Staged evaporation jet enhanced water source heat pump unit and control method thereof

Abstract

The present application relates to the technical field of compression heat pump cycle, and discloses a kind of staged evaporation jet augmenting enthalpy water source heat pump unit and control method thereof.Unit includes heat source side heat exchanger, user side heat exchanger, jet augmenting enthalpy variable frequency compressor, economizer, throttling component, suction convergence voltage regulation component, hot gas pulse regeneration branch and controller.Heat source water passage forms high temperature section and low temperature section along water flow direction, and two refrigerant evaporation branches are heat exchanged with low temperature section and high temperature section respectively;First branch pressure maintaining valve makes the evaporation saturation temperature of low temperature section corresponding branch higher.Controller grades adjustment compressor, throttle valve and first branch pressure maintaining valve according to cold end heat exchange safety parameter, branch superheat, user side heating load parameter and exhaust safety state, and implements hot gas pulse regeneration when conventional protection is invalid and exhaust safety state is normal.The present application can consider cold end protection, heating capacity and compressor operation safety.

Description

Technical Field

[0001] This invention relates to the field of compression heat pump cycle technology, and in particular to a staged evaporative jet enthalpy-increasing water source heat pump unit and its control method. Background Technology

[0002] A water source heat pump unit typically includes a compressor, a condenser heat exchanger, a throttling device, and an evaporator heat exchanger. The refrigerant absorbs heat from the water source and evaporates in the evaporator heat exchanger. After being compressed by the compressor, it releases heat to the user's circulating water in the condenser heat exchanger, thereby achieving heating.

[0003] In scenarios where centralized heating temperatures are insufficient, centralized heating water can be used as a low-grade heat source for water-source heat pump units. A compression heat pump cycle can then reheat the user-side heating water, improving the heating effect at user-side terminals such as underfloor heating and radiators. However, existing water-source heat pump units still have the following problems in such low-temperature centralized heating water source scenarios:

[0004] (1) Most existing water source heat pump units use a single evaporation channel to extract heat from the central heating water. The refrigerant evaporation temperature is usually difficult to match according to the temperature change of the central heating water along the process. When the temperature of the central heating water gradually decreases after flowing through the evaporator heat exchanger, the low-temperature water section may still be deeply heat extracted, which can easily cause the heat exchange temperature difference of the low-temperature section on the heat source side to be too large, affecting the operational stability of the evaporator side.

[0005] (2) Even if the existing parallel evaporation branches are equipped with throttling elements, they usually converge directly on the suction side. The outlet pressure of each evaporation branch tends to be consistent, making it difficult to form different evaporation pressures and different evaporation saturation temperatures. Therefore, it is not possible to effectively achieve graded evaporation control with the high-temperature water section as the main heat extractor and the low-temperature water section as the protective heat extractor.

[0006] (3) In the case of low-temperature centralized heating water source, it is common for the compressor to have low suction pressure and high discharge temperature. When ordinary variable frequency compressors rely on frequency increase to increase heating capacity, it is easy to cause the discharge temperature to rise, the compression ratio to increase and the operating efficiency to decrease, making it difficult to balance rapid heating and safe operation of the compressor.

[0007] (4) Although the existing jet enthalpy-enhancing heat pump system can improve the heating capacity under low temperature conditions through economizer and intermediate gas injection, the amount of gas injection is usually mainly adjusted according to the state of the compressor or condenser side, and it fails to coordinate with the staged heat extraction state of the evaporator side and the cold end protection state of the low temperature section, which easily leads to problems such as excessive gas injection, insufficient superheat of gas injection or unstable subcooling of the main circuit.

[0008] (5) When the temperature of the central heating water is low, the water flow is insufficient, or the local temperature of the heat exchanger is too low, the heat exchange area corresponding to the low temperature section of the evaporator is prone to local overcooling, reduced heat exchange capacity, or unstable operation. Existing systems usually protect themselves by reducing the compressor frequency or reducing the throttling opening, but the recovery speed is slow and it is difficult to improve the heat exchange status of the evaporator branch corresponding to the low temperature section in a timely manner.

[0009] (6) The control of existing water source heat pump units is mostly focused on the user-side supply water temperature, return water temperature or overall suction superheat. There is a lack of comprehensive control of the evaporation pressure, evaporation saturation temperature, branch superheat and low temperature outlet water temperature of different evaporation branches, which makes it difficult to coordinate the evaporation side protection, jet enthalpy injection and user-side heating load in low temperature centralized heating water source scenarios.

[0010] (7) Some existing water source heat pump units use the heat source water outlet temperature, heat exchange wall temperature, or refrigerant evaporation temperature as the sole basis for cold-end protection, and adjust the pressure regulating valve or throttle valve by a fixed range after the corresponding parameter exceeds the protection threshold. When multiple cold-end operating parameters approach their respective protection boundaries at different speeds, the controller has difficulty determining the most unfavorable parameter that currently restricts the safe operation of the unit. The fixed evaporation temperature difference control target and throttle valve opening limit are also difficult to adapt to changes in heat source water temperature, heat source water flow rate, and user-side heating load at the same time. This can easily lead to problems such as delayed intervention of cold-end protection, excessive protection level, or frequent reciprocating adjustment of valves near the protection boundary.

[0011] Therefore, it is necessary to provide a water source heat pump unit and its control method that can perform staged evaporation heat extraction based on the temperature changes of the central heating water along the process, and can determine the cold end safety level by comprehensively considering the outlet water temperature of the low-temperature section of the heat source water, the heat exchange wall temperature, and the cold end heat exchange temperature difference. This will allow for the coordination of the evaporation temperature and refrigerant flow of different refrigerant evaporation branches, and the combination of jet enthalpy injection, suction flow manifold pressure regulation, and hot gas pulse regeneration. This will improve the timeliness of cold end protection, refrigerant circulation stability, heating capacity, and compressor operation safety under low-temperature central heating water source conditions. Summary of the Invention

[0012] To address at least one of the technical problems in the prior art, the present invention aims to provide a staged evaporative jet enthalpy-enhancing water source heat pump unit.

[0013] To address at least one of the technical problems in the prior art, the present invention aims to provide a control method for a staged evaporative jet enthalpy-enhancing water source heat pump unit.

[0014] The first objective of this invention is achieved as follows:

[0015] A staged evaporative vapor-jet enthalpy-increasing water source heat pump unit includes a heat source-side heat exchanger, a user-side heat exchanger, a vapor-jet enthalpy-increasing variable frequency compressor, an economizer, a throttling component, a user-side circulating water pump, an intake manifold pressure regulating component, and a controller. The heat source-side heat exchanger is used to connect to a centralized heating water circuit, the user-side heat exchanger is used to release heat to the user-side heating water circuit, and the user-side circulating water pump is used to drive the user-side heating water to circulate between the user-side heat exchanger and the user-side heating water circuit. The vapor-jet enthalpy-increasing variable frequency compressor has an intake port, an exhaust port, and an intermediate gas injection port. The economizer includes a main refrigerant channel and a gas injection refrigerant channel.

[0016] The heat exchanger on the heat source side includes a heat source water channel, a first refrigerant evaporation branch, and a second refrigerant evaporation branch. The heat source water channel is formed in sequence along the flow direction of the central heating water into a high-temperature section and a low-temperature section. The first refrigerant evaporation branch is arranged to exchange heat with the low-temperature section of the heat source water, and the second refrigerant evaporation branch is arranged to exchange heat with the high-temperature section of the heat source water.

[0017] The exhaust port of the jet enthalpy-increasing variable frequency compressor, the refrigerant condensation channel of the user-side heat exchanger, and the main refrigerant channel of the economizer are connected in sequence. The outlet of the main refrigerant channel of the economizer is connected to the first refrigerant evaporation branch and the second refrigerant evaporation branch respectively through the throttling component. The outlets of the first refrigerant evaporation branch and the second refrigerant evaporation branch are connected to the suction port of the jet enthalpy-increasing variable frequency compressor through the suction manifold pressure regulating component to form a main refrigerant circulation loop.

[0018] The water source heat pump unit also includes a gas supply branch. One end of the gas supply branch is connected to the pipe section between the refrigerant condensation channel outlet of the user-side heat exchanger and the main refrigerant channel inlet of the economizer. The other end is connected to the gas supply refrigerant channel of the economizer via the throttling component. The gas supply refrigerant channel outlet of the economizer is connected to the intermediate gas supply port of the jet enthalpy-increasing variable frequency compressor to form an intermediate gas supply circuit.

[0019] The controller is used to control the throttling component and the suction manifold pressure regulating component so that the evaporation saturation temperature of the first branch corresponding to the first refrigerant evaporation branch is higher than the evaporation saturation temperature of the second branch corresponding to the second refrigerant evaporation branch.

[0020] By configuring the heat exchanger on the heat source side with a structure comprising a high-temperature section, a low-temperature section, a first refrigerant evaporation branch, and a second refrigerant evaporation branch, and ensuring that the first refrigerant evaporation branch exchanges heat with the low-temperature section of the heat source water, and the second refrigerant evaporation branch exchanges heat with the high-temperature section, the refrigerant evaporation heat extraction process can be zoned according to the temperature changes along the central heating water path. This avoids the problem of deep heat extraction in the low-temperature water section when existing water source heat pump units use a single evaporation channel. Simultaneously, an intermediate gas supply circuit is formed through an economizer and a jet-induced enthalpy-increasing variable frequency compressor. Furthermore, the suction manifold pressure regulating component ensures that the refrigerant evaporation saturation temperature corresponding to the first refrigerant evaporation branch is higher than that corresponding to the second refrigerant evaporation branch. This improves the cold-end protection capability of the low-temperature section of the heat source water, the operating safety of the compressor, and the heating effect on the user side.

[0021] The primary objective of this invention can also be achieved using the following technical measures:

[0022] Furthermore, the throttling assembly includes a first branch throttling valve, a second branch throttling valve, and a supplementary air throttling valve;

[0023] The main refrigerant channel outlet of the economizer is split to form a first evaporation branch and a second evaporation branch.

[0024] The first evaporation branch is connected to the first refrigerant evaporation branch via the first branch throttle valve, and the second evaporation branch is connected to the second refrigerant evaporation branch via the second branch throttle valve;

[0025] The gas supply branch is connected to the gas supply refrigerant channel of the economizer via the gas supply throttle valve, and the outlet of the gas supply refrigerant channel of the economizer is connected to the intermediate gas supply port.

[0026] By specifically configuring the throttling components as a first branch throttling valve, a second branch throttling valve, and a gas injection throttling valve, and ensuring that the main refrigerant outlet of the economizer enters the two refrigerant evaporation branches via the first and second branch throttling valves respectively, the refrigerant flow rate and evaporation state of the two evaporation branches can be adjusted independently. This solves the problem of difficulty in independent adjustment when the heat demand of different heat source water temperature ranges is inconsistent. The gas injection branch is connected to the gas injection refrigerant channel of the economizer via a gas injection throttling valve, allowing the refrigerant state entering the intermediate gas injection port to be regulated. This is beneficial for improving the heating capacity and the stability of the jet enthalpy-increasing operation under low-temperature water source conditions.

[0027] Furthermore, the intake manifold pressure regulating assembly includes a first branch pressure maintaining valve, an intake manifold chamber, and a gas-liquid separator;

[0028] The first branch pressure holding valve is located on the outlet side of the first refrigerant evaporation branch, and is used to ensure that the refrigerant pressure between the outlet of the first refrigerant evaporation branch and the inlet of the first branch pressure holding valve is higher than the refrigerant pressure at the outlet of the second refrigerant evaporation branch.

[0029] The outlet of the first refrigerant evaporation branch is connected to the suction manifold via the first branch pressure holding valve, and the outlet of the second refrigerant evaporation branch is connected to the suction manifold.

[0030] The intake manifold is connected to the intake port of the jet enthalpy-enhancing variable frequency compressor via the gas-liquid separator.

[0031] By incorporating a first branch pressure holding valve, a suction manifold, and a gas-liquid separator into the suction manifold pressure regulating assembly, the refrigerant pressure between the outlet of the first refrigerant evaporation branch and the inlet of the first branch pressure holding valve can be higher than the refrigerant pressure at the outlet of the second refrigerant evaporation branch. This solves the problem of parallel evaporation branches having uniform evaporation pressures and difficulty in achieving different evaporation saturation temperatures after direct confluence on the suction side. Consequently, the evaporation branch corresponding to the low-temperature section of the heat source water can maintain a higher evaporation temperature, reducing the risk of excessive heat extraction, while the gas-liquid separator reduces the possibility of liquid refrigerant entering the compressor, improving compressor operational reliability.

[0032] Furthermore, the heat source side heat exchanger includes a heat exchanger body, a heat source water channel baffle and a refrigerant flow channel baffle disposed within the heat exchanger body;

[0033] The heat source water channel partition is used to define the high-temperature section and the low-temperature section of the heat source water.

[0034] The refrigerant flow channel baffle is used to separate the first refrigerant evaporation branch and the second refrigerant evaporation branch from each other within the heat exchanger body;

[0035] The heat exchange area of ​​the first refrigerant evaporation branch is smaller than the heat exchange area of ​​the second refrigerant evaporation branch; and / or,

[0036] The refrigerant flow cross-sectional area of ​​the first refrigerant evaporation branch is larger than that of the second refrigerant evaporation branch.

[0037] By installing heat source water channel baffles and refrigerant flow channel baffles within the heat source-side heat exchanger, the corresponding heat transfer relationships between the high-temperature section and the low-temperature section of the heat source water, as well as between the two refrigerant evaporation branches, become clearer, which is beneficial for forming a stable zoned heat transfer structure. Furthermore, by making the heat transfer area of ​​the first refrigerant evaporation branch smaller than that of the second refrigerant evaporation branch, or by making the refrigerant flow cross-sectional area of ​​the first refrigerant evaporation branch larger than that of the second refrigerant evaporation branch, the heat transfer intensity in the corresponding region of the low-temperature section of the heat source water can be reduced, solving the problems of localized overcooling and excessively large temperature differences in the low-temperature water section, thus structurally improving the operational stability of the evaporation side.

[0038] Furthermore, the water source heat pump unit also includes a first branch evaporation pressure detection device, a second branch evaporation pressure detection device, a first branch outlet temperature detection device, a second branch outlet temperature detection device, a user-side return water temperature detection device, and a user-side supply water temperature detection device.

[0039] The first branch evaporation pressure detection device is located between the outlet of the first refrigerant evaporation branch and the inlet of the first branch pressure holding valve, and the second branch evaporation pressure detection device is located on the outlet side of the second refrigerant evaporation branch;

[0040] The first branch outlet temperature detector and the second branch outlet temperature detector are used to detect the outlet temperature of the corresponding refrigerant evaporation branch, respectively. The user-side return water temperature detector and the user-side supply water temperature detector are respectively installed in the user-side return water pipeline and the user-side supply water pipeline.

[0041] The controller determines the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch based on the pre-stored refrigerant pressure-saturation temperature relationship and the evaporation pressure of the two refrigerant evaporation branches, and determines the superheat of the first branch and the superheat of the second branch based on the outlet temperature and evaporation saturation temperature of the corresponding refrigerant evaporation branches.

[0042] When the superheat of the first branch is lower than the preset lower limit of the first branch superheat, the controller reduces the opening of the throttle valve of the first branch; when the superheat of the first branch is higher than the preset upper limit of the first branch superheat, the controller increases the opening of the throttle valve of the first branch; when the superheat of the second branch is lower than the preset lower limit of the second branch superheat, the controller reduces the opening of the throttle valve of the second branch; when the superheat of the second branch is higher than the preset upper limit of the second branch superheat, the controller increases the opening of the throttle valve of the second branch.

[0043] By setting pressure and outlet temperature sensors for two refrigerant evaporation branches, the controller can determine the superheat of the first and second branches respectively, and adjust the corresponding branch throttling valves according to the defined upper and lower limits of superheat. By setting return water and supply water temperature sensors on the user side, the controller can obtain the supply and return water temperatures on the user side and determine the heating load parameters on the user side, thus forming a complete detection and control chain.

[0044] Furthermore, the water source heat pump unit also includes a low-temperature section outlet water temperature detection device, a high-temperature section inlet water temperature detection device, a wall surface temperature detection device, an exhaust temperature detection device, and an exhaust pressure detection device; the controller determines the cold-end heat exchange temperature difference as the difference between the low-temperature section outlet water temperature and the evaporation saturation temperature of the first branch; when the cold-end heat exchange temperature difference is greater than the preset maximum heat exchange temperature difference threshold, the low-temperature section outlet water temperature is lower than the preset low-temperature protection temperature, or the heat exchange wall temperature is lower than the preset wall protection temperature, it is determined that the cold-end heat exchange safety parameters do not meet the preset safety conditions; when the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller reduces the opening of the first branch pressure holding valve or increases its set back pressure, applies a maximum opening limit for cold-end protection to the first branch throttle valve and reduces its opening; when the exhaust temperature is not higher than the preset exhaust temperature upper limit and the exhaust pressure is not higher than the preset exhaust pressure upper limit, the controller determines that the exhaust safety status is normal; otherwise, it determines that the exhaust safety status is abnormal.

[0045] The controller determines the user-side heating load parameters based on the user-side supply water temperature and user-side return water temperature detected by the user-side supply water temperature detector and the user-side return water temperature detector; when the user-side supply water temperature is lower than the user-side target supply water temperature, the temperature difference between the user-side supply water temperature and the user-side return water temperature increases, or the user-side return water temperature continues to decrease, the controller determines that the user-side heating load parameters increase;

[0046] When the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the heating load parameters on the user side increase, the exhaust safety status is normal, and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, the controller increases the opening of the throttle valve of the second branch while maintaining the superheat of the second branch within the preset range.

[0047] By clarifying the calculation direction and safety criteria for the cold-end heat exchange temperature difference, and by increasing the evaporation saturation temperature of the first branch and limiting the refrigerant mass flow rate of the first refrigerant evaporation branch when the cold-end heat exchange temperature difference is too large, the outlet water temperature of the low-temperature section of the heat source water is too low, or the heat exchange wall temperature is too low, the risk of deep heat extraction in the low-temperature section of the heat source water can be reduced. Under the conditions of meeting exhaust safety and the superheat constraint of the second branch, increasing the opening of the throttle valve of the second branch can allow the second refrigerant evaporation branch to undertake the main heat extraction, thus balancing heating capacity and cold-end protection.

[0048] Furthermore, the controller determines the difference between the preset maximum heat exchange temperature difference threshold and the cold end heat exchange temperature difference as the heat exchange temperature difference safety margin, the difference between the outlet water temperature of the low-temperature section of the heat source water and the preset low-temperature protection temperature as the outlet water temperature safety margin, and the difference between the heat exchange wall temperature and the preset wall protection temperature as the wall temperature safety margin; the controller determines the minimum value among the heat exchange temperature difference safety margin, the outlet water temperature safety margin, and the wall temperature safety margin as the cold end safety margin, and determines the target evaporation saturation of the first branch based on the cold end safety margin. The target temperature difference is obtained by subtracting the evaporation saturation temperature of the second branch from the temperature, and the target temperature difference is 2°C to 10°C. When the cold end safety margin decreases, the controller increases the target temperature difference, decreases the opening of the pressure holding valve of the first branch or increases the set back pressure of the pressure holding valve of the first branch, and decreases the maximum opening of the cold end protection of the throttle valve of the first branch. Only when the cold end safety margin is not lower than the preset recovery margin for multiple consecutive preset control cycles, the controller decreases the target temperature difference and gradually increases the maximum opening of the cold end protection of the throttle valve of the first branch.

[0049] By separately determining the safety margins for heat exchange temperature difference, outlet water temperature, and wall temperature, and defining the minimum of these three as the cold-end safety margin, the operating parameter closest to the protection boundary can be identified. This avoids problems such as judgment lag or incomplete protection basis when relying on a single parameter for cold-end protection. Furthermore, based on the cold-end safety margin, the target temperature difference between the two refrigerant evaporation branches and the maximum opening of the cold-end protection of the first branch throttling valve are dynamically determined. This allows the pressure maintaining valve and the first branch throttling valve to work together: when the cold-end safety margin decreases, the evaporation saturation temperature of the first branch is increased, and the restriction on the refrigerant mass flow rate of the first refrigerant evaporation branch is strengthened; once the cold-end safety margin stabilizes and recovers, the restriction is gradually lifted. This reduces insufficient or excessive protection caused by fixed-amplitude protection, lowers the possibility of frequent valve adjustments near the protection boundary, and balances cold-end protection of the low-temperature section of the heat source water, evaporation-side operational stability, and continuous heating capacity on the user side.

[0050] Furthermore, the water source heat pump unit also includes a gas supply temperature detection device, a gas supply pressure detection device, an exhaust temperature detection device, and an exhaust pressure detection device;

[0051] The gas injection temperature detection device and the gas injection pressure detection device are located between the gas injection refrigerant channel outlet of the economizer and the intermediate gas injection port; the exhaust temperature detection device and the exhaust pressure detection device are located in the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor.

[0052] The gas supply temperature detector is used to detect the gas supply temperature before it enters the intermediate gas supply port, the gas supply pressure detector is used to detect the gas supply pressure before it enters the intermediate gas supply port, and the exhaust temperature detector and the exhaust pressure detector are used to detect the exhaust temperature and exhaust pressure of the jet enthalpy-enhancing variable frequency compressor, respectively.

[0053] The controller determines the gas supply saturation temperature based on the gas supply pressure, and determines the gas supply superheat based on the gas supply temperature and the gas supply saturation temperature;

[0054] When the superheat of the replenished gas is lower than the preset lower limit of the superheat of the replenished gas, the controller reduces the opening of the replenished gas throttle valve;

[0055] When the superheat of the supplementary gas is higher than the preset upper limit of the superheat of the supplementary gas and the exhaust safety status is normal, the controller increases the opening of the supplementary gas throttle valve; when the exhaust safety status is abnormal, the controller prohibits the increase of the opening of the supplementary gas throttle valve and limits the increase of the operating frequency of the jet enthalpy-enhancing variable frequency compressor.

[0056] By establishing a closed loop of injection superheat and exhaust safety through injection gas temperature, injection gas pressure, exhaust temperature, and exhaust pressure, the injection gas volume can be adjusted according to the injection gas superheat when the exhaust safety condition is normal, and the injection gas and compressor frequency increase can be restricted when the exhaust temperature or exhaust pressure exceeds the upper limit, thereby improving the safety of jet enthalpy enhancement operation.

[0057] Furthermore, the water source heat pump unit also includes a hot gas pulse regeneration branch, one end of which is connected to the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor, and the other end is connected to the inlet side or the middle of the first refrigerant evaporation branch.

[0058] A hot gas regeneration valve is provided on the hot gas pulse regeneration branch, and a one-way valve and / or flow restrictor are provided between the hot gas regeneration valve and the first refrigerant evaporation branch.

[0059] When the cold-end heat exchange safety parameters do not meet the preset safety conditions, and the cold-end heat exchange safety parameters cannot be restored by adjusting the first branch pressure holding valve and the first branch throttle valve, the controller will control the hot gas regeneration valve to open in a pulse manner only when the exhaust safety status is normal; when the cold-end heat exchange safety parameters are restored or the exhaust safety status is abnormal, the controller will close the hot gas regeneration valve.

[0060] By setting up a hot gas pulse regeneration branch and an exhaust safety interlock, when the conventional cold end protection cannot be restored, the high-temperature refrigerant vapor discharged from the exhaust port of the jet enthalpy-increasing inverter compressor and diverted from the downstream pipe section of the exhaust port can be introduced into the first refrigerant evaporation branch for short-term hot gas regeneration. When the exhaust safety status is abnormal or the cold end status has been restored, the hot gas regeneration is stopped to avoid the exhaust temperature or exhaust pressure from continuing to rise due to hot gas regeneration.

[0061] The second objective of this invention is achieved as follows:

[0062] A control method for a staged evaporative vapor injection enthalpy-increasing water source heat pump unit is executed by a controller of the staged evaporative vapor injection enthalpy-increasing water source heat pump unit; the water source heat pump unit includes a heat source-side heat exchanger, a user-side heat exchanger, a vapor injection enthalpy-increasing variable frequency compressor, an economizer, a first branch throttling valve, a second branch throttling valve, a make-up gas throttling valve, a first branch pressure holding valve, a hot gas pulse regeneration branch, and a hot gas regeneration valve;

[0063] The economizer includes a main refrigerant channel and a makeup refrigerant channel. The outlet of the main refrigerant channel is connected to the first refrigerant evaporation branch and the second refrigerant evaporation branch via the first branch throttle valve and the second branch throttle valve, respectively. The makeup refrigerant branch branch branching off from the refrigerant condensation channel outlet of the user-side heat exchanger is connected to the makeup refrigerant channel via the makeup refrigerant throttle valve. The outlet of the makeup refrigerant channel is connected to the intermediate makeup refrigerant port of the jet enthalpy-increasing variable frequency compressor.

[0064] The heat exchanger on the heat source side includes a high-temperature section and a low-temperature section of heat source water formed sequentially along the flow direction of the heat source water, as well as a first refrigerant evaporation branch and a second refrigerant evaporation branch separated from each other; the first refrigerant evaporation branch is arranged to exchange heat with the low-temperature section of the heat source water, and the second refrigerant evaporation branch is arranged to exchange heat with the high-temperature section of the heat source water; the pressure maintaining valve of the first branch is arranged on the outlet side of the first refrigerant evaporation branch;

[0065] The hot gas pulse regeneration branch is connected between the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor and the first refrigerant evaporation branch, and the hot gas regeneration valve is installed in the hot gas pulse regeneration branch; the controller executes the control method according to the control priority decreasing in sequence according to exhaust safety, cold end protection and user-side load adjustment;

[0066] The control method includes the following steps:

[0067] S1, obtain the outlet water temperature of the low-temperature section of the heat source water, the inlet water temperature of the high-temperature section of the heat source water, the heat exchange wall temperature corresponding to the first refrigerant evaporation branch, the evaporation pressure and outlet temperature of the two refrigerant evaporation branches, the user-side supply water temperature and user-side return water temperature, the gas replenishment temperature and gas replenishment pressure, and the exhaust temperature and exhaust pressure.

[0068] S2, determine the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch based on the pre-stored refrigerant pressure-saturation temperature relationship and the evaporation pressure of the two refrigerant evaporation branches respectively, and determine the superheat of the first branch and the superheat of the second branch based on the outlet temperature and evaporation saturation temperature of the corresponding refrigerant evaporation branches; determine the makeup gas saturation temperature based on the makeup gas pressure, and determine the makeup gas superheat based on the makeup gas temperature and the makeup gas saturation temperature;

[0069] S3, the difference between the outlet temperature of the low-temperature section of the heat source water and the evaporation saturation temperature of the first branch is determined as the cold end heat exchange temperature difference, and the cold end heat exchange safety parameters are determined based on the cold end heat exchange temperature difference, the outlet temperature of the low-temperature section of the heat source water, and the heat exchange wall temperature; the user-side heating load parameters are determined based on the user-side supply water temperature and the user-side return water temperature; the exhaust safety status is determined based on the exhaust temperature and the exhaust pressure.

[0070] S4. When the cold end heat exchange safety parameters meet the preset safety conditions, adjust the operating frequency of the jet enthalpy-increasing variable frequency compressor and the opening degree of the first branch throttling valve, the second branch throttling valve and the gas injection throttling valve according to the user-side heating load parameters, the first branch superheat, the second branch superheat, the gas injection superheat and the exhaust safety status.

[0071] S5, when the cold-end heat exchange safety parameters do not meet the preset safety conditions, reduce the opening of the first branch pressure holding valve or increase the set back pressure of the first branch pressure holding valve to increase the evaporation saturation temperature of the first branch; apply a maximum opening limit for cold-end protection to the first branch throttle valve and reduce the opening of the first branch throttle valve to limit the refrigerant mass flow rate of the first refrigerant evaporation branch; when the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the user-side heating load parameters increase, the exhaust safety status is normal and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, increase the opening of the second branch throttle valve while maintaining the superheat of the second branch within the preset range.

[0072] S6, when the cold end heat exchange safety parameters still do not meet the preset safety conditions after adjustment in step S5, the hot gas regeneration valve is controlled to open in a pulse manner only when the exhaust safety status is normal; when the cold end heat exchange safety parameters recover or the exhaust safety status is abnormal, the hot gas regeneration valve is closed.

[0073] By comprehensively acquiring the operating parameters of the heat source side, the two refrigerant evaporation branches, the user side, the make-up gas branch, and the downstream of the exhaust port of the vapor injection enthalpy-enhancing inverter compressor, and by clearly calculating the branch evaporation saturation temperature, branch superheat, make-up gas superheat, cold-end heat exchange safety parameters, user-side heating load parameters, and exhaust safety status, each control action can have definite inputs, criteria, and execution directions. When the exhaust safety status is abnormal, make-up gas and compressor frequency increase are restricted first; when the cold end is unsafe, the first branch protection is implemented first; and hot gas regeneration is implemented only when conventional protection is ineffective and exhaust safety is achieved.

[0074] The second objective of this invention can also be achieved by the following technical measures:

[0075] Furthermore, when the cold end heat exchange temperature difference is not greater than the preset maximum heat exchange temperature difference threshold, the outlet water temperature of the low temperature section of the heat source water is not lower than the preset low temperature protection temperature, and the heat exchange wall temperature is not lower than the preset wall protection temperature, it is determined that the cold end heat exchange safety parameters meet the preset safety conditions.

[0076] When the exhaust temperature is not higher than the preset exhaust temperature limit and the exhaust pressure is not higher than the preset exhaust pressure limit, the exhaust safety status is determined to be normal.

[0077] When the exhaust safety status is normal and the cold-end heat exchange safety parameters meet the preset safety conditions, the controller enters the normal heating mode; when the exhaust safety status is normal and the cold-end heat exchange safety parameters meet the preset safety conditions, if the user-side heating load parameters do not increase, or if the user-side heating load parameters increase but the outlet temperature of the low-temperature section of the heat source water is lower than the preset enthalpy increase allowable temperature, the controller enters the normal heating mode; if the user-side heating load parameters increase and the outlet temperature of the low-temperature section of the heat source water is not lower than the preset enthalpy increase allowable temperature, the controller enters the enthalpy increase heating mode, and increases the opening of the air replenishment throttle valve under the condition that the air replenishment superheat is not lower than the preset air replenishment superheat lower limit;

[0078] When the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller enters the cold-end protection mode, increases the evaporation saturation temperature of the first branch through the first branch pressure holding valve, and limits the refrigerant mass flow rate of the first refrigerant evaporation branch through the first branch throttling valve.

[0079] When the cold end protection mode fails to restore the cold end heat exchange safety parameters and the exhaust safety status is normal, the controller enters the hot gas regeneration mode; the single opening time of the hot gas regeneration valve is 2s to 30s, and the interval between two adjacent openings is 30s to 300s; when the cold end heat exchange safety parameters are restored or the exhaust safety status is abnormal, the controller closes the hot gas regeneration valve and exits the hot gas regeneration mode.

[0080] By clearly defining the control priorities of exhaust safety, cold end protection, and user-side load regulation, and by limiting the entry and exit conditions of normal heating mode, enthalpy-increasing heating mode, cold end protection mode, and hot gas regeneration mode, conflicting control commands can be prevented when multiple actuators are adjusted simultaneously, enabling the unit to maintain cold end heat exchange and compressor exhaust safety while improving heating capacity.

[0081] The beneficial effects of this invention are as follows:

[0082] (1) This invention sets up two refrigerant evaporation branches in the heat exchanger on the heat source side, corresponding to the high-temperature section and the low-temperature section of the heat source water, respectively, so that the refrigerant evaporation heat extraction process can adapt to the characteristic of the temperature of the central heating water gradually decreasing along the path. Compared with a single evaporation channel, this invention enables the high-temperature section of the heat source water to undertake the main heat extraction task, and keeps the low-temperature section of the heat source water in a protected heat extraction state, thereby reducing the risk of excessive heat extraction from the low-temperature water section and improving the stability of the heat exchange process on the evaporation side.

[0083] (2) This invention, by setting up a suction manifold pressure regulating component and utilizing a first branch pressure holding valve, maintains a higher pressure in the first refrigerant evaporation branch before merging, ensuring that the refrigerant evaporation saturation temperature corresponding to the first refrigerant evaporation branch is higher than that corresponding to the second refrigerant evaporation branch. This setup overcomes the problem of pressure convergence after direct merging of parallel evaporation branches, provides more reliable cold-end protection for the evaporation branch corresponding to the low-temperature section of the heat source water, and reduces the risk of the compressor drawing in liquid refrigerant.

[0084] (3) This invention forms an intermediate gas supply circuit through an economizer, a gas supply throttle valve, and a jet enthalpy-increasing variable frequency compressor. The opening of the gas supply throttle valve is adjusted according to the gas supply temperature, gas supply pressure, and exhaust temperature to match the gas supply status with the unit's operating status. Therefore, when the temperature of the centralized heating water source is low or the heating load parameters on the user side increase, the heating capacity of the unit can be improved, while avoiding excessive gas supply or excessively high exhaust temperature, thus improving the compressor's operating safety and the heat pump's cycle efficiency.

[0085] (4) This invention forms a complete detection chain for cold-end heat exchange safety parameters, branch superheat, user-side heating load parameters, and exhaust safety status through the outlet water temperature detection device of the low-temperature section of the heat source water, the wall temperature detection device, the pressure and outlet temperature detection devices of the two refrigerant evaporation branches, the supply and return water temperature detection device on the user side, and the exhaust temperature and exhaust pressure detection devices. The controller executes control according to the priority of exhaust safety, cold-end protection, and user-side load regulation, and implements hot gas pulse regeneration under the condition that the exhaust safety status is normal, thereby improving the operational stability, continuous heating capacity, and overall safety under low-temperature conditions. Attached Figure Description

[0086] Figure 1 This is a schematic diagram of the overall structure of the staged evaporative jet enthalpy-enhancing water source heat pump unit according to an embodiment of the present invention.

[0087] Figure 2 This is a schematic diagram of the internal structure of the heat exchanger on the heat source side according to an embodiment of the present invention.

[0088] Figure 3 This is a schematic diagram showing the connection of the jet enthalpy-increasing variable frequency compressor, the user-side heat exchanger, the economizer, and the throttling component in an embodiment of the present invention.

[0089] Figure 4 This is a schematic diagram of the intake manifold pressure regulating assembly and the arrangement of various detection components according to an embodiment of the present invention.

[0090] Figure 5 This is a schematic diagram of the structure of the hot gas pulse regeneration branch in an embodiment of the present invention. Detailed Implementation

[0091] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are only for illustrating the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Where there is no conflict, the technical features in the following embodiments can be combined with each other.

[0092] Example 1, such as Figures 1 to 5 As shown, this embodiment provides a staged evaporative jet enthalpy-increasing water source heat pump unit 100. The water source heat pump unit 100 is used to connect to the centralized heating water circuit and uses the centralized heating water as a low-grade heat source on the evaporation side. The heating water on the user side is heated a second time through a compression heat pump circulation to supply heat to the underfloor heating manifold, radiators or other user-side heating terminals.

[0093] The water source heat pump unit 100 includes a heat source-side heat exchanger 10, a user-side heat exchanger 20, a vapor injection enthalpy-increasing variable frequency compressor 30, an economizer 40, a throttling component 50, a user-side circulating water pump 60, an intake manifold pressure regulating component 70, a hot gas pulse regeneration branch 80, and a controller 90. The heat source-side heat exchanger 10 is used to connect to the centralized heating water circuit, the user-side heat exchanger 20 is used to release heat to the user-side heating water circuit, and the user-side circulating water pump 60 is used to drive the user-side heating water to circulate between the user-side heat exchanger 20 and the user-side heating water circuit.

[0094] The jet-induced enthalpy-enhancing variable frequency compressor 30 has an intake port 31, an exhaust port 32, and an intermediate gas injection port 33. The economizer 40 includes a main refrigerant passage 41 and a gas injection refrigerant passage 42. The user-side heat exchanger 20 includes a refrigerant condensation passage 21 and a user water passage 22, the user water passage 22 having a user-side return water port 221 and a user-side supply water port 222. A user-side return water temperature sensor 993 is installed at the user-side return water port 221 or the user-side return water pipeline, and a user-side supply water temperature sensor 994 is installed at the user-side supply water port 222 or the user-side supply water pipeline. The user-side circulating water pump 60 is installed in the user-side return water pipeline or the user-side supply water pipeline, used to allow user-side heating water to flow through the user water passage 22 and be heated.

[0095] like Figure 1 and Figure 2As shown, the heat exchanger 10 on the heat source side includes a heat exchanger body 101, a heat source water channel 11, a first refrigerant evaporation branch 12, and a second refrigerant evaporation branch 13. The heat source water channel 11 has a heat source water inlet 111 and a heat source water outlet 112. The heat source water inlet 111 is connected to the central heating water inlet pipe, and the heat source water outlet 112 is connected to the central heating water return pipe. The heat source water channel 11 sequentially forms a high-temperature section 113 and a low-temperature section 114 along the flow direction of the central heating water. After entering through the heat source water inlet 111, the central heating water first flows through the high-temperature section 113, then through the low-temperature section 114, and finally exits through the heat source water outlet 112.

[0096] The first refrigerant evaporation branch 12 is configured to exchange heat with the low-temperature section 114 of the heat source water, and the second refrigerant evaporation branch 13 is configured to exchange heat with the high-temperature section 113 of the heat source water. In other words, the second refrigerant evaporation branch 13 mainly corresponds to the front section of the central heating water with a higher temperature, and is used for the main heat extraction; the first refrigerant evaporation branch 12 mainly corresponds to the rear section of the central heating water with a lower temperature, and is used for cold-end protection heat extraction.

[0097] Furthermore, the heat exchanger 10 on the heat source side is provided with a heat source water channel baffle 14 and a refrigerant flow channel baffle 15. The heat source water channel baffle 14 is used to define the high-temperature section 113 and the low-temperature section 114 of the heat source water, and the refrigerant flow channel baffle 15 is used to separate the first refrigerant evaporation branch 12 and the second refrigerant evaporation branch 13 from each other within the heat exchanger body 101. In some embodiments, the heat exchange area of ​​the first refrigerant evaporation branch 12 is smaller than the heat exchange area of ​​the second refrigerant evaporation branch 13; and / or, the refrigerant flow cross-sectional area of ​​the first refrigerant evaporation branch 12 is larger than the refrigerant flow cross-sectional area of ​​the second refrigerant evaporation branch 13. This reduces the depth heat extraction intensity in the corresponding area of ​​the low-temperature water section and lowers the risk of localized overcooling in the low-temperature section 114 of the heat source water.

[0098] like Figure 1 and Figure 3 As shown, the exhaust port 32 of the vapor injection enthalpy-increasing variable frequency compressor 30, the refrigerant condensation channel 21 of the user-side heat exchanger 20, and the main refrigerant channel 41 of the economizer 40 are sequentially connected. The outlet of the main refrigerant channel 41 of the economizer 40 is connected to the first refrigerant evaporation branch 12 and the second refrigerant evaporation branch 13 via the throttling assembly 50. The outlets of the first refrigerant evaporation branch 12 and the second refrigerant evaporation branch 13 are connected to the suction port 31 of the vapor injection enthalpy-increasing variable frequency compressor 30 via the suction manifold pressure regulating assembly 70 to form a main refrigerant circulation loop.

[0099] Specifically, the throttling assembly 50 includes a first branch throttling valve 51, a second branch throttling valve 52, and a gas injection throttling valve 53. The main refrigerant channel 41 outlet of the economizer 40 is branched to form a first evaporation branch 54 and a second evaporation branch 55. The first evaporation branch 54 is connected to the first refrigerant evaporation branch 12 via the first branch throttling valve 51, and the second evaporation branch 55 is connected to the second refrigerant evaporation branch 13 via the second branch throttling valve 52.

[0100] The water source heat pump unit 100 also includes a gas replenishment branch 56. One end of the gas replenishment branch 56 is connected to the pipe section between the outlet of the refrigerant condensation channel 21 of the user-side heat exchanger 20 and the inlet of the main refrigerant channel 41 of the economizer 40. The other end is connected to the gas replenishment refrigerant channel 42 of the economizer 40 via the gas replenishment throttling valve 53. The outlet of the gas replenishment refrigerant channel 42 of the economizer 40 is connected to the intermediate gas replenishment port 33 of the vapor injection enthalpy-increasing inverter compressor 30 to form an intermediate gas replenishment circuit. During operation, a portion of the liquid refrigerant enters the gas replenishment refrigerant channel 42 after being throttled by the gas replenishment throttling valve 53, and exchanges heat with the main refrigerant flowing through the main refrigerant channel 41 in the economizer 40, forming intermediate pressure refrigerant vapor before entering the intermediate gas replenishment port 33.

[0101] like Figure 1 and Figure 4 As shown, the suction manifold pressure regulating assembly 70 includes a first branch pressure maintaining valve 71, a suction manifold 72, and a gas-liquid separator 73. The first branch pressure maintaining valve 71 is located at the outlet side of the first refrigerant evaporation branch 12, and is used to ensure that the refrigerant pressure between the outlet of the first refrigerant evaporation branch 12 and the inlet of the first branch pressure maintaining valve 71 is higher than the refrigerant pressure at the outlet of the second refrigerant evaporation branch 13. The outlet of the first refrigerant evaporation branch 12 is connected to the suction manifold 72 via the first branch pressure maintaining valve 71, and the outlet of the second refrigerant evaporation branch 13 is also connected to the suction manifold 72. The suction manifold 72 is connected to the suction port 31 of the vapor injection enthalpy-enhancing variable frequency compressor 30 via the gas-liquid separator 73.

[0102] Therefore, although the first refrigerant evaporation branch 12 and the second refrigerant evaporation branch 13 ultimately converge at the suction port 31 of the jet enthalpy-increasing inverter compressor 30, the pressure holding function of the first branch pressure holding valve 71 enables the first refrigerant evaporation branch 12 to maintain a higher evaporation pressure and a higher refrigerant evaporation saturation temperature. In this embodiment, the refrigerant evaporation saturation temperature corresponding to the first refrigerant evaporation branch 12 is higher than that corresponding to the second refrigerant evaporation branch 13, and the temperature difference between the two is preferably 2°C to 10°C; or, the evaporation pressure of the first refrigerant evaporation branch 12 is higher than that of the second refrigerant evaporation branch 13, and the pressure difference between the two is preferably 0.05 MPa to 0.30 MPa.

[0103] Furthermore, the first branch pressure holding valve 71 can be an electronic back pressure valve or a mechanical pressure holding valve. When the evaporation saturation temperature of the first branch is lower than the target evaporation saturation temperature of the first branch, the controller 90 reduces the opening of the first branch pressure holding valve 71 or increases the set back pressure of the first branch pressure holding valve 71 to increase the refrigerant pressure between the outlet of the first refrigerant evaporation branch 12 and the inlet of the first branch pressure holding valve 71; when the superheat of the first branch is lower than the preset lower limit of the first branch superheat, the controller 90 reduces the opening of the first branch throttle valve 51; when the superheat of the first branch is higher than the preset upper limit of the first branch superheat and the cold end heat exchange safety parameters meet the preset safety conditions, the controller 90 increases the opening of the first branch throttle valve 51.

[0104] like Figure 4 As shown, the water source heat pump unit 100 also includes a first branch evaporation pressure detection device 91, a second branch evaporation pressure detection device 92, a first branch outlet temperature detection device 93, a second branch outlet temperature detection device 94, a heat source water low-temperature section outlet water temperature detection device 95, a wall surface temperature detection device 96, a gas supply temperature detection device 97, a gas supply pressure detection device 98, an exhaust temperature detection device 99, an exhaust pressure detection device 991, a heat source water high-temperature section inlet water temperature detection device 992, a user-side return water temperature detection device 993, and a user-side supply water temperature detection device 994.

[0105] The first branch evaporation pressure detection element 91 is located between the outlet of the first refrigerant evaporation branch 12 and the inlet of the first branch pressure holding valve 71, and the second branch evaporation pressure detection element 92 is located at the outlet side of the second refrigerant evaporation branch 13. The first branch outlet temperature detection element 93 and the second branch outlet temperature detection element 94 are used to detect the outlet temperature of the corresponding refrigerant evaporation branch. The heat source water low-temperature section outlet water temperature detection element 95 is located at the outlet side of the heat source water outlet 112 or the heat source water low-temperature section 114. The wall surface temperature detection element 96 is located on the heat exchange wall surface corresponding to the first refrigerant evaporation branch 12. The gas injection temperature detection element 97 and the gas injection pressure detection element 98 are located between the outlet of the gas injection refrigerant channel 42 of the economizer 40 and the intermediate gas injection port 33. The exhaust temperature detection element 99 and the exhaust pressure detection element 991 are located in the downstream pipe section of the exhaust port 32 of the jet enthalpy-increasing variable frequency compressor 30. The inlet water temperature detection device 992 of the high-temperature section of the heat source water is installed on the inlet side of the heat source water inlet 111 or the high-temperature section 113 of the heat source water. The user-side return water temperature detection device 993 and the user-side supply water temperature detection device 994 are respectively installed on the pipelines corresponding to the user-side return water inlet 221 and the user-side supply water inlet 222.

[0106] The preset maximum heat exchange temperature difference threshold is pre-calibrated based on the freezing temperature of the heat source water, the heat transfer temperature difference of the heat exchanger 10 on the heat source side, and the anti-freezing safety margin. The preset low-temperature protection temperature can be from 20℃ to 28℃, and the preset wall protection temperature can be from 2℃ to 8℃. The preset upper and lower limits of superheat of the first branch, the preset upper and lower limits of superheat of the second branch, and the preset upper and lower limits of superheat of the make-up gas are pre-calibrated based on the refrigerant type, the design conditions of the heat exchanger, and the operating envelope of the vapor injection enthalpy-increasing variable frequency compressor 30. The preset upper limit of exhaust temperature and the preset upper limit of exhaust pressure are determined based on the allowable exhaust temperature and allowable exhaust pressure of the vapor injection enthalpy-increasing variable frequency compressor 30. The preset high-temperature section heat extraction temperature can be pre-set based on the design inlet water temperature of the centralized heating water, the target supply water temperature on the user side, or the operating frequency range of the compressor. The preset allowable enthalpy-increasing temperature is higher than the preset low-temperature protection temperature and is pre-calibrated based on the available heat on the heat source side and the operating envelope of the vapor injection enthalpy-increasing variable frequency compressor 30.

[0107] The controller 90 is electrically connected to the jet enthalpy-increasing variable frequency compressor 30, the first branch throttle valve 51, the second branch throttle valve 52, the air replenishment throttle valve 53, the first branch pressure holding valve 71, the hot gas regeneration valve 82, the user-side circulating water pump 60, and the first branch evaporation pressure detection device 91, the second branch evaporation pressure detection device 92, the first branch outlet temperature detection device 93, the second branch outlet temperature detection device 94, the low-temperature section outlet temperature detection device 95 of the heat source water, the wall temperature detection device 96, the air replenishment temperature detection device 97, the air replenishment pressure detection device 98, the exhaust temperature detection device 99, the exhaust pressure detection device 991, the high-temperature section inlet temperature detection device 992 of the heat source water, the user-side return water temperature detection device 993, and the user-side supply water temperature detection device 994. The controller 90 generates control commands according to the control priority of exhaust safety, cold end protection and user-side load adjustment decreasing in sequence: when the exhaust safety status is abnormal, enthalpy increase and hot gas regeneration are prohibited and compressor frequency increase is limited; when the cold end heat exchange safety parameters do not meet the preset safety conditions, the cold end protection of the first refrigerant evaporation branch 12 is executed first; when the exhaust safety status is normal and the cold end heat exchange safety parameters meet the preset safety conditions, the heating capacity is adjusted according to the user-side heating load parameters.

[0108] The controller 90 converts the evaporation pressure of the first branch, the evaporation pressure of the second branch, and the makeup gas pressure into the evaporation saturation temperature of the first branch, the evaporation saturation temperature of the second branch, and the makeup gas saturation temperature, respectively, based on the pre-stored pressure-saturation temperature relationship corresponding to the refrigerant used. The controller 90 determines the superheat of the first branch and the second branch based on the difference between the corresponding outlet temperature and the evaporation saturation temperature, and determines the makeup gas superheat based on the difference between the makeup gas temperature and the makeup gas saturation temperature. When the corresponding superheat is lower than a preset lower limit, the controller 90 reduces the opening of the corresponding throttle valve; when the corresponding superheat is higher than a preset upper limit and the corresponding safety conditions permit, the controller 90 increases the opening of the corresponding throttle valve. During cold end protection, the opening of the first branch throttle valve 51 is also limited by the maximum opening of the cold end protection.

[0109] like Figure 5As shown, one end of the hot gas pulse regeneration branch 80 is connected to the downstream pipe section of the exhaust port 32 of the jet enthalpy-increasing inverter compressor 30, and the other end is connected to the inlet side or middle of the first refrigerant evaporation branch 12. A hot gas regeneration valve 82 is provided on the hot gas pulse regeneration branch 80, and a one-way valve 83 and / or a flow restrictor 84 are provided between the hot gas regeneration valve 82 and the first refrigerant evaporation branch 12. The one-way valve 83 is used to restrict the refrigerant in the first refrigerant evaporation branch 12 from flowing back into the hot gas pulse regeneration branch 80, and the flow restrictor 84 is used to restrict the flow rate of high-temperature refrigerant vapor diverted from the downstream pipe section of the exhaust port 32 of the jet enthalpy-increasing inverter compressor 30 and entering the first refrigerant evaporation branch 12 via the hot gas pulse regeneration branch 80.

[0110] During operation, the controller 90 acquires the outlet temperature of the low-temperature section of the heat source water, the inlet temperature of the high-temperature section of the heat source water, the heat exchange wall temperature corresponding to the first refrigerant evaporation branch 12, the evaporation pressure and outlet temperature of the two refrigerant evaporation branches, the user-side supply water temperature and user-side return water temperature, the make-up gas temperature and pressure, and the exhaust temperature and pressure. The controller 90 determines the evaporation saturation temperature of the first branch, the evaporation saturation temperature of the second branch, and the make-up gas saturation temperature based on the pre-stored refrigerant pressure-saturation temperature relationship, and further determines the superheat of the first branch, the superheat of the second branch, and the superheat of the make-up gas.

[0111] The controller 90 determines the cold-end heat exchange temperature difference ΔTc as the difference between the outlet temperature of the low-temperature section of the heat source water and the evaporation saturation temperature of the first branch. When the cold-end heat exchange temperature difference ΔTc is not greater than a preset maximum heat exchange temperature difference threshold, the outlet temperature of the low-temperature section of the heat source water is not lower than a preset low-temperature protection temperature, and the heat exchange wall temperature is not lower than a preset wall protection temperature, the controller 90 determines that the cold-end heat exchange safety parameters meet the preset safety conditions. When at least one of the above three conditions is not met, the controller 90 determines that the cold-end heat exchange safety parameters do not meet the preset safety conditions. Since the cold-end heat exchange temperature difference ΔTc is equal to the outlet temperature of the low-temperature section of the heat source water minus the evaporation saturation temperature of the first branch, increasing the evaporation saturation temperature of the first branch can reduce the cold-end heat exchange temperature difference ΔTc when the outlet temperature of the low-temperature section of the heat source water remains constant, causing the cold-end heat exchange temperature difference ΔTc to change in a direction not greater than the preset maximum heat exchange temperature difference threshold.

[0112] The controller 90 determines the user-side heating load parameters based on the user-side supply water temperature and the user-side return water temperature. The user-side heating load parameters are dimensionless parameters ranging from 0 to 100%. The controller 90 determines the supply water temperature deviation as the difference between the target user-side supply water temperature and the current user-side supply water temperature, and determines the supply and return water temperature difference as the difference between the current user-side supply water temperature and the current user-side return water temperature. The controller 90 divides the supply water temperature deviation and the supply and return water temperature difference by their respective preset calibration upper limits to obtain normalized values ​​for the supply water temperature deviation and the supply and return water temperature difference, both limited to the range of 0 to 1. The weighted sum of the two normalized values ​​multiplied by 100% is then used to determine the user-side heating load parameters, where both weights are greater than 0 and their sum is 1. The preset calibration upper limit and the two weights are pre-calibrated based on test data of the user-side supply water temperature, user-side return water temperature, and heating capacity under rated heating conditions. When the user-side water supply temperature is lower than the user-side target water supply temperature, the user-side heating load parameter increases relative to the baseline value when the user-side water supply temperature reaches the target. When the supply and return water temperature difference increases or the user-side return water temperature continues to decrease, the user-side heating load parameter increases relative to the previous control cycle. The user-side supply water temperature and the user-side return water temperature are collected by the user-side supply water temperature detection device 994 and the user-side return water temperature detection device 993, respectively.

[0113] When the exhaust safety status is normal and the cold-end heat exchange safety parameters meet the preset safety conditions, the controller 90 adjusts the operating frequency of the jet enthalpy-increasing variable frequency compressor 30 and the opening degree of each throttling valve according to the user-side heating load parameters, the superheat of the first branch, the superheat of the second branch, and the superheat of the make-up gas. When the user-side heating load parameters increase, the controller 90 gradually increases the compressor operating frequency, the refrigerant mass flow rate of the second refrigerant evaporation branch 13, and the make-up gas quantity within the exhaust safety and superheat constraints; when the user-side heating load parameters decrease, the controller 90 adjusts in the opposite direction.

[0114] When the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the heating load parameters on the user side increase, the exhaust safety status is normal, and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, the controller 90 increases the opening of the second branch throttle valve 52 while maintaining the superheat of the second branch within the preset range, so as to increase the refrigerant mass flow rate and heat extraction of the second refrigerant evaporation branch 13, so that the first refrigerant evaporation branch 12 undertakes cold end protection heat extraction, and the second refrigerant evaporation branch 13 undertakes main heat extraction.

[0115] When the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller 90 reduces the opening of the first branch pressure holding valve 71 or increases its set back pressure to increase the evaporation pressure and saturation temperature of the first branch. Simultaneously, it applies a maximum opening limit for cold-end protection to the first branch throttling valve 51 and reduces its opening to limit the refrigerant mass flow rate of the first refrigerant evaporation branch 12. When the superheat of the first branch is lower than the preset lower limit of the first branch superheat, the controller 90 further reduces the opening of the first branch throttling valve 51. Before the cold-end heat exchange safety parameters are restored, the first branch throttling valve 51 is not allowed to exceed the maximum opening limit for cold-end protection.

[0116] Furthermore, this embodiment employs a cold-end safety margin to implement continuous graded protection for the first refrigerant evaporation branch 12. The controller 90 determines the difference between the preset maximum heat exchange temperature difference threshold and the current cold-end heat exchange temperature difference ΔTc as the heat exchange temperature difference safety margin, the difference between the current low-temperature outlet temperature of the heat source water and the preset low-temperature protection temperature as the outlet water temperature safety margin, and the difference between the current heat exchange wall temperature and the preset wall protection temperature as the wall temperature safety margin. The minimum value among the three safety margins is taken as the current cold-end safety margin, thereby enabling the cold-end safety margin to characterize the cold-end operating parameter that is closest to the protection boundary. The controller 90 pre-stores the correspondence between the cold end safety margin, the target temperature difference, and the maximum opening of the cold end protection. This correspondence is obtained through unit prototype calibration tests: under multiple preset calibration conditions of heat source water inlet temperature, heat source water flow rate, user-side heating load parameters, and the operating frequency of the jet enthalpy-increasing variable frequency compressor 30, the set back pressure of the first branch pressure holding valve 71 and the opening of the first branch throttle valve 51 are changed step by step. The cold end safety margin, the temperature difference between the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch, and the opening of the first branch throttle valve 51 are recorded when the cold end heat exchange safety parameters meet the preset safety conditions and the superheat of the first branch is within the preset range. According to the value range of the cold end safety margin, the temperature difference that can maintain the above safety conditions and the maximum allowable opening of the first branch throttle valve 51 are determined as the target temperature difference and the maximum opening of the cold end protection for the corresponding range, respectively, and a lookup table is formed and stored in the controller 90. The target temperature difference is the difference between the target evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch, and is limited to a range of 2°C to 10°C. The smaller the cold-end safety margin, the larger the corresponding target temperature difference, and the smaller the maximum opening of the cold-end protection of the corresponding first branch throttle valve 51. The controller 90 reduces the opening of the first branch pressure holding valve 71 or increases its set back pressure to make the actual temperature difference between the evaporation saturation temperatures of the first and second branches approach the target temperature difference, and limits the opening of the first branch throttle valve 51 to within the corresponding maximum opening of the cold-end protection. When the cold-end safety margin is not lower than the preset recovery margin for 3 to 20 consecutive preset control cycles, the controller gradually decreases the target temperature difference and gradually increases the maximum opening of the cold-end protection. During the gradual release of the restriction, when the cold-end safety margin decreases again, the controller 90 re-increases the target temperature difference and decreases the maximum opening of the cold-end protection.Specifically, when calibrating the preset recovery margin, preset control cycle, and adjustment range, the detection sampling cycle is first determined based on the detection update cycle of each detection element; then, a preset small step is applied to the first branch pressure holding valve 71 and the first branch throttle valve 51 respectively, and the valve response time required for the valve position to reach stability and the heat source heat exchanger thermal response time required for the cold end heat exchange temperature difference ΔTc to reach a new stable value are recorded; the preset control cycle is set to be no less than the detection sampling cycle and the valve response time, and the holding time of the same level control quantity is no less than the heat source heat exchanger thermal response time; the preset recovery margin is determined based on the sum of the maximum fluctuation of the three safety margins under steady-state conditions and the measurement error of the corresponding detection element; the maximum change value of the control quantity that will not cause the cold end heat exchange safety parameter to cross the preset safety boundary and will not cause the valve to reciprocate within a single preset control cycle is used as the adjustment range for each adjustment.

[0117] If adjusting the first branch pressure holding valve 71 and the first branch throttle valve 51 fails to restore the cold-end heat exchange safety parameters, the controller 90 re-verifies the exhaust safety status. Only when the exhaust safety status is normal, the controller 90 controls the hot gas regeneration valve 82 to open in a pulse manner, and keeps the first branch pressure holding valve 71 and the first branch throttle valve 51 in the cold-end protection state, allowing the high-temperature refrigerant vapor discharged from the exhaust port 32 of the jet enthalpy-increasing variable frequency compressor 30 and diverted from the downstream pipe section of the exhaust port 32 to enter the first refrigerant evaporation branch 12 via the hot gas pulse regeneration branch 80. The single opening time of the hot gas regeneration valve 82 can be from 2s to 30s, and the interval between two adjacent openings can be from 30s to 300s. When the cold end heat exchange safety parameters return to the preset safety conditions, the controller 90 closes the hot gas regeneration valve 82 and exits hot gas regeneration; when the exhaust safety status is abnormal, the controller 90 immediately closes the hot gas regeneration valve 82, limits the opening of the supplementary gas throttle valve 53 and the operating frequency of the jet enthalpy-enhancing variable frequency compressor 30, and performs shutdown protection when the abnormality continues.

[0118] This embodiment also provides a control method for a staged evaporative jet enthalpy-increasing water source heat pump unit. The control method can be executed by the controller 90 and specifically includes the following steps:

[0119] S1, obtain the outlet water temperature of the low-temperature section of the heat source water, the inlet water temperature of the high-temperature section of the heat source water, the heat exchange wall temperature corresponding to the first refrigerant evaporation branch, the evaporation pressure and outlet temperature of the two refrigerant evaporation branches, the user-side supply water temperature and user-side return water temperature, the gas replenishment temperature and gas replenishment pressure, and the exhaust temperature and exhaust pressure.

[0120] S2, determine the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch based on the pre-stored refrigerant pressure-saturation temperature relationship and the evaporation pressure of the two refrigerant evaporation branches respectively, and determine the superheat of the first branch and the superheat of the second branch based on the outlet temperature and evaporation saturation temperature of the corresponding refrigerant evaporation branches; determine the makeup gas saturation temperature based on the makeup gas pressure, and determine the makeup gas superheat based on the makeup gas temperature and the makeup gas saturation temperature;

[0121] S3, the difference between the outlet temperature of the low-temperature section of the heat source water and the evaporation saturation temperature of the first branch is determined as the cold end heat exchange temperature difference, and the cold end heat exchange safety parameters are determined based on the cold end heat exchange temperature difference, the outlet temperature of the low-temperature section of the heat source water, and the heat exchange wall temperature; the user-side heating load parameters are determined based on the user-side supply water temperature and the user-side return water temperature; the exhaust safety status is determined based on the exhaust temperature and the exhaust pressure.

[0122] S4. When the cold end heat exchange safety parameters meet the preset safety conditions, adjust the operating frequency of the jet enthalpy-increasing variable frequency compressor and the opening degree of the first branch throttling valve, the second branch throttling valve and the gas injection throttling valve according to the user-side heating load parameters, the first branch superheat, the second branch superheat, the gas injection superheat and the exhaust safety status.

[0123] S5, when the cold-end heat exchange safety parameters do not meet the preset safety conditions, reduce the opening of the first branch pressure holding valve or increase the set back pressure of the first branch pressure holding valve to increase the evaporation saturation temperature of the first branch; apply a maximum opening limit for cold-end protection to the first branch throttle valve and reduce the opening of the first branch throttle valve to limit the refrigerant mass flow rate of the first refrigerant evaporation branch; when the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the user-side heating load parameters increase, the exhaust safety status is normal and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, increase the opening of the second branch throttle valve while maintaining the superheat of the second branch within the preset range.

[0124] S6, when the cold end heat exchange safety parameters still do not meet the preset safety conditions after adjustment in step S5, the hot gas regeneration valve is controlled to open in a pulse manner only when the exhaust safety status is normal; when the cold end heat exchange safety parameters recover or the exhaust safety status is abnormal, the hot gas regeneration valve is closed.

[0125] Furthermore, the controller 90 determines the exhaust safety status based on the exhaust temperature and exhaust pressure. When the exhaust temperature is not higher than the preset upper limit of exhaust temperature and the exhaust pressure is not higher than the preset upper limit of exhaust pressure, the exhaust safety status is determined to be normal; otherwise, the exhaust safety status is determined to be abnormal. The controller 90 processes control requests according to the control priority decreasing sequentially from exhaust safety, cold end protection, to user-side load regulation. Higher priority control requests can limit or cover lower priority control requests.

[0126] The controller 90 switches between normal heating mode M1, enthalpy-increasing heating mode M2, cold end protection mode M3, and hot gas regeneration mode M4 based on the cold end heat exchange safety parameters, user-side heating load parameters, exhaust safety status, and superheat of each branch. When the exhaust safety status is abnormal, the controller 90 prohibits entering enthalpy-increasing heating mode M2 ​​and hot gas regeneration mode M4.

[0127] When the exhaust safety status is normal and the cold-end heat exchange safety parameters meet the preset safety conditions, if the user-side heating load parameters do not increase, or if the user-side heating load parameters increase but the outlet water temperature of the low-temperature section of the heat source water is lower than the preset enthalpy increase allowable temperature, then the controller 90 enters the normal heating mode M1. In the normal heating mode M1, the controller 90 maintains the normal adjustment of the compressor and each throttling valve according to the user-side target water supply temperature and the superheat of each branch, so that the user-side water supply temperature is kept within the preset water supply temperature range.

[0128] When the exhaust safety status is normal, the cold-end heat exchange safety parameters meet the preset safety conditions, the user-side heating load parameters increase, and the outlet water temperature of the low-temperature section of the heat source water is not lower than the preset enthalpy-increasing allowable temperature, the controller 90 enters the enthalpy-increasing heating mode M2. In the enthalpy-increasing heating mode M2, the controller 90 increases the opening of the gas injection throttle valve 53 under the condition that the gas injection superheat is not lower than the preset lower limit of gas injection superheat, and can increase the operating frequency of the jet enthalpy-increasing variable frequency compressor 30; when the gas injection superheat is lower than the preset lower limit of gas injection superheat, the controller 90 decreases the opening of the gas injection throttle valve 53.

[0129] When the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller 90 enters the cold-end protection mode M3. In the cold-end protection mode M3, the controller 90 increases the evaporation pressure and saturation temperature of the first branch through the first branch pressure holding valve 71, and applies a maximum opening limit for cold-end protection to the first branch throttling valve 51 and reduces its opening, thereby reducing the refrigerant mass flow rate of the first refrigerant evaporation branch 12. After the cold-end heat exchange safety parameters are restored, the controller 90 exits the cold-end protection mode M3.

[0130] When the cold-end protection mode M3 fails to restore the cold-end heat exchange safety parameters and the exhaust safety status is normal, the controller 90 enters the hot gas regeneration mode M4. In the hot gas regeneration mode M4, the controller 90 pulses open the hot gas regeneration valve 82 and limits the increase in the operating frequency of the jet enthalpy-enhancing variable frequency compressor 30; when the cold-end heat exchange safety parameters are restored or the exhaust safety status is abnormal, the controller 90 immediately closes the hot gas regeneration valve 82 and exits the hot gas regeneration mode M4.

[0131] The above control process is repeated according to a preset control cycle. Within each control cycle, the controller 90 re-acquires operating parameters from the heat source side, the two refrigerant evaporation branches, the make-up gas branch, the user side, and downstream of the exhaust port 32 of the jet enthalpy-enhancing variable frequency compressor 30. To avoid frequent switching of valves and operating modes near thresholds, a preset hysteresis can be set between the entry and exit thresholds; the preset control cycle and preset hysteresis are pre-set based on the detection sampling cycle, valve response time, and compressor control cycle. Thus, the unit can continuously balance heating capacity, cold-end protection, and exhaust safety even when the central heating water temperature and user-side heating load parameters change.

[0132] It should be noted that the terms "first," "second," etc., used in this invention are only used to distinguish identical or similar components and do not indicate order, quantity, or importance; the directional terms such as "upper," "lower," "inner," "outer," "front," and "rear" are only for reference to the structure shown in the accompanying drawings and do not constitute a limitation on the actual installation direction. The above embodiments are only preferred embodiments of this invention, and equivalent substitutions or modifications made by those skilled in the art without departing from the concept of this invention should all fall within the protection scope of this invention.

Claims

1. A staged evaporative vapor injection enthalpy-increasing water source heat pump unit, comprising a heat source-side heat exchanger, a user-side heat exchanger, a vapor injection enthalpy-increasing variable frequency compressor, an economizer, a throttling component, a user-side circulating water pump, a suction manifold pressure regulating component, and a controller, wherein the heat source-side heat exchanger is used to connect to a centralized heating water circuit, the user-side heat exchanger is used to release heat to the user-side heating water circuit, and the user-side circulating water pump is used to drive the user-side heating water to circulate between the user-side heat exchanger and the user-side heating water circuit, characterized in that: The jet-induced enthalpy-enhancing variable frequency compressor has an intake port, an exhaust port, and an intermediate gas injection port; the economizer includes a main refrigerant channel and a gas injection refrigerant channel; the heat source side heat exchanger includes a heat source water channel, a first refrigerant evaporation branch, and a second refrigerant evaporation branch. The heat source water channel forms a high-temperature section and a low-temperature section of heat source water sequentially along the flow direction of the central heating water. The first refrigerant evaporation branch is arranged to exchange heat with the low-temperature section of the heat source water, and the second refrigerant evaporation branch is arranged to exchange heat with the high-temperature section of the heat source water. The exhaust port of the jet enthalpy-increasing variable frequency compressor, the refrigerant condensation channel of the user-side heat exchanger, and the main refrigerant channel of the economizer are connected in sequence. The outlet of the main refrigerant channel of the economizer is connected to the first refrigerant evaporation branch and the second refrigerant evaporation branch respectively through the throttling component. The outlets of the first refrigerant evaporation branch and the second refrigerant evaporation branch are connected to the suction port of the jet enthalpy-increasing variable frequency compressor through the suction manifold pressure regulating component to form a main refrigerant circulation loop. The water source heat pump unit also includes a gas supply branch. One end of the gas supply branch is connected to the pipe section between the refrigerant condensation channel outlet of the user-side heat exchanger and the main refrigerant channel inlet of the economizer. The other end is connected to the gas supply refrigerant channel of the economizer via the throttling component. The gas supply refrigerant channel outlet of the economizer is connected to the intermediate gas supply port of the jet enthalpy-increasing variable frequency compressor to form an intermediate gas supply circuit. The controller is used to control the throttling component and the suction manifold pressure regulating component so that the evaporation saturation temperature of the first branch corresponding to the first refrigerant evaporation branch is higher than the evaporation saturation temperature of the second branch corresponding to the second refrigerant evaporation branch.

2. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 1, characterized in that: The throttling assembly includes a first branch throttling valve, a second branch throttling valve, and a gas injection throttling valve; the main refrigerant channel outlet of the economizer is split to form a first evaporation branch and a second evaporation branch; The first evaporation branch is connected to the first refrigerant evaporation branch via the first branch throttle valve, and the second evaporation branch is connected to the second refrigerant evaporation branch via the second branch throttle valve; The gas supply branch is connected to the gas supply refrigerant channel of the economizer via the gas supply throttle valve, and the outlet of the gas supply refrigerant channel of the economizer is connected to the intermediate gas supply port.

3. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 2, characterized in that: The suction manifold pressure regulating assembly includes a first branch pressure holding valve, a suction manifold cavity, and a gas-liquid separator. The first branch pressure holding valve is located at the outlet side of the first refrigerant evaporation branch and is used to ensure that the refrigerant pressure between the outlet of the first refrigerant evaporation branch and the inlet of the first branch pressure holding valve is higher than the refrigerant pressure at the outlet of the second refrigerant evaporation branch. The outlet of the first refrigerant evaporation branch is connected to the suction manifold cavity via the first branch pressure holding valve, and the outlet of the second refrigerant evaporation branch is connected to the suction manifold cavity. The suction manifold cavity is connected to the suction port of the jet enthalpy-increasing variable frequency compressor via the gas-liquid separator.

4. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 1, characterized in that: The heat source side heat exchanger includes a heat exchanger body, a heat source water channel baffle and a refrigerant flow channel baffle disposed in the heat exchanger body. The heat source water channel partition is used to define the high-temperature section and the low-temperature section of the heat source water. The refrigerant flow channel baffle is used to separate the first refrigerant evaporation branch and the second refrigerant evaporation branch from each other within the heat exchanger body; The heat exchange area of ​​the first refrigerant evaporation branch is smaller than the heat exchange area of ​​the second refrigerant evaporation branch; and / or, The refrigerant flow cross-sectional area of ​​the first refrigerant evaporation branch is larger than that of the second refrigerant evaporation branch.

5. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 3, characterized in that: The water source heat pump unit also includes a first branch evaporation pressure detection device, a second branch evaporation pressure detection device, a first branch outlet temperature detection device, a second branch outlet temperature detection device, a user-side return water temperature detection device, and a user-side supply water temperature detection device. The first branch evaporation pressure detection device is located between the outlet of the first refrigerant evaporation branch and the inlet of the first branch pressure holding valve, and the second branch evaporation pressure detection device is located on the outlet side of the second refrigerant evaporation branch; The first branch outlet temperature detector and the second branch outlet temperature detector are used to detect the outlet temperature of the corresponding refrigerant evaporation branch, respectively. The user-side return water temperature detector and the user-side supply water temperature detector are respectively installed in the user-side return water pipeline and the user-side supply water pipeline of the user-side heat exchanger. The controller determines the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch based on the pre-stored refrigerant pressure-saturation temperature relationship and the evaporation pressure of the two refrigerant evaporation branches, and determines the superheat of the first branch and the superheat of the second branch based on the outlet temperature and evaporation saturation temperature of the corresponding refrigerant evaporation branches. When the superheat of the first branch is lower than the preset lower limit of the first branch superheat, the controller reduces the opening of the throttle valve of the first branch; when the superheat of the first branch is higher than the preset upper limit of the first branch superheat, the controller increases the opening of the throttle valve of the first branch; when the superheat of the second branch is lower than the preset lower limit of the second branch superheat, the controller reduces the opening of the throttle valve of the second branch; when the superheat of the second branch is higher than the preset upper limit of the second branch superheat, the controller increases the opening of the throttle valve of the second branch.

6. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 5, characterized in that: The water source heat pump unit also includes a heat source water low-temperature section outlet temperature detection device, a heat source water high-temperature section inlet temperature detection device, a wall temperature detection device, an exhaust temperature detection device, and an exhaust pressure detection device. The wall temperature detection device is used to detect the heat exchange wall temperature corresponding to the first refrigerant evaporation branch. The exhaust temperature detection device and the exhaust pressure detection device are installed in the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor. The controller determines the cold end heat exchange temperature difference as the difference between the outlet temperature of the low-temperature section of the heat source water and the evaporation saturation temperature of the first branch. When the cold end heat exchange temperature difference is greater than the preset maximum heat exchange temperature difference threshold, the outlet temperature of the low-temperature section of the heat source water is lower than the preset low-temperature protection temperature, or the heat exchange wall temperature is lower than the preset wall protection temperature, it is determined that the cold end heat exchange safety parameters do not meet the preset safety conditions. When the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller reduces the opening of the first branch pressure holding valve or increases the set back pressure of the first branch pressure holding valve to increase the evaporation saturation temperature of the first branch, and applies a maximum opening limit for cold-end protection to the first branch throttle valve and reduces the opening of the first branch throttle valve to limit the refrigerant mass flow rate of the first refrigerant evaporation branch. When the exhaust temperature is not higher than the preset exhaust temperature limit and the exhaust pressure is not higher than the preset exhaust pressure limit, the controller determines that the exhaust safety status is normal; otherwise, it determines that the exhaust safety status is abnormal. The controller determines the user-side heating load parameters based on the user-side supply water temperature and user-side return water temperature detected by the user-side supply water temperature detector and the user-side return water temperature detector; when the user-side supply water temperature is lower than the user-side target supply water temperature, the temperature difference between the user-side supply water temperature and the user-side return water temperature increases, or the user-side return water temperature continues to decrease, the controller determines that the user-side heating load parameters increase; When the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the heating load parameters on the user side increase, the exhaust safety status is normal, and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, the controller increases the opening of the throttle valve of the second branch while maintaining the superheat of the second branch within the preset range.

7. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 2, characterized in that: The water source heat pump unit also includes a gas supply temperature detection device, a gas supply pressure detection device, an exhaust temperature detection device, and an exhaust pressure detection device; The gas injection temperature detection device and the gas injection pressure detection device are located between the gas injection refrigerant channel outlet of the economizer and the intermediate gas injection port; the exhaust temperature detection device and the exhaust pressure detection device are located in the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor. The controller determines the gas supply saturation temperature based on the gas supply pressure detected by the gas supply pressure detection device, and determines the gas supply superheat based on the gas supply temperature detected by the gas supply temperature detection device and the gas supply saturation temperature. When the superheat of the replenished gas is lower than the preset lower limit of the superheat of the replenished gas, the controller reduces the opening of the replenished gas throttle valve; When the superheat of the replenished gas is higher than the preset upper limit of the superheat of the replenished gas, and the exhaust temperature is not higher than the preset upper limit of the exhaust temperature and the exhaust pressure is not higher than the preset upper limit of the exhaust pressure, the controller increases the opening of the replenished gas throttle valve to increase the amount of intermediate pressure refrigerant vapor entering the intermediate replenished gas port. When the exhaust temperature is higher than the preset exhaust temperature limit or the exhaust pressure is higher than the preset exhaust pressure limit, the controller prohibits the increase of the opening of the gas injection throttle valve and limits the increase of the operating frequency of the jet enthalpy-enhancing variable frequency compressor.

8. The staged evaporative jet enthalpy-increasing water source heat pump unit according to claim 6, characterized in that: The water source heat pump unit also includes a hot gas pulse regeneration branch, one end of which is connected to the downstream pipe section of the exhaust port of the jet enthalpy-increasing variable frequency compressor, and the other end is connected to the inlet side or the middle of the first refrigerant evaporation branch; a hot gas regeneration valve is provided on the hot gas pulse regeneration branch, and a one-way valve and / or flow restrictor are provided between the hot gas regeneration valve and the first refrigerant evaporation branch; Before opening the hot gas regeneration valve, the controller keeps the first branch pressure holding valve and the first branch throttle valve in cold end protection state, and then obtains the exhaust temperature detected by the exhaust temperature detection device and the exhaust pressure detected by the exhaust pressure detection device again. When the cold-end heat exchange safety parameter does not meet the preset safety conditions, and the cold-end heat exchange safety parameter cannot be restored by adjusting the first branch pressure holding valve and the first branch throttle valve, the controller controls the hot gas regeneration valve to open in a pulse manner only when the exhaust safety status is normal; when the cold-end heat exchange safety parameter is restored or the exhaust safety status is abnormal, the controller closes the hot gas regeneration valve and limits the increase in the operating frequency of the jet enthalpy-increasing variable frequency compressor.

9. A control method for a staged evaporative jet enthalpy-increasing water source heat pump unit, characterized in that, The process is executed by the controller of the staged evaporative jet enthalpy-increasing water source heat pump unit; the water source heat pump unit includes a heat source-side heat exchanger, a user-side heat exchanger, a jet enthalpy-increasing variable frequency compressor, an economizer, a first branch throttle valve, a second branch throttle valve, a make-up gas throttle valve, a first branch pressure holding valve, a hot gas pulse regeneration branch, and a hot gas regeneration valve. The heat exchanger on the heat source side includes a high-temperature section and a low-temperature section of heat source water formed sequentially along the flow direction of the heat source water, as well as a first refrigerant evaporation branch and a second refrigerant evaporation branch separated from each other; the first refrigerant evaporation branch is arranged to exchange heat with the low-temperature section of the heat source water, and the second refrigerant evaporation branch is arranged to exchange heat with the high-temperature section of the heat source water; the pressure maintaining valve of the first branch is arranged on the outlet side of the first refrigerant evaporation branch; The economizer includes a main refrigerant channel and a makeup refrigerant channel. The outlet of the main refrigerant channel is connected to the first refrigerant evaporation branch and the second refrigerant evaporation branch via the first branch throttle valve and the second branch throttle valve, respectively. The makeup refrigerant branch branching off from the refrigerant condensation channel outlet of the user-side heat exchanger is connected to the makeup refrigerant channel via the makeup refrigerant throttle valve. The outlet of the makeup refrigerant channel is connected to the intermediate makeup refrigerant port of the vapor injection enthalpy-increasing variable frequency compressor. The hot gas pulse regeneration branch is connected between the downstream pipe section of the exhaust port of the vapor injection enthalpy-increasing variable frequency compressor and the first refrigerant evaporation branch. The hot gas regeneration valve is located in the hot gas pulse regeneration branch. The controller executes the control method according to the control priority decreasing sequentially from exhaust safety, cold end protection and user-side load regulation. The control method includes the following steps: S1, obtain the outlet water temperature of the low-temperature section of the heat source water, the inlet water temperature of the high-temperature section of the heat source water, the heat exchange wall temperature corresponding to the first refrigerant evaporation branch, the evaporation pressure and outlet temperature of the two refrigerant evaporation branches, the user-side supply water temperature and user-side return water temperature, the gas replenishment temperature and gas replenishment pressure, and the exhaust temperature and exhaust pressure. S2, determine the evaporation saturation temperature of the first branch and the evaporation saturation temperature of the second branch based on the pre-stored refrigerant pressure-saturation temperature relationship and the evaporation pressure of the two refrigerant evaporation branches respectively, and determine the superheat of the first branch and the superheat of the second branch based on the outlet temperature and evaporation saturation temperature of the corresponding refrigerant evaporation branches; determine the makeup gas saturation temperature based on the makeup gas pressure, and determine the makeup gas superheat based on the makeup gas temperature and the makeup gas saturation temperature; S3, the difference between the outlet temperature of the low-temperature section of the heat source water and the evaporation saturation temperature of the first branch is determined as the cold end heat exchange temperature difference, and the cold end heat exchange safety parameters are determined based on the cold end heat exchange temperature difference, the outlet temperature of the low-temperature section of the heat source water, and the heat exchange wall temperature; the user-side heating load parameters are determined based on the user-side supply water temperature and the user-side return water temperature; the exhaust safety status is determined based on the exhaust temperature and the exhaust pressure. S4. When the cold end heat exchange safety parameters meet the preset safety conditions, adjust the operating frequency of the jet enthalpy-increasing variable frequency compressor and the opening degree of the first branch throttling valve, the second branch throttling valve and the gas injection throttling valve according to the user-side heating load parameters, the first branch superheat, the second branch superheat, the gas injection superheat and the exhaust safety status. S5, when the cold-end heat exchange safety parameters do not meet the preset safety conditions, reduce the opening of the first branch pressure holding valve or increase the set back pressure of the first branch pressure holding valve to increase the evaporation saturation temperature of the first branch; apply a maximum opening limit for cold-end protection to the first branch throttle valve and reduce the opening of the first branch throttle valve to limit the refrigerant mass flow rate of the first refrigerant evaporation branch; when the inlet water temperature of the high-temperature section of the heat source water is higher than the preset high-temperature section heat extraction temperature, the user-side heating load parameters increase, the exhaust safety status is normal and the superheat of the second branch is not lower than the preset lower limit of the superheat of the second branch, increase the opening of the second branch throttle valve while maintaining the superheat of the second branch within the preset range; S6, when the cold end heat exchange safety parameters still do not meet the preset safety conditions after adjustment in step S5, the hot gas regeneration valve is controlled to open in a pulse manner only when the exhaust safety status is normal; when the cold end heat exchange safety parameters recover or the exhaust safety status is abnormal, the hot gas regeneration valve is closed.

10. The control method for a staged evaporative jet enthalpy-enhancing water source heat pump unit according to claim 9, characterized in that: When the cold end heat exchange temperature difference is not greater than the preset maximum heat exchange temperature difference threshold, the outlet water temperature of the low temperature section of the heat source water is not lower than the preset low temperature protection temperature, and the heat exchange wall temperature is not lower than the preset wall protection temperature, the cold end heat exchange safety parameters are determined to meet the preset safety conditions; when the exhaust temperature is not higher than the preset exhaust temperature upper limit and the exhaust pressure is not higher than the preset exhaust pressure upper limit, the exhaust safety status is determined to be normal; otherwise, the exhaust safety status is determined to be abnormal. When the exhaust safety status is normal and the cold-end heat exchange safety parameters meet the preset safety conditions, if the user-side heating load parameters do not increase, or if the user-side heating load parameters increase but the outlet temperature of the low-temperature section of the heat source water is lower than the preset enthalpy increase allowable temperature, then the controller enters the normal heating mode; if the user-side heating load parameters increase and the outlet temperature of the low-temperature section of the heat source water is not lower than the preset enthalpy increase allowable temperature, then the controller enters the enthalpy increase heating mode, and increases the opening of the air replenishment throttle valve under the condition that the air replenishment superheat is not lower than the preset air replenishment superheat lower limit; When the cold-end heat exchange safety parameters do not meet the preset safety conditions, the controller enters the cold-end protection mode, increases the evaporation saturation temperature of the first branch through the first branch pressure holding valve, and limits the refrigerant mass flow rate of the first refrigerant evaporation branch through the first branch throttling valve. When the cold end protection mode fails to restore the cold end heat exchange safety parameters and the exhaust safety status is normal, the controller enters the hot gas regeneration mode; when the cold end heat exchange safety parameters are restored or the exhaust safety status is abnormal, the controller exits the hot gas regeneration mode and closes the hot gas regeneration valve. In the hot gas regeneration mode, the single opening time of the hot gas regeneration valve is 2s to 30s, and the interval between two adjacent openings is 30s to 300s. The controller limits the increase in the operating frequency of the jet enthalpy-increasing inverter compressor. The above control process is repeated according to a preset control cycle. In each control cycle, the controller reacquires the operating parameters of the heat source side, the two refrigerant evaporation branches, the make-up gas branch, the user side, and the downstream of the exhaust port of the jet enthalpy-increasing inverter compressor.

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