A dual-source energy storage heat pump unit based on minimum valve group and a multi-mode control method

Abstract

The application discloses a kind of based on minimum valve group's dual-source energy storage heat pump unit and multi-mode control method, it is related to heat pump and heat storage technology field, including the air side end of air source heat exchanger and energy storage side heat exchanger is connected common air side node, liquid side end is connected common liquid supply node by first, second two-position two-way valve respectively, first two-position two-way valve is connected with defrosting one-way bypass branch in parallel;When switching source, first make target branch and current branch overlap evaporation, target branch reaches the current branch liquid side after cutting off, and keep current branch air side communication suction side until refrigerant migration is completed;When defrosting is finished and energy storage side satisfies bridging condition, in turn execute energy storage side evaporation alone, two sources overlap evaporation and air source evaporation alone;The application does not increase active mode switching valve under the condition, consider dual-source smooth switching source, idle branch refrigerant migration and low-pressure stable recovery after defrosting.

Description

Technical Field

[0001] This invention relates to the field of heat pump and thermal energy storage technology, and in particular to a dual-source energy storage heat pump unit based on a minimum valve group and a multi-mode control method. Background Technology

[0002] Dual-source heat pump units can select either an air-source heat exchanger or a water-side heat exchanger as the evaporator based on the temperature conditions of the ambient air and water, the energy storage medium, or the process return water. For applications with simultaneous hot water and cooling needs, the water-side heat exchanger can also be used in conjunction with the energy storage medium to provide cooling to the storage medium while producing hot water, thereby achieving combined cooling and heating or cold storage. To reduce the cost, number of leakage points, and structural complexity of combined cooling and heating equipment, some dual-source heat pumps use a four-way reversing valve and two on / off valves respectively located on the two heat exchange branches to complete the heat source selection and reverse circulation defrosting.

[0003] Under stable operating conditions, the evaporation heat source can be changed by closing one source branch and opening another. However, the two source heat exchangers have different volumes, secondary heat capacities, and initial temperatures. If the source is switched directly in a fixed sequence of one-on-one switching, the target branch will bear the full refrigerant flow before establishing a stable evaporation state, which can easily cause sudden changes in suction pressure and superheat. At the same time, liquid refrigerant and lubricating oil may remain in the recently closed heat exchange branch, causing changes in the amount of refrigerant participating in the main cycle. These problems can be alleviated by adding solenoid valves, bypass regulating valves, or configuring multiple liquid receivers on the gas side of each branch, but this will weaken the advantages of the minimum valve assembly in terms of cost, reliability, and structural compactness.

[0004] After the air source heat exchanger completes reverse cycle defrosting, its coil temperature, surface moisture content, and internal refrigerant distribution differ significantly from the normal evaporation state. If the air source heat exchanger immediately assumes the full evaporation load after the four-way reversing valve resets, the transient heat exchange capacity of the cold coil and the refrigerant redistribution process may cause a rapid drop in suction pressure, thereby triggering low-pressure protection. Existing time delay, compressor frequency limiting, or high / low-pressure bypass measures do not simultaneously utilize the existing energy storage-side heat exchange branch of the dual-source unit, and typically cannot accommodate refrigerant migration in decommissioned branches.

[0005] Therefore, the core technical problem that needs to be solved is: how to achieve smooth source switching, refrigerant migration in decommissioned branches, and stable recovery after defrosting by utilizing the connection relationship of the dual-source branches without adding active mode switching valves. Summary of the Invention

[0006] To address the aforementioned problems in the existing technology, this invention provides a dual-source energy storage heat pump unit based on a minimum valve group and a multi-mode control method, which solves the problems of sudden changes in evaporation flow, refrigerant retention in idle branches, and easy drop in suction pressure after defrosting in dual-source units with minimum valve groups during source switching and defrosting recovery.

[0007] To address the aforementioned technical problems, this invention provides the following technical solution: This invention provides a dual-source energy storage heat pump unit based on a minimum valve group, comprising a variable frequency compressor, a four-way reversing valve, a hot water side heat exchanger, a throttling assembly, an air source heat exchanger, an energy storage side heat exchanger, and a controller. The air-side ends of the air source heat exchanger and the energy storage side heat exchanger are connected to a common air-side node, and their liquid-side ends are connected to a common liquid supply node downstream of the throttling assembly via a first two-position two-way valve and a second two-position two-way valve, respectively; the first two-position two-way valve is connected in parallel with a one-way bypass branch that leads from the air source heat exchanger to the common liquid supply node.

[0008] The four-way reversing valve, in its first reversing state, uses the hot water-side heat exchanger as a condenser and at least one source heat exchanger as an evaporator; in its second reversing state, it uses the air-source heat exchanger as a defrosting condenser. The controller is configured to, during source branch switching, first open the two-position two-way valve corresponding to the target branch and keep the two-position two-way valve corresponding to the current branch open; after the target branch meets the connection conditions, close the two-position two-way valve on the liquid side of the current branch and keep its gas side connected to the suction side until the current branch meets the refrigerant migration completion conditions; and, after defrosting is completed and the energy storage side meets the bridging conditions, sequentially execute energy storage-side independent evaporation, two-source overlapping evaporation, and air-source independent evaporation.

[0009] Preferably, the target branch meeting the connection conditions includes the target branch's secondary side heat exchange conditions reaching a set state, the variable frequency compressor's suction pressure not being lower than the lower limit of the connection pressure, the common suction superheat being within the connection superheat range, and the difference between the target branch's gas-side outlet temperature and the suction saturation temperature being within a stable range.

[0010] Preferably, the controller is based on the state difference ΔT of the decommissioned branch. r To determine whether refrigerant migration is complete, the state difference of the decommissioned branch must satisfy ΔT. r =T r,out -T sat (P s ), where T r,out T is the outlet temperature of the decommissioned branch gas side. sat (P s The suction pressure P of the variable frequency compressor is... s The corresponding refrigerant saturation temperature; when ΔT r Above the migration threshold, ΔT rWhen the rate of change is within a stable range and the suction pressure fluctuation is less than the fluctuation threshold, and the confirmation time is continuously set, it is determined that the refrigerant migration completion condition has been met.

[0011] Preferably, the controller determines the available bridging heat Q based on the energy storage medium temperature, the effective stored energy, and the minimum allowable temperature. b Furthermore, for sensible heat storage media, Q b =ρc p V eff (T s -T s,min ), where ρ is the density of the energy storage medium, and c p V represents the specific heat capacity of the energy storage medium. eff For the effective volume involved in bridging, T s T represents the current temperature of the energy storage medium. s,min The minimum allowable temperature for the energy storage medium; when Q b If the energy storage side meets the bridging conditions, it is determined that the energy storage side meets the bridging conditions when the energy storage volume is not lower than the bridging requirement and the energy storage status is normal. For energy storage side heat exchangers that use indirect refrigerant circulation, the energy storage side flow rate is also required to be normal.

[0012] Preferably, when entering the reverse cycle defrosting, both the first two-position two-way valve and the second two-position two-way valve are closed, and the four-way reversing valve switches to the second reversing state, so that the refrigerant discharged by the variable frequency compressor flows sequentially through the air source heat exchanger, the one-way bypass branch, the throttling component, and the hot water side heat exchanger before returning to the variable frequency compressor; when exiting the reverse cycle defrosting, the controller causes the four-way reversing valve to return to the first reversing state after the difference between the discharge pressure and the suction pressure of the variable frequency compressor is within the reversing pressure differential window.

[0013] Preferably, the controller starts the fan or circulating pump of the target branch before opening the two-position two-way valve corresponding to the target branch, and determines the preset opening degree of the throttling component according to the target branch type, source-side inlet temperature, frequency of the variable frequency compressor, exhaust pressure and suction pressure; during the two-source overlapping evaporation stage, the throttling component is adjusted according to the common suction superheat, and the variable frequency compressor is maintained in the migration frequency range that meets the refrigerant carrying requirements of the decommissioned branch.

[0014] Preferably, the variable frequency compressor has a gas injection port, which is connected to the economizer via a gas injection electronic expansion valve; the controller closes or reduces the opening of the gas injection electronic expansion valve during the switching of the four-way reversing valve and the overlapping evaporation of the two sources, and gradually restores the gas injection flow rate according to the compression ratio and exhaust temperature after the target branch or the energy storage side bridging branch reaches a stable condition.

[0015] Preferably, a multi-mode control method for a dual-source energy storage heat pump unit includes: when the four-way reversing valve is in the first reversing state, pre-establishing the secondary heat exchange conditions of the target branch, opening the two-position two-way valve corresponding to the target branch and keeping the two-position two-way valve corresponding to the current branch open, so that the two-source heat exchangers overlap evaporation; after the target branch reaches the connection conditions, closing the two-position two-way valve on the liquid side of the current branch and keeping the gas side end of the current branch connected to the suction side until the current branch reaches the refrigerant migration completion condition; when entering the reverse cycle defrosting, closing the two two-position two-way valves and switching the four-way reversing valve to the second reversing state, forming a defrosting cycle through the one-way bypass branch; when defrosting ends and the energy storage side meets the bridging conditions, restoring the four-way reversing valve to the first reversing state, and sequentially controlling the energy storage side heat exchanger to evaporate alone, the energy storage side heat exchanger and the air source heat exchanger to overlap evaporation, and the air source heat exchanger to evaporate alone.

[0016] Preferably, when the energy storage side meets the bridging conditions, during the independent evaporation of the energy storage side heat exchanger, the controller jointly adjusts the frequency of the variable frequency compressor and the opening of the throttling component according to the suction pressure, the superheat of the gas side outlet of the energy storage side heat exchanger and the exhaust temperature; when the suction pressure, the common suction superheat and the exhaust temperature enter the bridging exit window, the fan of the air source heat exchanger is started and the first two-position two-way valve is opened. After the air source heat exchanger meets the connection conditions, the second two-position two-way valve is closed and refrigerant migration is performed on the energy storage side heat exchanger.

[0017] Preferably, when the energy storage side does not meet the bridging conditions, i.e. when the available bridging heat is lower than the bridging requirement, the energy storage medium reaches the minimum allowable temperature, or the energy storage side flow is abnormal, the controller skips the energy storage side's separate evaporation, keeps the first two-position two-way valve and the second two-position two-way valve closed, until the four-way reversing valve returns to the first reversing state; then, the second two-position two-way valve is kept closed, the first two-position two-way valve is opened, the throttling component is adjusted to the preset opening degree of the air source recovery, and the frequency increase rate of the variable frequency compressor is limited, until the suction pressure and common suction superheat enter the air source recovery window.

[0018] The beneficial effects of this invention are as follows: 1. This invention connects the gas-side ends of two source heat exchangers to the suction side and configures two-position two-way valves only on each liquid-side end. This allows the target branch to establish an evaporation state in advance while the current branch is still supplying gas. It also allows the decommissioned branch to continue to use the compressor to remove residual refrigerant and lubricating oil after the liquid end is cut off. Thus, without adding gas-side active valves and additional refrigerant recovery containers, the suction fluctuations during the source switching process and the refrigerant retention in idle branches are reduced.

[0019] 2. The present invention utilizes a unidirectional bypass branch connected in parallel with the first two-position two-way valve and having a specified conduction direction to form a reverse circulation defrosting path when both two two-position two-way valves are closed. This enables the same set of active valves to have the functions of heat source selection, liquid end cut-off of the decommissioned branch, and defrosting isolation, forming a synergistic relationship in which the structure and control timing are mutually constrained.

[0020] 3. After defrosting, this invention first uses the heat exchanger on the energy storage side to establish a stable evaporation pressure based on the available heat on the energy storage side, and then smoothly switches to air source operation through overlapping evaporation of two sources. This not only utilizes the existing energy storage side branch to reduce the risk of low-pressure protection after defrosting, but also converts the heat obtained from the energy storage medium during the recovery process into storable or usable cold energy.

[0021] 4. The present invention determines the refrigerant migration end time based on the relationship between the branch outlet temperature and the suction saturation temperature. Compared with fixed delay control, it can adapt to the differences in volume, temperature, downtime and refrigerant retention of the two source heat exchangers. Attached Figure Description

[0022] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. 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.

[0023] Figure 1 This is a schematic diagram of the refrigerant circuit of the dual-source energy storage heat pump unit of the present invention; Figure 2 This is a schematic diagram showing the connection between the controller and the detection and execution components of the present invention; Figure 3 This is the control flowchart of the dual-source branch overlapping source switching and single-sided truncation migration of the present invention; Figure 4 This is the control flowchart of the reverse cycle defrosting and energy storage bridging recovery of the present invention; Figure 5 This is a schematic diagram illustrating the transition relationships between the various operating states of the present invention.

[0024] The accompanying figure is labeled as follows: 1. Variable frequency compressor; 2. Oil separator; 3. Four-way reversing valve; 4. Hot water side heat exchanger; 5. Liquid receiver; 6. Main electronic expansion valve; 7. Common liquid supply node; 8. First and second position two-way valve; 9. Air source heat exchanger; 10. One-way bypass branch; 11. Second two position two-way valve; 12. Energy storage side heat exchanger; 13. Common gas side node; 14. Gas-liquid separator; 15. Economizer; 16. Make-up gas electronic expansion valve; 17. Controller; 18. Fan; 19. Energy storage medium circulation pump; 20. Hot water circulation pump; 21. Pressure sensor group; 22. Branch outlet temperature sensor group; 23. Energy storage status sensor group; 24. Flow sensor; 25. Oil return throttling device. Detailed Implementation

[0025] To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the structure, control process, and technical effects of the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The thresholds, times, and frequencies mentioned below can be determined through prototype calibration based on the refrigerant type, compressor operating envelope, heat exchanger volume, and target water temperature, and should not be construed as limiting the scope of protection of the present invention.

[0026] See Figure 1 and Figure 2 As shown, this embodiment provides a dual-source energy storage heat pump unit. The unit includes a variable frequency compressor 1, an oil separator 2, a four-way reversing valve 3, a hot water side heat exchanger 4, a liquid receiver 5, a main electronic expansion valve 6 as a throttling component, a common liquid supply node 7, a first two-position two-way valve 8, an air source heat exchanger 9, a one-way bypass branch 10, a second two-position two-way valve 11, an energy storage side heat exchanger 12, a common gas side node 13, a gas-liquid separator 14, an economizer 15, a supplementary gas electronic expansion valve 16, a controller 17, a fan 18, an energy storage medium circulation pump 19, a hot water circulation pump 20, a pressure sensor group 21, a branch outlet temperature sensor group 22, an energy storage status sensor group 23, a flow sensor 24, and a return oil throttling element 25.

[0027] The discharge end of the variable frequency compressor 1 is connected to a four-way reversing valve 3 via an oil separator 2. The four-way reversing valve 3 is connected to the hot water side heat exchanger 4, the common gas side node 13, and the gas-liquid separator 14, respectively. The gas-liquid separator 14 is connected to the suction end of the variable frequency compressor 1. The lubricating oil separated by the oil separator 2 returns to the suction side of the variable frequency compressor 1 via the oil return throttling device 25. The other end of the hot water side heat exchanger 4 is connected to the common liquid supply node 7 via the liquid receiver 5, the main flow path of the economizer 15, and the main electronic expansion valve 6. The make-up gas branch is led out downstream of the liquid receiver 5 and connected to the make-up gas port of the variable frequency compressor 1 via the make-up gas electronic expansion valve 16 and the auxiliary flow path of the economizer 15.

[0028] The common liquid supply node 7 is divided into two paths. The first path connects to the liquid side of the air source heat exchanger 9 via a first two-position two-way valve 8, and the second path connects to the liquid side of the energy storage heat exchanger 12 via a second two-position two-way valve 11. The gas side ends of both the air source heat exchanger 9 and the energy storage heat exchanger 12 are connected to the common gas side node 13. The one-way bypass branch 10 is connected in parallel with the first two-position two-way valve 8, which allows refrigerant to flow from the liquid side of the air source heat exchanger 9 to the common liquid supply node 7 and prevents the throttling refrigerant during normal air source evaporation from bypassing the first two-position two-way valve 8. Thus, the first two-position two-way valve 8 and the second two-position two-way valve 11 constitute the liquid side selection valve of the source branch, and the gas side ends of the two source heat exchangers are not equipped with active valves that close with mode switching.

[0029] The hot water side heat exchanger 4 is a shell-and-tube, coaxial, or plate heat exchanger, connected to a hot water tank or heat-consuming terminal via a hot water circulation pump 20. The energy storage side heat exchanger 12 is a plate or shell-and-tube heat exchanger where the refrigerant directly enters the coil or is connected to the energy storage tank via a refrigerant circulation system. The energy storage medium is water, a mixture of water and antifreeze, or a phase change energy storage medium. When an indirect refrigerant circulation system is used, a flow sensor 24 is installed on the circulation pipeline corresponding to the energy storage medium circulation pump 19.

[0030] The controller 17 is electrically connected to the variable frequency compressor 1, the four-way reversing valve 3, the main electronic expansion valve 6, the first two-position two-way valve 8, the second two-position two-way valve 11, the supplementary air electronic expansion valve 16, the fan 18, the energy storage medium circulation pump 19, the hot water circulation pump 20, the pressure sensor group 21, the branch outlet temperature sensor group 22, the energy storage status sensor group 23, and the flow sensor 24. The pressure sensor group 21 detects at least the discharge pressure P of the variable frequency compressor 1. d and inhalation pressure P s The branch outlet temperature sensor group 22 detects the gas-side outlet temperature of the air source heat exchanger 9 and the energy storage side heat exchanger 12 near the common gas-side node 13, and also detects the common intake temperature T between the common gas-side node 13 and the gas-liquid separator 14. c The energy storage status sensor group 23 detects the temperature, level, phase change ratio, or other state parameters used to determine the current specific enthalpy of the energy storage medium. The flow sensor 24 detects the secondary circulation flow rate on the energy storage side and / or the hot water side.

[0031] Controller 17 based on inhalation pressure P s The suction saturation temperature T is obtained from the relationship between the refrigerant properties. sat (P s ), and in accordance with SH c =T c -T sat (P s Determine the common intake superheat SH cFor either air-source heat exchanger 9 or energy storage-side heat exchanger 12, the gas-side outlet superheat SH j According to SH j =T j,out -T sat (P s ) Determine, where T j,out The gas-side outlet temperature of the heat exchanger j near the common gas-side node 13.

[0032] When the four-way reversing valve 3 is in the first reversing state, the high-temperature and high-pressure refrigerant discharged from the variable frequency compressor 1 enters the hot water side heat exchanger 4 through the four-way reversing valve 3, circulates and releases heat to the hot water and condenses. The condensed refrigerant flows through the liquid receiver 5, the economizer 15 and the main electronic expansion valve 6 and then enters the common liquid supply node 7. When the first two-position two-way valve 8 is open and the second two-position two-way valve 11 is closed, the refrigerant enters the air source heat exchanger 9 to evaporate, forming an air source hot water production state. When the first two-position two-way valve 8 is closed and the second two-position two-way valve 11 is open, the refrigerant enters the energy storage side heat exchanger 12 to evaporate, forming an energy storage heat recovery state. The energy storage medium is cooled, and the hot water side heat exchanger 4 simultaneously produces hot water. When both two two-position two-way valves are open, the two source heat exchangers evaporate in parallel, forming a dual-source overlapping load state for source switching or defrosting recovery.

[0033] In air-source hot water production mode, the first two-position two-way valve 8 is open, the second two-position two-way valve 11 is closed, the fan 18 runs, and the energy storage medium circulation pump 19 stops. In this mode, the hot water side heat exchanger 4 acts as a condenser, and the air source heat exchanger 9 acts as an evaporator. For a 12-horsepower inverter prototype using R32 refrigerant, at the test point with an ambient dry-bulb temperature of 7°C and a wet-bulb temperature of 6°C, the heating capacity is 34.898kW, the input power is 9.224kW, and the coefficient of performance (COP) is 3.78; at the test point with an ambient dry-bulb temperature of -7°C and a wet-bulb temperature of -8°C, the heating capacity is 22.447kW, the input power is 8.791kW, and the COP is 2.55. The above data are used to illustrate that the actual circuit has the capability of low-temperature air-source hot water production and do not limit the capacity level of the present invention.

[0034] When there is a demand for hot water and the energy storage medium has a cold storage space or a cooling load requirement, the first two-position two-way valve 8 closes, the second two-position two-way valve 11 opens, the energy storage medium circulation pump 19 runs, and the unit enters the energy storage heat recovery state. At the test point where the hot water inlet temperature is approximately 40℃ and the outlet temperature is approximately 45℃, the energy storage inlet temperature is 11.99℃, the outlet temperature is 7.24℃, and the energy storage flow rate is 4.8 m³ / h, the cooling capacity is 26.557 kW, the input power is 9.69 kW, and the energy efficiency ratio is 2.74. Based on the specific heat capacity of water of 4.186 kJ / (kg·K), the heat exchange on the energy storage side is 4.186 × 4.8 × (11.99 - 7.24) / 3.6 = 26.51 kW, which matches the measured cooling capacity, indicating that the heat exchanger 12 on the energy storage side can provide cooling while releasing heat on the hot water side.

[0035] If the "close the current branch and open the target branch" actions are performed simultaneously between the two aforementioned steady-state conditions, the target branch may not yet have established secondary-side flow and evaporation status. Therefore, please refer to [the relevant documentation / reference]. Figure 3 As shown, controller 17 performs source switching in the order of pre-adjustment, overlapping load, target takeover, unilateral cutoff, and migration confirmation.

[0036] Figure 3 In the diagram, S101 indicates receiving a source switching command, S102 indicates pre-establishing the secondary heat exchange conditions of the target branch, S103 indicates opening the target branch and entering dual-source overlapping load mode, S104 indicates determining whether the target branch has met the connection conditions, S105 indicates closing the two-position two-way valve on the liquid side of the current branch, S106 indicates determining whether the decommissioned branch has met the refrigerant migration completion conditions, and S107 indicates entering the stable operation state of the target branch.

[0037] After receiving the source switching command, the controller 17 first identifies the current branch and the target branch. When the target branch is an air source branch, the controller 17 starts the fan 18 and confirms that the secondary heat exchange conditions of the air source heat exchanger 9 have been established based on the fan operation feedback, fan speed, or air flow rate. When the target branch is an indirect energy storage side branch using refrigerant circulation, the controller 17 starts the energy storage medium circulation pump 19 and confirms that the secondary circulation flow rate on the energy storage side has reached the set flow rate through the flow sensor 24. When the target branch is a direct energy storage side branch where the refrigerant coil is directly installed in the energy storage medium, the controller 17 confirms that the current state of the energy storage medium is within the allowable heat exchange range based on the energy storage medium temperature, liquid level, or phase change state detected by the energy storage state sensor group 23.

[0038] After the secondary heat exchange conditions of the target branch are established, the controller 17 determines the target branch type, target source inlet temperature, current frequency of the variable frequency compressor 1, and discharge pressure P. d and inhalation pressure P sDetermine the preset opening degree of the main electronic expansion valve 6. The preset opening degree is determined by the calibration relationship corresponding to different target branches and different operating conditions, or it is calculated based on the current estimated refrigerant mass flow rate and the heat exchange capacity of the target branch.

[0039] After the secondary heat exchange conditions of the target branch are established, the controller 17 opens the corresponding two-position two-way valve of the target branch, while keeping the corresponding two-position two-way valve of the current branch open, allowing the air source heat exchanger 9 and the energy storage side heat exchanger 12 to evaporate in parallel for a short period. The controller 17 adjusts the main electronic expansion valve 6 according to the common suction superheat and limits the frequency change rate of the variable frequency compressor 1, so that the target branch gradually takes over the refrigerant flow while the current branch continues to provide continuous suction mass flow. The overlap time is not the duration of a fixed operating mode, but rather is based on the target branch reaching the take-over conditions as the exit criterion, and a maximum allowable time is set to prevent long-term overlap due to abnormal operation.

[0040] The conditions for the target branch to meet the requirements for connection include: when the target branch is an air source branch, the fan 18 reaches the set operating state or the air flow reaches the set air volume; when the target branch is an indirect energy storage side branch, the energy storage medium circulation pump 19 is in operation and the secondary circulation flow on the energy storage side reaches the set flow rate; when the target branch is a direct energy storage side branch, the current temperature of the energy storage medium is higher than the minimum allowable temperature and the energy storage state is within the allowable heat exchange range; and, the suction pressure P s Not lower than the lower limit of the control pressure, common intake superheat SH c Within the superheat range of the control line, the superheat SH at the gas-side outlet of the target branch is... j It is in the stable control range, and the inhalation pressure P s The rate of change does not exceed the threshold for the rate of change of the pipe pressure.

[0041] Controller 17 requires the above conditions to be continuously met for the required connection confirmation time before determining that the target branch has met the connection conditions, in order to filter out instantaneous disturbances caused by the operation of the two-position two-way valve, the frequency adjustment of the variable frequency compressor, and sensor sampling. If the above conditions are not all met within the maximum allowable overlap time, controller 17 exits the current power switching process or maintains the operation of the current branch and outputs a target branch connection failure signal.

[0042] Once the target branch meets the takeover conditions, controller 17 closes the corresponding two-position two-way valve of the current branch to block the continued supply of throttled refrigerant from the common liquid supply node 7 to the current branch. The gas side of the current branch remains connected to the suction side of the variable frequency compressor 1 through the common gas side node 13. The residual liquid refrigerant in the current branch continues to evaporate under the action of heat on the source side and migrates to the common gas side node 13 under the suction action of the variable frequency compressor 1. For the air source branch, the one-way bypass branch 10 prevents the common liquid supply node 7 from supplying liquid to the air source heat exchanger 9, but allows the liquid side of the air source heat exchanger 9 to release refrigerant to the common liquid supply node 7 when its pressure is higher than that of the common liquid supply node 7.

[0043] Controller 17 based on the state difference ΔT of the decommissioned branch r To determine whether refrigerant migration is complete, the condition difference of the decommissioned branch must satisfy: ΔT r =T r,out -T sat (P s In the formula, T r,out T is the outlet temperature of the decommissioned branch gas side. sat (P s (This is related to the inhalation pressure P) s The corresponding refrigerant saturation temperature.

[0044] Controller 17 calculates ΔT using the sampled data within a preset sliding time window W. r The rate of change and the inspiratory pressure fluctuation, wherein the inspiratory pressure fluctuation is the inspiratory pressure P within the sliding time window W. s The difference between the maximum and minimum values. When ΔT r Not lower than the migration threshold, ΔT r When the absolute value of the rate of change is not greater than the rate of change threshold, the fluctuation of the suction pressure is not greater than the fluctuation threshold, and the above conditions are continuously met for the migration confirmation time, the controller 17 determines that the refrigerant migration is complete, releases the migration frequency limit of the variable frequency compressor 1, and stops the fan or circulating pump corresponding to the decommissioned branch. Thus, the migration end time is determined based on the refrigerant evaporation state and the main circulation suction stability within the decommissioned branch, avoiding insufficient migration or ineffective delays caused by relying solely on fixed-time control.

[0045] In one optional calibration method, controller 17 also establishes the branch refrigerant retention index R. j : R j = α1·t idle,j / t ref + α2·[T sat (P s )-T j,out ] + / T ref + α3·V j / V ref ; In the formula, j represents the air source branch or the energy storage side branch; t idle,j The duration of the outage for this branch road; T j,out V is the gas-side outlet temperature of this branch; j This is the effective volume of the refrigerant side of this branch; t ref T ref and V ref These are the normalized baseline values; [x] + This indicates taking the larger value between x and 0; α1, α2, and α3 are non-negative weights whose sum is 1. R j This calibration method is used to correct the pre-opening time of the target branch, the maximum permissible time for overlap between two sources, or the confirmation time for a decommissioned branch. It still uses existing temperature, pressure, and pattern records and does not require the addition of new active valves.

[0046] In one control threshold calibration method, the exhaust pressure P is continuously collected during the processes of switching from the air source branch to the energy storage branch, switching from the energy storage branch to the air source branch, and bridging from the energy storage side to the air source branch after defrosting. d Inhalation pressure P s Common intake temperature T c The parameters include the gas-side outlet temperature of each heat exchanger, the frequency of the variable frequency compressor, the opening degree of the main electronic expansion valve, and the secondary side flow rate. The lower limit of the inlet pressure is determined based on the allowable operating envelope and low-pressure protection value of variable frequency compressor 1, with a safety margin set above the low-pressure protection value. The inlet superheat range is determined based on the common suction superheat range during stable evaporation of the target branch. The migration threshold is based on ΔT after the decommissioned branch stops supplying liquid. r The state difference corresponding to the rise and entry into the stable platform is determined; the change rate threshold, fluctuation threshold and corresponding confirmation time are determined based on the sensor filter cycle, the action time of the two-position two-way valve and the refrigerant migration time in the branch.

[0047] For any operating condition to be calibrated, controller 17 verifies the intake pressure P during the source switching process. s The suction pressure is not lower than the lower limit of the allowable suction pressure of the variable frequency compressor 1, and the common suction superheat SH is not lower than the lower limit of the allowable suction pressure. c The temperature is not lower than the lower limit of allowable superheat and the exhaust temperature does not exceed the upper limit of allowable exhaust temperature. The parameter combination that satisfies the above constraints is written into the calibration table of controller 17, which is used to determine the corresponding control threshold based on the target branch type, source-side inlet temperature and variable frequency compressor frequency.

[0048] When the air source heat exchanger 9 reaches the defrosting start condition, the controller 17 reduces the frequency of the variable frequency compressor 1, closes or reduces the opening of the supplementary air electronic expansion valve 16, and adjusts the main electronic expansion valve 6. The controller 17 closes the first two-position two-way valve 8 and the second two-position two-way valve 11, and adjusts the discharge pressure P accordingly. dand inhalation pressure P s Determine the switching pressure difference ΔP of the four-way directional valve 3. v , where ΔP v =P d -P s When the commutation pressure difference ΔP v When the pressure difference is within the preset switching range, the controller 17 causes the four-way switching valve 3 to enter the second switching state.

[0049] In the second reversing state, the high-temperature refrigerant discharged from the variable frequency compressor 1 enters the common gas-side node 13 through the four-way reversing valve 3 and flows into the air source heat exchanger 9 for condensation and heat release. The condensed refrigerant flows from the liquid side of the air source heat exchanger 9 through the one-way bypass branch 10 to the common liquid supply node 7, and then returns to the variable frequency compressor 1 through the main electronic expansion valve 6 and the hot water-side heat exchanger 4. The second two-position two-way valve 11 remains closed to prevent the refrigerant from forming a continuous flow loop through the energy storage-side heat exchanger 12.

[0050] Since the gas side of the energy storage heat exchanger 12 is connected to the common gas side node 13, when the four-way reversing valve 3 enters the second reversing state, some high-pressure refrigerant can enter the gas side space of the energy storage heat exchanger 12 and make it briefly equalize pressure with the common gas side node 13. However, since the second two-position two-way valve 11 is closed, the energy storage heat exchanger 12 does not form a continuous refrigerant flow loop. The energy storage heat exchanger 12 and the second two-position two-way valve 11 are selected according to the design pressure not lower than the highest discharge pressure during defrosting. For the energy storage heat exchanger 12 that adopts an indirect refrigerant circulation, the energy storage medium circulation pump 19 is stopped during the reverse cycle defrosting to reduce the amount of refrigerant condensation in the energy storage heat exchanger 12. After the four-way reversing valve 3 returns to the first reversing state, the common gas side node 13 reconnects to the suction side of the variable frequency compressor 1, and the refrigerant that enters the gas side space of the energy storage heat exchanger 12 returns to the suction side under the action of pressure difference; when the energy storage side bridging is subsequently performed, the refrigerant circulation in the energy storage side branch is further restored by opening the second two-position two-way valve 11.

[0051] The hot water circulation pump 20 continues to operate during reverse circulation defrosting to ensure that the hot water side heat exchanger 4 receives a continuous water flow when acting as a defrosting evaporator, and performs antifreeze protection based on the hot water side temperature and flow rate.

[0052] After defrosting, the air source heat exchanger 9 switches back to evaporator from a condenser. Because the temperature of its coils and surface defrost water is low, immediately activating the full evaporation load may cause P... s Descending. See also Figure 4 As shown, the controller 17 determines whether the energy storage side has bridging capability before or during the restoration of the four-way reversing valve 3 to the first reversing state.

[0053] Figure 4In the above, S201 indicates whether the defrosting entry condition has been met, S202 indicates closing the two two-position two-way valves and switching the four-way reversing valve, S203 indicates performing reverse cycle defrosting, S204 indicates whether the defrosting exit condition has been met, and S205 indicates whether the energy storage side meets the bridging condition. If the bridging condition is met, the energy storage side separate evaporation shown in S206, the two-source overlapping evaporation shown in S207, and the air source separate evaporation shown in S208 are executed in sequence. If the bridging condition is not met, the direct air source frequency limiting recovery shown in S209 is executed.

[0054] For sensible heat storage media, the available heat for bridging is Q. b Determine Q using the following formula: b =ρ·c p ·V eff ·(T s -T s,min ); In the formula, ρ is the density of the energy storage medium, and c p V represents the specific heat capacity of the energy storage medium. eff T represents the effective volume involved in heat exchange during this bridging process. s T represents the current temperature of the energy storage medium. s,min This is the minimum allowable temperature for the energy storage medium.

[0055] For phase change energy storage media, the available bridging heat Q b Determine Q using the following formula: b =m eff ·(h s -h min ); In the formula, m eff h represents the effective mass of the phase change energy storage medium participating in heat exchange during this bridging process. s h represents the specific enthalpy of the phase change energy storage medium at its current temperature and current phase change ratio. min The specific enthalpy corresponds to the minimum allowable temperature and minimum allowable phase change ratio of the phase change energy storage medium. The controller 17 determines h based on the temperature and phase change ratio detected by the energy storage state sensor group 23, using the pre-stored temperature-phase change ratio-specific enthalpy relationship. s and h min .

[0056] For direct energy storage side heat exchangers, V eff or m eff The value is determined based on the total effective storage medium volume in the energy storage tank, the temperature stratification state, and the proportion expected to participate in heat exchange during the bridging period; for indirect energy storage side heat exchangers, V eff The value is determined based on the integral of the secondary circulation flow rate on the energy storage side over the expected bridging duration, and does not exceed the volume of the energy storage medium in the energy storage tank that is in an allowable heat exchange state.

[0057] Bridging demand Qreq Based on the expected bridging duration t b The internal evaporation load demand is determined and satisfies: Q req =∫0^t b e,req (t)dt; in, e,req (t) represents the evaporative heat absorption power required to maintain the operation of the variable frequency compressor 1 within the allowable suction pressure and allowable discharge temperature range during bridging. e,req (t) is determined based on the bridging frequency of the variable frequency compressor 1, the hot water side load, the condensation heat release and the compressor input power.

[0058] When Q b Not lower than Q req When the current state of the energy storage medium is higher than the minimum allowable state and the energy storage state sensor group 23 detects that it is normal, the controller 17 determines that the energy storage side meets the bridging conditions; for the energy storage side heat exchanger 12 that uses indirect refrigerant circulation, the secondary circulation flow rate of the energy storage side is also required to be within the normal range.

[0059] When the energy storage side meets the bridging conditions, for the energy storage side heat exchanger 12 using an indirect refrigerant circulation, the controller 17 first starts the energy storage medium circulation pump 19 and confirms that the secondary circulation flow rate on the energy storage side is within the normal range; for the direct energy storage side heat exchanger 12, the controller 17 confirms that the current state of the energy storage medium is within the allowable heat exchange range. The switching pressure difference ΔP of the four-way reversing valve 3... v After entering the preset reversing pressure differential range, the controller 17 restores the four-way reversing valve 3 to its first reversing state, keeps the first two-position two-way valve 8 closed, and opens the second two-position two-way valve 11, making the energy storage side heat exchanger 12 the sole evaporator after defrosting. The main electronic expansion valve 6 adopts a bridged preset opening, the variable frequency compressor 1 operates in the bridged frequency range, and the controller 17 adjusts the suction pressure P according to the preset opening. s The frequency of the variable frequency compressor and the opening of the main electronic expansion valve are jointly adjusted by the superheat of the gas outlet on the energy storage side and the exhaust temperature to establish a stable intake state.

[0060] During the separate evaporation of the heat exchanger 12 on the energy storage side, when the suction pressure P s Not lower than the lower limit of bridging exit pressure and common intake superheat SH c When the bridging exit overheating range is in effect, the exhaust temperature is not higher than the upper limit of the bridging exhaust temperature, and the above conditions are continuously met for the bridging exit confirmation time, the controller 17 determines that it is entering the bridging exit window.

[0061] After entering the bridging exit window, controller 17 starts fan 18, and after fan 18 reaches the set operating state, opens the first two-position two-way valve 8 to allow the energy storage side heat exchanger 12 and air source heat exchanger 9 to overlap and evaporate. After air source heat exchanger 9 reaches the connection conditions, controller 17 closes the second two-position two-way valve 11 to block the common liquid supply node 7 from supplying liquid to energy storage side heat exchanger 12. While the gas side of energy storage side heat exchanger 12 remains connected to the suction side, the controller operates according to the aforementioned decommissioned branch state difference ΔT. r Refrigerant migration is performed on the energy storage side heat exchanger 12 until it enters the air source separate evaporation state.

[0062] When bridging is available, heat Q b Below the bridging demand Q req When the energy storage medium reaches the minimum allowable state, the energy storage state sensor group 23 detects an abnormality, or the energy storage medium circulation pump 19 of the indirect energy storage side branch malfunctions or the secondary circulation flow is abnormal, the controller 17 executes the direct air source recovery procedure. The controller 17 keeps the first two-position two-way valve 8 and the second two-position two-way valve 11 closed until the four-way reversing valve 3 returns to the first reversing state; after the four-way reversing valve 3 returns to the first reversing state, the second two-position two-way valve 11 is kept closed, the first two-position two-way valve 8 is opened, and the main electronic expansion valve 6 is adjusted to the preset opening degree for air source recovery, while limiting the frequency increase rate of the variable frequency compressor 1.

[0063] When the inhalation pressure P s Not lower than the lower limit of air source recovery pressure and common intake superheat SH c When the air source is in the superheat recovery range and the above conditions continue to meet the air source recovery confirmation time, the controller 17 determines that it has entered the air source recovery window and gradually increases the frequency of the inverter compressor 1 and the speed of the fan 18. This fallback path can avoid forcibly executing energy storage side bridging when the energy storage side is unavailable.

[0064] The supplementary gas electronic expansion valve 16 is controlled in coordination with the above-mentioned state switching. In the early stages of the four-way reversing valve 3 switching, the target branch just opening, or the overlapping evaporation of the two sources, the controller 17 closes the supplementary gas electronic expansion valve 16 or reduces the opening of the supplementary gas electronic expansion valve 16 to reduce the interference of the supplementary gas mass flow rate on the establishment of high and low pressure and the judgment of common intake superheat.

[0065] When the inhalation pressure P s Within a stable pressure range, common intake superheat SH c When the target branch or energy storage side bridging branch reaches a stable condition, the exhaust temperature is not higher than the upper limit of the stable exhaust temperature, and the rate of change of the above parameters within the preset sliding time window does not exceed the corresponding stable rate of change threshold and the stability confirmation duration is continuously met, the controller 17 determines that the target branch or energy storage side bridging branch has reached a stable condition. After reaching the stable condition, the controller 17 determines the stable condition based on the compression ratio P.d / P s As the exhaust temperature gradually recovers, the opening of the electronic expansion valve 16 is adjusted. When calculating the compression ratio, P... d and P s Absolute pressure is used in all cases.

[0066] When the exhaust temperature approaches the upper limit of the allowable exhaust temperature of the variable frequency compressor 1, the opening adjustment of the supplementary air electronic expansion valve 16 takes priority over continuing to increase the frequency of the variable frequency compressor 1; when the common suction superheat SH c When the temperature is below the lower limit of the allowable superheat, the controller 17 limits the opening of the supplementary gas electronic expansion valve 16 to reduce the risk of liquid carryover during gas intake.

[0067] See Figure 5 As shown, M1 represents the air-source heat pump water heating state, M2 represents the energy storage heat recovery state, M3 represents the dual-source overlapping load state, M4 represents the reverse circulation defrosting state, and M5 represents the post-defrosting energy storage bridging state. M1 and M2 are switched via M3; after M4 exits, priority is given to Q. b Entering M5, then through M3 to M1. M3 is a transient state subject to takeover conditions and maximum permissible time constraints, and does not replace the stable operating mode selected based on long-term load.

[0068] In this paper, the minimum valve group refers to a four-way directional valve 3, a first two-position two-way valve 8, and a second two-position two-way valve 11 used for switching refrigerant operating modes. It does not include the main electronic expansion valve 6 for continuously regulating refrigerant flow, the electronic expansion valve 16 for replenishing gas, or the one-way bypass branch 10 that is passively opened by pressure difference. The first two-position two-way valve 8 and the second two-position two-way valve 11 are preferably electromagnetically driven normally closed two-position two-way valves, or electric valves capable of achieving the same switching function.

[0069] This invention does not require the energy storage-side heat exchanger 12 to operate under all conditions. The controller 17 selects between air-source hot water production and energy storage heat recovery modes based on ambient temperature, energy storage medium temperature, hot water demand, cooling demand, time-of-use electricity pricing, or user settings. However, the switching between any stable source branches preferentially employs overlapping load and single-sided cutoff migration processes. For scenarios where there is no cooling demand but the energy storage side still has an allowable temperature margin, the energy storage-side heat exchanger 12 only briefly assumes a bridging function after defrosting.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can make equivalent adjustments to the threshold, control cycle, and actuator type based on the refrigerant type, heat exchanger structure, and application load without departing from the scope of the present invention; all equivalent changes or modifications made based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A dual-source energy storage heat pump unit based on a minimum valve group, comprising a variable frequency compressor, a four-way reversing valve, a hot water side heat exchanger, a throttling assembly, an air source heat exchanger, an energy storage side heat exchanger, and a controller, characterized in that, The air source heat exchanger and the energy storage heat exchanger are connected to a common air-side node on their gas-side ends, and connected to a common liquid supply node downstream of the throttling assembly via a first two-position two-way valve and a second two-position two-way valve, respectively. The first two-position two-way valve is connected in parallel with a one-way bypass branch that leads from the air source heat exchanger to the common liquid supply node. The four-way reversing valve, in the first reversing state, enables the hot water-side heat exchanger to act as a condenser and at least one source heat exchanger to act as an evaporator, and in the second reversing state, enables the air source heat exchanger to act as a defrosting condenser. The controller is configured to first open the two-position two-way valve corresponding to the target branch and keep the two-position two-way valve corresponding to the current branch open when the source branch is switched. After the target branch meets the connection conditions, the controller closes the two-position two-way valve on the liquid side of the current branch and keeps its gas-side end connected to the suction side until the current branch meets the refrigerant migration completion conditions. And when defrosting is completed and the energy storage side meets the bridging conditions, the controller sequentially performs energy storage side independent evaporation, two-source overlapping evaporation, and air source independent evaporation. The controller is based on the state difference ΔT of the decommissioned branch. r To determine whether refrigerant migration is complete, the state difference of the decommissioned branch must satisfy ΔT. r =T r,out -T sat (P s ), where T r,out T is the outlet temperature of the decommissioned branch gas side. sat (P s The suction pressure P of the variable frequency compressor is... s The corresponding refrigerant saturation temperature; when ΔT r Above the migration threshold, ΔT r When the rate of change is within a stable range and the suction pressure fluctuation is less than the fluctuation threshold, and the confirmation time is continuously set, it is determined that the refrigerant migration completion condition has been met. The controller determines the available bridging heat Qb based on the storage medium temperature, effective stored energy, and minimum allowable temperature. For sensible heat storage medium, Qb = ρcpVeff(Ts - Ts,min), where ρ is the density of the storage medium, cp is the specific heat capacity of the storage medium, Veff is the effective volume participating in bridging, Ts is the current temperature of the storage medium, and Ts,min is the minimum allowable temperature of the storage medium. When Qb is not lower than the bridging requirement and the energy storage status is detected normally, the energy storage side is deemed to meet the bridging conditions. For energy storage side heat exchangers using indirect refrigerant circulation, normal flow rate on the energy storage side is also required.

2. The dual-source energy storage heat pump unit according to claim 1, characterized in that, The conditions for the target branch to meet the connection conditions include the secondary side heat exchange conditions of the target branch reaching the set state, the suction pressure of the variable frequency compressor not being lower than the lower limit of the connection pressure, the common suction superheat being within the connection superheat range, and the difference between the gas side outlet temperature of the target branch and the suction saturation temperature being within the stable range.

3. The dual-source energy storage heat pump unit according to claim 1, characterized in that, When entering the reverse cycle defrosting, both the first two-position two-way valve and the second two-position two-way valve are closed, and the four-way reversing valve switches to the second reversing state, so that the refrigerant discharged by the variable frequency compressor flows sequentially through the air source heat exchanger, the one-way bypass branch, the throttling component and the hot water side heat exchanger before returning to the variable frequency compressor; When exiting the reverse cycle defrosting, the controller causes the four-way reversing valve to return to the first reversing state after the difference between the discharge pressure and the suction pressure of the variable frequency compressor is within the reversing pressure differential window.

4. The dual-source energy storage heat pump unit according to claim 1, characterized in that, Before opening the two-position two-way valve corresponding to the target branch, the controller starts the fan or circulating pump of the target branch and determines the preset opening degree of the throttling component according to the target branch type, source-side inlet temperature, frequency of the variable frequency compressor, exhaust pressure and suction pressure; during the two-source overlapping evaporation stage, the controller adjusts the throttling component according to the common suction superheat and keeps the variable frequency compressor in the migration frequency range that meets the refrigerant carrying requirements of the decommissioned branch.

5. The dual-source energy storage heat pump unit according to claim 1, characterized in that, The variable frequency compressor has a gas injection port, which is connected to the economizer via a gas injection electronic expansion valve. The controller closes or reduces the opening of the gas injection electronic expansion valve during the switching of the four-way reversing valve and the overlapping evaporation of the two sources. After the target branch or the energy storage side bridging branch reaches a stable condition, the controller gradually restores the gas injection flow rate according to the compression ratio and exhaust temperature.

6. A multi-mode control method for a dual-source energy storage heat pump unit according to any one of claims 1 to 5, characterized in that, include: When the four-way reversing valve is in the first reversing state, the secondary heat exchange conditions of the target branch are established in advance, the two-position two-way valve corresponding to the target branch is opened and the two-position two-way valve corresponding to the current branch is kept open, so that the two-source heat exchangers overlap and evaporate. After the target branch meets the conditions for refrigerant transfer, close the two-position two-way valve on the liquid side of the current branch and keep the gas side of the current branch connected to the suction side until the current branch meets the conditions for refrigerant migration to be completed. When entering the reverse cycle defrosting, close the two two-position two-way valves and switch the four-way reversing valve to the second reversing state, forming a defrosting cycle through the one-way bypass branch; When defrosting is completed and the energy storage side meets the bridging conditions, the four-way reversing valve is restored to the first reversing state, and the energy storage side heat exchanger is controlled to evaporate alone, the energy storage side heat exchanger and the air source heat exchanger are overlapped and evaporated, and the air source heat exchanger is controlled to evaporate alone in sequence.

7. The multi-mode control method according to claim 6, characterized in that, During the independent evaporation of the energy storage side heat exchanger, the controller jointly adjusts the frequency of the variable frequency compressor and the opening of the throttling component based on the suction pressure, the superheat of the gas side outlet of the energy storage side heat exchanger, and the exhaust temperature. When the suction pressure, common suction superheat, and exhaust temperature enter the bridging exit window, the fan of the air source heat exchanger is started and the first two-position two-way valve is opened. After the air source heat exchanger meets the connection conditions, the second two-position two-way valve is closed, and refrigerant migration is performed on the energy storage side heat exchanger.

8. The multi-mode control method according to claim 6, characterized in that, When the available heat for bridging is lower than the bridging requirement, the energy storage medium reaches the minimum allowable temperature, or the flow rate on the energy storage side is abnormal, the controller skips the energy storage side's separate evaporation, keeps the first and second position two-way valves closed, until the four-way reversing valve returns to the first reversing state; then, keeping the second position two-way valve closed, the first position two-way valve is opened, the throttling component is adjusted to the preset opening degree of the air source recovery, and the frequency increase rate of the variable frequency compressor is limited, until the suction pressure and common suction superheat enter the air source recovery window.

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