Control method for efficient operation of water chilling unit

Abstract

The invention discloses a control method for efficient operation of a water chilling unit, and belongs to the technical field of heating, ventilation and air conditioning. A cooling water inlet temperature set value is obtained by comparing a cooling water temperature minimum value determined by outdoor wet bulb temperature and approximation degree with a cooling water optimal temperature value determined by a cold source system as a whole, so that a cooling tower exerts cooling capacity, and meanwhile, the cooling capacity of the cooling tower is improved. The overall efficiency of the cold source system and the lowest water temperature limit of the condensation side inlet of the water chilling unit are ensured; a plurality of chilled water outlet temperature assumed values are obtained through the cold load change trend at the adjacent moments, and corresponding efficient operation intervals of all kinds of water chilling units are obtained under the parameter condition; and then, according to the cold load requirement, in combination with the efficient operation interval and the unit operation time of the water chilling units, the operation number, the start-stop state and the operation parameters of the water chilling units are adjusted, so that the refrigeration efficiency is optimal during operation of the water chilling units.

Description

Technical Field

[0001] The invention belongs to the technical field of heating, ventilation and air conditioning, and in particular relates to a control method for efficient operation of a chiller. Background Art

[0002] Refrigeration rooms often use a combination of large and small units to solve the problem of regulating a wide range of cooling loads. However, due to the characteristics of the chiller itself, it still does not have a high cooling efficiency under low-load operation. In order to further reduce energy consumption, high-efficiency machine rooms have come into being. As a new energy-saving technology, variable frequency technology has gradually become known to the public. Although variable frequency chillers have high equipment investment, they are also used in refrigeration systems in small quantities due to their high cooling efficiency under variable working conditions. As a result, various types of chillers appear in refrigeration rooms. How to efficiently regulate these chillers has become the main factor in whether a machine room is an efficient machine room.

[0003] The refrigeration efficiency of the chiller is determined by the unit's own characteristics and external factors. The unit's own characteristics mainly depend on the type of compressor, the number of units and the type of refrigerant. From the perspective of automatic control, the unit's own characteristics are set at the factory, and only external factors are controllable. For the same cooling capacity, the energy consumption of the chiller can be reduced by reducing the condensing pressure. Lower condensing pressure requires lower cooling water temperature. For every 1°C decrease in cooling water temperature, the COP of the chiller can be increased by 2% to 3%. A lower cooling water temperature will increase the energy consumption of the cooling water pump and cooling tower fan, and vice versa. Therefore, when the cooling capacity of the chiller is determined, the cold source system composed of the cooling water pump, cooling tower and chiller has an optimal cooling water temperature value.

[0004] Since the cooling tower uses the wet bulb temperature of the air for cooling, it can play a cooling role as long as the wet bulb temperature is lower than the cooling water temperature, so the water temperature out of the cooling tower can approach the wet bulb temperature of the surrounding air. Therefore, the minimum cooling water temperature determined by the outdoor wet bulb temperature and the degree of approximation and the optimal cooling water temperature determined by the overall cold source system are compared to determine the cooling water inlet temperature setting value. It can not only meet the cooling capacity of the cooling tower, but also ensure the overall efficiency of the cold source system and the minimum inlet water temperature limit of the chiller condensing side.

[0005] The refrigeration efficiency of the chiller is mainly determined by the cooling water inlet temperature and the chilled water outlet temperature. When the cooling water inlet temperature and the chilled water outlet temperature are determined, the high-efficiency operation range of each chiller is determined, and the load rate of each chiller is allocated within the high-efficiency operation range to ensure that the chiller is in the best operating condition. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a control method for the efficient operation of a chiller, which reasonably distributes the load of each chiller on the premise of meeting the system cooling load, so that each chiller is in a suitable operating condition and reduces the overall power consumption of the refrigeration system.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A control method for efficient operation of a chiller, comprising the following steps:

[0009] Step A. Obtain the cooling load demand forecast value Q at time t t(pre) , obtain the real-time parameter values ​​at time t-1, including the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , outdoor air wet bulb temperature t sq、t ;

[0010] Step B. According to the power consumption rate curve f(t) of the cooling water pump, cooling tower and chiller at different cooling water temperatures, obtain the optimal cooling water temperature t with the lowest overall power consumption rate of the cooling water pump, cooling tower and chiller under the same cooling capacity lq(best) , f lqxt (t lq(best) )=min(f lqsb+lq t(t lq )+f lsj (t lq );

[0011] Among them, f lqxt (t lq(best) ) is the optimal cooling water temperature t lq(best) Power consumption of cooling water system under lqsb+lqt (t lq ) is the cooling water temperature t lq Power consumption of cooling water pump and cooling tower under lsj (t lq ) is the cooling water temperature t lq Power consumption of chillers under

[0012] Step C: Assume the outlet temperature of air-conditioning chilled water at time t ld1(ass)、t , according to the outdoor wet bulb temperature t sq、t and the optimal cooling water temperature t lq(best)、t , calculate and obtain the cooling water inlet temperature setting value t lq2(set)、t ;According to the change trend of cooling load at adjacent moments, obtain multiple hypothetical values ​​of chilled water outlet temperature t ld1(ass)、t ; At the cooling water inlet temperature setting value t lq2(set)、t, Assumed value of chilled water outlet temperature t ld1(ass)、t Under the working conditions, combined with the chiller characteristic curve, the efficient operation range of the chiller under the corresponding working conditions is obtained;

[0013] Step D. The total number of chillers is n, and the number of operating chillers is m; when the total cooling capacity of each operating chiller is Q t(pre) Under the premise of combining the characteristic curves of each chiller, each running chiller is in the high-efficiency operation range, and the running chiller has the lowest power consumption, so as to obtain the start and stop status and operation parameters of all chillers;

[0014] Step E. Set the chiller cumulative running time limit T max(set) , obtain the start / stop status and cumulative running time of each chiller at time t-1. i、t-1 =T max(set) When , the i-th chiller switches from the on state to the stopped state. If the running chillers include the i-th chiller, that is, the i-th chiller needs to participate in the cooling at time t, then the number of running chillers and the operating parameters of each chiller are redistributed without considering the i-th chiller.

[0015] As a further preferred embodiment of a control method for efficient operation of a chiller according to the present invention, in step A, the cooling load is in a changing state all the time. When the time is measured in units of 1 hour, the cooling load control is not precise enough. When the time is measured in units of 1 second, the control system operation is relatively frequent and the energy consumption is relatively high. Therefore, the time unit is selected as 30 minutes, i.e., 0.5 hours.

[0016] The water temperature changes continuously, and the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , Outdoor air wet bulb temperature t sq、t Take it as the average temperature within the time range;

[0017] As a further preferred embodiment of the control method for efficient operation of a chiller of the present invention, in step C, the characteristic curves of each chiller at time t are based on external factors, including the air conditioning chilled water outlet temperature t ld1、t , Cooling water inlet temperature t lq2、t , Air conditioning chilled water flow G ld、t , Cooling water flow G lq、t .

[0018] As a further preferred embodiment of the control method for efficient operation of a chiller according to the present invention, in step C, the temperature difference between the inlet and outlet water of the cooling water is maintained at the design value Δtlq(des) , the temperature difference between the chilled water inlet and outlet is the design value Δt ld(des) ; Cooling water inlet temperature setting value at time t lq2(set)、t According to the outdoor air wet bulb temperature t sq、t , approximation Δt and optimal cooling water temperature t lq(best)、t Calculate, when t lq(best)、t ≥t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t sq、t +Δt.

[0019] As a further preferred embodiment of the control method for efficient operation of a chiller according to the present invention, in step C, according to the change of the predicted value of the cooling load demand at time t relative to the real-time value of the cooling load at time t-1, and in combination with the real-time value of the outlet water temperature of the air conditioner at time t-1, ld1、t-1 , assuming that the air conditioning chilled water outlet temperature at time t ld1(ass)、t ; When Q t(pre) ≥Q t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The air conditioning chilled water outlet temperature t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) is the selected value range and is assumed to decrease by 0.5℃ within this temperature range; when Q t(pre) t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass) , t The air conditioning chilled water outlet temperature t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) is the selected value interval and it is assumed that the temperature increases by 0.5℃ within this temperature interval; then, the cooling water inlet temperature setting value t at time t lq2(set)、t The assumed value of the chilled water outlet temperature of each air conditioner is t ld1(ass)、t , combined with the chiller characteristic curve, obtain the efficient operation range of the chiller under the corresponding working conditions.

[0020] As a further preferred embodiment of the control method for efficient operation of a chiller according to the present invention, in step D, the predicted value of cooling load demand Q at time t is t(pre) Under the premise of , assuming that the number of chillers in operation is m, where m is 1, 2, 3, ..., n respectively, the load rate and chilled water outlet temperature setting value t of each chiller are allocated among the m chillers in operation. ld1(set)、t ​, Cooling water inlet temperature setting value t lq2(set)、t , so that the running chiller is in the high-efficiency operation range. At the same time, since the power consumption of the chilled water pump is much lower than that of the chiller, the chilled water pump is ignored and only the power consumption of the chiller is considered, so that the total power consumption of the running chiller is the lowest, that is,

[0021] As a further preferred embodiment of the control method for efficient operation of a chiller according to the present invention, in step D, the cooling water inlet temperature t lq2、t Adjust by:

[0022] When t lq2、t >t lq2(set)、t When the cooling tower is turned on, the number of fans gradually increases and the frequency of fan operation increases;

[0023] When t lq2、t <t lq2(set)、t When the cooling tower is running, the number of fans turned on will be gradually reduced, the frequency of fan operation will be lowered or the fans will be turned off.

[0024] As a further preferred embodiment of the control method for efficient operation of a chiller according to the present invention, in step D, the load rate of each chiller obtained by allocation, the chilled water outlet temperature setting value t ld1(set)、t , Cooling water inlet temperature setting value t lq2(set)、t And the design value of the cooling water inlet and outlet temperature difference Δt lq(des) , Design value of chilled water inlet and outlet temperature difference Δt ld(des) Calculate the chilled water flow rate G ld(set)、t , Cooling water flow G lq(set)、t At the same time, the chilled water flow G ld(set)、t , Cooling water flow G lq(set)、t The determination of the chilled water flow rate G of the chiller air conditioner under the design condition ld(des) , Cooling water flow G lq(des) Related to the minimum frequency of the pump:

[0025] when When G ld(set)、t =0.5G ld(des) ;

[0026] when When G lq(set)、t =0.5G lq(des) .

[0027] The control method for efficient operation of a chiller described in the present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0028] The present invention discloses a control method for efficient operation of a chiller. In the same project, in order to meet a wider range of cooling load requirements and higher system operation efficiency, a combination of large and small units and a combination of variable frequency and fixed frequency are often used. The cooling efficiency of the chiller is determined by the outlet temperature and flow rate of air-conditioning chilled water and the inlet temperature and flow rate of cooling water. Under the same air-conditioning chilled water and cooling water working conditions, different types of chillers have different cooling efficiencies. The minimum cooling water temperature determined by the outdoor wet-bulb temperature and the degree of approach is compared with the optimal cooling water temperature determined by the cold source system as a whole, and a cooling water inlet temperature setting value is obtained, so that the cooling tower can exert its cooling capacity while ensuring the overall efficiency of the cold source system and the minimum limit of the inlet water temperature on the condensing side of the chiller. According to the change trend of the cold load at adjacent moments, several hypothetical values ​​of the chilled water outlet temperature are obtained, and under this parameter condition, the corresponding efficient operation ranges of various types of chillers are obtained. Then, according to the cooling load demand, combined with the efficient operation range of the chiller and the operation time of the unit, the number of operating chillers, the start-stop state, and the operation parameters of the chiller are adjusted, so that the cooling efficiency of the chiller is optimal when it is running. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 A flow chart of a method for efficiently controlling the operation of a chiller designed for the present invention. DETAILED DESCRIPTION

[0031] The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The present invention is described in detail below based on the drawings and preferred embodiments, and the purpose and effect of the present invention will become clearer. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.

[0033] According to the designed cooling load, the chiller is reasonably configured, and the corresponding cooling water pump, refrigeration water pump and cooling tower are matched. There are at least 2 chillers with different capacities; the water pumps are all variable frequency water pumps, and the water pump flow, head and power consumption are adjusted by reducing the operating frequency of the water pump during operation; the cooling tower and the chiller are composed of a corresponding relationship, and the cooling tower fan is set to variable frequency. At the same time, the temperature design value is clarified, that is, the cooling water inlet and outlet water temperature and the refrigeration water inlet and outlet water temperature of the design condition.

[0034] The present invention designs a control method for efficient operation of a chiller. In practical applications, Figure 1 As shown, specifically perform the following steps A to E.

[0035] Step A. Obtain the cooling load demand forecast value Q at time t t(pre) , obtain the real-time parameter value at time t-1, such as the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , outdoor air wet bulb temperature t sq、t ;

[0036] Step B. According to the power consumption rate curve f(t) of the cooling water pump, cooling tower and chiller at different cooling water temperatures, obtain the optimal cooling water temperature t with the lowest overall power consumption rate of the cooling water pump, cooling tower and chiller under the same cooling capacity lq(best) , f lqxt (t lq(best) )=min(f lqsb+lqt (t lq )+f lsj (t lq ));

[0037] Among them, f lqxt (t lq(best) ) is the optimal cooling water temperature t lq(best) Power consumption of cooling water system under lqsb+lq t(t lq ) is the cooling water temperature t lq Power consumption of cooling water pump and cooling tower under lsj (t lq ) is the cooling water temperature t lq Power consumption of chillers under

[0038] Step C: Assume that the air conditioning chilled water outlet temperature at time t ld1(ass)、t , according to the outdoor wet bulb temperature t sq、t and the optimal cooling water temperature t lq(best)、t , calculate and obtain the cooling water inlet temperature setting value t lq2(set)、t;According to the change trend of cooling load at adjacent moments, obtain multiple hypothetical values ​​of chilled water outlet temperature t ld1(ass)、t ; At the cooling water inlet temperature setting value t lq2(set)、t , Assumed value of chilled water outlet temperature t ld1(ass)、t Under the working conditions, combined with the chiller characteristic curve, the efficient operation range of the chiller under the corresponding working conditions is obtained;

[0039] Step D. The total number of chillers is n, and the number of operating chillers is m. The total cooling capacity of each chiller in operation is Q t(pre) Under the premise of combining the characteristic curves of each chiller, each running chiller is in the high-efficiency operation range, and the running chiller has the lowest power consumption, so as to obtain the start and stop status and operation parameters of all chillers;

[0040] Step E. Set the chiller cumulative running time limit T max(set) , obtain the start / stop status and cumulative running time of each chiller at time t-1. i、t-1 =T max(set) When , the i-th chiller switches from the on state to the stopped state. If the running chillers include the i-th chiller, that is, the i-th chiller needs to participate in the cooling at time t, then the number of running chillers and the operating parameters of each chiller are redistributed without considering the i-th chiller.

[0041] As a preferred technical solution of the present invention: in step A, the cooling load is in a changing state all the time. When the time is measured in units of 1 hour, the cooling load control is not precise enough. When the time is measured in units of 1 second, the control system operation is more frequent and the energy consumption is higher. Therefore, the time unit is selected as 30 minutes (0.5 hours).

[0042] The water temperature changes continuously, and the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , Outdoor air wet bulb temperature t sq、t Take it as the average temperature within the time range;

[0043] As a preferred technical solution of the present invention: in step C, the characteristic curves of each chiller at time t are based on external factors, including the air conditioning chilled water outlet temperature t ld1、t , Cooling water inlet temperature t lq2、t , Air conditioning chilled water flow G ld、t , Cooling water flow G lq、t ;

[0044] As a preferred technical solution of the present invention: in step C, the temperature difference between the inlet and outlet of the cooling water is maintained at the design value Δt lq(des) , the temperature difference between the chilled water inlet and outlet is the design value Δt lq(des) . Cooling water inlet temperature setting value at time t lq2(set)、t According to the outdoor air wet bulb temperature t sq、t , approximation Δt and optimal cooling water temperature t lq(best)、t Calculate, when t lq(bset)、t ≥t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t sq、t +Δt;

[0045] As a preferred technical solution of the present invention: in step C, according to the change of the predicted value of the cooling load demand at time t relative to the real-time value of the cooling load at time t-1, combined with the real-time value of the outlet temperature of the air conditioner chilled water at time t-1, ld1、t-1 , assuming that the air conditioning chilled water outlet temperature at time t ld1(ass)、t When Q t(pre) ≥Q t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The air conditioning chilled water outlet temperature t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) is the selected value range and is assumed to decrease by 0.5℃ within this temperature range; when Q t(pre) t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The air conditioning chilled water outlet temperature t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) is the selected value interval and it is assumed that the temperature increases by 0.5℃ within this temperature interval; then, the cooling water inlet temperature setting value t at time t lq2(set)、t The assumed value of the chilled water outlet temperature of each air conditioner is t ld1(ass)、t , combined with the chiller characteristic curve, obtain the efficient operation range of the chiller under the corresponding working conditions;

[0046] As a preferred technical solution of the present invention: in step D, the cooling load demand forecast value Q at time t t(pre) Under the premise of , assuming that the number of chillers in operation is m, where m is 1, 2, 3, ..., n respectively, the load rate and chilled water outlet temperature setting value t of each chiller are allocated among the m chillers in operation. ld1(set)、t ​, Cooling water inlet temperature setting value t lq2(set)、t , so that the running chiller is in the high-efficiency operation range. At the same time, since the power consumption of the chilled water pump is much lower than that of the chiller, the chilled water pump is ignored and only the power consumption of the chiller is considered, so that the total power consumption of the running chiller is the lowest, that is,

[0047] As a preferred technical solution of the present invention: in step D, the cooling water inlet temperature t lq2、t Adjust by:

[0048] When t lq2、t >t lq2(set)、t When the cooling tower is turned on, the number of fans gradually increases and the frequency of fan operation increases;

[0049] When t lq2、t <t lq2(set)、t When the cooling tower is in a state of low temperature, the number of fans turned on will be gradually reduced, the frequency of fans running will be lowered or fans will be turned off;

[0050] As a preferred technical solution of the present invention: in the step D, the load rate of each chiller obtained by allocation, the chilled water outlet temperature setting value t ld1(set)、t , Cooling water inlet temperature setting value t lq2(set)、t And the design value of the cooling water inlet and outlet temperature difference Δt lq(des) , Design value of chilled water inlet and outlet temperature difference Δt ld(des) Calculate the chilled water flow rate G ld(set)、t , Cooling water flow G lq(set)、t At the same time, the chilled water flow G ld(set)、t , Cooling water flow G lq(set)、t The determination of the chilled water flow rate G of the chiller air conditioner under the design condition ld(des) , Cooling water flow G lq(des) Related to the minimum frequency of the pump:

[0051] when When G ld(set)、t =0.5G ld(des) ;

[0052] when When G lq(set)、t =0.5G lq(des) .

[0053] The control method for efficient operation of the chiller designed by the above technical scheme, in the same project, in order to meet a wider range of cooling load requirements and higher system operation efficiency, large and small units are often matched, and variable frequency and fixed frequency are matched. The cooling efficiency of the chiller is determined by the outlet temperature and flow rate of the air-conditioning chilled water and the inlet temperature and flow rate of the cooling water. Under the same air-conditioning chilled water and cooling water conditions, different types of chillers have different cooling efficiencies. The minimum cooling water temperature determined by the outdoor wet-bulb temperature and the degree of approach is compared with the optimal cooling water temperature determined by the cold source system as a whole, and the cooling water inlet temperature setting value is obtained, so that the cooling tower can exert its cooling capacity while ensuring the overall efficiency of the cold source system and the minimum limit of the inlet water temperature on the condensing side of the chiller. Through the trend of cold load changes at adjacent moments, several hypothetical values ​​of the chilled water outlet temperature are obtained. Under this parameter condition, the corresponding efficient operation ranges of various types of chillers are obtained. Then, according to the cold load demand, combined with the efficient operation range of the chiller and the unit operation time, the number of operating units, start and stop status, and operation parameters of the chiller are adjusted to achieve the best cooling efficiency when the chiller is running.

[0054] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A control method for efficient operation of a chiller, characterized in that: The specific steps include: Step A. Obtain the cooling load demand forecast value Q at time t t(pre) , obtain the real-time parameter values ​​at time t-1, including the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , outdoor air wet bulb temperature t sq、t ; Step B. According to the power consumption rate curve f(t) of the cooling water pump, cooling tower and chiller at different cooling water temperatures, obtain the optimal cooling water temperature t with the lowest overall power consumption rate of the cooling water pump, cooling tower and chiller under the same cooling capacity lq(best) , f lqxt (t lq(best) )=min(f lqsb+lqt (t lq )+f lsj (t lq )); Among them, f lqxt (t lq(best) ) is the optimal cooling water temperature t lq(best) Power consumption of cooling water system under lqsb+lqt (t lq ) is the cooling water temperature t lq Power consumption of cooling water pump and cooling tower under lsj (t lq ) is the cooling water temperature t lq Power consumption of chillers under Step C: Assume the outlet temperature of air-conditioning chilled water at time t ld1(ass)、t , according to the outdoor wet bulb temperature t sq、t and the optimal cooling water temperature t lq(best)、t , calculate and obtain the cooling water inlet temperature setting value t lq2(set)、t ;According to the change trend of cooling load at adjacent moments, obtain multiple hypothetical values ​​of chilled water outlet temperature t ld1(ass)、t ; At the cooling water inlet temperature setting value t lq2(set)、t , Assumed value of chilled water outlet temperature t ld1(ass)、t Under the working conditions, combined with the chiller characteristic curve, the efficient operation range of the chiller under the corresponding working conditions is obtained; Step D. The total number of chillers is n, and the number of operating chillers is m; when the total cooling capacity of each operating chiller is Q t(pre) Under the premise of combining the characteristic curves of each chiller, each running chiller is in the high-efficiency operation range, and the running chiller has the lowest power consumption, so as to obtain the start and stop status and operation parameters of all chillers; Step E. Set the chiller cumulative running time limit T max(set) , obtain the start / stop status and cumulative running time of each chiller at time t-1. i、t-1 =T max(set) When , the i-th chiller switches from the on state to the stopped state. If the running chillers include the i-th chiller, that is, the i-th chiller needs to participate in the cooling at time t, then the number of running chillers and the operating parameters of each chiller are redistributed without considering the i-th chiller.

2. A control method for efficient operation of a chiller according to claim 1, characterized in that: In step A, the cooling load is in a changing state every moment. When the time is measured in units of 1 hour, the cooling load control is not precise enough. When the time is measured in units of 1 second, the control system operation is more frequent and the energy consumption is higher. Therefore, the time unit is selected as 30 minutes, i.e. 0.5 hours. The water temperature changes continuously, and the air conditioning chilled water inlet temperature t ld2、t-1 , Air conditioning chilled water outlet temperature t ld1、t-1 , Cooling water inlet temperature t lq2、t-1 , Cooling water outlet temperature t lq1、t-1 , Outdoor air wet bulb temperature t sq、t Taken as the average temperature within the time range.

3. A control method for efficient operation of a chiller according to claim 1, characterized in that: In step C, the characteristic curves of each chiller at time t are based on external factors, including the air conditioning chilled water outlet temperature t ld1、t , Cooling water inlet temperature t lq2、t , Air conditioning chilled water flow G ld、t , Cooling water flow G lq、t .

4. A control method for efficient operation of a chiller according to claim 3, characterized in that: In step C, the temperature difference between the inlet and outlet of the cooling water is maintained at the design value Δt lq(des) , the temperature difference between the chilled water inlet and outlet is the design value Δt ld(des) ; Cooling water inlet temperature setting value at time t lq2(set)、t According to the outdoor air wet bulb temperature t sq、t , approximation Δt and optimal cooling water temperature t lq(best) , t calculation, when t lq(best) , t≥t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, cooling water inlet temperature setting value t lq2(set)、t =t sq、t +Δt.

5. A control method for efficient operation of a chiller according to claim 4, characterized in that: In step C, according to the change of the predicted value of cooling load demand at time t relative to the real-time value of cooling load at time t-1, combined with the real-time value of air conditioning chilled water outlet temperature at time t-1, ld1、t-1 , assuming that the air conditioning chilled water outlet temperature at time t ld1(ass)、t ; When Q t(pre) ≥Q t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The air conditioning chilled water outlet temperature t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) is the selected value range and is assumed to decrease by 0.5℃ within this temperature range; when Q t(pre) <Q t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The air conditioning chilled water outlet temperature t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) is the selected value interval and it is assumed that the temperature increases by 0.5℃ within this temperature interval; then, the cooling water inlet temperature setting value t at time t lq2(set)、t The assumed value of the chilled water outlet temperature of each air conditioner is t ld1(ass)、t , combined with the chiller characteristic curve, obtain the efficient operation range of the chiller under the corresponding working conditions.

6. A control method for efficient operation of a chiller according to claim 1, characterized in that: In step D, the cooling load demand forecast value Q at time t is t(pre) Under the premise of , assuming that the number of chillers in operation is m, where m is 1, 2, 3, ..., n respectively, the load rate of each chiller and the chilled water outlet temperature setting value t are allocated to each chiller in the m chillers in operation. ld1(set)、t , Cooling water inlet temperature setting value t lq2(set)、t , so that the running chiller is in the high-efficiency operation range. At the same time, since the power consumption of the chilled water pump is much lower than that of the chiller, the chilled water pump is ignored and only the power consumption of the chiller is considered, so that the total power consumption of the running chiller is the lowest, that is, 7. A control method for efficient operation of a chiller according to claim 1, characterized in that: In step D, the cooling water inlet temperature t lq2、t Adjust by: When t lq2、t >t lq2(set)、t When the cooling tower is turned on, the number of fans gradually increases and the frequency of fan operation increases; When t lq2、t <t lq2(set)、t When the cooling tower is running, the number of fans turned on will be gradually reduced, the frequency of fan operation will be lowered or the fans will be turned off.

8. A control method for efficient operation of a chiller according to claim 7, characterized in that: In step D, the load rate of each chiller obtained by allocation, the chilled water outlet temperature setting value t ld1(set)、t , Cooling water inlet temperature setting value t lq2(set)、t And the design value of the cooling water inlet and outlet temperature difference Δt lq(des) , Design value of chilled water inlet and outlet temperature difference Δt ld(des) Calculate the chilled water flow rate G ld(set)、t , Cooling water flow G lq(set)、t At the same time, the chilled water flow G ld(set)、t , Cooling water flow G lq(set)、t The determination of the chilled water flow rate G of the chiller air conditioner under the design condition ld(des) , Cooling water flow G lq(des) Related to the minimum frequency of the pump: when When G ld(set)、t =0.5G ld(des) ; when When G lq(set)、t =0.5G lq(des) .

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