A control method for efficient operation of a water chiller

Abstract

The application discloses a kind of control methods of chiller high-efficiency operation, belong to the technical field of air conditioning, by the minimum value of cooling water temperature determined by outdoor wet bulb temperature and approximation degree and the optimal temperature value of cooling water determined by the whole of cold source system are compared, the set value of cooling water inlet temperature is obtained, so that cooling tower plays cooling capacity, while ensuring the overall efficiency of cold source system and the minimum limit value of chiller condensing side inlet water temperature;Through the change trend of adjacent time cold load, obtain several chilled water outlet temperature assumption values, under this parameter condition, obtain the corresponding high-efficiency operation interval of various chillers;Then, according to the demand of cold load, combined with chiller high-efficiency operation interval and unit operation time, adjust chiller operation number, start-stop state, operating parameter, so that the refrigeration efficiency is best when chiller operates.

Description

Technical Field

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

[0002] Refrigeration equipment rooms often use a combination of large and small chillers to address the problem of regulating a wide range of cooling loads. However, due to the inherent characteristics of chillers, cooling efficiency remains low even under low loads. To further reduce energy consumption, high-efficiency equipment rooms have emerged. Inverter technology, a new energy-saving technology, is becoming increasingly popular. While inverter chillers require high equipment investment, they are also being used in limited quantities in refrigeration systems due to their high cooling efficiency under varying operating conditions. Consequently, a wide variety of chiller types are now used in refrigeration equipment rooms, and the ability to efficiently regulate these chillers has become a key factor in determining whether a room is efficient.

[0003] The cooling efficiency of a chiller is determined by both the unit's own characteristics and external factors. The unit's own characteristics are primarily determined by the type and number of compressors, as well as the type of refrigerant. From an automatic control perspective, the unit's own characteristics are set at the factory, and only external factors are controllable. For the same cooling capacity, the chiller's energy consumption can be reduced by lowering the condensing pressure. A lower condensing pressure requires a lower cooling water temperature. For every 1°C decrease in cooling water temperature, the chiller's COP can be increased by 2% to 3%. However, 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 chiller's cooling capacity is determined, the cold source system consisting of the cooling water pump, cooling tower, and chiller has an optimal cooling water temperature value.

[0004] Since cooling towers utilize the wet-bulb temperature of the air for cooling, they can achieve cooling as long as the wet-bulb temperature is lower than the cooling water temperature. Therefore, the water temperature at the cooling tower outlet can approach the wet-bulb temperature of the surrounding air. Therefore, by comparing the minimum cooling water temperature, determined by the outdoor wet-bulb temperature and the degree of approximation, with the optimal cooling water temperature determined by the overall cooling system, the cooling water inlet temperature setpoint is determined. This ensures that the cooling tower's cooling capacity is fully utilized while ensuring the overall efficiency of the cooling system and the minimum inlet water temperature limit on the chiller's condensing side.

[0005] The cooling 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 operating range of each chiller is determined, and the load rate of each chiller is allocated within the high-efficiency operating range to ensure that the chiller is in the optimal 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. Under the premise of meeting the cooling load of the system, the load of each chiller is reasonably distributed so that each chiller is in a suitable operating condition and the overall power consumption of the refrigeration system is reduced.

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

[0008] A method for controlling the efficient operation of a chiller comprises 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. Based on 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 temperature of cooling water 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 The power consumption of the chiller under

[0012] Step C. Assume the outlet temperature of 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 cooling load change trend 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, Chilled water outlet temperature assumed value 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 made to operate in the efficient operating range, and the power consumption of the running chiller is the lowest, so as to obtain the start and stop status and operating parameters of all chillers;

[0014] Step E. Set the chiller cumulative operating time limit T max(set) , obtain the start and stop status and cumulative running time of each chiller at time t-1, when T i、t-1 =T max(set) When t, 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 the control method for efficient operation of a chiller according to the present invention, in step A, the cooling load is in a changing state at all times. When the time is measured in units of one hour, the cooling load control is not precise enough. When the time is measured in units of one second, the control system operates more frequently and consumes more energy. 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 according to 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 inlet and outlet of the chilled water 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, the cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, the 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 cooling load demand forecast value at time t relative to the real-time cooling load value at time t-1, and in combination with the real-time value of the air-conditioning chilled water outlet temperature at time t-1, ld1、t-1 , assuming that the outlet temperature of the air-conditioning chilled water 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 outlet temperature of air-conditioning chilled water is t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) It is assumed that the temperature is decreased by 0.5℃ within the selected range; when Q t(pre) t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass) 、 t The outlet temperature of air-conditioning chilled water is t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) Assume that the temperature is increased by 0.5℃ within the selected range; then, the cooling water inlet temperature setting value 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 cooling load demand forecast value Q at time t is t(pre) Under the premise of , assuming that the number of running chillers is m, where m is 1, 2, 3, ..., n, the load rate of each chiller and the chilled water outlet temperature set value t are allocated to each chiller in the m running chillers. 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 running, the number of fans opened will be gradually increased and the fan operating frequency will be increased;

[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 of 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) , chilled water inlet and outlet temperature difference design value 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 under the design condition ld(des) , cooling water flow G lq(des) Related to the minimum frequency of the water pump:

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

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

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

[0028] The present invention provides a control method for the efficient operation of a chiller. In the same project, in order to meet a wider range of cooling load requirements and higher system operating efficiency, a combination of large and small units and a combination of variable frequency and fixed frequency units are often adopted. The cooling efficiency of the chiller is determined by the air-conditioning chilled water outlet temperature and flow rate and the cooling water inlet temperature and flow rate. Under the same air-conditioning chilled water and cooling water operating conditions, different types of chillers have different cooling efficiencies. The minimum cooling water temperature determined by the outdoor wet-bulb temperature and the proximity is compared with the optimal cooling water temperature determined by the entire cold source system to obtain a cooling water inlet temperature set value, 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 chiller condensing side inlet water temperature. Based on the cooling load change trend at adjacent moments, several hypothetical values ​​of the chilled water outlet temperature are obtained. Under these parameter conditions, the corresponding efficient operating ranges of various types of chillers are obtained. Then, according to the cooling load demand, combined with the efficient operating range of the chiller and the unit operating time, the number of operating chillers, the start and stop status, and the operating parameters are adjusted to achieve the optimal cooling efficiency when the chiller is operating. 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 The present invention is a flow chart of a method for controlling the efficient operation of a chiller. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention will be further described in detail below with reference to 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 of the present invention, all other embodiments obtained by ordinary technicians in this field without making 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. The purpose and effect of the present invention will become more clear. 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] Chillers should be rationally configured based on the design cooling load, with corresponding cooling water pumps, chilled water pumps, and cooling towers. At least two chillers should be used, each with different capacities. All pumps should be variable-frequency pumps, and the pump flow, head, and power consumption should be adjusted by reducing the pump frequency during operation. The cooling tower and chiller components should correspond, and the cooling tower fan should be variable-frequency. Furthermore, the design temperature values ​​should be clearly defined, i.e., the cooling water inlet and outlet temperatures and the chilled water inlet and outlet temperatures for the design operating conditions.

[0034] The present invention designs a control method for efficient operation of a chiller. In practical applications, such as 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. Based on 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 temperature of cooling water 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 The power consumption of the chiller under

[0038] Step C: Assume that the outlet temperature of the chilled water at time t is 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 cooling load change trend 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 , Chilled water outlet temperature assumed value 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 chillers in operation 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 made to operate in the efficient operating range, and the power consumption of the running chiller is the lowest, so as to obtain the start and stop status and operating parameters of all chillers;

[0040] Step E. Set the chiller cumulative operating time limit T max(set) , obtain the start and stop status and cumulative running time of each chiller at time t-1, when T i、t-1 =T max(set) When t, 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 every moment. If the time is measured in units of 1 hour, the cooling load control is not precise enough. If 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 inlet and outlet of the chilled water is the design value Δt lq(des) The 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, the cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, the 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 cooling load demand forecast value at time t relative to the real-time cooling load value at time t-1, combined with the real-time value of the air-conditioning chilled water outlet temperature at time t-1, ld1、t-1 , assuming that the outlet temperature of the air-conditioning chilled water 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 outlet temperature of air-conditioning chilled water is t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) It is assumed that the temperature is decreased by 0.5℃ within the selected range; when Q t(pre) t-1 When the air conditioning chilled water outlet temperature is assumed to be t ld1(ass)、t The outlet temperature of air-conditioning chilled water is t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) Assume that the temperature is increased by 0.5℃ within the selected range; then, the cooling water inlet temperature setting value 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 operating 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 running chillers is m, where m is 1, 2, 3, ..., n, the load rate of each chiller and the chilled water outlet temperature set value t are allocated to each chiller in the m running chillers. 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 running, the number of fans opened will be gradually increased and the fan operating frequency will be increased;

[0049] When t lq2、t <t lq2(set)、t When the cooling tower is running, the number of fans opened will be gradually reduced, the frequency of fan operation 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) , chilled water inlet and outlet temperature difference design value 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 under the design condition ld(des) , cooling water flow G lq(des) Related to the minimum frequency of the water pump:

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

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

[0053] The control method for efficient chiller operation designed in the above technical solution often utilizes a combination of large and small units, as well as variable and fixed frequency units, to meet a wide range of cooling load demands and maintain high system efficiency within the same project. Chiller efficiency is determined by the chilled water outlet temperature and flow rate, and the cooling water inlet temperature and flow rate. Under the same chilled water and cooling water operating conditions, different chiller types exhibit varying cooling efficiencies. By comparing the minimum cooling water temperature, determined by the outdoor wet-bulb temperature and proximity, with the optimal cooling water temperature, determined by the overall cooling source system, a setpoint for the cooling water inlet temperature is determined. This allows the cooling tower to maximize its cooling capacity while ensuring the overall efficiency of the cooling source system and the minimum inlet water temperature on the chiller's condensing side. By analyzing cooling load trends at adjacent moments, several hypothetical chilled water outlet temperature values ​​are derived. Under these parameters, the corresponding high-efficiency operating ranges for each type of chiller are determined. Then, based on the cooling load demand, the chiller's high-efficiency operating range, and the chiller's operating time, the number of operating chillers, their start / stop status, and operating parameters are adjusted to achieve optimal cooling efficiency during chiller operation.

[0054] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in this field without departing from the spirit 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. Based on 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 temperature of cooling water 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 The power consumption of the chiller under Step C. Assume the outlet temperature of 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 cooling load change trend 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 , Chilled water outlet temperature assumed value 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 made to operate in the efficient operating range, and the power consumption of the running chiller is the lowest, so as to obtain the start and stop status and operating parameters of all chillers; Step E. Set the chiller cumulative operating time limit T max(set) , obtain the start and stop status and cumulative running time of each chiller at time t-1, when T i、t-1 =T max(set) When t, 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 method for controlling 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. If the time is measured in 1 hour, the cooling load control is not precise enough. If the time is measured in 1 second, the control system operation is more frequent and the energy consumption is higher. Therefore, the time unit is selected as 30 minutes, that is, 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. The method for controlling 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. The method for controlling 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 kept at the design value Δt lq(des) , the temperature difference between the inlet and outlet of the chilled water 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, the cooling water inlet temperature setting value t lq2(set)、t =t lq(best)、t When t lq(best)、t <t sq、t +Δt, the cooling water inlet temperature setting value t lq2(set)、t =t sq、t +Δt.

5. The method for controlling efficient operation of a chiller according to claim 4, characterized in that: In step C, the predicted value of cooling load demand at time t is compared with the real-time value of cooling load at time t-1, and the real-time value of air-conditioning chilled water outlet temperature at time t-1 is combined with the real-time value of cooling load demand demand at time t-1. ld1、t-1 , assuming that the outlet temperature of the air-conditioning chilled water 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 outlet temperature of air-conditioning chilled water is t ld1、t-1 The chilled water outlet temperature of the chiller at the design condition is t ld1(des) It is assumed that the temperature is decreased by 0.5℃ within the selected 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 outlet temperature of air-conditioning chilled water is t ld1、t-1 To the maximum limit of chilled water outlet temperature of the chiller t ld1(max) Assume that the temperature is increased by 0.5℃ within the selected range; then, the cooling water inlet temperature setting value 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. The method for controlling 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 running chillers is m, where m is 1, 2, 3, ..., n, the load rate of each chiller and the chilled water outlet temperature set value t are allocated to each chiller in the m running chillers. 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. The method for controlling 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 running, the number of fans opened will be gradually increased and the fan operating frequency will be increased; 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. The method for controlling 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 set 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) , chilled water inlet and outlet temperature difference design value 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 under the design condition ld(des) , cooling water flow G lq(des) Related to the minimum frequency of the water pump: when When maintaining G ld(set)、t =0.5G ld(des) ; when When maintaining G lq(set)、t =0.5G lq(des) .

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