A multi-parallel carbon dioxide heat pump control method based on target load control

Abstract

This invention discloses a control method for multiple parallel carbon dioxide heat pumps based on target load control, belonging to the field of heat pump system control technology. The method includes collecting energy-consuming side temperature data, solar-side heat exchange data, and operating data of each parallel carbon dioxide heat pump unit from a dual-condition solar heat pump air conditioning unit. It then performs load conversion and load upper limit correction based on the difference in solar-side heat exchange compensation under cooling and heating conditions to obtain a target load determination value. Using this target load determination value as a load demand constraint, it comprehensively matches the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation, and operational stability of each parallel carbon dioxide heat pump unit to determine the priority of each unit in undertaking the target load, forming a unit load-bearing sequence. This invention avoids mismatch between target load and actual demand by determining a target load determination value that is compatible with cooling, heating, and solar-side heat exchange compensation.

Description

Technical Field

[0001] This invention relates to the field of heat pump system control technology, and in particular to a control method for multiple parallel carbon dioxide heat pumps based on target load control. Background Technology

[0002] Dual-mode solar heat pump air conditioning units typically combine solar-side heat exchange loops, energy-consuming-side heat exchange loops, and multiple carbon dioxide heat pump units to meet dynamic load demands under both cooling and heating conditions. As the requirements for energy efficiency and stability increase in building air conditioning, hot water supply, and multi-energy utilization scenarios, the control of multiple parallel carbon dioxide heat pumps is gradually evolving from single start-stop control to target load control, load coordination and distribution, and multi-parameter linkage adjustment. Because the high-pressure side of the carbon dioxide heat pump is pressure-sensitive, and the solar-side heat exchange capacity in dual-mode solar heat pump air conditioning units fluctuates with environmental changes, accurately determining the target load and coordinating the load-bearing capacity of multiple parallel units has become a key issue affecting system operating efficiency and control stability.

[0003] However, existing methods have some shortcomings. The target load determination process does not adequately consider the load conversion differences between cooling and heating conditions and the compensation for solar heat exchange, which can easily lead to a mismatch between the target load and actual demand, resulting in ineffective load increases or frequent adjustments. In addition, the unit load allocation is mostly based on a fixed sequence, number of operating units, or rated capacity ratio, without taking into account real-time energy efficiency ratings, compressor frequency margin, discharge pressure deviation, and operational stability. It also lacks linkage control of air cooler target pressure, compressor target frequency, and electronic expansion valve target opening, which can easily lead to inaccurate load allocation, increased pressure fluctuations, and reduced synergistic operation effects. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a control method for multiple parallel carbon dioxide heat pumps based on target load control to solve the problems of inaccurate target load determination and insufficient coordination of load distribution and linkage control of multiple parallel units under dual operating conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: This invention provides a control method for multiple parallel carbon dioxide heat pumps based on target load control. The method includes: collecting energy-consuming side temperature data, solar-side heat exchange data, and operating data of each parallel carbon dioxide heat pump unit from a dual-condition solar heat pump air conditioning unit; performing load calculation and load upper limit correction based on the difference in solar-side heat exchange compensation under cooling and heating conditions to obtain a target load determination value; using the target load determination value as a load demand constraint, comprehensively matching the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation, and operational stability of each parallel carbon dioxide heat pump unit. The priority of each parallel carbon dioxide heat pump unit in undertaking the target load is determined to form a unit load undertaking sequence. The target load judgment value is differentiated and allocated along the unit load undertaking sequence. The unit at the front of the sequence is determined as the basic load undertaking object, and the unit at the back of the sequence is determined as the compensation load undertaking object, so as to obtain the target load share corresponding to each parallel carbon dioxide heat pump unit. According to the target load share and load adjustment status of each parallel carbon dioxide heat pump unit, the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve are determined in a coordinated manner to form multi-parallel carbon dioxide heat pump control commands.

[0007] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps according to the present invention, the specific steps for obtaining the target load determination value are as follows: Collect energy-consuming side temperature data, solar-side heat exchange data, and operating data of each parallel carbon dioxide heat pump unit within the same unified sampling period for dual-condition solar heat pump air conditioning units, and align them by time to obtain effective collected data; Based on the effective collected data, the current operating conditions are identified, and the supply and return water temperature difference on the energy consumption side, the set temperature deviation on the energy consumption side, and the heat exchange on the solar energy side are determined to obtain the operating load conversion data. The load demand is determined based on the converted load data, and the load demand is corrected by combining the operating data of each parallel carbon dioxide heat pump unit to obtain the target load judgment value.

[0008] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps described in this invention, the specific steps for forming the unit load-sharing sequence are as follows: Based on the operating data of each parallel carbon dioxide heat pump unit, the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation and operating stability are determined to obtain load-bearing evaluation data. Using the target load determination value as a load demand constraint, the load sharing evaluation data is comprehensively matched to obtain the load sharing matching results of each parallel carbon dioxide heat pump unit. Based on the load-bearing matching results, the priority of each parallel carbon dioxide heat pump unit in bearing the target load is determined, and the parallel carbon dioxide heat pump units are arranged according to the priority to form a unit load-bearing sequence.

[0009] As a preferred embodiment of the target load control-based multi-parallel carbon dioxide heat pump control method of the present invention, the specific steps for obtaining the load occupancy evaluation data are as follows: The real-time energy efficiency rating is determined based on the compressor operating frequency, the upper limit of the compressor's allowable frequency, the rated load of a single unit, and the compressor's input power. The compressor frequency margin is determined based on the difference between the compressor's allowable upper frequency limit and the compressor's operating frequency. The exhaust pressure deviation is determined based on the absolute difference between the exhaust pressure and the corresponding exhaust pressure reference value. The degree of operational stability is determined based on the absolute differences in compressor operating frequency, discharge pressure, and electronic expansion valve opening between adjacent unified sampling periods. By combining the real-time energy efficiency rating, compressor frequency margin, discharge pressure deviation, and operational stability corresponding to the same unit number, load occupancy evaluation data is obtained.

[0010] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps described in this invention, the specific steps for obtaining the load-bearing matching results of each parallel carbon dioxide heat pump unit are as follows: The real-time energy efficiency evaluation value is obtained by comparing the real-time energy efficiency characterization value with the maximum real-time energy efficiency characterization value within the same unified sampling period. The frequency margin evaluation value is obtained by comparing the compressor frequency margin with the maximum compressor frequency margin within the same unified sampling period. The pressure state evaluation value is obtained by comparing the ratio between the exhaust pressure reference value and the sum of the exhaust pressure reference value and the exhaust pressure deviation, and the degree of operational stability is used as the stability evaluation value. The target load matching value is obtained based on the compressor frequency margin, the compressor's allowable frequency limit, the single unit's rated load, and the target load determination value. When the maximum value of the real-time energy efficiency characterization value is zero, the real-time energy efficiency evaluation value is recorded as zero; When the maximum value of the compressor frequency margin is zero, the frequency margin evaluation value is recorded as zero. When the target load determination value is zero, the target load adaptation value is recorded as zero; The load-bearing matching value is obtained based on the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value, stability evaluation value, and target load adaptation value.

[0011] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps described in this invention, the specific steps of arranging the parallel carbon dioxide heat pump units according to priority are as follows: Compare the load-bearing matching values ​​of each parallel carbon dioxide heat pump unit, and rank the parallel carbon dioxide heat pump unit with the larger load-bearing matching value first. When two or more parallel carbon dioxide heat pump units have the same load matching value, the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value and stability evaluation value are compared in sequence, and the arrangement position is determined according to the comparison results. When the load matching value, real-time energy efficiency evaluation value, frequency margin evaluation value, pressure status evaluation value and stability evaluation value are all the same, the arrangement position is determined according to the unit number in ascending order; Record the unit number and load matching value according to the arrangement position.

[0012] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps described in this invention, the specific steps for determining the preceding unit in the sequence as the basic load bearer and the following unit in the sequence as the compensation load bearer are as follows: The unit number and load matching value of each parallel carbon dioxide heat pump unit are determined from front to back along the unit load sharing sequence, and the parallel carbon dioxide heat pump units with a load sharing matching value of zero are excluded to obtain the effective load sharing sequence. The total effective matching value is obtained by summing the load matching values ​​of each parallel carbon dioxide heat pump unit in the effective load-bearing sequence. The load-bearing matching value is accumulated sequentially from front to back along the effective load-bearing sequence. When the accumulated matching value of the current position is not less than half of the total effective matching value for the first time, the number of parallel carbon dioxide heat pump units participating in the accumulation is taken as the number of basic load-bearing objects. Parallel carbon dioxide heat pump units whose positions in the effective load bearing sequence fall within the range of the number of basic load bearing objects are identified as basic load bearing objects, and the remaining parallel carbon dioxide heat pump units are identified as compensation load bearing objects. When the effective load-sharing sequence is empty, each parallel carbon dioxide heat pump unit will be identified as an object that does not participate in the load-sharing of the current unified sampling period.

[0013] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps according to the present invention, the specific steps for differentially allocating the target load determination value along the unit load-bearing sequence are as follows: Calculate the sum of the load-bearing matching values ​​for the basic load-bearing objects and the compensation load-bearing objects respectively to obtain the total basic matching value and the total compensation matching value; Based on the total value of basic matching, the total value of compensation matching, and the target load determination value, the basic load allocation and compensation load allocation are obtained. The target load share of each basic load-bearing object is determined based on the proportion of its load-bearing matching value in the total basic matching value. The target load share of each compensation load-bearing object is determined based on the proportion of its load-bearing matching value in the total compensation matching value. Record the target load shares of the basic load-bearing objects and the compensation load-bearing objects according to the unit number; When the total value of the basic matching is zero, the target load share of the basic load-bearing object is recorded as zero; When the total value of compensation matching is zero, the target load share of the compensation load-bearing object is recorded as zero.

[0014] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps described in this invention, the specific steps for determining the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve in a coordinated manner are as follows: The target load share is matched with the corresponding parallel carbon dioxide heat pump unit operating data according to the unit number to obtain the control quantity determination data; The load regulation status is determined based on the difference between the target load share and the load occupancy characteristic value at the current frequency; The target load ratio is obtained by comparing the target load share with the rated load of a single unit, and the target frequency of the compressor is determined based on the target load ratio. Based on the target load ratio and load regulation status, determine the adjustment direction and pressure correction amount of the air cooler target pressure relative to the air cooler pressure reference value; The target opening of the electronic expansion valve is determined based on the compressor's target frequency, the air cooler's target pressure, and the electronic expansion valve's full opening. Record the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve corresponding to the same unit number to obtain the linkage control parameters.

[0015] As a preferred embodiment of the target load control method for multiple parallel carbon dioxide heat pumps according to the present invention, the specific steps for generating control commands for the multiple parallel carbon dioxide heat pumps are as follows: The linkage control parameters are verified one by one according to the unit number. If any data of the air cooler target pressure, compressor target frequency and electronic expansion valve target opening is missing under the same unit number, the corresponding parallel carbon dioxide heat pump unit will not be included in the multi-parallel carbon dioxide heat pump control command of the current unified sampling cycle. Perform range verification on the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve, and correct data that exceed the corresponding range according to the boundary values; The target opening degree of the electronic expansion valve is checked for consistency based on the compressor's target frequency, and the target pressure of the air cooler is checked for consistency based on the load regulation status. The target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve after verification are combined according to the unit number to generate a single-unit control command; The control commands for each individual unit are arranged in ascending order of unit number to form control commands for multiple parallel carbon dioxide heat pumps.

[0016] The beneficial effects of this invention are as follows: By identifying the operating conditions and performing load conversion processing on the energy consumption side temperature data, solar energy side heat exchange data, and operating data of each parallel carbon dioxide heat pump unit, a target load judgment value that is compatible with the cooling, heating, and solar energy side heat exchange compensation is determined, avoiding mismatch between the target load and actual demand, and reducing ineffective load increases and frequent adjustments; by forming a unit load-bearing sequence through real-time energy efficiency characterization values, compressor frequency margin, exhaust pressure deviation, and operating stability, and by differentiating the basic load-bearing objects and compensation load-bearing objects, the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve are determined in conjunction, so that the load distribution and control parameter adjustment are consistent, thereby improving the coordinated operation stability and overall energy efficiency of multiple parallel carbon dioxide heat pump units. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a control method for multiple parallel carbon dioxide heat pumps based on target load control.

[0019] Figure 2 A flowchart is generated for determining the target load value.

[0020] Figure 3 Flowchart for load-bearing sequence and differential allocation.

[0021] Figure 4 Generate flowcharts for linkage control parameters and control commands.

[0022] Figure 5 This is a comparison chart of collaborative operation stability data.

[0023] Figure 6 This is a heat map of the overall energy efficiency coefficient. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Reference Figures 1-6 This is one embodiment of the present invention, which provides a control method for multiple parallel carbon dioxide heat pumps based on target load control, including the following steps: The dual-condition solar heat pump air conditioning unit includes a solar-side heat exchange loop, an energy-consuming side heat exchange loop, and multiple parallel-connected carbon dioxide heat pump units. Each parallel-connected carbon dioxide heat pump unit jointly undertakes the load regulation of the energy-consuming side under either cooling or heating conditions. The solar-side heat exchange loop is used to provide heat exchange compensation to the energy-consuming side load under heating conditions, and the multiple parallel-connected carbon dioxide heat pump units are used to undertake the remaining load demand when the solar-side heat exchange compensation is insufficient. This embodiment incorporates dual-condition identification, solar-side heat exchange compensation, the load-bearing matching degree of each parallel carbon dioxide heat pump unit, and the linkage relationship between air cooler pressure, compressor frequency, and electronic expansion valve opening into the target load control process for coordinated load regulation of multiple parallel carbon dioxide heat pump units.

[0028] S1. Collect the energy consumption side temperature data, solar side heat exchange data and the operating data of each parallel carbon dioxide heat pump unit of the dual-condition solar heat pump air conditioning unit, and combine the difference in solar side heat exchange compensation under cooling and heating conditions to perform load conversion and load upper limit correction to obtain the target load judgment value.

[0029] S1.1 Collect the energy consumption side temperature data, solar side heat exchange data and the operating data of each parallel carbon dioxide heat pump unit within the same unified sampling period of the dual-condition solar heat pump air conditioning unit, and perform time alignment to obtain effective collected data.

[0030] It should be noted that the solar-side heat exchange data includes the solar-side inlet temperature, solar-side outlet temperature, and solar-side circulation flow rate; the data acquisition configuration of the energy-consuming side temperature acquisition point, the solar-side temperature acquisition point, the solar-side circulation flow rate acquisition point, and the operating data interface of each parallel carbon dioxide heat pump unit is obtained, the longest interval among the data reporting intervals is taken as the unified sampling period, and the end time of the unified sampling period is taken as the data alignment time.

[0031] Within each unified sampling period, the following data are collected: supply water temperature on the energy consumption side, return water temperature on the energy consumption side, set temperature on the energy consumption side, inlet temperature on the solar energy side, outlet temperature on the solar energy side, circulation flow rate on the solar energy side, compressor operating frequency, exhaust pressure, air cooler outlet pressure, electronic expansion valve opening, compressor input power, and unit start-stop status of each parallel carbon dioxide heat pump unit, to obtain the raw collected data.

[0032] The original collected data is assigned to the corresponding unified sampling period according to the collection time, and the equipment communication address of each parallel carbon dioxide heat pump unit is used as the unit number to collect the operating data of each parallel carbon dioxide heat pump unit, thus obtaining periodic collected data.

[0033] Time alignment is performed on the periodically collected data; when multiple collected values ​​exist within the same unified sampling period, the last collected value no later than the end of the unified sampling period is selected as the corresponding data; if any data is missing from either the energy consumption side temperature data or the solar energy side heat exchange data within the same unified sampling period, the data for the corresponding unified sampling period is discarded; if any data is missing from either the compressor operating frequency, exhaust pressure, air cooler outlet pressure, electronic expansion valve opening, or compressor input power of the parallel carbon dioxide heat pump unit in operation, the operating data of the parallel carbon dioxide heat pump unit within the corresponding unified sampling period is discarded; the time-aligned data is then combined to obtain the valid collected data.

[0034] S1.2. Identify the current operating conditions of the dual-condition solar heat pump air conditioning unit based on the effective collected data, and determine the temperature difference between the supply and return water on the energy consumption side, the set temperature deviation on the energy consumption side, and the heat exchange on the solar side to obtain the operating condition load conversion data.

[0035] It should be noted that within the unified sampling period corresponding to the valid data collection, the energy-consuming side supply water temperature and the energy-consuming side return water temperature are compared; when the energy-consuming side supply water temperature is lower than the energy-consuming side return water temperature, it is identified as cooling operation; when the energy-consuming side supply water temperature is higher than the energy-consuming side return water temperature, it is identified as heating operation; when the two are equal, the current operating condition of the previous unified sampling period is used; if the previous unified sampling period does not exist, the valid data collection of the current unified sampling period is removed.

[0036] After identifying the current operating condition, the absolute difference between the energy-consuming side supply water temperature and the energy-consuming side return water temperature is calculated to obtain the energy-consuming side supply and return water temperature difference; under cooling condition, the difference between the energy-consuming side return water temperature and the energy-consuming side set temperature is calculated to obtain the energy-consuming side set temperature deviation; under heating condition, the difference between the energy-consuming side set temperature and the energy-consuming side return water temperature is calculated to obtain the energy-consuming side set temperature deviation; when the calculation result is less than zero, the energy-consuming side set temperature deviation is recorded as zero.

[0037] Calculate the absolute value of the temperature difference between the solar energy side inlet temperature and the solar energy side outlet temperature to obtain the solar energy side inlet and outlet temperature difference. When the solar energy side circulation flow rate is a mass flow rate, calculate the product of the solar energy side inlet and outlet temperature difference, the solar energy side circulation flow rate, and the specific heat capacity of the solar energy side circulation medium to obtain the solar energy side heat exchange. When the solar energy side circulation flow rate is a volumetric flow rate, first convert it to a mass flow rate according to the density of the solar energy side circulation medium, and then calculate the product of the solar energy side inlet and outlet temperature difference, the converted mass flow rate, and the specific heat capacity of the solar energy side circulation medium to obtain the solar energy side heat exchange. The specific heat capacity and density of the solar energy side circulation medium are obtained from the commissioning parameters and circulation medium physical property parameter table of the dual-condition solar heat pump air conditioning unit according to the circulation medium type.

[0038] Simultaneously, the difference between the solar energy side outlet temperature and the solar energy side inlet temperature is calculated to obtain the difference in the solar energy side heat exchange direction. When the difference in the solar energy side heat exchange direction is greater than zero, it is determined that the solar energy side heat exchange circuit is in the heat exchange direction that provides heating compensation to the energy consumption side. When the difference in the solar energy side heat exchange direction is not greater than zero, it is determined that the solar energy side heat exchange circuit has not formed effective heating compensation.

[0039] The operating conditions, the temperature difference between the supply and return water on the energy consumption side, the set temperature deviation on the energy consumption side, and the heat exchange on the solar energy side are combined to obtain the calculated operating load data.

[0040] S1.3 Determine the load demand of the dual-condition solar heat pump air conditioning unit based on the load conversion data, and correct the load demand by combining the operating data of each parallel carbon dioxide heat pump unit to obtain the target load judgment value.

[0041] It should be noted that the rated cooling load, rated heating load, and the single-unit rated load of each parallel carbon dioxide heat pump unit adopt the parameters on the equipment nameplate; the rated supply and return water temperature difference in cooling mode, the rated supply and return water temperature difference in heating mode, the allowable set temperature deviation in cooling mode, and the allowable set temperature deviation in heating mode adopt the commissioning parameters of the dual-mode solar heat pump air conditioning unit.

[0042] When the current operating condition is cooling mode, calculate the ratio of the supply and return water temperature difference on the energy consumption side to the rated supply and return water temperature difference for cooling mode to obtain the cooling heat exchange load ratio; calculate the ratio of the set temperature deviation on the energy consumption side to the allowable set temperature deviation for cooling mode to obtain the cooling regulation load ratio; calculate the product of the rated cooling load and the cooling heat exchange load ratio and the cooling regulation load ratio respectively to obtain the cooling heat exchange load and the cooling regulation load; if the sum of the cooling heat exchange load and the cooling regulation load is not greater than the rated cooling load, the sum is used as the basic load demand on the energy consumption side under cooling mode; if the sum is greater than the rated cooling load, the rated cooling load is used as the basic load demand on the energy consumption side under cooling mode.

[0043] When the current operating condition is heating, the ratio of the supply and return water temperature difference on the energy consumption side to the rated supply and return water temperature difference under heating conditions is calculated to obtain the heating heat exchange load ratio; the ratio of the set temperature deviation on the energy consumption side to the allowable set temperature deviation under heating conditions is calculated to obtain the heating regulation load ratio; the products of the rated heating load and the heating heat exchange load ratio and the heating regulation load ratio are calculated respectively to obtain the heating heat exchange load amount and the heating regulation load amount; if the sum of the heating heat exchange load amount and the heating regulation load amount is not greater than the rated heating load, the sum is used as the basic load demand on the energy consumption side under heating conditions; if the sum is greater than the rated heating load, the rated heating load is used as the basic load demand on the energy consumption side under heating conditions.

[0044] When the current operating condition is heating, and the outlet temperature of the solar panel is higher than the inlet temperature, the heat exchange on the solar panel is recorded as the effective compensation heat exchange. When the current operating condition is heating, and the outlet temperature of the solar panel is not higher than the inlet temperature, the effective compensation heat exchange on the solar panel is recorded as zero, and the corresponding unified sampling period is marked as no effective heating compensation is formed on the solar panel. When the current operating condition is cooling, the effective compensation heat exchange on the solar panel is recorded as zero. The difference between the basic load demand on the energy consumption side and the effective compensation heat exchange on the solar panel is used as the initial load demand. When the initial load demand is less than zero, the load demand is recorded as zero. When the initial load demand is not less than zero, the initial load demand is used as the load demand.

[0045] The effective compensation heat exchange on the solar side is used to characterize the portion of the heating load borne by the solar side heat exchange circuit under heating conditions. Under cooling conditions, the solar side heat exchange is not used as a reduction in the cooling load on the energy consumption side, so the effective compensation heat exchange on the solar side is recorded as zero. This allows the target load determination value to be adjusted according to the current operating conditions and changes in the actual heat exchange capacity of the solar side, avoiding the repeated burden of compensation on the solar side caused by determining the target load solely based on the temperature deviation on the energy consumption side.

[0046] For parallel carbon dioxide heat pump units whose start-stop status is "operating", the rated load of a single unit is used as the current upper limit of the available load; for parallel carbon dioxide heat pump units whose start-stop status is "shutdown", the current upper limit of the available load is recorded as zero.

[0047] The target load share allocation in this embodiment is for parallel carbon dioxide heat pump units that are already in operation and can be continuously adjusted within the current unified sampling period. Parallel carbon dioxide heat pump units that are in shutdown state have not yet established a stable refrigerant cycle and do not participate in the load sharing of the current unified sampling period.

[0048] The total available load of each parallel carbon dioxide heat pump unit is obtained by summing the current available upper limits of the load. When the total available load of the unit is not less than the load demand, the load demand is used as the target load determination value. When the total available load of the unit is less than the load demand, the total available load of the unit is used as the target load determination value.

[0049] The formula for calculating the target load determination value is: ; ; in, Indicates the first Target load determination value for a unified sampling period; superscript Indicates target load determination; Indicates a unified sampling period number; Indicates the first Energy-side basic load demand for a unified sampling period; superscript Indicates the energy-consuming side; Indicates the first Effective heat exchange compensation on the solar side within a unified sampling period; superscript This indicates effective compensation on the solar energy side; Indicates the first Solar-side heat exchange in a unified sampling period; superscript Indicates the solar energy side; Indicates the first Current operating conditions for a unified sampling period; Indicates the heating condition; Indicates the cooling operating condition; Indicates the first to the second Summation of the parallel carbon dioxide heat pump units; Indicates the serial number of the parallel carbon dioxide heat pump unit; Indicates the total number of parallel carbon dioxide heat pump units; Indicates the first The parallel carbon dioxide heat pump units were in the first Unit start-up and shutdown status within a unified sampling period Indicates the running status. Indicates a shutdown status; Indicates the first Rated load of a single unit of a parallel carbon dioxide heat pump unit; superscript Indicates the rated value; Indicates the first Solar-side outlet temperature for a uniform sampling period; superscript Indicates the solar panel outlet; Indicates the first Solar-side inlet temperature for a uniform sampling period; superscript This indicates the solar energy side inlet.

[0050] S2. Using the target load determination value as the load demand constraint, the real-time energy efficiency characterization value, compressor frequency margin, exhaust pressure deviation and operating stability of each parallel carbon dioxide heat pump unit are comprehensively matched to determine the priority of each parallel carbon dioxide heat pump unit in undertaking the target load, thus forming a unit load undertaking sequence.

[0051] S2.1. Based on the operating data of each parallel carbon dioxide heat pump unit, determine the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation, and operating stability of each parallel carbon dioxide heat pump unit to obtain load-bearing evaluation data.

[0052] It should be noted that the rated load of a single unit and the upper limit of the allowable frequency of the compressor are based on the parameters on the equipment nameplate; the full opening of the electronic expansion valve adopts the commissioning parameters of each parallel carbon dioxide heat pump unit, and the full opening of the electronic expansion valve and the collected electronic expansion valve opening are in the same unit.

[0053] For parallel carbon dioxide heat pump units in the running state when the unit is in start-stop mode, calculate the ratio of the compressor operating frequency to the upper limit of the compressor's allowable frequency to obtain the frequency operating ratio; calculate the product of the single unit's rated load and the frequency operating ratio to obtain the current load characterization value; when the compressor input power is not zero, calculate the ratio of the current load characterization value to the compressor input power to obtain the real-time energy efficiency characterization value; when the compressor input power is zero, record the real-time energy efficiency characterization value as zero; for parallel carbon dioxide heat pump units in the shutdown state when the unit is in start-stop mode, record the real-time energy efficiency characterization value as zero; the real-time energy efficiency characterization value is used to characterize the ability of parallel carbon dioxide heat pump units to bear the load with a unit compressor input power within the same unified sampling period, and is not used as the unit's rated energy efficiency parameter.

[0054] For parallel carbon dioxide heat pump units whose start-stop state is running, calculate the difference between the upper limit of the compressor's allowable frequency and the compressor's operating frequency to obtain the compressor's frequency margin; for parallel carbon dioxide heat pump units whose start-stop state is shut down, record the compressor's frequency margin as zero.

[0055] The reference values ​​for exhaust pressure under cooling and heating conditions are recorded in the commissioning parameters of each parallel CO2 heat pump unit according to the unit number. The reference value for exhaust pressure under cooling conditions is the average exhaust pressure of the corresponding parallel CO2 heat pump unit during the stable operation phase under rated load commissioning in cooling conditions. The reference value for exhaust pressure under heating conditions is the average exhaust pressure of the corresponding parallel CO2 heat pump unit during the stable operation phase under rated load commissioning in heating conditions. When the current operating condition is cooling, the reference value for exhaust pressure under cooling conditions under the same unit number is read. When the current operating condition is heating, the reference value for exhaust pressure under heating conditions under the same unit number is read.

[0056] For parallel carbon dioxide heat pump units in the running state when the unit is in start-stop state, the absolute difference between the exhaust pressure and the corresponding exhaust pressure reference value is calculated to obtain the exhaust pressure deviation; for parallel carbon dioxide heat pump units in the shutdown state when the unit is in start-stop state, the exhaust pressure deviation is recorded as the corresponding exhaust pressure reference value.

[0057] For parallel carbon dioxide heat pump units whose start-stop status is running, if there is operating data for the same unit number in the previous unified sampling period, the absolute difference in compressor operating frequency, absolute difference in discharge pressure, and absolute difference in electronic expansion valve opening between the current unified sampling period and the previous unified sampling period are calculated respectively. The ratios of the absolute difference in compressor operating frequency to the upper limit of the compressor's allowable frequency, the absolute difference in discharge pressure to the corresponding discharge pressure reference value, and the absolute difference in electronic expansion valve opening to the full opening of the electronic expansion valve are calculated respectively to obtain the frequency fluctuation ratio, pressure fluctuation ratio, and valve opening fluctuation ratio. The sum of the frequency fluctuation ratio, pressure fluctuation ratio, and valve opening fluctuation ratio is calculated to obtain the operating fluctuation amount, and 1 is calculated as the reciprocal of the sum of the operating fluctuation amounts to obtain the operating stability level. If there is no operating data for the same unit number in the previous unified sampling period, the operating stability level is recorded as 1. For parallel carbon dioxide heat pump units whose start-stop status is shut down, the operating stability level is recorded as zero.

[0058] By combining the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation, and operational stability of the same unit number, the load-bearing evaluation data of the corresponding parallel carbon dioxide heat pump units can be obtained.

[0059] S2.2 Using the target load determination value as the load demand constraint, the load-bearing evaluation data is comprehensively matched to obtain the load-bearing matching results of each parallel carbon dioxide heat pump unit.

[0060] It should be noted that within the same unified sampling period, the real-time energy efficiency characterization values ​​of each parallel carbon dioxide heat pump unit are compared and the maximum value is taken; when the maximum value is not zero, the ratio of the real-time energy efficiency characterization value of each parallel carbon dioxide heat pump unit to the maximum value is calculated to obtain the real-time energy efficiency evaluation value; when the maximum value is zero, the real-time energy efficiency evaluation value is recorded as zero.

[0061] Compare the compressor frequency margins of each parallel carbon dioxide heat pump unit and take the maximum value; when the maximum value is not zero, calculate the ratio of the compressor frequency margin of each parallel carbon dioxide heat pump unit to the maximum value to obtain the frequency margin evaluation value; when the maximum value is zero, record the frequency margin evaluation value as zero.

[0062] The pressure status evaluation value is obtained by calculating the ratio between the exhaust pressure reference value and the sum of the exhaust pressure reference value and the exhaust pressure deviation; when the exhaust pressure deviation is zero, the pressure status evaluation value is 1; the degree of operational stability is used as the stability evaluation value.

[0063] Using the target load determination value as the load demand constraint, the ratio of the compressor frequency margin to the compressor's allowable frequency upper limit is calculated to obtain the load increase ratio; the product of the single unit's rated load and the load increase ratio is calculated to obtain the load increase characterization value; when the target load determination value is not zero, the ratio of the load increase characterization value to the target load determination value is calculated to obtain the target load adaptation value, and it is recorded as 1 when the target load adaptation value is greater than 1; when the target load determination value is zero, the target load adaptation value is recorded as zero.

[0064] The basic matching value is obtained by summing the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value, and stability evaluation value; the load-bearing matching value of the corresponding parallel carbon dioxide heat pump unit is obtained by multiplying the basic matching value and the target load adaptation value.

[0065] The formula for calculating the load-bearing matching value is: ; in, Indicates the first The parallel carbon dioxide heat pump units were in the first Load borne matching value within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first Real-time energy efficiency characterization values ​​within a unified sampling period; Indicates the first The maximum value among the real-time energy efficiency characterization values ​​of each parallel carbon dioxide heat pump unit within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first Compressor frequency margin within a unified sampling period; Indicates the first The maximum value among the compressor frequency margins of each parallel carbon dioxide heat pump unit within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The exhaust pressure benchmark value within a unified sampling period; superscript Indicates exhaust pressure; superscript Indicates the baseline value; Indicates the first The parallel carbon dioxide heat pump units were in the first Exhaust pressure deviation within a uniform sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The summation of the operational fluctuations within a unified sampling period, corresponding to the frequency fluctuation ratio, pressure fluctuation ratio, and valve opening fluctuation ratio; Indicates the first The upper limit of the allowable frequency of the compressor in a parallel carbon dioxide heat pump unit.

[0066] The real-time energy efficiency evaluation value, frequency margin evaluation value, pressure status evaluation value, stability evaluation value, target load adaptation value, and load assignment matching value corresponding to the same unit number are combined to obtain the load assignment matching results of each parallel carbon dioxide heat pump unit.

[0067] S2.3. Based on the load-bearing matching results of each parallel carbon dioxide heat pump unit, determine the priority of each parallel carbon dioxide heat pump unit in bearing the target load, and arrange each parallel carbon dioxide heat pump unit according to the priority to form a unit load-bearing sequence.

[0068] It should be noted that when comparing the load-bearing matching values ​​of each parallel carbon dioxide heat pump unit, the parallel carbon dioxide heat pump units with larger load-bearing matching values ​​are arranged first, and the parallel carbon dioxide heat pump units with smaller load-bearing matching values ​​are arranged last.

[0069] When two or more parallel CO2 heat pump units have the same load matching value, the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value, and stability evaluation value are compared in that order. The parallel CO2 heat pump unit with the larger real-time energy efficiency evaluation value is ranked first. If the real-time energy efficiency evaluation values ​​are the same, the parallel CO2 heat pump unit with the larger frequency margin evaluation value is ranked first. If the frequency margin evaluation values ​​are the same, the parallel CO2 heat pump unit with the larger pressure state evaluation value is ranked first. If the pressure state evaluation values ​​are the same, the parallel CO2 heat pump unit with the larger stability evaluation value is ranked first.

[0070] When the load matching value, real-time energy efficiency evaluation value, frequency margin evaluation value, pressure status evaluation value, and stability evaluation value are all the same, the parallel carbon dioxide heat pump units are arranged in ascending order of unit number, so that each parallel carbon dioxide heat pump unit has a unique arrangement position.

[0071] Record the unit number and load matching value of each parallel carbon dioxide heat pump unit according to their arrangement position to form a unit load assignment sequence.

[0072] It should also be noted that existing technologies typically adjust the unit start-up and shutdown, compressor frequency, and electronic expansion valve opening directly by the difference between the target load and the actual load, mainly addressing the question of "whether the total load is met." This solution comprehensively matches each parallel carbon dioxide heat pump unit using real-time energy efficiency ratings, compressor frequency margin, exhaust pressure deviation, and operational stability, forming a unit load-sharing sequence. Before load allocation, it can determine the suitability of each unit for the target load, prioritizing units with high real-time energy efficiency ratings and delaying the participation of units with low frequency margin, low pressure status, and low stability ratings. This reduces the blindness of load allocation between units, lowers the risk of frequent adjustments and pressure fluctuations, and improves the load response stability, operational coordination, and overall energy efficiency of multiple parallel carbon dioxide heat pump units.

[0073] S3. Differentiate the target load determination value along the unit load bearing sequence, determine the unit at the front of the sequence as the basic load bearing object, and determine the unit at the back of the sequence as the compensation load bearing object, so as to obtain the target load share corresponding to each parallel carbon dioxide heat pump unit.

[0074] S3.1. Based on the load-bearing sequence of the units and the load-bearing matching results of each parallel carbon dioxide heat pump unit, the units at the front of the sequence are determined as the basic load-bearing objects, and the units at the back of the sequence are determined as the compensation load-bearing objects, thus obtaining the load-bearing object division results.

[0075] It should be noted that the unit number and load matching value of each parallel carbon dioxide heat pump unit are determined from front to back along the arrangement position of the unit load-bearing sequence. Parallel carbon dioxide heat pump units with a load-bearing matching value of zero are not included in the load-bearing object division of the current unified sampling period.

[0076] The parallel CO2 heat pump units participating in the division are arranged in their original order according to their position in the unit load-sharing sequence to obtain the effective load-sharing sequence. The number of parallel CO2 heat pump units in the effective load-sharing sequence is then counted to obtain the effective quantity. When the effective quantity is zero, the target load share of each parallel CO2 heat pump unit is recorded as zero.

[0077] When the effective quantity is not zero, the load-bearing matching values ​​of each parallel CO2 heat pump unit in the effective load-bearing sequence are summed to obtain the total effective matching value. The load-bearing matching values ​​are accumulated sequentially from front to back along the effective load-bearing sequence to obtain the cumulative matching value of the previous position. When the cumulative matching value of the previous position is not less than half of the total effective matching value for the first time, the number of parallel CO2 heat pump units participating in the accumulation is taken as the number of basic load-bearing objects. The parallel CO2 heat pump units in the effective load-bearing sequence whose positions are within the range of the number of basic load-bearing objects are determined as basic load-bearing objects, and the remaining parallel CO2 heat pump units in the effective load-bearing sequence are determined as compensation load-bearing objects, so that the units with higher matching contributions at the front position bear the basic load portion, and the remaining units that can participate in the adjustment bear the compensation load portion.

[0078] The above-mentioned effective matching total value is half of the basic division ratio used when determining the number of basic load bearing objects. In this embodiment, it is taken as 0.5. The basic division ratio is determined according to the load fluctuation test during the commissioning stage of the multi-parallel carbon dioxide heat pump unit. In the step load increase and step load decrease test, after the current cumulative matching value reaches half of the effective matching total value, the previous unit participating in the accumulation is taken as the basic load bearing object. This enables the unit with higher matching contribution to bear the stable load part, and the remaining units to bear the compensation load part, thereby reducing the air cooler pressure fluctuation and compressor frequency fluctuation caused by the synchronous large adjustment of all units.

[0079] The load-bearing object division results are obtained by combining the unit number, arrangement position and load-bearing matching value corresponding to the basic load-bearing object and the unit number, arrangement position and load-bearing matching value corresponding to the compensation load-bearing object.

[0080] It should also be noted that the basic load-bearing object is used to prioritize the stable load portion within the current unified sampling period, while the compensation load-bearing object is used to bear the remaining adjustment portion of the target load judgment value caused by changes in operating conditions. In the subsequent determination of linkage control parameters, the target load share of the basic load-bearing object serves as the basis for continuous adjustment, and the target load share of the compensation load-bearing object is used to compensate for the remaining load, so that the front-end units with a high degree of matching maintain a continuous load state and reduce pressure fluctuations caused by synchronous large-scale adjustments of all units.

[0081] S3.2 Based on the load-bearing object division results, the target load judgment value is differentiated and split to form the basic load allocation and compensation load allocation, thus obtaining differentiated load allocation data.

[0082] It should be noted that the summation results of the load-bearing matching values ​​corresponding to the basic load-bearing objects and the summation results of the load-bearing matching values ​​corresponding to the compensation load-bearing objects are calculated separately to obtain the basic matching total value and the compensation matching total value; the summation results of the basic matching total value and the compensation matching total value are calculated to obtain the total allocation matching value.

[0083] When the total value of the allocation matching is not zero, calculate the ratio of the total value of the basic matching to the total value of the allocation matching to obtain the basic load allocation ratio; calculate the ratio of the total value of the compensation matching to the total value of the allocation matching to obtain the compensation load allocation ratio; calculate the product of the target load judgment value and the basic load allocation ratio to obtain the basic load allocation amount; calculate the product of the target load judgment value and the compensation load allocation ratio to obtain the compensation load allocation amount.

[0084] When the total value of the allocation matching is zero, both the basic load allocation and the compensation load allocation are recorded as zero.

[0085] Record the corresponding basic load-bearing objects, compensation load-bearing objects, basic load allocation, compensation load allocation, basic matching total value, and compensation matching total value to obtain differentiated load allocation data.

[0086] S3.3. Based on the differentiated load allocation data, the allocation ratio is determined by combining the load-bearing matching results of each parallel carbon dioxide heat pump unit. The basic load allocation is allocated to the basic load-bearing objects, and the compensation load allocation is allocated to the compensation load-bearing objects, so as to obtain the target load share corresponding to each parallel carbon dioxide heat pump unit.

[0087] It should be noted that, for the basic load-bearing objects, when the total basic matching value is not zero, the ratio of the load-bearing matching value of each basic load-bearing object to the total basic matching value is calculated to obtain the basic object allocation ratio; the product of the basic load allocation amount and the basic object allocation ratio is calculated to obtain the target load share of the corresponding basic load-bearing object; when the total basic matching value is zero, the target load share of the basic load-bearing object is recorded as zero.

[0088] For each load-bearing object, when the total compensation matching value is not zero, calculate the ratio of the load-bearing matching value of each load-bearing object to the total compensation matching value to obtain the allocation ratio of the load-bearing object; calculate the product of the compensation load allocation amount and the allocation ratio of the load-bearing object to obtain the target load share of the corresponding load-bearing object; when the total compensation matching value is zero, record the target load share of the load-bearing object as zero.

[0089] The target load share of the basic load-bearing object and the target load share of the compensation load-bearing object are recorded according to the unit number; for parallel carbon dioxide heat pump units that have not participated in the current unified sampling period load-bearing object division, the target load share is recorded as zero, thus obtaining the target load share corresponding to each parallel carbon dioxide heat pump unit.

[0090] The formula for calculating the target load share is: ; ; in, Indicates the number of entities bearing the basic load; subscript Indicates the object that bears the basic load; This indicates the cumulative number of positions from the first position to the second position. Each arrangement position; Indicates the position number in the cumulative process of the previous position; Indicates the number of units in the load-sharing sequence The numbers of the parallel carbon dioxide heat pump units corresponding to the arrangement positions; Indicates the first Within a unified sampling period, the unit load occupancy sequence of the [number]th [unit] [item]. Each arrangement position corresponds to the load-bearing matching value of the unit; Indicates the first The set of unit numbers corresponding to the effective load undertaking sequence within a unified sampling period; Indicates the first The summation of load sharing matching values ​​of all units in the effective load sharing sequence within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The target load share within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first Load borne matching value within a unified sampling period; Indicates the first The summation of the load sharing matching values ​​of each unit in the effective load sharing sequence within a unified sampling period; This represents the unit numbers in the set of unit numbers corresponding to the effective load-sharing sequence that are included in the summation, used to distinguish the currently assigned unit numbers. ; Indicates the first The parallel carbon dioxide heat pump units belong to the effective load-bearing sequence; Indicates the first The parallel carbon dioxide heat pump units are not part of the effective load-bearing sequence.

[0091] It should also be noted that existing technologies typically allocate target loads by averaging the number of units, allocating them proportionally based on rated capacity, or allocating them in a fixed sequence. This easily overlooks the differences in load matching between units, leading to inaccurate load allocation, frequent unit adjustments, and increased operational fluctuations. This solution, through the unit load-bearing sequence and load-bearing matching results, identifies the units at the beginning of the sequence as the basic load-bearing units and the units at the end of the sequence as the compensation load-bearing units. The target load determination value is broken down into basic load allocation and compensation load allocation, and then the target load share of each unit is determined according to the load-bearing matching value. This allows units with high matching degrees to take on stable loads first, and allows the units at the end of the sequence to take on compensation loads, avoiding load mismatch caused by simple average allocation, reducing the risk of single-unit overload and repeated adjustments, and improving load allocation stability, unit collaborative operation effect, and overall energy efficiency.

[0092] S4. Based on the target load share and load regulation status of each parallel carbon dioxide heat pump unit, determine the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve in a coordinated manner to form control commands for multiple parallel carbon dioxide heat pumps.

[0093] S4.1. Match the target load share of each parallel carbon dioxide heat pump unit with the operating data of each parallel carbon dioxide heat pump unit according to the unit number, determine the current load-bearing capacity of each parallel carbon dioxide heat pump unit, and obtain the control quantity determination data.

[0094] It should be noted that the target load share is matched with the corresponding parallel carbon dioxide heat pump unit operating data according to the unit number, so that the same unit number simultaneously has the target load share, compressor operating frequency, exhaust pressure, air cooler outlet pressure, electronic expansion valve opening, compressor input power and unit start-stop status.

[0095] For parallel carbon dioxide heat pump units in the running state when the unit is in start-stop state, calculate the ratio of the compressor operating frequency to the upper limit of the compressor's allowable frequency to obtain the current frequency load ratio; calculate the product of the single unit's rated load and the current frequency load ratio to obtain the load load characterization value at the current frequency; for parallel carbon dioxide heat pump units in the shutdown state when the unit is in start-stop state, record the load load characterization value at the current frequency as zero.

[0096] Calculate the difference between the target load share and the load occupancy characteristic value at the current frequency to obtain the load regulation difference; when the load regulation difference is greater than zero, the load regulation state is recorded as the load increase regulation state; when the load regulation difference is less than zero, the load regulation state is recorded as the load decrease regulation state; when the load regulation difference is equal to zero, the load regulation state is recorded as the load maintenance regulation state.

[0097] Record the target load share, load occupancy value at the current frequency, load regulation difference, load regulation status, compressor operating frequency, exhaust pressure, air cooler outlet pressure, electronic expansion valve opening degree, and unit start-up / shutdown status corresponding to the same unit number to obtain control quantity determination data.

[0098] S4.2. Based on the control quantity determination data, the target load share corresponding to each parallel carbon dioxide heat pump unit is linked and converted with the current load bearing capacity to determine the target pressure of the air cooler, the target frequency of the compressor and the target opening degree of the electronic expansion valve corresponding to each parallel carbon dioxide heat pump unit, and thus obtain the linkage control parameters.

[0099] It should be noted that the air cooler pressure reference value, air cooler pressure regulation limit, compressor minimum allowable frequency, minimum opening degree of electronic expansion valve, and full opening degree of electronic expansion valve are all based on the commissioning parameters of each parallel carbon dioxide heat pump unit. The current operating condition is the cooling or heating condition obtained after the aforementioned operating condition identification and processing. The air cooler pressure reference value is the average air cooler outlet pressure of the corresponding parallel carbon dioxide heat pump unit during the rated load commissioning and stable operation phase under the current operating condition. The air cooler pressure regulation limit is the maximum allowable correction range of the air cooler target pressure relative to the air cooler pressure reference value.

[0100] For the control quantity determination data under the same unit number, calculate the ratio of the target load share to the rated load of a single unit to obtain the target load ratio; when the target load ratio is greater than 1, the target load ratio is recorded as 1; when the target load ratio is less than 0, the target load ratio is recorded as 0.

[0101] When the target load share is greater than zero, the product of the compressor's allowable upper frequency and the target load ratio is calculated to obtain the frequency calculation value. When the frequency calculation value is less than the compressor's minimum allowable frequency, the compressor's minimum allowable frequency is used as the compressor's target frequency. When the frequency calculation value is not less than the compressor's minimum allowable frequency, the frequency calculation value is used as the compressor's target frequency. When the target load share is zero, the compressor's target frequency is recorded as zero. The corresponding parallel carbon dioxide heat pump unit does not bear the target load within the current unified sampling period. The air cooler's target pressure is only used as the pressure boundary verification value before shutdown and is not used as a continuous pressure increase or decrease control quantity. The electronic expansion valve's target opening degree is corrected to the electronic expansion valve's minimum opening degree in subsequent consistency verification.

[0102] The pressure correction is obtained by multiplying the air cooler pressure regulation limit by the target load ratio. When the load regulation state is an increased load regulation state, the target pressure of the air cooler is obtained by summing the air cooler pressure reference value and the pressure correction. When the load regulation state is a decreased load regulation state, the target pressure of the air cooler is obtained by calculating the difference between the air cooler pressure reference value and the pressure correction. When the load regulation state is a maintained regulation state, the air cooler pressure reference value is used as the target pressure of the air cooler.

[0103] Calculate the ratio of the compressor's target frequency to the compressor's allowable upper frequency limit to obtain the target frequency ratio; calculate the ratio of the air cooler's target pressure to the air cooler's pressure reference value to obtain the target pressure ratio; calculate the product of the electronic expansion valve's full opening, the target frequency ratio, and the target pressure ratio to obtain the calculated opening value; if the calculated opening value is less than the electronic expansion valve's minimum opening, the minimum opening of the electronic expansion valve is taken as the electronic expansion valve's target opening value; if the calculated opening value is not less than the electronic expansion valve's minimum opening and not greater than the electronic expansion valve's full opening, the calculated opening value is taken as the electronic expansion valve's target opening value.

[0104] Record the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve corresponding to the same unit number to obtain the linkage control parameters.

[0105] The formula for calculating the linkage control parameters is: ; ; ; ; in, Indicates the first The parallel carbon dioxide heat pump units were in the first The target load ratio within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The target load share within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The compressor target frequency within a unified sampling period; Indicates the first Minimum allowable frequency of compressors in parallel carbon dioxide heat pump units; Indicates the first The upper limit of the allowable frequency of the compressor in a parallel carbon dioxide heat pump unit; Indicates the first The parallel carbon dioxide heat pump units were in the first The target pressure of the air cooler within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first The reference value of the air cooler pressure within a unified sampling period; Indicates the first The parallel carbon dioxide heat pump units were in the first Load regulation status within a unified sampling period Indicates the load adjustment status. Indicates the load reduction adjustment status. This indicates that the system is in a state of adjustment. Indicates the first Pressure regulation limits for air coolers in parallel carbon dioxide heat pump units; superscript Indicates the adjustment limit; Indicates the first The parallel carbon dioxide heat pump units were in the first The target opening degree of the electronic expansion valve within a unified sampling period; Indicates the first Full opening of the electronic expansion valve of the parallel carbon dioxide heat pump unit; Indicates the first Minimum opening of the electronic expansion valve of a parallel carbon dioxide heat pump unit; This indicates the target frequency ratio, which corresponds to the ratio of the compressor's target frequency to the compressor's maximum allowable frequency. This indicates the target pressure ratio, which corresponds to the ratio of the target pressure of the air cooler to the reference pressure value of the air cooler.

[0106] It should also be noted that the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve of the same parallel carbon dioxide heat pump unit are all determined by the target load share and the load regulation status, so that the changes in single-unit load, high-pressure side pressure correction, and throttling opening are in the same control direction. When the target load share increases, the target opening of the electronic expansion valve increases in conjunction with the target frequency and target pressure ratios by increasing the target frequency and target pressure. When the target load share decreases, the target opening of the electronic expansion valve decreases in conjunction with the target frequency and target pressure ratios by decreasing the target frequency and target pressure. This avoids the situation where adjusting only the electronic expansion valve opening or only the compressor frequency causes the air cooler side pressure to be inconsistent with the load regulation direction.

[0107] S4.3. Based on the linkage control parameters, perform consistency verification on the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve corresponding to the same parallel carbon dioxide heat pump unit, and combine them according to the number of each parallel carbon dioxide heat pump unit to form a multi-parallel carbon dioxide heat pump control command.

[0108] It should be noted that the linkage control parameters are verified one by one according to the unit number; if any of the data of the air cooler target pressure, compressor target frequency and electronic expansion valve target opening is missing under the same unit number, the corresponding parallel carbon dioxide heat pump unit will not be included in the multi-parallel carbon dioxide heat pump control command of the current unified sampling period.

[0109] For parallel CO2 heat pump units with complete data, calculate the difference between the air cooler pressure reference value and the air cooler pressure regulation limit value to obtain the lower limit value of the air cooler pressure; calculate the sum of the air cooler pressure reference value and the air cooler pressure regulation limit value to obtain the upper limit value of the air cooler pressure; verify whether the target pressure of the air cooler is between the lower limit value and the upper limit value of the air cooler pressure, verify whether the target frequency of the compressor is between zero and the upper limit of the compressor's allowable frequency, and verify whether the target opening degree of the electronic expansion valve is between the minimum opening degree and the full opening degree of the electronic expansion valve; data exceeding the corresponding range are corrected according to the boundary values ​​of the corresponding range.

[0110] After completing the range verification, the target frequency of the compressor and the target opening of the electronic expansion valve under the same unit number are checked for consistency. When the compressor target frequency is zero, the target opening of the electronic expansion valve is corrected to the minimum opening of the electronic expansion valve, and the target pressure of the air cooler in the corresponding single unit control command is used as the shutdown boundary record value and is not used as the active pressure regulation command of the air cooler. When the compressor target frequency is not zero, the target opening of the electronic expansion valve after the range verification is retained.

[0111] Based on the load regulation status, the target pressure of the air cooler under the same unit number is checked for load consistency. When the load regulation status is the load increase regulation status and the target pressure of the air cooler is lower than the air cooler pressure reference value, the target pressure of the air cooler is corrected to the air cooler pressure reference value. When the load regulation status is the load decrease regulation status and the target pressure of the air cooler is higher than the air cooler pressure reference value, the target pressure of the air cooler is corrected to the air cooler pressure reference value. When the load regulation status is the maintenance regulation status, the target pressure of the air cooler is corrected to the air cooler pressure reference value.

[0112] After completing the consistency verification, the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve are combined according to the unit number to generate the single-unit control command corresponding to each parallel carbon dioxide heat pump unit; the single-unit control commands are arranged in ascending order of the unit number to form the multi-parallel carbon dioxide heat pump control command.

[0113] The control commands for multiple parallel carbon dioxide heat pumps are sent to the corresponding parallel carbon dioxide heat pump units according to the unit number, so that the corresponding parallel carbon dioxide heat pump units can perform load regulation within the current unified sampling period according to the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve in the single unit control command.

[0114] Figure 5 The results show the changes in the coordinated operation stability of the present invention and various control schemes within a continuous and unified sampling period. The present invention is a scheme that fully adopts target load determination, load matching, differentiated allocation, and three-control quantity linkage control. Control scheme A is a scheme that does not distinguish the difference in solar heat exchange compensation between cooling and heating conditions. Control scheme B is a scheme that allocates the target load according to the rated capacity ratio. Control scheme C is a scheme that allocates the target load according to a fixed unit number or fixed order. Control scheme D is a scheme that does not determine the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve in a linkage manner. Figure 5 The horizontal axis represents the unified sampling period number, and the vertical axis represents the cooperative operation stability rate; the higher the value, the more stable the unit's cooperative operation. Figure 5 It is evident that the solution of this invention has a higher overall stability and less fluctuation, indicating that this solution can reduce pressure fluctuations and frequent adjustments under dynamic loads, and improve the coordinated operation stability of multiple parallel carbon dioxide heat pump units.

[0115] Figure 6 The distribution of the comprehensive energy efficiency coefficients of the present invention and various control schemes under different uniform sampling period segments is shown. Figure 6 The meaning of each scheme and Figure 5Consistent, the horizontal axis represents the unified sampling period segmentation, the vertical axis represents different control schemes, and the color scale on the right represents the comprehensive energy efficiency coefficient. The closer the value is to 1, the lower the input power, the more stable the load tracking, and the smaller the fluctuation of control parameters under similar load demand; Figure 6 It is evident that the present invention maintains a high and continuous comprehensive energy efficiency coefficient in most cycle segments, indicating that the present invention can reduce ineffective load increases, reduce control fluctuations, and improve overall energy efficiency through target load determination value, target load share allocation, and three-control quantity linkage control.

[0116] In summary, this invention identifies and calculates the operating conditions and loads of the energy-consuming temperature data, solar energy heat exchange data, and operating data of each parallel carbon dioxide heat pump unit to determine a target load value that is compatible with the cooling, heating, and solar energy heat exchange compensation conditions. This avoids mismatch between the target load and actual demand, reducing ineffective load increases and frequent adjustments. Furthermore, it establishes a unit load-bearing sequence based on real-time energy efficiency ratings, compressor frequency margin, exhaust pressure deviation, and operational stability, and differentiates the allocation of basic load-bearing objects and compensation load-bearing objects. Then, it coordinates the determination of the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve, ensuring that load allocation and control parameter adjustments are consistent. This improves the coordinated operational stability and overall energy efficiency of multiple parallel carbon dioxide heat pump units.

[0117] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A control method for multiple parallel carbon dioxide heat pumps based on target load control, characterized in that, include: Collect energy consumption side temperature data, solar side heat exchange data and operation data of each parallel carbon dioxide heat pump unit of dual-condition solar heat pump air conditioning unit, and combine the difference in solar side heat exchange compensation under cooling and heating conditions to perform load conversion and load upper limit correction to obtain the target load judgment value. Using the target load determination value as the load demand constraint, the real-time energy efficiency characterization value, compressor frequency margin, exhaust pressure deviation and operating stability of each parallel carbon dioxide heat pump unit are comprehensively matched to determine the priority of each parallel carbon dioxide heat pump unit in undertaking the target load, thus forming a unit load undertaking sequence. The target load determination value is differentiated and allocated along the unit load bearing sequence. The unit at the front of the sequence is determined as the basic load bearing object, and the unit at the back of the sequence is determined as the compensation load bearing object, so as to obtain the target load share corresponding to each parallel carbon dioxide heat pump unit. Based on the target load share and load regulation status of each parallel carbon dioxide heat pump unit, the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve are determined in a coordinated manner to form control commands for multiple parallel carbon dioxide heat pumps.

2. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 1, characterized in that, The specific steps for obtaining the target load determination value are as follows: Collect energy-consuming side temperature data, solar-side heat exchange data, and operating data of each parallel carbon dioxide heat pump unit within the same unified sampling period for dual-condition solar heat pump air conditioning units, and align them by time to obtain effective collected data; Based on the effective collected data, the current operating conditions are identified, and the supply and return water temperature difference on the energy consumption side, the set temperature deviation on the energy consumption side, and the heat exchange on the solar energy side are determined to obtain the operating load conversion data. The load demand is determined based on the converted load data, and the load demand is corrected by combining the operating data of each parallel carbon dioxide heat pump unit to obtain the target load judgment value.

3. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 1, characterized in that, The specific steps for forming the unit load-sharing sequence are as follows: Based on the operating data of each parallel carbon dioxide heat pump unit, the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation and operating stability are determined to obtain load-bearing evaluation data. Using the target load determination value as a load demand constraint, the load sharing evaluation data is comprehensively matched to obtain the load sharing matching results of each parallel carbon dioxide heat pump unit. Based on the load matching results, the priority of each parallel carbon dioxide heat pump unit to undertake the target load is determined, and the parallel carbon dioxide heat pump units are arranged according to the priority to form a unit load undertaking sequence.

4. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 3, characterized in that, The specific steps for obtaining the load-bearing evaluation data are as follows: The real-time energy efficiency rating is determined based on the compressor operating frequency, the upper limit of the compressor's allowable frequency, the rated load of a single unit, and the compressor's input power. The compressor frequency margin is determined based on the difference between the compressor's allowable upper frequency limit and the compressor's operating frequency. The exhaust pressure deviation is determined based on the absolute difference between the exhaust pressure and the corresponding exhaust pressure reference value. The degree of operational stability is determined based on the absolute differences in compressor operating frequency, discharge pressure, and electronic expansion valve opening between adjacent unified sampling periods. By combining the real-time energy efficiency rating, compressor frequency margin, exhaust pressure deviation, and operational stability corresponding to the same unit number, load occupancy evaluation data is obtained.

5. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 3, characterized in that, The specific steps for obtaining the load-bearing matching results of each parallel carbon dioxide heat pump unit are as follows: The real-time energy efficiency evaluation value is obtained by comparing the real-time energy efficiency characterization value with the maximum real-time energy efficiency characterization value within the same unified sampling period. The frequency margin evaluation value is obtained by comparing the compressor frequency margin with the maximum compressor frequency margin within the same unified sampling period. The pressure state evaluation value is obtained by comparing the ratio between the exhaust pressure reference value and the sum of the exhaust pressure reference value and the exhaust pressure deviation, and the degree of operational stability is used as the stability evaluation value. The target load matching value is obtained based on the compressor frequency margin, the compressor's allowable frequency limit, the single unit's rated load, and the target load determination value. When the maximum value of the real-time energy efficiency characterization value is zero, the real-time energy efficiency evaluation value is recorded as zero; When the maximum value of the compressor frequency margin is zero, the frequency margin evaluation value is recorded as zero. When the target load determination value is zero, the target load adaptation value is recorded as zero; The load-bearing matching value is obtained based on the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value, stability evaluation value, and target load adaptation value.

6. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 3, characterized in that, The specific steps for arranging the parallel carbon dioxide heat pump units according to priority are as follows: Compare the load-bearing matching values ​​of each parallel carbon dioxide heat pump unit, and rank the parallel carbon dioxide heat pump unit with the larger load-bearing matching value first. When two or more parallel carbon dioxide heat pump units have the same load matching value, the real-time energy efficiency evaluation value, frequency margin evaluation value, pressure state evaluation value and stability evaluation value are compared in sequence, and the arrangement position is determined according to the comparison results. When the load matching value, real-time energy efficiency evaluation value, frequency margin evaluation value, pressure status evaluation value and stability evaluation value are all the same, the arrangement position is determined according to the unit number in ascending order; Record the unit number and load matching value according to the arrangement position.

7. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 1, characterized in that, The specific steps for determining the preceding units in the sequence as the basic load bearers and the following units as the compensation load bearers are as follows: The unit number and load matching value of each parallel carbon dioxide heat pump unit are determined from front to back along the unit load sharing sequence, and the parallel carbon dioxide heat pump units with a load sharing matching value of zero are excluded to obtain the effective load sharing sequence. The total effective matching value is obtained by summing the load matching values ​​of each parallel carbon dioxide heat pump unit in the effective load-bearing sequence. The load-bearing matching value is accumulated sequentially from front to back along the effective load-bearing sequence. When the accumulated matching value of the current position is not less than half of the total effective matching value for the first time, the number of parallel carbon dioxide heat pump units participating in the accumulation is taken as the number of basic load-bearing objects. Parallel carbon dioxide heat pump units whose positions in the effective load bearing sequence fall within the range of the number of basic load bearing objects are identified as basic load bearing objects, and the remaining parallel carbon dioxide heat pump units are identified as compensation load bearing objects. When the effective load-sharing sequence is empty, each parallel carbon dioxide heat pump unit will be identified as an object that does not participate in the load-sharing of the current unified sampling period.

8. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 7, characterized in that, The specific steps for differentially allocating the target load determination value along the unit load occupancy sequence are as follows: Calculate the sum of the load-bearing matching values ​​for the basic load-bearing objects and the compensation load-bearing objects respectively to obtain the total basic matching value and the total compensation matching value; Based on the total value of basic matching, the total value of compensation matching, and the target load determination value, the basic load allocation and compensation load allocation are obtained. The target load share of each basic load-bearing object is determined based on the proportion of its load-bearing matching value in the total basic matching value. The target load share of each compensation load-bearing object is determined based on the proportion of its load-bearing matching value in the total compensation matching value. Record the target load shares of the basic load-bearing objects and the compensation load-bearing objects according to the unit number; When the total value of the basic matching is zero, the target load share of the basic load-bearing object is recorded as zero; When the total value of compensation matching is zero, the target load share of the compensation load-bearing object is recorded as zero.

9. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 1, characterized in that, The steps for determining the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve in conjunction with the target load share and load regulation status of each parallel carbon dioxide heat pump unit are as follows: The target load share is matched with the corresponding parallel carbon dioxide heat pump unit operating data according to the unit number to obtain the control quantity determination data; The load regulation status is determined based on the difference between the target load share and the load occupancy characteristic value at the current frequency; The target load ratio is obtained by comparing the target load share with the rated load of a single unit, and the target frequency of the compressor is determined based on the target load ratio. Based on the target load ratio and load regulation status, determine the adjustment direction and pressure correction amount of the air cooler target pressure relative to the air cooler pressure reference value; The target opening of the electronic expansion valve is determined based on the compressor's target frequency, the air cooler's target pressure, and the electronic expansion valve's full opening. Record the target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve corresponding to the same unit number to obtain the linkage control parameters.

10. The control method for multiple parallel carbon dioxide heat pumps based on target load control as described in claim 9, characterized in that, The specific steps for generating control commands for multiple parallel carbon dioxide heat pumps are as follows: The linkage control parameters are verified one by one according to the unit number. If any data of the air cooler target pressure, compressor target frequency and electronic expansion valve target opening is missing under the same unit number, the corresponding parallel carbon dioxide heat pump unit will not be included in the multi-parallel carbon dioxide heat pump control command of the current unified sampling cycle. Perform range verification on the target pressure of the air cooler, the target frequency of the compressor, and the target opening of the electronic expansion valve, and correct data that exceed the corresponding range according to the boundary values; The target opening degree of the electronic expansion valve is checked for consistency based on the compressor's target frequency, and the target pressure of the air cooler is checked for consistency based on the load regulation status. The target pressure of the air cooler, the target frequency of the compressor, and the target opening degree of the electronic expansion valve after verification are combined according to the unit number to generate a single-unit control command; The control commands for each individual unit are arranged in ascending order of unit number to form control commands for multiple parallel carbon dioxide heat pumps.

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