it is determined whether at least one refrigerant system that is not turned on exists in the multi-system chiller, whether the refrigerant system that is not turned on has no fault and whether the current shutdown time is longer than or equal to a first preset time, and if at least one refrigerant system that is not turned on exists in the multi-system chiller and the refrigerant system that is not turned on has no fault and the current shutdown time is longer than or equal to the first preset time, the subsequent steps are executed.
In a judgment logic, steps S2 and S3 are executed, that is, the controller is capable of obtaining the actual rotational speed, the surge rotational speed and the locked rotational speed of the compressors of all refrigerant systems in an open state and the outlet water temperature of the chilled water supply system, and selectively increasing the number of the refrigerant systems in the open state according to the actual rotational speed, the surge rotational speed and the locked rotational speed of the compressors of all refrigerant systems in the open state and the outlet water temperature of the chilled water supply system.
It should be noted that, the present invention does not limit the specific obtaining manner of each parameter, and the technical staff can set the parameters according to the actual use requirement; in addition, the present invention does not limit the specific determination logic, and it is within the protection scope of the present invention as long as the number of the refrigerant systems to be opened is selectively increased according to the actual rotation speed, the surge rotation speed and the locked rotation speed of the compressors of all the refrigerant systems in the opened state and the outlet water temperature of the chilled water supply system, for example, the determination may be performed according to the value range of each parameter, or may be performed according to whether each parameter satisfies the preset relational expression.
In another judgment logic, step S4 and step S5 are executed, that is, the controller is capable of acquiring the operation loads of the compressors of all the refrigerant systems in the on state and the outlet water temperature of the chilled water supply system, and selectively increasing the number of the on refrigerant systems according to the operation loads of the compressors of all the refrigerant systems in the on state and the outlet water temperature of the chilled water supply system.
It should be noted that, the present invention does not limit the specific obtaining manner of each parameter, and the technical staff can set the parameters according to the actual use requirement; in addition, the present invention does not limit the specific determination logic, and it is within the protection scope of the present invention to selectively increase the number of the refrigerant systems to be turned on according to the operation loads of the compressors of all the refrigerant systems in the on state and the outlet water temperature of the chilled water supply system, for example, the determination may be performed according to the value ranges of the parameters, or may be performed according to whether the parameters satisfy the preset relational expression.
Referring next to fig. 2, a flowchart of the specific steps of the system quantity increasing portion of the preferred embodiment of the control method of the present invention is shown. As shown in fig. 2, based on the multi-system water chilling unit described in the foregoing embodiment, the part for increasing the number of systems in the preferred embodiment of the control method of the present invention specifically includes the following steps:
s101: at least one refrigerant system which is not started exists in the multi-system water chilling unit, and the refrigerant system which is not started has no fault and the shutdown time is longer than or equal to a first preset time;
s102: acquiring the actual rotating speed, surge rotating speed, locked-rotor rotating speed and running load of compressors of all refrigerant systems in an opening state and the outlet water temperature of a chilled water supply system;
s103: calculating the ratio of the difference value between the actual rotating speed and the surging rotating speed to the difference value between the locked-rotor rotating speed and the surging rotating speed;
s104: if the ratio is continuously greater than or equal to the preset ratio for a second preset time period, and the outlet water temperature is continuously greater than or equal to the first preset outlet water temperature for a third preset time period;
s105: if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a fourth preset time length, and the outlet water temperature is continuously greater than or equal to a second preset outlet water temperature for a fifth preset time length;
s106: if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a sixth preset time length, and the outlet water temperature is continuously greater than or equal to the target outlet water temperature for a fifth preset time length;
s107: determining the increasing quantity of the refrigerant systems according to the total quantity of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature;
s108: and if the compressor of the newly added refrigerant system has surge, controlling the compressor of the newly added refrigerant system to operate at the surge rotating speed of the refrigerant system in an open state.
Firstly, in step S101, before determining to increase the number of systems, it is determined whether at least one refrigerant system that is not started exists in the multi-system chiller, whether the refrigerant system that is not started has no fault and whether the current shutdown time is greater than or equal to a first preset time, and if at least one refrigerant system that is not started exists in the multi-system chiller and the refrigerant system that is not started has no fault and the current shutdown time is greater than or equal to the first preset time, the subsequent steps are executed. If the precondition is not satisfied, subsequent judgment is not needed, and judgment for adding a refrigerant system is not needed.
It should be noted that, the specific value of the first preset duration is not limited, and a technician can set the value according to actual use requirements; preferably, the first preset time period is set to 600S.
Next, in step S102, the controller may obtain the actual rotation speed, the surge rotation speed, the locked rotation speed, and the operation load of the compressors of all the refrigerant systems in the on state, and the outlet water temperature of the chilled water supply system; wherein the surge speed takes zero if the compressor is surge free. It should be noted that, the present invention does not set any limit to the specific obtaining manner and the obtaining sequence of each parameter, and the technical staff can set the obtaining manner and the obtaining sequence according to the actual use requirement. In addition, as can be understood by those skilled in the art, although the actual rotation speed, the surge rotation speed, the stall rotation speed and the operation load of the compressors of all the refrigerant systems in the on state and the outlet water temperature of the chilled water supply system are obtained simultaneously in the preferred embodiment, this is not a limiting obtaining manner, and the technicians may also obtain some of the parameters according to the actual use requirements.
Further, in step S103, a ratio of a difference between the actual rotation speed and the surge rotation speed to a difference between the locked-rotor rotation speed and the surge rotation speed is calculated; it should be noted that, the specific execution timing of step S103 is not limited in the present invention, and the skilled person may set itself according to the actual usage requirement, for example, step S103 may be executed just before step S104.
Next, step S104 to step S106 are executed, and in the preferred embodiment, under the condition that at least one refrigerant system which is not started exists in the multi-system chiller, and the refrigerant system which is not started has no fault and the shutdown time of this time is greater than or equal to the first preset time, the number of started refrigerant systems is increased as long as any one of the three conditions corresponding to step S104 to step S106 is satisfied.
In step S104, if the ratio is continuously greater than or equal to the preset ratio for the second preset duration, and the outlet water temperature is continuously greater than or equal to the first preset outlet water temperature for the third preset duration, increasing the number of the refrigerant systems to be turned on; the first preset outlet water temperature is greater than the target outlet water temperature. It should be noted that, the specific value of the preset ratio is not limited by the present invention, and the technical personnel can set the value according to the actual use requirement, for example, the value may be a fixed value or a variable value; as a preferred setting, the preset ratio is equal to a preset full load of a compressor of the refrigerant system multiplied by an operating load of the compressor of the refrigerant system, where the preset full load is generally 70%, and the operating load is between 10% and 100%.
In addition, it should be noted that, the present invention does not limit the specific values of the first preset outlet temperature, the second preset time and the third preset time, and the technical staff can set the values according to the actual use requirement; as a preferable setting, the first preset outlet water temperature is set to be 0.5 ℃ higher than a target outlet water temperature, and the second preset period and the third preset period are set to be 30S. It is understood that the target outlet water temperature in the preferred embodiment may be set by the user, or the multi-system chiller may be set based on other control logic, which is not limited.
In step S105, if the operation loads of the compressors of all the refrigerant systems in the on state all reach the maximum operation load and the duration time reaches the fourth preset time period, and the outlet water temperature continues to be greater than or equal to the second preset outlet water temperature for the fifth preset time period, increasing the number of the on state of the refrigerant systems; and the second preset outlet water temperature is greater than the target outlet water temperature.
It should be noted that, in the present invention, specific values of the second preset outlet water temperature, the fourth preset time period and the fifth preset time period are not limited, and a technician can set the values according to actual use requirements; as a preferable setting, the second preset outlet water temperature is set to be 0.5 ℃ higher than the target outlet water temperature, the fourth preset time period is set to be 180S, and the fifth preset time period is set to be 30S.
In step S106, if the operation loads of the compressors of all the refrigerant systems in the on state all reach the maximum operation load and the duration time reaches the sixth preset time period, and the outlet water temperature continues to be greater than or equal to the target outlet water temperature for the fifth preset time period, increasing the number of the on-state refrigerant systems; and the sixth preset time length is greater than the fourth preset time length. It should be noted that, the specific value of the sixth preset time period is not limited in any way, as long as the sixth preset time period is longer than the fourth preset time period; as a preferable setting manner, the sixth preset time period is ten times of the fourth preset time period, and correspondingly, when the fourth preset time period is set to 180S, the sixth preset time period is set to 1800S.
And increasing the starting number of the refrigerant systems under the condition that the three conditions corresponding to the steps S104 to S106 meet any one, wherein the specific number of the increased opening systems is determined through the step S107, namely, the increased opening number of the refrigerant systems is determined according to the total number of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature. It should be noted that, the present invention does not limit the specific determination manner, and a technician may set the determination manner according to actual requirements, and it is within the protection scope of the present invention to determine the increase number of the refrigerant systems according to the total number of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature, and the target outlet water temperature.
As a preferred determination mode, the increased number of the refrigerant systems is equal to the total number of the refrigerant systems divided by the standard condition temperature difference preset value and then multiplied by the calculation result of the difference value between the outlet water temperature and the target outlet water temperature to obtain a whole; wherein, the technical staff can set the standard condition temperature difference preset value according to the actual use requirement, preferably, the standard condition temperature difference preset value is set to be 5 ℃. Preferably, the rounding is performed in such a way that if the decimal point of the calculation result is one digit more than zero, the integer part is added with 1, for example, if the calculation result is 0.5, the result after rounding is 1. In addition, it should be noted that when the calculated increase number is greater than the number of the remaining unopened non-fault systems of the multi-system water chilling unit, all the remaining unopened non-fault systems are controlled.
In addition, when the calculated increase quantity is smaller than the quantity of the remaining unopened non-fault systems of the multi-system water chilling unit, specifically, which refrigerant system is opened is judged preferably through historical accumulated operation time length, and the refrigerant system with the short length in the accumulated operation time length is preferably opened firstly; after the refrigerant system is increased once, the increase judgment is stopped for a certain period of time (preferably, 180S), and then the judgment is continued, and if the above conditions are satisfied again, the refrigerant system is increased again.
Next, in step S108, before the newly added refrigerant system is started, a chain switch between the refrigerant system and the refrigerant system already in the operating state is closed, so that the newly added refrigerant system can be normally started; at the moment, if the compressor of the newly added refrigerant system has surge, the compressor of the newly added refrigerant system is controlled to run at the surge rotating speed of the refrigerant system in the starting state, and after the starting is finished, the compressor and other refrigerant systems which are originally in the starting state enter PID regulation together.
In addition, after the newly-added refrigerant system is started, if the pressure difference of suction and exhaust gases of the newly-added refrigerant system is greater than a preset pressure difference (preferably set to be 0.3Mpa), the refrigerant system in the starting state keeps running according to the minimum capacity state, and after the newly-added refrigerant system is started, the compressors of all the refrigerant systems enter automatic regulation together; and if the pressure difference between the suction pressure and the exhaust pressure is less than or equal to the preset pressure difference, the newly added compressor of the refrigerant system can be directly started to operate.
In order to ensure the reliability of the control, as a preferable setting mode, if the compressor of a certain refrigerant system is under a preventive control logic, namely, if part of parameters of the compressor are abnormal but normal use is not influenced, the condition judgment of the expansion system is not influenced by the system. In addition, if the unit sends a signal for opening the system, but the residual system has a fault and no system which can be opened is available, the opening signal is directly cleared to ensure the normal operation of the unit.
Referring next to fig. 3, a flowchart illustrating the specific steps of the system quantity reduction portion of the preferred embodiment of the control method of the present invention is shown. As shown in fig. 3, based on the multi-system water chilling unit described in the above embodiment, the part for reducing the number of systems in the preferred embodiment of the control method of the present invention specifically includes the following steps:
s201: under the condition that the number of the refrigerant systems in the starting state is more than or equal to two, acquiring the outlet water temperature of the chilled water supply system and the operation loads of the compressors of all the refrigerant systems in the starting state;
s202: if the outlet water temperature is continuously lower than the third preset outlet water temperature for a seventh preset time, reducing the number of refrigerant systems in an open state;
s203: and if the outlet water temperature is continuously lower than the target outlet water temperature for a seventh preset time period and the duration of the operation load of the compressors of all the refrigerant systems in the opening state is less than or equal to the low-efficiency load preset value for an eighth preset time period, reducing the number of the refrigerant systems in the opening state.
Specifically, as another preferred embodiment, the present invention further provides a control method for determining whether the number of the refrigerant systems needs to be reduced, in step S201, when the number of the refrigerant systems in the on state is greater than or equal to two, the controller may obtain the outlet water temperature of the chilled water supply system and the operation loads of the compressors of all the refrigerant systems in the on state, so as to selectively reduce the number of the refrigerant systems in the on state according to the outlet water temperature of the chilled water supply system and/or the operation loads of the compressors of all the refrigerant systems in the on state.
It should be noted that, the present invention does not limit the specific obtaining manner of each parameter, and the technical staff can set the parameters according to the actual use requirement; the present invention also does not limit the specific determination logic, and it is within the protection scope of the present invention that the number of the refrigerant systems in the on state is selectively reduced according to the outlet water temperature of the chilled water supply system and/or the operation load of the compressors of all the refrigerant systems in the on state, for example, the determination may be performed according to the value range of each parameter, or may be performed according to whether each parameter satisfies a preset relational expression.
As a preferable setting manner, in step S202, if the outlet water temperature is continuously lower than the third preset outlet water temperature for the seventh preset time period, the number of the refrigerant systems in the on state is reduced; and the third preset outlet water temperature is lower than the target outlet water temperature. It should be noted that, the specific value of the third preset outlet water temperature is not limited, and a technician can set the third preset outlet water temperature according to actual use requirements as long as the third preset outlet water temperature is lower than the target outlet water temperature; as a preferred setting mode, the third preset outlet water temperature is equal to a calculation result obtained by subtracting one half of the preset shutdown temperature difference from the target outlet water temperature, wherein a specific value of the preset shutdown temperature difference can be set according to actual use requirements.
Further, in step S203, if the outlet water temperature is continuously less than the target outlet water temperature for the seventh preset time period and the duration of the operating load of the compressors of all the refrigerant systems in the on state being less than or equal to the low-efficiency load preset value for the eighth preset time period, the number of the refrigerant systems in the on state is reduced; wherein the eighth preset duration is greater than the seventh preset duration. It should be noted that, in the present invention, specific values of the low-efficiency load preset value, the seventh preset time period, and the eighth preset time period are not limited, and a technician may set the values according to actual use requirements; as a preferable setting, the low efficiency load preset value is set to 30%, the seventh preset time period is set to 30S, and the eighth preset time period is set to 180S.
In summary, when the number of the refrigerant systems in the on state is greater than or equal to two, the number of the refrigerant systems in the on state is reduced as long as any one of the two conditions corresponding to step S202 and step S203 is satisfied. In addition, under the condition that the refrigerant systems are determined to be required to be reduced, only one refrigerant system is preferably closed each time, and the specific closed refrigerant system is preferably judged through historical accumulated operation time, and is preferably closed firstly; after the refrigerant system is reduced once, the reduction determination is stopped for a while (preferably, stopped for 60S), and then the determination is continued, and if the above conditions are satisfied again, the refrigerant system is reduced again.
In addition, if the outlet water temperature of the chilled water supply system is rapidly reduced to the temperature corresponding to the shutdown temperature difference and maintained for a period of time (preferably maintained for 30S), the shutdown instruction is superior to the reduction system instruction, namely the multi-system water chilling unit is directly shut down, and the operation of the reduction system is not required to be executed.
So far, the technical solutions of the present invention have been described in connection with the preferred embodiments shown in the drawings, but it is easily understood by those skilled in the art that the scope of the present invention is obviously not limited to these specific embodiments. Equivalent changes or substitutions of related technical features can be made by those skilled in the art without departing from the principle of the invention, and the technical scheme after the changes or substitutions can fall into the protection scope of the invention.
Claims (10)
1. A control method of a multi-system water chilling unit comprises a plurality of refrigerant systems which are arranged in parallel and a chilled water supply system which can exchange heat with the refrigerant systems, and is characterized by comprising the following steps:
under the condition that at least one refrigerant system which is not started exists in the multi-system water chilling unit, the refrigerant system which is not started has no fault, and the shutdown time is longer than or equal to a first preset time, acquiring the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of compressors of all refrigerant systems which are in a starting state and the outlet water temperature of the chilled water supply system;
selectively increasing the opening number of the refrigerant systems according to the actual rotating speed, the surge rotating speed and the locked-rotor rotating speed of the compressors of the refrigerant systems in the opening state and the outlet water temperature of the chilled water supply system; and/or
Under the condition that at least one refrigerant system which is not started exists in the multi-system water chilling unit, the refrigerant system which is not started has no fault, and the shutdown time is longer than or equal to the first preset time, the running load of the compressors of all the refrigerant systems which are in a starting state and the outlet water temperature of the chilled water supply system are obtained;
and selectively increasing the opening number of the refrigerant systems according to the running loads of the compressors of the refrigerant systems in the opening states and the outlet water temperature of the chilled water supply system.
2. The control method as claimed in claim 1, wherein the step of selectively increasing the number of the refrigerant systems being turned on according to the actual rotational speed, the surge rotational speed and the stall rotational speed of the compressors of all the refrigerant systems being turned on and the outlet water temperature of the chilled water supply system comprises:
calculating the ratio of the difference value between the actual rotating speed and the surging rotating speed to the difference value between the locked-rotor rotating speed and the surging rotating speed;
if the ratio is continuously greater than or equal to a preset ratio for a second preset time period, and the outlet water temperature is continuously greater than or equal to a first preset outlet water temperature for a third preset time period, increasing the starting number of the refrigerant systems;
the first preset outlet water temperature is greater than the target outlet water temperature.
3. The control method of claim 2, wherein the predetermined ratio is equal to a preset full load of a compressor of the refrigerant system multiplied by an operating load of the compressor of the refrigerant system.
4. The control method as claimed in claim 1, wherein the step of selectively increasing the number of the refrigerant systems turned on according to the operation loads of the compressors of all the refrigerant systems turned on and the leaving water temperature of the chilled water supply system comprises:
if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a fourth preset time length, and the water outlet temperature is continuously greater than or equal to a second preset water outlet temperature for a fifth preset time length, increasing the starting number of the refrigerant systems;
and the second preset outlet water temperature is greater than the target outlet water temperature.
5. The control method as claimed in claim 4, wherein the step of selectively increasing the number of the refrigerant systems that are turned on according to the operating loads of the compressors of all the refrigerant systems that are turned on and the leaving water temperature of the chilled water supply system further comprises:
if the operation loads of the compressors of all the refrigerant systems in the starting state reach the maximum operation load, the duration time reaches a sixth preset time length, and the effluent temperature is continuously greater than or equal to the target effluent temperature for a fifth preset time length, increasing the starting number of the refrigerant systems;
and the sixth preset time length is greater than the fourth preset time length.
6. The control method as claimed in any one of claims 1 to 5, wherein the step of increasing the number of the refrigerant systems that are turned on further comprises:
and determining the increasing quantity of the refrigerant systems according to the total quantity of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature.
7. The control method according to claim 6, wherein the step of determining the increased number of the refrigerant systems according to the total number of the refrigerant systems, the standard condition temperature difference preset value, the outlet water temperature and the target outlet water temperature specifically comprises:
and the increased number of the refrigerant systems is equal to the total number of the refrigerant systems divided by the standard condition temperature difference preset value and then multiplied by the calculation result of the difference value between the outlet water temperature and the target outlet water temperature, and the calculation result is rounded.
8. The control method according to any one of claims 1 to 5, characterized by further comprising:
under the condition that the number of the refrigerant systems in the starting state is more than or equal to two, acquiring the outlet water temperature of the chilled water supply system and the operation loads of the compressors of all the refrigerant systems in the starting state;
and selectively reducing the number of the refrigerant systems in the starting state according to the outlet water temperature of the chilled water supply system and/or the running load of the compressors of all the refrigerant systems in the starting state.
9. The method as claimed in claim 8, wherein the step of selectively reducing the number of the refrigerant systems in an on state according to a leaving water temperature of the chilled water supply system and/or an operation load of compressors of all the refrigerant systems in an on state comprises:
if the outlet water temperature is continuously lower than a third preset outlet water temperature for a seventh preset time, reducing the number of the refrigerant systems in an opening state;
and the third preset outlet water temperature is lower than the target outlet water temperature.
10. The method as claimed in claim 9, wherein the step of selectively reducing the number of the refrigerant systems in an on state according to a leaving water temperature of the chilled water supply system and/or an operation load of compressors of all the refrigerant systems in an on state further comprises:
if the outlet water temperature is continuously lower than the target outlet water temperature for the seventh preset time period and the duration that the operation load of the compressors of all the refrigerant systems in the opening state is smaller than or equal to the low-efficiency load preset value is reached for the eighth preset time period, reducing the number of the refrigerant systems in the opening state;
wherein the eighth preset duration is greater than the seventh preset duration.
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