A control method for a heat pump system

Abstract

This invention provides a control method for a heat pump system. Based on operating parameters and the current value of compressor 1, control parameters for the main circuit electronic expansion valve 8 are determined. Based on the operating parameters, combined with the current value of compressor 1 and the opening degree of the main circuit electronic expansion valve 8, control parameters for the auxiliary circuit electronic expansion valve 4 are determined. This method addresses the problems of excessive opening of the main circuit electronic expansion valve due to an unreasonable target return gas superheat setting, which results in insufficient auxiliary circuit flow, leading to poor heating capacity or compressor exhaust high temperature protection shutdown under high pressure ratio; and the problems of excessive refrigerant accumulation in the condenser due to an unreasonable target return gas superheat setting, causing excessive compressor exhaust pressure protection shutdown, or excessive auxiliary circuit flow, causing compressor overload and excessive compressor current protection shutdown. This significantly reduces the probability of unit failure and downtime, and improves product reliability.

Description

Technical Field

[0001] This invention relates to the field of heat pump control technology, and in particular to a control method for a heat pump system. Background Technology

[0002] For low-temperature air source heat pumps, the low ambient temperature in cold weather causes the evaporation pressure to be low during heat pump operation, resulting in a significant reduction in heating capacity. To solve this problem, the industry generally adopts vapor injection enthalpy enhancement to improve the heating capacity of heat pump systems at low temperatures.

[0003] When a heat pump is operating in heating mode, the economizer acts as an intermediate heat exchanger. The main electronic expansion valve controls the refrigerant flow to the evaporator, while the auxiliary electronic expansion valve controls the refrigerant injection into the compressor. Currently, the main electronic expansion valve's opening is controlled primarily based on the target return gas superheat, while the auxiliary electronic expansion valve's opening is controlled based on the auxiliary superheat and the compressor discharge temperature. The target return gas superheat is typically a manually set fixed value in the control software. Once set, the target return gas superheat remains unchanged. However, due to factors such as changes in operating conditions, a set target superheat is unlikely to be applicable to all operating conditions, leading to the main electronic expansion valve opening being too large or too small. When the main electronic expansion valve opening is too large, the auxiliary flow is too small, resulting in poor heating capacity or compressor high-temperature protection shutdown under high pressure ratios. When the main electronic expansion valve opening is too small, excessive refrigerant accumulation in the condenser leads to compressor high discharge pressure protection shutdown, or excessive auxiliary flow causes the compressor to work under heavy load, leading to compressor high current protection shutdown. The above problems are particularly pronounced for heat pump systems that use fixed-frequency compressors. Summary of the Invention

[0004] This invention provides a control method for a heat pump system to solve the problems mentioned in the background art.

[0005] A control method for a heat pump system, comprising:

[0006] S1: Obtain the structural distribution of the heat pump system and collect the operating parameters of the heat pump system from the structural distribution;

[0007] S2: Based on the aforementioned operating parameters and the compressor's current value, determine the control parameters for the main circuit electronic expansion valve;

[0008] S3: Based on the aforementioned operating parameters, combined with the compressor's current value and the opening degree of the main circuit electronic expansion valve, determine the control parameters for the auxiliary circuit electronic expansion valve.

[0009] Preferably, in step S1, the structural distribution of the heat pump system is obtained, including a compressor, a liquid supply pipe connected to the compressor, the other end of the liquid supply pipe being connected to an economizer, an auxiliary outlet temperature sensor being installed on the liquid supply pipe, a connecting pipe being connected to one end of the economizer, the other end of the connecting pipe being connected to a water-side heat exchanger, one end of the water-side heat exchanger being connected to valve C of a four-way valve via the connecting pipe, valve E of the four-way valve being connected to a finned tube heat exchanger via the connecting pipe, an ambient temperature sensor being installed on the finned tube heat exchanger, the other end of the finned tube heat exchanger being connected to the economizer via the connecting pipe, a main electronic expansion valve being installed on the connecting pipe between the finned tube heat exchanger and the economizer, a branch connecting pipe being installed on the connecting pipe between the finned tube heat exchanger and the economizer, the other end of the branch connecting pipe being connected back to the other end of the economizer, and an auxiliary electronic expansion valve and an auxiliary inlet temperature sensor being installed on the branch connecting pipe.

[0010] Preferably, the D valve of the four-way valve is connected to the compressor through a first connecting pipe, and an exhaust temperature sensor is provided on the connecting pipe. The D valve of the four-way valve is connected to the compressor through a second connecting pipe, and a return gas temperature sensor and a low pressure sensor are sequentially provided on the second connecting pipe.

[0011] Preferably, in step S1, the operating parameters of the heat pump system are collected from the structural distribution, including:

[0012] The return gas pressure of the heat pump system is collected from the low-pressure sensor, the return gas temperature value is collected from the return gas temperature sensor 3, the ambient temperature value is collected from the ambient temperature sensor, the auxiliary outlet temperature value is collected from the auxiliary inlet temperature sensor, the auxiliary inlet temperature value is collected from the auxiliary inlet temperature sensor, and the exhaust temperature value is collected from the exhaust temperature sensor.

[0013] Preferably, in step S2, based on the operating parameters and in conjunction with the compressor's current value, the control parameters for the main circuit electronic expansion valve are determined, including:

[0014] When the auxiliary electronic expansion valve is open, the control method for the main electronic expansion valve is as follows:

[0015] When the compressor current is greater than or equal to the first preset current, the main circuit electronic expansion valve is gradually opened in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the main circuit electronic expansion valve.

[0016] When the compressor current is less than the first preset current and greater than or equal to the second preset current, the main circuit electronic expansion valve is controlled according to the target return gas superheat and is not allowed to close too much.

[0017] When the compressor current is less than the second preset current, the main circuit electronic expansion valve is controlled according to the target return gas superheat.

[0018] Preferably, the actual value of the target return gas superheat is the difference between the return gas pressure-temperature value and the return gas pressure-saturation temperature value. The correction method for the actual value of the target return gas superheat is as follows:

[0019] When the exhaust temperature is greater than the first preset exhaust temperature, and the opening of the auxiliary electronic expansion valve exceeds 80% of its maximum opening, or when the compressor current limits the opening of the auxiliary electronic expansion valve, the target return gas superheat is corrected by 2°C in each judgment cycle based on the actual value. The corrected target return gas superheat is less than or equal to the sum of the default setting value and 4°C.

[0020] When the ambient temperature is less than the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the second preset exhaust temperature, the target return gas superheat value remains unchanged.

[0021] When the ambient temperature is less than the first preset ambient temperature and the exhaust temperature is less than the second preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C.

[0022] When the ambient temperature is greater than or equal to the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature but greater than or equal to the third preset exhaust temperature, the target return gas superheat value remains unchanged.

[0023] When the ambient temperature is greater than or equal to the first preset ambient temperature and the exhaust temperature is less than the third preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C.

[0024] Preferably, in step S3, based on the operating parameters, and in conjunction with the compressor's current value and the opening degree of the main circuit electronic expansion valve, the control parameters for the auxiliary circuit electronic expansion valve are determined, including:

[0025] When the compressor current is greater than or equal to the first preset current, and the opening of the main circuit electronic expansion valve exceeds 80% of its maximum opening, the auxiliary circuit electronic expansion valve is gradually closed in each adjustment cycle, and the step size of each action does not exceed 2% of the maximum opening of the auxiliary circuit electronic expansion valve.

[0026] When the compressor current is less than the first preset current and greater than or equal to the second preset current, the auxiliary electronic expansion valve is controlled according to the target injection superheat or the target exhaust temperature, and is not allowed to open too wide.

[0027] When the compressor current is less than the second preset current, the auxiliary electronic expansion valve is controlled according to the target injection superheat or the target exhaust temperature.

[0028] The target injection superheat is determined by the difference between the outlet temperature and the inlet temperature.

[0029] Preferably, the specific selection for control based on the target injection superheat or target exhaust temperature is as follows:

[0030] When the exhaust temperature is greater than the first preset exhaust temperature, the auxiliary electronic expansion valve is controlled according to the target exhaust temperature.

[0031] When the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the fourth preset exhaust temperature, the auxiliary electronic expansion valve is controlled according to the target injection superheat.

[0032] When the exhaust temperature is less than the fourth preset exhaust temperature, the auxiliary electronic expansion valve is gradually closed in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the auxiliary electronic expansion valve.

[0033] Preferably, it also includes: obtaining the refrigerant flow rate controlled by the main electronic expansion valve of the heat pump system and the refrigerant injection amount determined by the auxiliary electronic expansion valve under the control of the heat pump system according to S1-S3;

[0034] Obtain the flow-injection correspondence between the refrigerant flow rate and the refrigerant injection quantity in the same time series, and obtain the main control parameters and auxiliary control parameters under the flow-injection correspondence;

[0035] Based on the flow rate-injection quantity correspondence, and in combination with the main control parameters and auxiliary control parameters, the secondary adjustment parameters for the main control parameters and auxiliary control parameters are determined.

[0036] Preferably, the determination of secondary adjustment parameters for the main control parameters and auxiliary control parameters based on the flow-injection quantity correspondence, combined with the main control parameters and auxiliary control parameters, includes:

[0037] The difference curve between flow rate and injection quantity is determined from the flow rate-injection quantity correspondence. A first time range in which the difference is greater than a first preset difference is obtained from the difference curve, and a second time range in which the difference is less than the first preset difference is obtained.

[0038] The second opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the second time range is obtained from the main control parameters and the auxiliary control parameters, and the reference optimal opening degree ratio between the main opening degree and the auxiliary opening degree is determined based on the second opening degree relationship.

[0039] Obtain the first opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the first time range from the main control parameters and the auxiliary control parameters, and establish the correspondence between the first opening degree relationship and the difference greater than the first preset difference value;

[0040] Based on the correspondence, a proportional curve between the opening degree and the difference is obtained. Based on the wave degree of the proportional curve, a correction weight for the reference optimal opening degree ratio is determined. The reference optimal opening degree ratio is corrected according to the correction weight to obtain the target optimal opening degree ratio.

[0041] When the difference between the real-time detected flow rate and the injection volume is greater than the first preset difference, the main control parameters and auxiliary control parameters are adjusted a second time according to the target optimal opening ratio.

[0042] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0043] By acquiring the structural distribution of the heat pump system and collecting its operating parameters from this distribution, and based on these parameters and the compressor current value, control parameters for the main circuit electronic expansion valve are determined. Similarly, control parameters for the auxiliary circuit electronic expansion valve are determined based on these operating parameters, the compressor current value, and the opening degree of the main circuit electronic expansion valve. This addresses two issues: First, an improperly set target return gas superheat setting leads to an excessively large opening of the main circuit electronic expansion valve, resulting in insufficient auxiliary flow and poor heating capacity, or compressor exhaust high-temperature protection shutdown under high pressure ratio. Second, an improperly set target return gas superheat setting leads to an excessively small opening of the main circuit electronic expansion valve, resulting in excessive refrigerant accumulation in the condenser and compressor exhaust pressure too high, causing protection shutdown. Third, an improperly set target return gas superheat setting leads to an excessively small opening of the main circuit electronic expansion valve, resulting in excessive refrigerant accumulation in the condenser and compressor exhaust pressure too high, causing protection shutdown. Fourth, an excessively large auxiliary flow causes the compressor to work under heavy load, leading to compressor current too high, causing protection shutdown. This significantly reduces the probability of unit failure and downtime, and improves product reliability.

[0044] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in this application.

[0045] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0046] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0047] Figure 1 This is a flowchart of a control method for a heat pump system according to an embodiment of the present invention;

[0048] Figure 2 This is a structural diagram of the heat pump system in an embodiment of the present invention;

[0049] Figure 3 This is a flowchart for determining the control parameters of the auxiliary electronic expansion valve in an embodiment of the present invention. Detailed Implementation

[0050] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0051] Example 1:

[0052] This invention provides a control method for a heat pump system, such as... Figure 1 As shown, it includes:

[0053] S1: Obtain the structural distribution of the heat pump system and collect the operating parameters of the heat pump system from the structural distribution;

[0054] S2: Based on the aforementioned operating parameters and the current value of compressor 1, determine the control parameters for the main circuit electronic expansion valve 8;

[0055] S3: Based on the aforementioned operating parameters, and in conjunction with the current value of compressor 1 and the opening degree of main circuit electronic expansion valve 8, determine the control parameters for auxiliary circuit electronic expansion valve 4.

[0056] In this embodiment, the operating parameters of the heat pump system include the detection parameters of each sensor.

[0057] In this embodiment, the control parameter for the main electronic expansion valve 8 is the control of its opening degree.

[0058] In this embodiment, the control parameter for the auxiliary electronic expansion valve 4 is the control of its opening degree.

[0059] The beneficial effects of the above design scheme are as follows: By acquiring the structural distribution of the heat pump system and collecting its operating parameters from the structural distribution, and based on these operating parameters, combined with the current value of compressor 1, the control parameters for the main circuit electronic expansion valve 8 are determined. Based on these operating parameters, combined with the current value of compressor 1 and the opening degree of the main circuit electronic expansion valve 8, the control parameters for the auxiliary circuit electronic expansion valve 4 are determined. This solves the problem that an unreasonable target return gas superheat setting leads to an excessively large opening of the main circuit electronic expansion valve, resulting in low auxiliary circuit flow, poor heating capacity, or compressor exhaust high temperature protection shutdown under high pressure ratio. It also solves the problem that an unreasonable target return gas superheat setting leads to an excessively small opening of the main circuit electronic expansion valve, resulting in excessive refrigerant accumulation in the condenser, causing compressor exhaust pressure too high and protection shutdown, or excessive auxiliary circuit flow, causing compressor overload and compressor current too high and protection shutdown. This significantly reduces the probability of unit failure and downtime, and improves product reliability.

[0060] Example 2:

[0061] Based on Embodiment 1, this embodiment of the invention provides a control method for a heat pump system, such as... Figure 2 As shown, in S1, the structural distribution of the heat pump system is obtained, including a compressor 1, a liquid supply pipe connected to the compressor 1, the other end of the liquid supply pipe being connected to an economizer 9, an auxiliary outlet temperature sensor 10 being installed on the liquid supply pipe, a connecting pipe being connected to one end of the economizer 9, the other end of the connecting pipe being connected to a water-side heat exchanger 7, one end of the water-side heat exchanger 7 being connected to the C valve of a four-way valve 12 via the connecting pipe, the E valve of the four-way valve 12 being connected to a finned tube heat exchanger 5 via the connecting pipe, an ambient temperature sensor 6 being installed on the finned tube heat exchanger 5, the other end of the finned tube heat exchanger 5 being connected to the economizer 9 via the connecting pipe, a main electronic expansion valve 8 being installed on the connecting pipe between the finned tube heat exchanger 5 and the economizer 9, a branch connecting pipe being installed on the connecting pipe between the finned tube heat exchanger 5 and the economizer 9, the other end of the branch connecting pipe being connected back to the other end of the economizer 9, and an auxiliary electronic expansion valve 4 and an auxiliary inlet temperature sensor 11 being installed on the branch connecting pipe.

[0062] The beneficial effects of the above design scheme are: it provides the structural distribution of the heat pump system and provides a structural basis for the control of the heat pump system.

[0063] Example 3:

[0064] Based on Embodiment 2, this embodiment of the invention provides a control method for a heat pump system, such as... Figure 2As shown, the D valve of the four-way valve 12 is connected to the compressor 1 through the first connecting pipe, and an exhaust temperature sensor 13 is provided on the connecting pipe. The D valve of the four-way valve 12 is connected to the compressor 1 through the second connecting pipe, and a return gas temperature sensor 3 and a low pressure sensor 2 are provided in sequence on the second connecting pipe.

[0065] The beneficial effects of the above design scheme are: it provides the structural distribution of the heat pump system and provides a structural basis for the control of the heat pump system.

[0066] Example 4:

[0067] Based on Embodiment 1, this embodiment of the invention provides a control method for a heat pump system. In step S1, the operating parameters of the heat pump system are collected from the structural distribution, including:

[0068] The return gas pressure of the heat pump system is collected from the low-pressure sensor 2, the return gas temperature value is collected from the return gas temperature sensor 3, the ambient temperature value is collected from the ambient temperature sensor 6, the auxiliary outlet temperature value is collected from the auxiliary outlet temperature sensor 10, the auxiliary inlet temperature value is collected from the auxiliary inlet temperature sensor 11, and the exhaust temperature value is collected from the exhaust temperature sensor 13.

[0069] The beneficial effect of the above design scheme is that by collecting the parameters of each sensor, the operating parameters are obtained, providing a parameter basis for the control of the heat pump system.

[0070] Example 5:

[0071] Based on Embodiment 1, this embodiment of the invention provides a control method for a heat pump system. In step S2, based on the operating parameters and in conjunction with the current value of the compressor 1, control parameters for the main circuit electronic expansion valve 8 are determined, including:

[0072] When the auxiliary electronic expansion valve 4 is opened, the control method for the main electronic expansion valve 8 is as follows:

[0073] When the current value of compressor 1 is greater than or equal to the first preset current, the main circuit electronic expansion valve 8 is gradually opened in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the main circuit electronic expansion valve 8.

[0074] When the current value of compressor 1 is less than the first preset current and greater than or equal to the second preset current, the main circuit electronic expansion valve 8 is controlled according to the target return gas superheat and is not allowed to be closed.

[0075] When the current value of compressor 1 is less than the second preset current, the main circuit electronic expansion valve 8 is controlled according to the target return gas superheat.

[0076] In this embodiment, the first preset current is generally the maximum operating current allowed by the compressor's technical specifications minus 1 to 2 A, and the difference between the first preset current and the second preset current is generally between 1 and 3 A.

[0077] In this embodiment, the return gas superheat is the difference between the return gas temperature and the return gas pressure saturation temperature, which is calculated from the return gas pressure.

[0078] In this embodiment, the target return gas superheat is adjustable.

[0079] The beneficial effects of the above design scheme are as follows: By controlling the opening based on the target return gas superheat, it solves the problems of the main circuit electronic expansion valve opening being too large due to an unreasonable target return gas superheat setting, resulting in a small auxiliary circuit flow, leading to poor heating capacity or compressor exhaust high temperature protection shutdown under high pressure ratio; and the main circuit electronic expansion valve opening being too small due to an unreasonable target return gas superheat setting, resulting in excessive refrigerant accumulation in the condenser, leading to compressor exhaust pressure too high protection shutdown, or the auxiliary circuit flow being too large, causing the compressor to work under heavy load, leading to compressor current too high protection shutdown.

[0080] Example 6:

[0081] Based on Example 5, this embodiment of the invention provides a control method for a heat pump system. The actual value of the target return gas superheat is the difference between the return gas pressure temperature and the return gas pressure saturation temperature. The correction method for the actual value of the target return gas superheat is as follows:

[0082] When the exhaust temperature is greater than the first preset exhaust temperature, and the opening of the auxiliary electronic expansion valve 4 exceeds 80% of its maximum opening, or when the current value of the compressor 1 limits the opening of the auxiliary electronic expansion valve 4, the target return gas superheat is corrected by 2°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is less than or equal to the sum of the default setting value and 4°C.

[0083] When the ambient temperature is less than the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the second preset exhaust temperature, the target return gas superheat value remains unchanged.

[0084] When the ambient temperature is less than the first preset ambient temperature and the exhaust temperature is less than the second preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C.

[0085] When the ambient temperature is greater than or equal to the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature but greater than or equal to the third preset exhaust temperature, the target return gas superheat value remains unchanged.

[0086] When the ambient temperature is greater than or equal to the first preset ambient temperature and the exhaust temperature is less than the third preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C.

[0087] In this embodiment, the first preset temperature is generally the maximum discharge temperature allowed by the compressor's technical specifications minus 5 to 10°C; the difference between the first preset temperature and the second preset temperature is generally between 10 and 20°C; the third preset temperature is greater than the second preset temperature, and the difference between the third preset temperature and the second preset temperature is generally between 5 and 10°C, to prevent the main circuit electronic expansion valve from opening too small when the ambient temperature is high, which could lead to high pressure protection or current protection problems for the compressor; the value of the first preset ambient temperature is generally between -10°C and -15°C.

[0088] The beneficial effects of the above design scheme are as follows: By adjusting the target return gas superheat based on the exhaust temperature and ambient temperature, the scheme solves the problems of: an unreasonable target return gas superheat setting causing the main circuit electronic expansion valve to open too wide, resulting in insufficient auxiliary circuit flow and poor heating capacity or compressor exhaust high temperature protection shutdown under high pressure ratio; an unreasonable target return gas superheat setting causing the main circuit electronic expansion valve to open too small, resulting in excessive refrigerant accumulation in the condenser and compressor exhaust pressure too high and protection shutdown; or an excessive auxiliary circuit flow causing the compressor to work under heavy load and compressor current too high and protection shutdown.

[0089] Example 7:

[0090] Based on Embodiment 1, this embodiment of the invention provides a control method for a heat pump system, wherein in S3, as follows: Figure 3 As shown, based on the aforementioned operating parameters, combined with the current value of compressor 1 and the opening degree of the main circuit electronic expansion valve 8, the control parameters for the auxiliary circuit electronic expansion valve 4 are determined, including:

[0091] When the current value of compressor 1 is greater than or equal to the first preset current, and the opening degree of the main circuit electronic expansion valve 8 exceeds 80% of its maximum opening degree, the auxiliary circuit electronic expansion valve 4 is gradually closed in each adjustment cycle, and the step size of each action does not exceed 2% of the maximum opening degree of the auxiliary circuit electronic expansion valve 4.

[0092] When the current value of compressor 1 is less than the first preset current and greater than or equal to the second preset current, the auxiliary electronic expansion valve 4 is controlled according to the target injection superheat or target exhaust temperature, and is not allowed to open too wide.

[0093] When the current value of compressor 1 is less than the second preset current, the auxiliary electronic expansion valve 4 is controlled according to the target injection superheat or the target exhaust temperature.

[0094] The target injection superheat is determined by the difference between the outlet temperature and the inlet temperature.

[0095] The beneficial effects of the above design scheme are as follows: By controlling the auxiliary circuit electronic expansion valve 4 according to the target injection superheat or target exhaust temperature, where the target exhaust temperature is adjustable, the scheme solves the problems of the main circuit electronic expansion valve opening being too large due to an unreasonable target return gas superheat setting, resulting in a small auxiliary circuit flow, leading to poor heating capacity or compressor exhaust high temperature protection shutdown under high pressure ratio. Conversely, the scheme of the main circuit electronic expansion valve opening being too small due to an unreasonable target return gas superheat setting, leading to excessive refrigerant accumulation in the condenser, resulting in compressor exhaust pressure too high protection shutdown, or excessive auxiliary circuit flow, causing the compressor to work under heavy load, resulting in compressor current too high protection shutdown.

[0096] Example 8:

[0097] Based on Example 7, this embodiment of the invention provides a control method for a heat pump system, wherein the specific selection of control according to the target injection superheat or the target exhaust temperature is as follows:

[0098] When the exhaust temperature is greater than the first preset exhaust temperature, the auxiliary electronic expansion valve 4 is controlled according to the target exhaust temperature.

[0099] When the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the fourth preset exhaust temperature, the auxiliary electronic expansion valve 4 is controlled according to the target injection superheat.

[0100] When the exhaust temperature is less than the fourth preset exhaust temperature, the auxiliary electronic expansion valve 4 is gradually closed in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the auxiliary electronic expansion valve 4.

[0101] In this embodiment, the fourth preset exhaust temperature is generally between 55 and 65 degrees Celsius.

[0102] The beneficial effects of the above design scheme are as follows: when the exhaust temperature is greater than the first preset exhaust temperature, the auxiliary electronic expansion valve 4 is controlled according to the target exhaust temperature; when the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the fourth preset exhaust temperature, the auxiliary electronic expansion valve 4 is controlled according to the target injection superheat; when the exhaust temperature is less than the fourth preset exhaust temperature, the auxiliary electronic expansion valve 4 is gradually closed in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the auxiliary electronic expansion valve 4, thereby achieving control of the auxiliary electronic expansion valve 4.

[0103] Example 9:

[0104] Based on Embodiment 1, this embodiment of the invention provides a control method for a heat pump system, which further includes: obtaining the refrigerant flow rate controlled by the main electronic expansion valve 8 and the refrigerant injection amount determined by the auxiliary electronic expansion valve 4 under the control of the heat pump system according to S1-S3.

[0105] Obtain the flow-injection correspondence between the refrigerant flow rate and the refrigerant injection quantity in the same time series, and obtain the main control parameters and auxiliary control parameters under the flow-injection correspondence;

[0106] Based on the flow rate-injection quantity correspondence, and in combination with the main control parameters and auxiliary control parameters, the secondary adjustment parameters for the main control parameters and auxiliary control parameters are determined.

[0107] In this embodiment, the main control parameter is the control parameter for the main circuit electronic expansion valve 8, and the auxiliary control parameter is the control parameter for the auxiliary circuit electronic expansion valve 4.

[0108] The beneficial effects of the above design scheme are: by obtaining the flow-injection quantity correspondence between the refrigerant flow rate and the refrigerant injection quantity in the same time series, and obtaining the main control parameters and auxiliary control parameters under the flow-injection quantity correspondence; based on the flow-injection quantity correspondence, combined with the main control parameters and auxiliary control parameters, the secondary adjustment parameters for the main control parameters and auxiliary control parameters are determined, thereby realizing the real-time adjustment of the main control parameters and auxiliary control parameters.

[0109] Example 10:

[0110] Based on Embodiment 9, this embodiment of the invention provides a control method for a heat pump system. The method involves determining secondary adjustment parameters for the main control parameters and auxiliary control parameters based on the flow-ejection quantity correspondence and combining main control parameters and auxiliary control parameters. This includes:

[0111] The difference curve between flow rate and injection quantity is determined from the flow rate-injection quantity correspondence. A first time range in which the difference is greater than a first preset difference is obtained from the difference curve, and a second time range in which the difference is less than the first preset difference is obtained.

[0112] The second opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the second time range is obtained from the main control parameters and the auxiliary control parameters, and the reference optimal opening degree ratio between the main opening degree and the auxiliary opening degree is determined based on the second opening degree relationship.

[0113] Obtain the first opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the first time range from the main control parameters and the auxiliary control parameters, and establish the correspondence between the first opening degree relationship and the difference greater than the first preset difference value;

[0114] Based on the correspondence, a proportional curve between the opening degree and the difference is obtained. Based on the wave degree of the proportional curve, a correction weight for the reference optimal opening degree ratio is determined. The reference optimal opening degree ratio is corrected according to the correction weight to obtain the target optimal opening degree ratio.

[0115] When the difference between the real-time detected flow rate and the injection volume is greater than the first preset difference, the main control parameters and auxiliary control parameters are adjusted a second time according to the target optimal opening ratio.

[0116] The beneficial effects of the above design scheme are as follows: by obtaining the flow-injection correspondence between the refrigerant flow rate and the refrigerant injection quantity in the same time series, and obtaining the main control parameters and auxiliary control parameters under the flow-injection correspondence; based on the flow-injection correspondence, combined with the main control parameters and auxiliary control parameters, the secondary adjustment parameters for the main control parameters and auxiliary control parameters are determined, thereby realizing the real-time adjustment of the main control parameters and auxiliary control parameters, significantly reducing the probability of heat pump system failure and downtime and maintenance rate, and improving product reliability.

[0117] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of this application and its equivalents, this invention also intends to include these modifications and variations.

Claims

1. A control method for a heat pump system, characterized in that, include: S1: Obtain the structural distribution of the heat pump system and collect the operating parameters of the heat pump system from the structural distribution; S2: Based on the operating parameters and the current value of the compressor (1), determine the control parameters for the main circuit electronic expansion valve (8), including: when the auxiliary circuit electronic expansion valve (4) is open, the control method for the main circuit electronic expansion valve (8) is as follows: When the current value of the compressor (1) is greater than or equal to the first preset current, the main circuit electronic expansion valve (8) is gradually opened in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the main circuit electronic expansion valve (8). When the current value of the compressor (1) is less than the first preset current and greater than or equal to the second preset current, the main circuit electronic expansion valve (8) is controlled according to the target return gas superheat and is not allowed to be closed. When the current value of the compressor (1) is less than the second preset current, the main circuit electronic expansion valve (8) is controlled according to the target return gas superheat. S3: Based on the aforementioned operating parameters, combined with the current value of the compressor (1) and the opening degree of the main electronic expansion valve (8), determine the control parameters for the auxiliary electronic expansion valve (4), including: When the current value of the compressor (1) is greater than or equal to the first preset current, and the opening degree of the main circuit electronic expansion valve (8) exceeds 80% of its maximum opening degree, the auxiliary circuit electronic expansion valve (4) is gradually closed in each adjustment cycle, and the step size of each action does not exceed 2% of the maximum opening degree of the auxiliary circuit electronic expansion valve (4). When the current value of the compressor (1) is less than the first preset current and greater than or equal to the second preset current, the auxiliary electronic expansion valve (4) is controlled according to the target injection superheat or the target exhaust temperature, and is not allowed to open too wide; When the current value of the compressor (1) is less than the second preset current, the auxiliary electronic expansion valve (4) is controlled according to the target injection superheat or the target exhaust temperature. The target injection superheat is determined by the difference between the outlet temperature and the inlet temperature.

2. The control method for a heat pump system according to claim 1, characterized in that, In S1, the structural distribution of the heat pump system is obtained, including a compressor (1), a liquid supply pipe connected to the compressor (1), the other end of the liquid supply pipe being connected to an economizer (9), an auxiliary outlet temperature sensor (10) also being installed on the liquid supply pipe, a connecting pipe being connected to one end of the economizer (9), the other end of the connecting pipe being connected to a water-side heat exchanger (7), one end of the water-side heat exchanger (7) being connected to the C valve of a four-way valve (12) through the connecting pipe, and the E valve of the four-way valve (12) being connected to a finned tube heat exchanger (5) through the connecting pipe. An ambient temperature sensor (6) is installed on the finned tube heat exchanger (5). The other end of the finned tube heat exchanger (5) is connected to the economizer (9) through a connecting pipe. A main electronic expansion valve (8) is installed on the connecting pipe between the finned tube heat exchanger (5) and the economizer (9). A branch connecting pipe is installed on the connecting pipe between the finned tube heat exchanger (5) and the economizer (9). The other end of the branch connecting pipe is connected back to the other end of the economizer (9). An auxiliary electronic expansion valve (4) and an auxiliary temperature sensor (11) are installed on the branch connecting pipe.

3. The control method for a heat pump system according to claim 2, characterized in that, The D valve of the four-way valve (12) is connected to the compressor (1) through the first connecting pipe, and an exhaust temperature sensor (13) is installed on the connecting pipe. The D valve of the four-way valve (12) is connected to the compressor (1) through the second connecting pipe, and a return gas temperature sensor (3) and a low pressure sensor (2) are installed on the second connecting pipe in sequence.

4. The control method for a heat pump system according to claim 3, characterized in that, In step S1, the operating parameters of the heat pump system are collected from the structural distribution, including: The return gas pressure of the heat pump system is collected from the low-pressure sensor (2), the return gas temperature value is collected from the return gas temperature sensor (3), the ambient temperature value is collected from the ambient temperature sensor (6), the auxiliary outlet temperature value is collected from the auxiliary outlet temperature sensor (10), the auxiliary inlet temperature value is collected from the auxiliary inlet temperature sensor (11), and the exhaust temperature value is collected from the exhaust temperature sensor (13).

5. The control method for a heat pump system according to claim 1, characterized in that, The actual value of the target return gas superheat is the difference between the return gas pressure-temperature value and the return gas pressure-saturation temperature value. The correction method for the actual value of the target return gas superheat is as follows: When the exhaust temperature is greater than the first preset exhaust temperature, and the opening of the auxiliary electronic expansion valve (4) exceeds 80% of its maximum opening, or when the current value of the compressor (1) limits the opening of the auxiliary electronic expansion valve (4), the target return gas superheat is corrected by 2°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is less than or equal to the sum of the default setting value and 4°C. When the ambient temperature is less than the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the second preset exhaust temperature, the target return gas superheat value remains unchanged. When the ambient temperature is less than the first preset ambient temperature and the exhaust temperature is less than the second preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C. When the ambient temperature is greater than or equal to the first preset ambient temperature, and the exhaust temperature is less than or equal to the first preset exhaust temperature but greater than or equal to the third preset exhaust temperature, the target return gas superheat value remains unchanged. When the ambient temperature is greater than or equal to the first preset ambient temperature and the exhaust temperature is less than the third preset exhaust temperature, the target return gas superheat value is reduced by 1°C in each judgment cycle based on the actual value. The corrected target return gas superheat value is greater than or equal to the difference between the default value and 4°C.

6. The control method for a heat pump system according to claim 1, characterized in that, The specific selection for control based on the target injection superheat or target exhaust temperature is as follows: When the exhaust temperature is greater than the first preset exhaust temperature, the auxiliary electronic expansion valve (4) is controlled according to the target exhaust temperature; When the exhaust temperature is less than or equal to the first preset exhaust temperature and greater than or equal to the fourth preset exhaust temperature, the auxiliary electronic expansion valve (4) is controlled according to the target injection superheat. When the exhaust temperature is less than the fourth preset exhaust temperature, the auxiliary electronic expansion valve (4) is gradually closed in each adjustment cycle, and the step size of each action does not exceed two percent of the maximum opening of the auxiliary electronic expansion valve (4).

7. The control method for a heat pump system according to claim 1, characterized in that, It also includes: obtaining the refrigerant flow rate controlled by the main electronic expansion valve (8) of the heat pump system and the refrigerant injection amount determined by the auxiliary electronic expansion valve (4) under the control of the heat pump system according to S1-S3; Obtain the flow-injection correspondence between the refrigerant flow rate and the refrigerant injection quantity in the same time series, and obtain the main control parameters and auxiliary control parameters under the flow-injection correspondence; Based on the flow rate-injection quantity correspondence, and in combination with the main control parameters and auxiliary control parameters, the secondary adjustment parameters for the main control parameters and auxiliary control parameters are determined.

8. The control method for a heat pump system according to claim 7, characterized in that, The determination of secondary adjustment parameters for the main and auxiliary control parameters based on the flow-injection quantity correspondence, combined with the main control parameters and auxiliary control parameters, includes: The difference curve between flow rate and injection quantity is determined from the flow rate-injection quantity correspondence. A first time range in which the difference is greater than a first preset difference is obtained from the difference curve, and a second time range in which the difference is less than the first preset difference is obtained. The second opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the second time range is obtained from the main control parameters and the auxiliary control parameters, and the reference optimal opening degree ratio between the main opening degree and the auxiliary opening degree is determined based on the second opening degree relationship. Obtain the first opening degree relationship between the main opening degree and the auxiliary opening degree corresponding to the first time range from the main control parameters and the auxiliary control parameters, and establish the correspondence between the first opening degree relationship and the difference greater than the first preset difference; Based on the correspondence, a proportional curve between the opening degree and the difference is obtained. Based on the wave degree of the proportional curve, a correction weight for the reference optimal opening degree ratio is determined. The reference optimal opening degree ratio is corrected according to the correction weight to obtain the target optimal opening degree ratio. When the difference between the real-time detected flow rate and the injection volume is greater than the first preset difference, the main control parameters and auxiliary control parameters are adjusted a second time according to the target optimal opening ratio.

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