Air source heat pump water temperature compensation device and method

Abstract

The invention provides an air source heat pump water temperature compensation device and method, and belongs to the technical field of air source heat pumps, the air source heat pump water temperature compensation device comprises a control circuit, a power supply circuit, a water outlet temperature compensation circuit, a water return temperature compensation circuit and an RS485 communication circuit; the control circuit comprises a single-chip microcomputer MCU, and the control function of the whole device is achieved through the ADC, UART and GPIO functions integrated in an MCU chip. The water temperature compensation device for the air source heat pump is clear in implementation principle, has universal adaptability and can be applied to most of air source heat pump energy-saving transformation projects in the market at present. And the device is low in manufacturing cost and obvious in energy-saving effect, and has good popularization and application values in energy-saving transformation application of the air source heat pump.

Description

Technical Field

[0001] The present invention relates to the technical field of air source heat pumps, and specifically provides an air source heat pump water temperature compensation device and method. Background Art

[0002] Air source heat pump is an energy-saving device that uses high-level energy to make heat flow from low-level heat source air to high-level heat source. It is driven by electric energy, extracts heat from the air, and transports it to the heating network to achieve the heating function. Depending on the scale of the heating system, the heating system can use one air source heat pump or multiple air source heat pumps in a network.

[0003] According to the principle of air source heat pump, the energy efficiency ratio (COP) of air source heat pump is related to the outlet water temperature. The higher the outlet water temperature, the lower the COP of air source heat pump; conversely, the lower the outlet water temperature, the higher the COP of air source heat pump. Therefore, according to the heat load demand, real-time control of the outlet water temperature of air source heat pump is an effective means to achieve energy saving of air source heat pump system.

[0004] At present, the target outlet water temperature or target return water temperature of air source heat pumps is generally set by means of "wire controller". The wire controller is the operating device of the air source heat pump, and the "host" in a group of air source heat pumps is the control core. The host controls the group of air source heat pumps to load or unload according to the manually set target water temperature and the currently detected water temperature, and controls the actual outlet water temperature to be near the set target outlet water temperature. The target water temperature of most air source heat pumps is a fixed value, which needs to be modified manually and cannot be changed dynamically according to environmental changes.

[0005] According to the survey, existing air source heat pumps generally use NTC thermistors as temperature sensors. In the air source heat pump control circuit, a pull-up resistor is connected in series with the NTC resistor. The voltage value across the NTC resistor is collected through the ADC, and the NTC resistance value is calculated, and then the detected temperature value is obtained by looking up the table. Summary of the invention

[0006] During the entire winter heating process, the actual heating demand is also changing due to environmental changes, which requires the air source heat pump system to dynamically adjust the target water temperature according to environmental changes to achieve energy-saving operation of the entire system. At present, there are two main solutions to this problem: one is to set up a dedicated person to adjust the target water temperature at any time based on experience. This method has the disadvantages of untimely and inaccurate adjustment and occupies manpower; the other is that the air source heat pump's wire controller has an RS485 communication interface and can be connected to the upper platform, such as the PLC automatic control system, etc. The upper platform realizes the dynamic adjustment function of the target water temperature. This method can realize automatic control of the water temperature.

[0007] Although the second method can solve the above problems, it still has limitations. Not all air source heat pump wire controllers support RS485 communication interface, especially most of the earlier products cannot communicate. Under the existing technology, this type of air source heat pump products cannot achieve dynamic control.

[0008] The present invention realizes a universal air source heat pump water temperature compensation device, which can dynamically adjust the target water temperature of the air source heat pump according to environmental changes and is suitable for most models of air source heat pumps on the market: (1) According to environmental changes, the resistance value of the air source heat pump temperature sensor is compensated, and the air source heat pump is guided to be controlled according to the compensated water temperature.

[0009] (2) It has a communication interface and can be connected to the host platform to achieve remote water temperature control by remotely adjusting the compensation value.

[0010] The technology of the present invention can be widely used in the field of energy-saving transformation of existing air source heat pump systems. Therefore, the present invention provides an air source heat pump water temperature compensation device and method to solve the above problems.

[0011] On one hand, the present invention provides an air source heat pump water temperature compensation device, the air source heat pump water temperature compensation device comprising: a control circuit, a power supply circuit, an outlet water temperature compensation circuit, a return water temperature compensation circuit, and an RS485 communication circuit; The control circuit comprises a single-chip microcomputer MCU, and utilizes the ADC, UART, and GPIO functions integrated in the MCU chip to realize the control function of the entire device; The air source heat pump water temperature compensation device is powered by the +5V power output port of the control circuit, and generates the 3.3V voltage required by the MCU and ADC through the voltage regulator chip; The air source heat pump water temperature compensation device is short-circuited with the ground wire of the control circuit; The outlet water temperature compensation circuit and the return water temperature compensation circuit perform resistance compensation processing on the temperature sensor, connect a digital potentiometer in parallel at both ends of the outlet water temperature sensor, and then connect another digital potentiometer in series to form a compensable temperature sensor. The control circuit achieves fine-tuning of the resistance value of the temperature sensor by modifying the resistance value of the two digital potentiometers.

[0012] The RS485 communication circuit includes an RS485 interface chip to realize the communication function with the host computer.

[0013] Furthermore, the external interfaces of the air source heat pump water temperature compensation device include: power supply interface, temperature sensor input interface, temperature sensor output interface, RS485 communication interface, wherein: The power interface is connected to the +5V power supply of the control circuit; The air source heat pump water temperature compensation device has three temperature sensor input interfaces: an ambient temperature sensor input interface, an outlet water temperature sensor input interface, and a return water temperature sensor input interface, wherein: The ambient temperature sensor input interface is connected to the standard temperature sensor to detect the outdoor ambient temperature as the basis for temperature compensation; The outlet water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the outlet water temperature compensation circuit as the reference resistor of the outlet water temperature compensation circuit; The return water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the return water temperature compensation circuit as the reference resistor of the return water temperature compensation circuit; The warm air source heat pump water temperature compensation device has two temperature sensor output interfaces: an outlet water temperature sensor output interface and a return water temperature sensor output interface, wherein: The outlet water temperature sensor output interface is connected to the outlet water temperature sensor interface in the air source heat pump control circuit, and the outlet water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The return water temperature sensor output interface is connected to the return water temperature sensor interface in the air source heat pump control circuit, and the return water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The air source heat pump water temperature compensation device is provided with an RS485 communication interface, supports the ModbusRTU protocol, and is used to connect to a host computer; through the RS485 communication interface, the sensor resistance table and compensation parameters of the air source heat pump water temperature compensation device are set, and the ambient temperature, outlet water temperature, and return water temperature are collected.

[0014] Furthermore, the control circuit comprises an MCU chip U1, wherein the chip U1 comprises: The P1.0 / A0 pin is an ADC port, which is used to collect the voltage of the ambient temperature sensor R3IN and calculate the ambient temperature value; The P1.4 / A4 and P1.5 / A5 pins are ADC ports, which are used to collect the voltages of V1A and V1B in the outlet water temperature compensation circuit and calculate the actual outlet water temperature value; The P1.6 / A6 and P1.7 / A7 pins are ADC ports, which are used to collect the voltages of V2A and V2B in the return water temperature compensation circuit and calculate the actual return water temperature value; P1.1 / RXD and P1.2 / TXD pins are UART ports, realizing RS485 communication function; The pins P2.0, P2.1, P2.2, P2.3, P2.4, and P2.5 are GPIO ports, which realize the SPI control function of the U4, U5, U6, and U7 digital potentiometer chips; MCU has built-in FLASH memory to save and read compensation parameters; The MCU has a built-in timer to implement the real-time clock function and synchronize the clock with the host computer through communication.

[0015] Furthermore, the power supply circuit adopts a step-down DC / DC conversion chip to convert the +5V voltage into a 3.3V voltage; The RS485 communication circuit is implemented by the RS485 interface chip U3.

[0016] Furthermore, the outlet water temperature sensor compensation circuit uses a digital potentiometer chip to realize the compensation of the resistance value of the outlet water temperature sensor R1IN. First, a digital potentiometer U5 is connected in parallel at both ends of R1IN, and the parallel resistor is then connected in series with the digital potentiometer U4. Among them, R0 is the resistance inside the air source heat pump controller circuit, U4 uses a 5KΩ / 256 tap digital potentiometer, and U5 uses a 100KΩ / 256 tap digital potentiometer.

[0017] The return water temperature sensor compensation circuit is similar to the outlet water temperature sensor compensation circuit.

[0018] In another aspect, the present invention provides a method for compensating water temperature of an air source heat pump. Based on any of the above-mentioned water temperature compensation devices for air source heat pumps, the method is implemented as follows: (1) Read the parameter table; (2) Check whether there is communication data; (3) If communication data is found, the communication function is executed: Parameter table reading; Parameter table updated; Clock setting; (4) If no communication data is found, perform the following operations: Collect ambient temperature; Outlet water temperature compensation; Return water temperature compensation.

[0019] Furthermore, the method includes the following contents: (1) Connect the total outlet water temperature sensor and the total return water temperature sensor of the air source heat pump unit to the water temperature compensation device, and connect digital potentiometers in parallel and series to adjust the resistance value; The adjusted resistor is reconnected to the original sensor position of the air source heat pump; the water temperature is compensated by compensating the sensor resistance value; (2) The water temperature compensation device is equipped with an ambient temperature sensor to collect the ambient temperature; The water temperature compensation device has a real-time clock function and is calibrated by communicating with the upper platform; The collected ambient temperature and real-time clock value are used as the basis for water temperature compensation; (3) The water temperature compensation device is equipped with an RS485 interface, supports ModbusRTU protocol, and can be connected to PLC and DTU devices; The water temperature compensation device has built-in ambient temperature compensation parameter table and time compensation parameter table. The upper platform customizes the compensation strategy of the water temperature compensation device by updating the temperature compensation parameter table and the time compensation parameter table. (4) The water temperature compensation device calculates the temperature compensation value according to the contents of the temperature compensation parameter table and the time compensation parameter table, as well as the current outlet water temperature and return water temperature, and obtains the compensated outlet water temperature and return water temperature, and then calculates the outlet water temperature sensor resistance value and the return water temperature sensor resistance value by using the table lookup interpolation method; (5) The water temperature compensation device uses a circular comparison method to find the compensation value of the parallel digital potentiometer and the compensation value of the series digital potentiometer with the smallest error based on the calculated resistance value of the outlet water temperature sensor and the resistance value of the return water temperature sensor, and outputs them so that the resistance value of the temperature sensor is close to the required resistance value and the error is minimized; (6) The air source heat pump controller collects the compensated resistance values ​​of the outlet water temperature sensor and the return water temperature sensor. The detected temperature deviates from the actual water temperature. The deviation is used to guide the air source heat pump controller to perform corresponding heat pump load increase and decrease operations, so that the actual supply and return water temperatures reach the compensated supply and return water temperature set values, thereby achieving control of the entire system.

[0020] Furthermore, the water temperature compensation is achieved by calculating the resistance values ​​of digital potentiometers U4 and U5, and the process is as follows: (1) Collect voltages V1A and V1B; (2) Calculate the water temperature sensor resistance R1IN; (3) Check the resistance table to calculate the current water outlet temperature T1; (4) Calculate the compensated water outlet temperature T2 according to the compensation table; (5) Calculate the resistance R1OUT of the water temperature sensor by looking up the resistance table; (6) Calculate the compensation resistor values ​​RU4 and RU5; (7) Output through digital potentiometer.

[0021] The calculation process of the return water temperature compensation is similar to the calculation process of the outlet water temperature compensation.

[0022] Furthermore, the calculation process of the outlet water temperature compensation is as follows: (1) Collect voltages V1A and V1B through ADC; (2) According to Ohm's law, the resistance of the water outlet temperature sensor is calculated using the following formula:

[0023] (3) According to the resistance value R1IN and the sensor temperature resistance table, interpolate and calculate the current water outlet temperature T1; (4) According to the ambient temperature value and the ambient temperature / water temperature compensation table, the ambient temperature compensation value TA is calculated by interpolation. According to the current time and the time / water temperature compensation table, the time compensation value TB is interpolated and calculated; Calculate the compensated water outlet temperature value:

[0024] (5) According to the outlet water temperature T2 and the sensor temperature resistance table, interpolate and calculate the compensated outlet water temperature sensor resistance value R1OUT.

[0025] Furthermore, the calculation process of the compensation resistors RU4 and RU5 is as follows: (1) According to Ohm’s law, R U5 Calculated as follows:

[0026] If it exceeds the digital potentiometer resistance range, the minimum resistance or maximum resistance is used; (2) According to Ohm’s law, recalculate R U4 , so that the error of the entire circuit is minimized, calculated according to the following formula:

[0027] According to the calculated results, R U4 and R U5 , write to the digital potentiometer chips U4 and U5 through the SPI bus.

[0028] Compared with the prior art, the air source heat pump water temperature compensation device and method of the present invention has the following outstanding beneficial effects: The air source heat pump water temperature compensation device designed by the present invention has a clear implementation principle and universal adaptability, and can be applied to most of the air source heat pump energy-saving transformation projects currently on the market. In addition, the device has low manufacturing cost and obvious energy-saving effect, and has a good promotion and application value in the energy-saving transformation application of air source heat pumps. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a block diagram of the air source heat pump water temperature compensation device of the present invention; Figure 2This is a circuit diagram of the water temperature compensation device for an air source heat pump of the present invention; Figure 3 is an equivalent circuit diagram of a temperature sensor compensation circuit of the present invention; Figure 4 is a flow chart of the compensation method of the present invention; Figure 5 This is a flow chart of the water outlet temperature compensation of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0031] like Figure 1 As shown, an air source heat pump water temperature compensation device, the air source heat pump water temperature compensation device comprises: a control circuit, a power supply circuit, an outlet water temperature compensation circuit, a return water temperature compensation circuit, and an RS485 communication circuit; The control circuit comprises a single-chip microcomputer MCU, and utilizes the ADC, UART, and GPIO functions integrated in the MCU chip to realize the control function of the entire device; The air source heat pump water temperature compensation device is powered by the +5V power output port of the control circuit, and generates the 3.3V voltage required by the MCU and ADC through the voltage regulator chip; The air source heat pump water temperature compensation device is short-circuited with the ground wire of the control circuit; The outlet water temperature compensation circuit and the return water temperature compensation circuit perform resistance compensation processing on the temperature sensor, connect a digital potentiometer in parallel at both ends of the outlet water temperature sensor, and then connect another digital potentiometer in series to form a compensable temperature sensor. The control circuit achieves fine-tuning of the resistance value of the temperature sensor by modifying the resistance value of the two digital potentiometers.

[0032] The RS485 communication circuit includes an RS485 interface chip to realize the communication function with the host computer.

[0033] Furthermore, the external interfaces of the air source heat pump water temperature compensation device include: power supply interface, temperature sensor input interface, temperature sensor output interface, RS485 communication interface, wherein: The power interface is connected to the +5V power supply of the control circuit; The air source heat pump water temperature compensation device has three temperature sensor input interfaces: an ambient temperature sensor input interface, an outlet water temperature sensor input interface, and a return water temperature sensor input interface, wherein: The ambient temperature sensor input interface is connected to the standard temperature sensor to detect the outdoor ambient temperature as the basis for temperature compensation; The outlet water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the outlet water temperature compensation circuit as the reference resistor of the outlet water temperature compensation circuit; The return water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the return water temperature compensation circuit as the reference resistor of the return water temperature compensation circuit; The warm air source heat pump water temperature compensation device has two temperature sensor output interfaces: an outlet water temperature sensor output interface and a return water temperature sensor output interface, wherein: The outlet water temperature sensor output interface is connected to the outlet water temperature sensor interface in the air source heat pump control circuit, and the outlet water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The return water temperature sensor output interface is connected to the return water temperature sensor interface in the air source heat pump control circuit, and the return water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The air source heat pump water temperature compensation device is provided with an RS485 communication interface, supports the ModbusRTU protocol, and is used to connect to a host computer; through the RS485 communication interface, the sensor resistance table and compensation parameters of the air source heat pump water temperature compensation device are set, and the ambient temperature, outlet water temperature, and return water temperature are collected.

[0034] like Figure 2 As shown, the control circuit comprises an MCU chip U1, wherein the chip U1 has: The P1.0 / A0 pin is an ADC port, which is used to collect the voltage of the ambient temperature sensor R3IN and calculate the ambient temperature value; The P1.4 / A4 and P1.5 / A5 pins are ADC ports, which are used to collect the voltages of V1A and V1B in the outlet water temperature compensation circuit and calculate the actual outlet water temperature value; The P1.6 / A6 and P1.7 / A7 pins are ADC ports, which are used to collect the voltages of V2A and V2B in the return water temperature compensation circuit and calculate the actual return water temperature value; P1.1 / RXD and P1.2 / TXD pins are UART ports, realizing RS485 communication function; The pins P2.0, P2.1, P2.2, P2.3, P2.4, and P2.5 are GPIO ports, which realize the SPI control function of the U4, U5, U6, and U7 digital potentiometer chips; MCU has built-in FLASH memory to save and read compensation parameters; The MCU has a built-in timer to implement the real-time clock function and synchronize the clock with the host computer through communication.

[0035] Furthermore, the power supply circuit adopts a step-down DC / DC conversion chip to convert the +5V voltage into a 3.3V voltage; The RS485 communication circuit is implemented by the RS485 interface chip U3.

[0036] like Figure 3 As shown, the outlet water temperature sensor compensation circuit uses a digital potentiometer chip to realize the compensation of the resistance value of the outlet water temperature sensor R1IN. First, a digital potentiometer U5 is connected in parallel at both ends of R1IN, and the parallel resistor is then connected in series with the digital potentiometer U4; Among them, R0 is the resistance inside the air source heat pump controller circuit, U4 uses a 5KΩ / 256 tap digital potentiometer, and U5 uses a 100KΩ / 256 tap digital potentiometer.

[0037] The return water temperature sensor compensation circuit is similar to the outlet water temperature sensor compensation circuit.

[0038] like Figure 4 As shown, a method for water temperature compensation of an air source heat pump is provided, and the implementation process of the method is as follows: (1) Read the parameter table; (2) Check whether there is communication data; (3) If communication data is found, the communication function is executed: Parameter table reading; Parameter table updated; Clock setting; (4) If no communication data is found, perform the following operations: Collect ambient temperature; Outlet water temperature compensation; Return water temperature compensation.

[0039] Furthermore, the method includes the following contents: (1) Connect the total outlet water temperature sensor and the total return water temperature sensor of the air source heat pump unit to the water temperature compensation device, and connect digital potentiometers in parallel and series to adjust the resistance value; The adjusted resistor is reconnected to the original sensor position of the air source heat pump; the water temperature is compensated by compensating the sensor resistance value; (2) The water temperature compensation device is equipped with an ambient temperature sensor to collect the ambient temperature; The water temperature compensation device has a real-time clock function and is calibrated by communicating with the upper platform; The collected ambient temperature and real-time clock value are used as the basis for water temperature compensation; (3) The water temperature compensation device is equipped with an RS485 interface, supports ModbusRTU protocol, and can be connected to PLC and DTU devices; The water temperature compensation device has built-in ambient temperature compensation parameter table and time compensation parameter table. The upper platform customizes the compensation strategy of the water temperature compensation device by updating the temperature compensation parameter table and the time compensation parameter table. (4) The water temperature compensation device calculates the temperature compensation value according to the contents of the temperature compensation parameter table and the time compensation parameter table, as well as the current outlet water temperature and return water temperature, and obtains the compensated outlet water temperature and return water temperature, and then calculates the outlet water temperature sensor resistance value and the return water temperature sensor resistance value by using the table lookup interpolation method; (5) The water temperature compensation device uses a circular comparison method to find the compensation value of the parallel digital potentiometer and the compensation value of the series digital potentiometer with the smallest error based on the calculated resistance value of the outlet water temperature sensor and the resistance value of the return water temperature sensor, and outputs them so that the resistance value of the temperature sensor is close to the required resistance value and the error is minimized; (6) The air source heat pump controller collects the compensated resistance values ​​of the outlet water temperature sensor and the return water temperature sensor. The detected temperature deviates from the actual water temperature. The deviation is used to guide the air source heat pump controller to perform corresponding heat pump load increase and decrease operations, so that the actual supply and return water temperatures reach the compensated supply and return water temperature set values, thereby achieving control of the entire system.

[0040] like Figure 5 As shown, the water temperature compensation is achieved by calculating the resistance values ​​of digital potentiometers U4 and U5, and the process is as follows: (1) Collect voltages V1A and V1B; (2) Calculate the water temperature sensor resistance R1IN; (3) Check the resistance table to calculate the current water outlet temperature T1; (4) Calculate the compensated water outlet temperature T2 according to the compensation table; (5) Calculate the resistance R1OUT of the water temperature sensor by looking up the resistance table; (6) Calculate the compensation resistor values ​​RU4 and RU5; (7) Output through digital potentiometer.

[0041] The calculation process of the return water temperature compensation is similar to the calculation process of the outlet water temperature compensation.

[0042] Examples of known conditions: Comparison table of some temperature resistance values ​​of air source heat pump temperature sensors: Ambient temperature compensation value in the current environment: TA = -2°C Time compensation value at current time: TB = 0.2°C The ADC collected voltage for this sampling: V1A=1.101V V1B=0.873V The digital potentiometer resistance before this calculation: RU4=1.035.2Ω(53 taps), RU5=15234.4Ω (39 taps) Furthermore, the calculation process of the outlet water temperature compensation is as follows: (1) Collect voltages V1A and V1B through ADC (V1A=1.101V, V1B=0.873V); (2) According to Ohm's law, calculate the resistance of the outlet water temperature sensor using the following formula (substitute the actual value for calculation):

[0043]

[0044] = 5357.7Ω (3) According to the resistance value R1IN and the sensor temperature resistance table, interpolate and calculate the current water outlet temperature T1; T1 = 39.8℃ According to the ambient temperature value and the ambient temperature / water temperature compensation table, the ambient temperature compensation value TA is calculated by interpolation. According to the current time and the time / water temperature compensation table, the time compensation value TB is interpolated and calculated; Calculate the compensated water outlet temperature value: = 39.8+2-0.2 = 41.6℃ (5) According to the outlet water temperature T2 and the sensor temperature resistance table, interpolate and calculate the compensated outlet water temperature sensor resistance value R1OUT.

[0045] R1OUT = 4986.6Ω Furthermore, the calculation process of the compensation resistors RU4 and RU5 is as follows: (1) According to Ohm’s law, R U5 Calculated as follows:

[0046] = 15054.0Ω If it exceeds the digital potentiometer resistance range, the minimum resistance or maximum resistance is used; U5 tap number = 38.52, take 39 taps Corrected U5 resistance value = 15234.4Ω (2) According to Ohm’s law, recalculate R U4 , so that the error of the entire circuit is minimized, calculated according to the following formula:

[0047] = 1022.9Ω U4 tap number = 52.37, take 52 taps; According to the calculated results, R U4 and R U5 , write the 52-tap into the digital potentiometer chip U4 and the 39-tap into the digital potentiometer chip U5 through the SPI bus.

[0048] The embodiments described above are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. An air source heat pump water temperature compensation device, characterized in that: The air source heat pump water temperature compensation device comprises: a control circuit, a power supply circuit, an outlet water temperature compensation circuit, a return water temperature compensation circuit, and an RS485 communication circuit; The control circuit comprises a single-chip microcomputer MCU, and utilizes the ADC, UART, and GPIO functions integrated in the MCU chip to realize the control function of the entire device; The air source heat pump water temperature compensation device is powered by the +5V power output port of the control circuit, and generates the 3.3V voltage required by the MCU and ADC through the voltage regulator chip; The air source heat pump water temperature compensation device is short-circuited with the ground wire of the control circuit; The outlet water temperature compensation circuit and the return water temperature compensation circuit perform resistance compensation processing on the temperature sensor, connect a digital potentiometer in parallel at both ends of the outlet water temperature sensor, and then connect another digital potentiometer in series to form a compensable temperature sensor. The control circuit realizes fine adjustment of the resistance value of the temperature sensor by modifying the resistance value of the two digital potentiometers. The RS485 communication circuit includes an RS485 interface chip to realize the communication function with the host computer.

2. The air source heat pump water temperature compensation device according to claim 1, characterized in that: The external interfaces of the air source heat pump water temperature compensation device include: power supply interface, temperature sensor input interface, temperature sensor output interface, RS485 communication interface, among which: The power interface is connected to the +5V power supply of the control circuit; The air source heat pump water temperature compensation device has three temperature sensor input interfaces: an ambient temperature sensor input interface, an outlet water temperature sensor input interface, and a return water temperature sensor input interface, wherein: The ambient temperature sensor input interface is connected to the standard temperature sensor to detect the outdoor ambient temperature as the basis for temperature compensation; The outlet water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the outlet water temperature compensation circuit as the reference resistor of the outlet water temperature compensation circuit; The return water temperature sensor input interface is connected to the sensor configured in the original air source heat pump, and is connected to the return water temperature compensation circuit as the reference resistor of the return water temperature compensation circuit; The warm air source heat pump water temperature compensation device has two temperature sensor output interfaces: an outlet water temperature sensor output interface and a return water temperature sensor output interface, wherein: The outlet water temperature sensor output interface is connected to the outlet water temperature sensor interface in the air source heat pump control circuit, and the outlet water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The return water temperature sensor output interface is connected to the return water temperature sensor interface in the air source heat pump control circuit, and the return water temperature sensor resistance value detected by the air source heat pump controller is the compensated resistance value; The air source heat pump water temperature compensation device is provided with an RS485 communication interface, supports the ModbusRTU protocol, and is used to connect to a host computer; through the RS485 communication interface, the sensor resistance table and compensation parameters of the air source heat pump water temperature compensation device are set, and the ambient temperature, outlet water temperature, and return water temperature are collected.

3. The air source heat pump water temperature compensation device according to claim 1, characterized in that: The control circuit comprises an MCU chip U1, wherein the chip U1 comprises: The P1.0 / A0 pin is an ADC port, which is used to collect the voltage of the ambient temperature sensor R3IN and calculate the ambient temperature value; The P1.4 / A4 and P1.5 / A5 pins are ADC ports, which are used to collect the voltages of V1A and V1B in the outlet water temperature compensation circuit and calculate the actual outlet water temperature value; The P1.6 / A6 and P1.7 / A7 pins are ADC ports, which are used to collect the voltages of V2A and V2B in the return water temperature compensation circuit and calculate the actual return water temperature value; P1.1 / RXD and P1.2 / TXD pins are UART ports, realizing RS485 communication function; The pins P2.0, P2.1, P2.2, P2.3, P2.4, and P2.5 are GPIO ports, which realize the SPI control function of the U4, U5, U6, and U7 digital potentiometer chips; MCU has built-in FLASH memory to save and read compensation parameters; The MCU has a built-in timer to implement the real-time clock function and synchronize the clock with the host computer through communication.

4. The air source heat pump water temperature compensation device according to claim 1, characterized in that: The power supply circuit adopts a step-down DC / DC conversion chip to convert the +5V voltage into a 3.3V voltage; The RS485 communication circuit is implemented by the RS485 interface chip U3.

5. The air source heat pump water temperature compensation device according to claim 1, characterized in that: The outlet water temperature sensor compensation circuit adopts a digital potentiometer chip to realize the compensation of the resistance value of the outlet water temperature sensor R1IN. First, a digital potentiometer U5 is connected in parallel at both ends of R1IN, and the parallel resistor is then connected in series with the digital potentiometer U4. Among them, R0 is the resistance inside the air source heat pump controller circuit, U4 uses a 5KΩ / 256 tap digital potentiometer, and U5 uses a 100KΩ / 256 tap digital potentiometer.

6. A water temperature compensation method for an air source heat pump, characterized in that: Based on the air source heat pump water temperature compensation device according to any of the above claims, the method implementation process is as follows: (1) Read the parameter table; (2) Check whether there is communication data; (3) If communication data is found, the communication function is executed: Parameter table reading; Parameter table updated; Clock setting; (4) If no communication data is found, perform the following operations: Collect ambient temperature; Outlet water temperature compensation; Return water temperature compensation.

7. The air source heat pump water temperature compensation method according to claim 6, characterized in that: The method includes the following contents: (1) Connect the total outlet water temperature sensor and the total return water temperature sensor of the air source heat pump unit to the water temperature compensation device, and connect digital potentiometers in parallel and series to adjust the resistance value; The adjusted resistor is reconnected to the original sensor position of the air source heat pump; the water temperature is compensated by compensating the sensor resistance value; (2) The water temperature compensation device is equipped with an ambient temperature sensor to collect the ambient temperature; The water temperature compensation device has a real-time clock function and is calibrated by communicating with the upper platform; The collected ambient temperature and real-time clock value are used as the basis for water temperature compensation; (3) The water temperature compensation device is equipped with an RS485 interface, supports ModbusRTU protocol, and can be connected to PLC and DTU devices; The water temperature compensation device has built-in ambient temperature compensation parameter table and time compensation parameter table. The upper platform customizes the compensation strategy of the water temperature compensation device by updating the temperature compensation parameter table and the time compensation parameter table. (4) The water temperature compensation device calculates the temperature compensation value according to the contents of the temperature compensation parameter table and the time compensation parameter table, as well as the current outlet water temperature and return water temperature, and obtains the compensated outlet water temperature and return water temperature, and then calculates the outlet water temperature sensor resistance value and the return water temperature sensor resistance value by using the table lookup interpolation method; (5) The water temperature compensation device uses a circular comparison method to find the compensation value of the parallel digital potentiometer and the compensation value of the series digital potentiometer with the smallest error based on the calculated resistance value of the outlet water temperature sensor and the resistance value of the return water temperature sensor, and outputs them so that the resistance value of the temperature sensor is close to the required resistance value and the error is minimized; (6) The air source heat pump controller collects the compensated resistance values ​​of the outlet water temperature sensor and the return water temperature sensor. The detected temperature deviates from the actual water temperature. The deviation is used to guide the air source heat pump controller to perform corresponding heat pump load increase and decrease operations, so that the actual supply and return water temperatures reach the compensated supply and return water temperature set values, thereby achieving control of the entire system.

8. The air source heat pump water temperature compensation method according to claim 7, characterized in that: The water temperature compensation is achieved by calculating the resistance values ​​of digital potentiometers U4 and U5. The process is as follows: (1) Collect voltages V1A and V1B; (2) Calculate the water temperature sensor resistance R1IN; (3) Check the resistance table to calculate the current water outlet temperature T1; (4) Calculate the compensated water outlet temperature T2 according to the compensation table; (5) Calculate the resistance R1OUT of the water temperature sensor by looking up the resistance table; (6) Calculate the compensation resistor values ​​RU4 and RU5; (7) Output through digital potentiometer.

9. The air source heat pump water temperature compensation method according to claim 8, characterized in that: The calculation process of the outlet water temperature compensation is as follows: (1) Collect voltages V1A and V1B through ADC; (2) According to Ohm's law, the resistance of the water outlet temperature sensor is calculated using the following formula: ； (3) According to the resistance value R1IN and the sensor temperature resistance table, interpolate and calculate the current water outlet temperature T1; (4) According to the ambient temperature value and the ambient temperature / water temperature compensation table, the ambient temperature compensation value TA is calculated by interpolation. According to the current time and the time / water temperature compensation table, the time compensation value TB is interpolated and calculated; Calculate the compensated water outlet temperature value: ； (5) According to the outlet water temperature T2 and the sensor temperature resistance table, interpolate and calculate the compensated outlet water temperature sensor resistance value R1OUT.

10. The air source heat pump water temperature compensation method according to claim 9, characterized in that: The calculation process of the compensation resistors RU4 and RU5 is as follows: (1) According to Ohm’s law, R U5 Calculated as follows: ； If it exceeds the digital potentiometer resistance range, the minimum resistance or maximum resistance is used; (2) According to Ohm’s law, recalculate R U4 , so that the error of the entire circuit is minimized, calculated according to the following formula: ； According to the calculated results, R U4 and R U5 , write to the digital potentiometer chips U4 and U5 through the SPI bus.

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