阅读说明：本技术 一种冷水机组和补气控制方法 (Water chilling unit and air supplementing control method ) 是由 任艳君 王锡元 吉磊 邵存东 于 2020-12-25 设计创作，主要内容包括：本发明公开了一种冷水机组和补气控制方法,该冷水机组的控制器被配置为：若检测压缩机启动指令,启动所述压缩机并基于预设初始开度确定所述补气调节阀的目标开度；若检测到所述压缩机的预设报警信号或所述压缩机进入预设稳定状态,根据所述压缩机的频率负荷和所述压缩机的导叶开度确定所述目标开度；其中,所述频率负荷为所述压缩机的运行频率与满负荷频率的比值,从而既避免了传统的补气不调节引起的经济器带液及部分负荷补气不起作用的现象,又避免了板式换热器以补气过热度控制补气量所引起的补气性能的衰减现象,提高了压缩机的效率和稳定性。(The invention discloses a water chilling unit and a gas supplementing control method, wherein a controller of the water chilling unit is configured to: if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening; if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor; the frequency load is the ratio of the running frequency and the full load frequency of the compressor, so that the phenomena of liquid carrying of an economizer and gas supplementing non-function of partial load caused by the fact that traditional gas supplementing is not adjusted are avoided, the attenuation phenomenon of gas supplementing performance caused by the fact that a plate heat exchanger controls gas supplementing quantity by the superheat degree of gas supplementing is avoided, and the efficiency and the stability of the compressor are improved.)

1. A chiller, comprising:

the compressor is of a two-stage centrifugal type and is used for compressing low-temperature and low-pressure refrigerant gas into high-temperature and high-pressure refrigerant gas and discharging the high-temperature and high-pressure refrigerant gas to the condenser;

the condenser is used for condensing the high-temperature and high-pressure refrigerant gas, reducing the pressure of the refrigerant gas through the first throttling valve and then discharging the refrigerant gas to the economizer;

the economizer is a flash tank type and is used for carrying out gas-liquid separation on the refrigerant, the separated gas enters a high-pressure stage of the compressor after being merged with low-pressure stage exhaust gas of the compressor through a gas supplementing pipeline, and the separated liquid is discharged to the evaporator through the second throttling valve;

the evaporator is used for evaporating the low-temperature and low-pressure refrigerant to reduce the temperature of the chilled water and sending low-temperature and low-pressure refrigerant gas into the compressor;

the water chilling unit is characterized in that an air supplementing adjusting valve is arranged on the air supplementing pipeline, and a controller of the water chilling unit is configured to:

if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening;

if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

2. The water chiller according to claim 1, wherein the controller is further configured to:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

3. The water chiller according to claim 1 wherein the control appliance body is configured to:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

4. The water chiller according to claim 2 wherein the control appliance is configured to:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

5. The chiller according to claim 4, wherein the controller is further configured to:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

6. The air supplement control method of the water chilling unit is applied to the water chilling unit comprising a compressor, a condenser, a first throttling valve, an economizer, a second throttling valve, an evaporator and a controller, and is characterized in that an air supplement regulating valve is arranged on an air supplement pipeline of the economizer, and the method comprises the following steps:

if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening;

if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

7. The method of claim 6, wherein the method further comprises:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

8. The method according to claim 6, characterized in that if a preset alarm signal of the compressor is detected or the compressor enters a preset steady state, the target opening is determined according to the frequency load of the compressor and the guide vane opening of the compressor, specifically:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

9. The method according to claim 7, wherein if a shutdown command is detected, controlling the target opening according to the frequency load and stopping the compressor, specifically:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

10. The method of claim 9, wherein the method further comprises:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

Technical Field

The application relates to the field of water chilling unit control, in particular to a water chilling unit and a gas supplementing control method.

Background

For the intermediate air supply control scheme with an economizer, most of the current research documents only give qualitative analysis of a volume compressor, and only give analysis of the influence of air supply on the unit performance under the full-load working condition, give qualitative conclusion that the optimal air supply pressure and the optimal air supply amount exist, and do not give concrete schemes of air supply control under the full load and the partial load aiming at a speed type centrifuge, some documents simply adopt Pm ═ Pc × Pe (Pm is the intermediate pressure, Pc is the condensing pressure, and Pe is the evaporating pressure) to calculate the optimal intermediate pressure and the intermediate temperature, but the optimal air supply pressure is continuously changed along with the working condition and the stage change of the operation in the actual operation process of the unit, the air supply control is simply carried out according to the formula, the unit cannot have the optimal performance under all the working conditions, and especially does not play the role of the corresponding air supply in the partial load operation, and because the air supply pressure is not reasonably selected, the adverse effects such as liquid carrying or performance reduction of air supply are easily caused.

In addition, most manufacturers have the scheme that no valve is added in an air supply pipeline and air supply is not adjusted at present in practical application, and in the scheme, in the initial starting process of the compressor, because normal operation pressure difference is not established yet and the opening degree of the air supply is too large, the flash tank type economizer is easily filled with refrigerant due to instant negative pressure, air supply liquid is carried, and irreversible damage is caused to the compressor.

At present, a more air supplement control scheme is applied in the magnetic suspension market, namely, a plate heat exchanger is adopted by an economizer, the liquid supply amount of a refrigerant entering the plate economizer is controlled by controlling the air supplement superheat degree of a refrigerant gas outlet of the plate heat exchanger, the scheme is only directed at the liquid supply amount entering the plate economizer and is not started from the angle of air supplement amount of a compressor, and the scheme adopts the air supplement superheat degree for control, so that the air supplement superheat degree is selected to be larger between 8 and 10 ℃, but according to a two-stage compression air supplement enthalpy increase principle, the larger the air supplement superheat degree is, the poorer the air supplement effect of the compressor is, and the performance advantage of air supplement on the compressor cannot be fully exerted.

Therefore, how to provide a water chilling unit capable of improving the efficiency and stability of a compressor is a technical problem to be solved at present.

Disclosure of Invention

The invention provides a water chilling unit, which is used for solving the technical problems that the air supplementing effect of the water chilling unit is poor and the stability of the unit is not high in the prior art.

This cooling water set includes:

the compressor is of a two-stage centrifugal type and is used for compressing low-temperature and low-pressure refrigerant gas into high-temperature and high-pressure refrigerant gas and discharging the high-temperature and high-pressure refrigerant gas to the condenser;

the condenser is used for condensing the high-temperature and high-pressure refrigerant gas, reducing the pressure of the refrigerant gas through the first throttling valve and then discharging the refrigerant gas to the economizer;

the economizer is a flash tank type and is used for carrying out gas-liquid separation on the refrigerant, the separated gas enters a high-pressure stage of the compressor after being merged with low-pressure stage exhaust gas of the compressor through a gas supplementing pipeline, and the separated liquid is discharged to the evaporator through the second throttling valve;

the evaporator is used for evaporating the low-temperature and low-pressure refrigerant to reduce the temperature of the chilled water and sending low-temperature and low-pressure refrigerant gas into the compressor;

the air supply pipeline is provided with an air supply adjusting valve, and a controller of the water chilling unit is configured to:

if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening;

if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

In some embodiments of the present application, the controller is further configured to:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

In some embodiments of the present application, the control appliance is configured to:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

In some embodiments of the present application, the control appliance is configured to:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

In some embodiments of the present application, the controller is further configured to:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

Correspondingly, the invention also provides an air supplement control method of the water chilling unit, which is applied to the water chilling unit comprising a compressor, a condenser, a first throttle valve, an economizer, a second throttle valve, an evaporator and a controller, wherein an air supplement regulating valve is arranged on an air supplement pipeline of the economizer, and the method comprises the following steps:

if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening;

if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

In some embodiments of the present application, the method further comprises:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

In some embodiments of the present application, if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, the target opening degree is determined according to the frequency load of the compressor and the guide vane opening degree of the compressor, specifically:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

In some embodiments of the present application, if a shutdown instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor, specifically:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

In some embodiments of the present application, the method further comprises:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

Compared with the prior art, the invention has the following beneficial effects:

the invention discloses a water chilling unit and a gas supplementing control method, wherein a controller of the water chilling unit is configured to: if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening; if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor; the frequency load is the ratio of the running frequency and the full load frequency of the compressor, so that the phenomena of liquid carrying of an economizer and gas supplementing non-function of partial load caused by the fact that traditional gas supplementing is not adjusted are avoided, the attenuation phenomenon of gas supplementing performance caused by the fact that a plate heat exchanger controls gas supplementing quantity by the superheat degree of gas supplementing is avoided, and the efficiency and the stability of the compressor are improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 is a schematic diagram illustrating a refrigeration cycle of a water chiller according to an embodiment of the present invention;

FIG. 2 shows a refrigeration cycle pressure enthalpy diagram in an embodiment of the present invention;

fig. 3 is a schematic flow chart illustrating a method for controlling air make-up of a chiller according to an embodiment of the present invention

Fig. 4 is a schematic flow chart illustrating a method for controlling air make-up of a chiller according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the description of the present application, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience in describing the present application and simplifying the description, but do not indicate or imply that the referred device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and thus should not be construed as limiting the present application.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more unless otherwise specified.

In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

The embodiment of the invention provides a water chilling unit, as shown in fig. 1, the water chilling unit comprises a refrigerant circulation loop consisting of a compressor 100, a condenser 200, a first throttle valve 300, an economizer 400, a second throttle valve 600 and an evaporator 700, the compressor 100 is a magnetic suspension two-stage centrifugal compressor, the economizer 400 is a flash tank type economizer, an air supplementing pipeline is connected with a refrigerant gas outlet at the top of the economizer 400 and an air supplementing port in the middle of the compressor 100, and the air supplementing pipeline is provided with an air supplementing adjusting valve 500 for air supplementing adjustment.

During cooling, low-pressure refrigerant vapor in the evaporator 700 (state point 1) → compression of the low-pressure stage of the compressor 100 to an intermediate pressure (state point 2) → merging with intermediate-pressure gas separated in the economizer 400 (state point 3) → compression of the high-pressure stage of the compressor 100 to a condensing pressure (state point 4) → condensation of high-pressure liquid condensed in the condenser 200 (state point 5) → primary throttling to an intermediate pressure (state point 6) → gas-liquid separation in the economizer 400 → saturated gas separated in the economizer 400 (state point 7) joins with low-pressure stage discharge gas of the compressor 100 (state point 2) (state point 3) and enters high-pressure stage compression, separated liquid (state point 8) enters evaporation pressure (state point 9) through secondary throttling → evaporation refrigeration of the evaporator 700 → low-pressure vapor (state point 1) and enters low-pressure stage compression of the compressor 100, this completes a refrigeration cycle.

The evaporator 700 of this embodiment is also connected to the user side, and the chilled water in the evaporator 700 enters the user side after the temperature of the chilled water is lowered, and the chilled water in the evaporator 700 can be replenished from the user side.

As shown in figure 2, the gas separated from the flash tank type economizer does not undergo the compression of a low-pressure stage, but directly enters a high-pressure stage for compression as intermediate air supplement, so that the power consumption of the low-pressure stage is reduced, the unit volume refrigerating capacity of the refrigerant is improved, and the improved refrigerating capacity is the enthalpy difference (h9-h6) between a state point 9 and a state point 6, so that the energy efficiency of a unit is greatly improved. Therefore, the reasonable air supply control scheme has important significance for the magnetic suspension double-stage compression centrifugal unit.

The invention reasonably controls the gas compensation amount of the saturated gas (state point 7) separated from the economizer as the middle gas compensation and the low-pressure stage exhaust (state point 2) of the compressor (state point 3) after the gas is converged into the high-pressure stage compression process, namely the adjustment of the EMV opening of the gas compensation adjusting valve, ensures that the economizer and the evaporator keep reasonable liquid levels under various working conditions, and ensures that the unit stably and efficiently operates under various working conditions.

The controller of the water chilling unit is configured to:

if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening;

if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

In the embodiment, if a compressor starting instruction is detected, the compressor is started, the compressor enters a starting stage, at this time, because the compressor is in a loading process and is not fully loaded in the starting stage, the running state of the unit is unstable, and if the air supply adjusting valve is adjusted according to load or frequency, frequent actions of the valve can exist to cause unstable liquid level of an economizer and current fluctuation of the unit, so that the unit is easy to cause failure shutdown alarm; if the air supply adjusting valve is fully opened at the stage, because the pressure ratio is not established in the starting process, the full opening of the air supply adjusting valve easily causes the pressure reduction in the economizer to cause air supply liquid carrying, which easily causes unit failure alarm and damages to the compressor, therefore, the target opening of the air supply adjusting valve is determined based on the preset initial opening, and the air supply adjusting valve is maintained at the preset initial opening. The preset initial opening can be reasonably set through experiments according to the type of the selected valve and the size of the configured gas supplementing pipeline.

The compressor comprises guide vanes, the opening degree of the guide vanes can be adjusted along with the load of the compressor, the frequency of the compressor can also be adjusted along with the load, if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, the air supply adjusting valve is made to exit from a preset initial opening degree, the target opening degree of the air supply adjusting valve is determined according to the frequency load of the compressor and the opening degree of the guide vanes of the compressor, and the frequency load is the ratio of the running frequency of the compressor to the full load frequency.

The preset alarm signal can be an early warning of low suction pressure, an early warning of low exhaust superheat degree or an early warning of high exhaust pressure, if the alarm is detected, the gas supply regulating valve is controlled, the state of the unit is adjusted in advance through load limitation or preset operation corresponding to the alarm to reduce the shutdown times, and the unit is prevented from directly achieving the function of fault shutdown.

To further improve the stability of the chiller, in some embodiments of the present application, the controller is further configured to:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

In the embodiment, as the compressor is in the unloading process in the shutdown process, if the air supplement regulating valve is completely closed in the unloading process, the liquid levels of the economizer and the evaporator are low in the shutdown stage, and the low evaporation pressure fault is caused; if the air supply adjusting valve is fully opened, the air supply of the economizer is easy to carry liquid due to too large opening degree of the air supply adjusting valve in the unloading process of the compressor, so that the compressor is damaged, and therefore the target opening degree of the air supply adjusting valve is controlled according to the frequency load, and the compressor is stopped.

In order to determine an accurate target opening degree when a preset alarm signal of the compressor is detected or the compressor enters a preset steady state, in a preferred embodiment of the present application, the controller is configured to:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

In this embodiment, the opening degree of the air supply adjusting valve needs to be adjusted according to the actual operation Load of the compressor, the actual operation Load of the compressor is related to the opening degree IGV and the operation frequency of the guide vane in the operation process of the compressor, and the operation frequency Load P of the compressor can linearly compare the actual operation Load of the compressor when the opening degree IGV of the guide vane is fixed. However, when the operating frequency of the compressor is fixed, the guide vane opening IGV of the compressor corresponds to the actual operating Load of the compressor in a nonlinear manner, and a corresponding relation curve between the guide vane opening and the compressor Load can be obtained from a compressor manufacturer, or the corresponding relation between the guide vane opening IGV of the compressor and the actual operating Load of the compressor can be obtained through experimental verification under the condition that the frequency of the compressor is fixed, the frequency of the compressor can be fixed at 100% of the full Load frequency, different guide vane openings are selected, the actual corresponding relation between the guide vane opening and the compressor Load can be obtained under the same operating condition, and the experimental data is fitted into a relation equation of the guide vane opening IGV and the actual operating Load of the compressor:

Load＝a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e (1)

and (3) synthesizing the relationship between the frequency and the opening degree of the guide vane and the actual load of the compressor to obtain the actual operation load of the magnetic suspension compressor as follows:

Load＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P (2)

according to the set flow characteristic curve of the air supply regulating valve, the corresponding relation between the target opening EMV of the air supply regulating valve and the actual operation Load of the compressor is obtained, the flow curve of the air supply regulating valve can be similar to the linear correspondence between the flow and the valve opening, and then the target opening EMV of the air supply regulating valve can be linearly corresponding to the actual operation Load of the compressor, so that a target opening control equation of the air supply regulating valve is obtained:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P (3)

it should be noted that the above solution of the preferred embodiment is only one specific implementation solution proposed in the present application, and other ways of determining the target opening degree according to the frequency load of the compressor and the guide vane opening degree all belong to the protection scope of the present application.

In order to determine an accurate target opening during shutdown, in a preferred embodiment of the present application, the controller is configured to:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

In this embodiment, during the shutdown of the unit, the opening of the air supply regulating valve can be linearly corresponding to the frequency load P of the compressor, and the minimum frequency load P of the compressor₀When the compressor is in the maximum frequency load Pmax, the air supply adjusting valve can be closed to the minimum opening EMVmin, and when the compressor is in the maximum frequency load Pmax, the air supply adjusting valve can be closed to the minimum opening EMVminThe valve may be opened to a maximum EMVmax; frequency load of compressor at P₀When P is less than Pmax, the valve opening degree is linearly corresponding to the compressor frequency, and the equation is obtained:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin (4)

it should be noted that the frequency regulation period of the compressor and the opening regulation period of the air supply regulating valve are respectively controlled within a reasonable preset range. Namely, the frequency regulation period of the compressor is in a first preset range and the opening regulation period of the air supply regulating valve is in a second preset range.

It should be noted that the above solution of the preferred embodiment is only one specific implementation solution proposed in the present application, and other ways of controlling the target opening degree according to the frequency load all belong to the protection scope of the present application.

To further improve the stability of the chiller, in some embodiments of the present application, the controller is further configured to:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

In this embodiment, the preset minimum opening is smaller than the preset initial opening, and after the compressor completely stops, the opening of the air supply regulating valve is reduced to the preset minimum opening, so that the compressor can be started next time.

By applying the above technical solution, the controller of the water chilling unit is configured to: if a compressor starting instruction is detected, starting the compressor and determining the target opening of the air supply regulating valve based on a preset initial opening; if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor; the frequency load is the ratio of the running frequency and the full load frequency of the compressor, so that the phenomena of liquid carrying of an economizer and gas supplementing non-function of partial load caused by the fact that traditional gas supplementing is not adjusted are avoided, the attenuation phenomenon of gas supplementing performance caused by the fact that a plate heat exchanger controls gas supplementing quantity by the superheat degree of gas supplementing is avoided, and the efficiency and the stability of the compressor are improved.

In order to further illustrate the technical idea of the present invention, the technical solution of the present invention will now be described with reference to specific application scenarios.

The embodiment of the invention provides an air supplement control method of a water chilling unit, which is applied to the water chilling unit comprising a compressor, a condenser, a first throttle valve, an economizer, a second throttle valve, an evaporator and a controller, wherein an air supplement regulating valve is arranged on an air supplement pipeline of the economizer, and as shown in figure 3, the air supplement control method comprises the following steps:

in step S301, EMV is EMVmin.

Before the compressor is started, the target opening EMV of the air supply regulating valve is a preset minimum opening EMVmin.

Step S302, determine whether there is a compressor start, if yes, execute step S303, otherwise execute step S301.

In step S303, EMV is equal to EMVi, and step S304 and step S305 are executed.

In the starting process of the compressor, the target opening EMV of the air supply regulating valve is a preset initial opening EMVi.

Step S304, determine whether there is a preset alarm, if so, execute step S306, otherwise, execute step S303.

Step S305, if the load is in the steady state, step S306 is executed, otherwise step S303 is executed.

In step S306, EMV ═ a × IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P。

And determining the target opening EMV of the air replenishing regulating valve according to the guide vane opening IGV and the frequency load P of the compressor.

Step S307, whether a shutdown command is received, if yes, step S308 is executed, otherwise step S306 is executed.

Step S308, EMV ═ P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin。

And determining the target opening EMV of the air replenishing regulating valve according to the frequency load P of the compressor.

Step S309, determine whether the compressor is completely stopped, if so, perform step S310, otherwise, perform step S308.

In step S310, EMV is EMVmin.

And adjusting the target opening EMV of the air supply adjusting valve to a preset minimum opening EMVmin.

Corresponding to the water chilling unit in the embodiment of the present application, the embodiment of the present application further provides a method for controlling air supply of the water chilling unit, which is applied to the water chilling unit including a compressor, a condenser, a first throttle valve, an economizer, a second throttle valve, an evaporator and a controller, wherein an air supply regulating valve is arranged on an air supply pipeline of the economizer, as shown in fig. 4, the method includes:

step S401, if a compressor starting instruction is detected, starting the compressor and determining a target opening degree of the air supply regulating valve based on a preset initial opening degree;

step S402, if a preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to the frequency load of the compressor and the guide vane opening of the compressor;

wherein the frequency load is a ratio of an operating frequency of the compressor to a full load frequency.

In order to determine an accurate target opening degree when detecting a preset alarm signal of the compressor or when the compressor enters a preset stable state, in a preferred embodiment of the present application, if detecting the preset alarm signal of the compressor or when the compressor enters the preset stable state, the target opening degree is determined according to a frequency load of the compressor and a guide vane opening degree of the compressor, specifically:

if the preset alarm signal of the compressor is detected or the compressor enters a preset stable state, determining the target opening according to a first formula, wherein the first formula specifically comprises the following steps:

EMV＝(a×IGV⁴+b×IGV³+c×IGV²+d×IGV+e)×P

and EMV is the target opening degree, IGV is the guide vane opening degree, P is the frequency load, and a, b, c, d and e are preset constants.

To further improve the stability of the chiller, in some embodiments of the present application, the method further comprises:

and if a stop instruction is detected, controlling the target opening according to the frequency load, and stopping the compressor.

In order to determine an accurate target opening degree in the shutdown process, in a preferred embodiment of the present application, if a shutdown instruction is detected, the target opening degree is controlled according to the frequency load, and the compressor is stopped, specifically:

if the shutdown instruction is detected and the frequency load is a preset maximum load, determining the target opening degree based on the preset maximum opening degree, and stopping the compressor;

if the shutdown instruction is detected and the frequency load is a preset minimum load, determining the target opening degree based on the preset minimum opening degree, and stopping the compressor;

if the shutdown instruction is detected, and the frequency load is smaller than the preset maximum load and larger than the preset minimum load, determining the target opening based on a second formula, and stopping the compressor, wherein the second formula specifically comprises:

EMV＝(P-P₀)×(EMVmax-EMVmin)/(Pmax-P₀)+EMVmin

wherein EMV is the target opening, P is the frequency load, P is₀And for the preset minimum load, Pmax is the preset maximum load, EMVmax is the preset maximum opening, and EMVmin is the preset minimum opening.

In order to further improve the stability of the water chilling unit, in some embodiments of the present application, the method further includes:

and if the compressor is detected to stop and the opening of the air supply regulating valve is not the preset minimum opening, closing the opening of the air supply regulating valve to the preset minimum opening.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit the same; although the present application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not necessarily depart from the spirit and scope of the corresponding technical solutions in the embodiments of the present application.