A high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system and method

Abstract

This application discloses a high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system and method. The control system includes a data acquisition module, a control module, and a storage module. The control module executes different control logics according to different operating states of the centrifugal heat pump unit: during shutdown, it controls the on / off state of multi-stage oil heaters based on the oil tank temperature using a hysteresis switching method; during startup, it calculates the oil temperature difference based on the pre-stored refrigerant saturation temperature-pressure relationship data according to the oil tank pressure; during operation, it controls the start / stop of each stage of heaters based on the oil temperature difference, and simultaneously controls the opening of two oil cooling valves independently using a PID algorithm with bearing temperature as feedback. When the compressor shaft oil temperature difference or motor shaft oil temperature difference exceeds the limit, it automatically lowers the target temperature to enhance cooling. This application achieves full-condition management of lubricating oil temperature by introducing an oil temperature difference index, graded heating, and a sensor failure degradation mechanism, reducing the risk of bearing damage due to poor lubrication or overheating.

Description

Technical Field

[0001] This application relates to the field of lubricating oil temperature control technology for centrifugal heat pump units, specifically to a high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system and method. Background Technology

[0002] In centrifugal refrigeration / heat pump units, the compressor bearings require lubricating oil for lubrication and cooling. The temperature of the lubricating oil directly affects its viscosity and purity, which in turn affects the lubrication effect and service life of the bearings.

[0003] In conventional centrifugal refrigeration units, the evaporator and condenser operate at relatively low temperatures. The lubricating oil only needs to be heated to a relatively low temperature to maintain its purity, preventing excessive dissolution of the refrigerant. Therefore, traditional oil temperature control schemes typically rely solely on the oil bath temperature, managing oil temperature by controlling the start and stop of the oil heater.

[0004] However, the operating conditions of high-pressure-ratio, high-temperature centrifugal heat pump units differ significantly from those of conventional refrigeration units. The evaporators and condensers of high-temperature centrifugal heat pump units operate at high temperatures, which presents the following challenges to lubrication management:

[0005] (1) When the oil temperature is too high, the viscosity of the lubricating oil decreases (becomes thinner), the oil supply temperature is too high, the lubrication and cooling effect on the bearings becomes worse, and in severe cases, the lubricating oil may even carbonize.

[0006] (2) When the oil temperature is too low, the refrigerant content in the lubricating oil is too high, and the lubricating effect of the lubricating oil is greatly reduced, which may cause damage to the bearing;

[0007] (3) Due to the wide operating temperature range and large pressure ratio of the high-pressure-ratio high-temperature centrifugal heat pump unit, the saturation temperature of the refrigerant in the oil tank varies greatly with the operating conditions. Under different operating conditions, even if the oil tank temperature is the same, the degree of dissolution of the refrigerant in the lubricating oil may vary greatly. The existing control scheme based solely on the absolute temperature of the oil tank is difficult to adapt to this characteristic of variable operating conditions.

[0008] (4) The existing solution has shortcomings in handling the failure of bearing temperature sensor. When the sensor fails, it is difficult to balance the availability of centrifugal heat pump unit and the safety protection of bearing.

[0009] Therefore, there is a need for an oil temperature management system and method that can comprehensively consider multiple operating parameters, perform hierarchical and precise control, and have sensor failure protection capabilities to ensure the safe and stable operation of high-pressure-ratio high-temperature centrifugal heat pump units. Summary of the Invention

[0010] To address the technical problems of insufficient lubricating oil temperature control accuracy, inaccurate judgment of lubricating oil quality before startup, and insufficient sensor failure protection capability in existing high-pressure-ratio high-temperature centrifugal heat pump units, this application provides a high-pressure-ratio high-temperature centrifugal heat pump oil temperature control system and method.

[0011] The purpose of this application is to provide a high-pressure-ratio high-temperature centrifugal heat pump oil temperature control system and method. By monitoring multiple parameters such as oil tank temperature, oil supply temperature, oil temperature difference, bearing temperature, and shaft-oil temperature difference, the system controls the oil heater and oil cooling device in stages and has the ability to degrade protection in case of sensor failure, so that the compressor lubricating oil always works within a suitable temperature range, thereby ensuring the safe and stable operation of the high-pressure-ratio centrifugal heat pump.

[0012] To achieve the above objectives, this application provides a high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system for controlling the lubricating oil system of a centrifugal heat pump unit. The lubricating oil system includes: an oil tank, an oil pump, a compressor bearing oil cooler, a motor bearing oil cooler, a compressor bearing oil cooling valve, a motor bearing oil cooling valve, and a multi-stage oil heater disposed within the oil tank. The multi-stage oil heater includes at least two independently switched heating units. The inlet of the oil pump is connected to the outlet of the oil tank, and the outlet of the oil pump is divided into a first oil supply branch and a second oil supply branch via a diversion structure. The oil-side inlet of the compressor bearing oil cooler is connected to the first oil supply branch, and its oil-side outlet is connected to... The compressor bearing's oil supply port is connected; the oil-side inlet of the motor bearing oil cooler is connected to the second oil supply branch, and its oil-side outlet is connected to the motor bearing's oil supply port; the compressor bearing oil cooling valve is installed on the refrigerant inlet pipe of the compressor bearing oil cooler, used to regulate the refrigerant flow through the compressor bearing oil cooler; the motor bearing oil cooling valve is installed on the refrigerant inlet pipe of the motor bearing oil cooler, used to regulate the refrigerant flow through the motor bearing oil cooler; the return oil ports of both the compressor bearing and the motor bearing are connected to the oil sump, forming a lubricating oil circulation loop; characterized in that the high-pressure-ratio high-temperature centrifugal heat pump oil temperature control system includes:

[0013] The data acquisition module is electrically connected to the oil tank temperature sensor, oil tank pressure sensor, compressor oil supply temperature sensor, motor oil supply temperature sensor, compressor bearing temperature sensor, and motor bearing temperature sensor, respectively, and is used to periodically collect the oil tank temperature at a preset fixed sampling period. Pressure of the vapor space in the oil tank Compressor oil supply temperature Motor oil supply temperature Compressor bearing temperature and motor bearing temperature ;

[0014] The control module is electrically connected to the primary oil heater, the secondary oil heater, the compressor bearing oil cooling valve, the motor bearing oil cooling valve, and the oil pump. The control module is also communicatively connected to the main controller of the centrifugal heat pump unit, and is used to receive operating status signals and start-up request signals from the main controller. The control module executes different control logics based on different operating states of the centrifugal heat pump unit, including:

[0015] When the centrifugal heat pump unit is in a shutdown state, the control module is based on With heating start-up temperature limit and upper limit of heating stop temperature The on / off state of the multi-stage oil heater is controlled by a switching control method to maintain the oil tank temperature within a preset range.

[0016] When the centrifugal heat pump unit is in the start-up phase, the control module according to The saturated refrigerant temperature in the oil tank is obtained by querying the pre-stored saturated temperature-pressure relationship data corresponding to the refrigerant used in the centrifugal heat pump unit. Calculate the oil temperature difference It employs a startup request-startup license interaction mechanism; upon receiving a startup request, it will only grant a license if... The system sends a start permission signal to the compressor when the start is in time; otherwise, it remains in the start-prevented state. At the same time, the control module continues to run the oil heating control to continuously heat the lubricating oil to increase the oil temperature difference.

[0017] When the centrifugal heat pump unit is in operation, the control module continuously adjusts according to... Query the saturation temperature-pressure relationship data to obtain Real-time calculation and based on The system uses a multi-level start-stop threshold calculated based on a reference oil temperature difference and a step temperature difference to control the start-stop of each heating unit in a graded manner; simultaneously, it uses... and As a feedback quantity, the opening degree of the compressor bearing oil cooling valve and the motor bearing oil cooling valve is controlled by a PID algorithm; and the compressor shaft oil temperature difference is calculated in real time. and motor shaft oil temperature difference ,when Exceeding the preset upper limit of compressor side shaft oil temperature difference At that time, the preset correction temperature difference of the PID control target temperature of the compressor bearing is adjusted to enhance cooling. Fall back to no more than Then restore the original target temperature; when Exceeding the preset upper limit of motor side shaft oil temperature difference At that time, the preset correction temperature difference of the PID control target temperature of the motor bearing is adjusted to enhance cooling. After the temperature drops, the original target temperature will be restored.

[0018] This application also provides a method for controlling the oil temperature of a high-pressure-ratio, high-temperature centrifugal heat pump, used to control the lubricating oil system of a centrifugal heat pump unit. The lubricating oil system includes: an oil tank (1), an oil pump (2), a compressor bearing oil cooler (31), a motor bearing oil cooler (32), a compressor bearing oil cooling valve (41), a motor bearing oil cooling valve (42), and a multi-stage oil heater disposed in the oil tank. The multi-stage oil heater includes at least two independently switched heating units. The inlet of the oil pump (2) is connected to the outlet of the oil tank (1), and the outlet of the oil pump (2) is divided into a first oil supply branch and a second oil supply branch via a diversion structure (21). The oil-side inlet of the device (31) is connected to the first oil supply branch, and its oil-side outlet is connected to the oil supply port of the compressor bearing (51); the oil-side inlet of the motor bearing oil cooler (32) is connected to the second oil supply branch, and its oil-side outlet is connected to the oil supply port of the motor bearing (52); the compressor bearing oil cooling valve (41) is installed on the refrigerant inlet pipe of the compressor bearing oil cooler (31) to regulate the refrigerant flow through the compressor bearing oil cooler (31); the motor bearing oil cooling valve (42) is installed on the refrigerant inlet pipe of the motor bearing oil cooler (32) to regulate the refrigerant flow through the motor bearing oil cooler (32); the oil return ports of the compressor bearing (51) and the motor bearing (52) are both connected to the oil sump to form a lubricating oil circulation loop, characterized in that the high pressure ratio high temperature centrifugal heat pump oil temperature control method includes:

[0019] Data acquisition steps: Collect data periodically at a preset fixed sampling period. , , , , and The validity of the output signal of each sensor is checked in each sampling period, including range overrun detection and continuous failure timing.

[0020] Oil temperature control steps during shutdown: Based on on / off control. and , The comparison, with hysteresis control of the multi-stage oil heater on / off; when At the same time, all heating units are activated to raise the oil temperature as quickly as possible; when At the same time, all heating units are turned off; when At this time, the current on / off state remains unchanged;

[0021] Startup phase oil temperature control steps: Query pre-stored saturation temperature-pressure relationship data corresponding to the refrigerant used, and calculate... It adopts a startup request-startup license interaction mechanism, and only when... Issue startup permission at the appropriate time; if If the start-prevention state is maintained, the oil temperature control steps during the shutdown phase will continue to heat the lubricating oil to increase the oil temperature difference until... Then issue a startup license;

[0022] Oil temperature control steps during operation: Based on The start-up and shutdown of each heating unit is controlled in stages according to thresholds, with the start-up oil temperature difference of the first-stage oil heater being the primary factor. and step temperature difference Calculate the start / stop thresholds for each stage of the heater to achieve orderly, hierarchical control of the first-stage heater (start first, then stop) and the second-stage heater (start last, then stop). And respectively... , To provide feedback for controlling the opening of the two oil cooling valves using a PID algorithm, after startup, the opening of each valve is initialized to its preset minimum opening, which is then used as the lower limit of the PID output opening. When the compressor shaft oil temperature difference... Or motor shaft oil temperature difference When the temperature exceeds the preset high limit, the target temperature of the corresponding bearing is lowered to enhance cooling. After the temperature difference returns to normal, the target temperature is restored.

[0023] Sensor failure degradation control steps: When the compressor bearing temperature sensor fails, the PID closed-loop calculation of the compressor bearing temperature is terminated, and the compressor bearing oil cooling valve is kept at a preset safe fixed opening; when the motor bearing temperature sensor fails, the PID closed-loop calculation of the motor bearing temperature is terminated, and the motor bearing oil cooling valve is kept at a preset safe fixed opening; the two degradation controls are independent of each other.

[0024] State switching steps: When the centrifugal heat pump unit switches from the running state to the shutdown state, the control is switched from the oil temperature control step during the running phase to the oil temperature control step during the shutdown phase. The two oil cooling valves are closed to their minimum opening, the PID calculation is stopped, and the control is switched to on / off control based on the oil tank temperature. When a start request is received again, the oil temperature control step during the start phase is executed to determine the preconditions for start-up.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. By collecting oil tank pressure and querying pre-stored refrigerant saturation temperature-pressure relationship data, the oil temperature difference (the difference between the oil tank temperature and the saturated refrigerant temperature in the oil tank) is calculated in real time. Whether the oil temperature difference exceeds a preset lower limit is used as a prerequisite for sending a start-up permission signal to the compressor. Compared with the traditional scheme that only uses oil tank temperature as the control basis, the oil temperature difference can quantitatively reflect the degree of refrigerant solubility in the lubricating oil, avoiding starting the compressor when the lubricating oil quality does not meet the requirements, thereby reducing the risk of bearing damage due to poor lubrication.

[0027] 2. During operation, based on the comparison results between the oil temperature difference and multiple graded thresholds (calculated from the reference oil temperature difference and the step temperature difference), orderly graded control is achieved, with the first-stage heater starting first and then stopping, and the second-stage heater starting last and stopping first. The start-up threshold of each heater is lower than its shut-off threshold, forming a hysteresis control band with the oil temperature difference as the variable. This prevents each heater from repeatedly switching on and off at the same temperature point, extending the service life of the heaters. Furthermore, the heating power during operation can be gradually increased or decreased according to changes in the oil temperature difference, reducing oil temperature fluctuations.

[0028] 3. During operation, the compressor shaft oil temperature difference and motor shaft oil temperature difference are calculated in real time. When the temperature difference of either shaft oil exceeds the preset high limit, the PID control target temperature of the corresponding bearing is automatically lowered to the preset correction temperature difference, which causes the oil cooling valve opening to increase and the refrigerant flow to increase. After the shaft oil temperature difference returns to normal, the target temperature is restored. When the bearing temperature sensor fails, the corresponding PID closed-loop calculation is automatically terminated and the corresponding oil cooling valve is kept at the preset safe fixed opening. The two protection mechanisms are independent of each other, and the failure of one circuit does not affect the normal operation of the other circuit. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the lubricating oil system and oil temperature control system of this application;

[0030] Figure 2 This is a flowchart of the oil temperature control process during the shutdown phase of this application;

[0031] Figure 3 This is a flowchart of the graded control process for the oil heater during the operation phase of this application;

[0032] Figure 4 This is a flowchart of the compressor bearing oil cooling valve control process in this application;

[0033] Figure 5 This is a flowchart of the control process for the motor bearing oil cooling valve in this application.

[0034] Figure 6 This is the logic diagram for sensor failure degradation control in this application.

[0035] Explanation of reference numerals in the attached diagram: 1. Oil tank; 11. Primary oil heater; 12. Secondary oil heater; 13. Oil tank temperature sensor; 14. Oil tank pressure sensor; 2. Oil pump; 21. Diverter structure; 31. Compressor bearing oil cooler; 32. Motor bearing oil cooler; 41. Compressor bearing oil cooling valve; 42. Motor bearing oil cooling valve; 51. Compressor bearing; 52. Motor bearing; 53. Compressor; 54. Motor; 61. Refrigerant inlet pipe; 62. Refrigerant outlet pipe; 71. Compressor oil supply temperature sensor; 72. Motor oil supply temperature sensor; 73. Compressor bearing temperature sensor; 74. Motor bearing temperature sensor; 8. High-pressure-ratio high-temperature centrifugal heat pump oil temperature control system; 81. Data acquisition module; 82. Control module; 83. Storage module. Detailed Implementation

[0036] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of this application, but are not limited thereto. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are also within the protection scope of this application.

[0037] Note: In this application, the "SP-" prefix in each parameter symbol represents "Set Point", that is, the pre-set control parameter value.

[0038] This application achieves the effect of ensuring the lubricating oil operates within a suitable temperature range and guaranteeing the safe and stable operation of the centrifugal heat pump unit by monitoring multiple operating parameters, controlling oil temperature in stages, and implementing a degradation strategy to deal with sensor failure. The following is a further detailed description of this application.

[0039] Example 1

[0040] Please refer to Figure 1The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system 8 provided in this application includes a data acquisition module 81, a control module 82, and a storage module 83. The data acquisition module 81 is electrically connected to each sensor in the lubricating oil system to collect measurement data. The control module 82 is electrically connected to each actuator in the lubricating oil system to execute different control logics according to different operating states of the centrifugal heat pump unit. The storage module 83 is electrically connected to both the data acquisition module 81 and the control module 82 to store saturation temperature-pressure relationship data and the set values ​​of each control parameter. In this embodiment, the data acquisition module 81, control module 82, and storage module 83 are integrated into the same programmable logic controller (PLC). The storage module 83 can be implemented using the PLC's internal Flash memory or an external EEPROM storage chip. The saturation temperature-pressure relationship data is stored in the form of a lookup table. The rows of the lookup table are pressure values ​​(unit: kPa), and the columns are the corresponding saturation temperature values ​​(unit: °C). The intervals of the pressure values ​​are set according to the refrigerant characteristics, with smaller intervals used in ranges with large pressure change rates to improve interpolation accuracy. Through the coordinated operation of the data acquisition module 81, control module 82 and storage module 83, the lubricating oil temperature is precisely controlled in stages by comprehensively considering multiple operating parameters. It also has sensor failure protection capabilities, ensuring the safe and stable operation of the high-pressure-ratio high-temperature centrifugal heat pump unit.

[0041] Please refer to Figure 1The lubricating oil system includes an oil tank 1, an oil pump 2, a compressor bearing oil cooler 31, a motor bearing oil cooler 32, a compressor bearing oil cooling valve 41, a motor bearing oil cooling valve 42, and a multi-stage oil heater disposed within the oil tank 1. The multi-stage oil heater includes at least two independently operated heating units: a primary oil heater 11 and a secondary oil heater 12. The inlet of the oil pump 2 is connected to the outlet of the oil tank 1, and the outlet of the oil pump 2 is divided into a first oil supply branch and a second oil supply branch via a diversion structure 21. The oil-side inlet of the compressor bearing oil cooler 31 is connected to the first oil supply branch, and its oil-side outlet is connected to the oil supply port of the compressor bearing 51; the oil-side inlet of the motor bearing oil cooler 32 is connected to the second oil supply branch, and its oil-side outlet is connected to the oil supply port of the motor bearing 52. The compressor bearing oil cooling valve 41 is installed on the refrigerant inlet pipe of the compressor bearing oil cooler 31 to regulate the refrigerant flow through the compressor bearing oil cooler 31; the motor bearing oil cooling valve 42 is installed on the refrigerant inlet pipe of the motor bearing oil cooler 32 to regulate the refrigerant flow through the motor bearing oil cooler 32. The refrigerant sides of the compressor bearing oil cooler 31 and the motor bearing oil cooler 32 are connected to the refrigerant circulation system of the centrifugal heat pump unit through the refrigerant inlet pipe 61 and the refrigerant outlet pipe 62, respectively. The refrigerant exchanges heat with the lubricating oil in the oil cooler, absorbing heat from the lubricating oil, thereby achieving cooling and regulation of the oil supply temperature. The oil return ports of the compressor bearing 51 and the motor bearing 52 are both connected to the oil sump 1, forming a lubricating oil circulation loop. The compressor bearing 51 is mounted on the compressor 53, and the motor bearing 52 is mounted on the motor 54. The motor 54 drives the compressor 53 to operate.

[0042] In the aforementioned lubricating oil circulation loop, lubricating oil is drawn from oil tank 1 by oil pump 2 and then divided into two paths by flow divider 21: the first supply branch sends lubricating oil to compressor bearing oil cooler 31 for cooling before supplying it to compressor bearing 51; the second supply branch sends lubricating oil to motor bearing oil cooler 32 for cooling before supplying it to motor bearing 52. After lubricating and cooling the bearings, the lubricating oil flows back to oil tank 1 through the return ports of each bearing, completing a complete cycle. By setting up two independent supply branches and oil coolers, the temperature of compressor bearing 51 and motor bearing 52 can be controlled separately for different operating conditions. Since the heat generation, heat dissipation conditions, and allowable maximum operating temperatures of compressor bearings and motor bearings may differ, the two independent controls allow the oil supply temperature of each bearing to be adjusted to its respective optimal range.

[0043] Specifically, the data acquisition module 81 is electrically connected to the oil tank temperature sensor 13, the oil tank pressure sensor 14, the compressor oil supply temperature sensor 71, the motor oil supply temperature sensor 72, the compressor bearing temperature sensor 73, and the motor bearing temperature sensor 74, respectively, to receive the output signals of each sensor. The oil tank temperature sensor 13 can be a thermocouple or a resistance temperature detector (RTD). Thermocouples have a fast response time, while RTDs offer higher measurement accuracy. It is installed inside the oil tank 1 to accurately measure the temperature of the lubricating oil within the oil tank 1. The oil tank pressure sensor 14 is typically a pressure transmitter, which converts the pressure signal in the gas phase space of the oil tank 1 into an electrical signal. It is installed in the gas phase space of the oil tank 1 to obtain accurate pressure data. The compressor oil supply temperature sensor 71 and the motor oil supply temperature sensor 72 can also be thermocouples or RTDs, installed on the oil supply pipes of the compressor bearing 51 and the motor bearing 52, respectively, to measure the corresponding oil supply temperature. The compressor bearing temperature sensor 73 and the motor bearing temperature sensor 74 can be temperature probes, installed near the compressor bearing 51 and the motor bearing 52, to monitor the bearing temperature in real time. These sensors periodically collect the oil tank temperature at a preset fixed sampling period. Pressure of the vapor space in the oil tank Compressor oil supply temperature Motor oil supply temperature Compressor bearing temperature and motor bearing temperature The collected data is then transmitted to the control module 82.

[0044] The control module 82 is electrically connected to the primary oil heater 11, the secondary oil heater 12, the compressor bearing oil cooling valve 41, the motor bearing oil cooling valve 42, and the oil pump 2, respectively, and is used to send control commands to each actuator, thereby controlling each actuator. The control module 82 is also electrically connected to the data acquisition module 81, and is used to receive data from various sensors collected by the data acquisition module 81. The control module 82 is also communicatively connected to the main controller of the centrifugal heat pump unit, and is used to receive the operating status signal and start-up request signal of the centrifugal heat pump unit sent by the main controller. The storage module 83 is electrically connected to both the data acquisition module 81 and the control module 82, and is used to store the saturation temperature-pressure relationship data corresponding to the refrigerant used in the centrifugal heat pump unit, as well as the set values ​​of various control parameters, for the control module 82 to query and recall at different operating stages.

[0045] Please refer to Figure 1 and Figure 2 Specifically, when the centrifugal heat pump unit is in a stopped state, the control module 82 determines the temperature of the oil tank based on the temperature of the oil tank. With heating start-up temperature limit and upper limit of heating stop temperature The comparison results are used to control the on / off state of the multi-stage oil heater using a switch control method. The multi-stage oil heater includes at least two independently controllable heating units, such as a primary oil heater 11 and a secondary oil heater 12. These are typically electric heaters, independently controllable, and installed inside the oil tank 1. When At the same time, control module 82 simultaneously connects the power supply circuits of each heating unit, causing the multi-stage oil heaters to start simultaneously, raising the oil temperature as quickly as possible, and preventing the refrigerant from dissolving in the lubricating oil at low temperatures. At that time, control module 82 simultaneously disconnects the power supply circuits of each heating unit, shutting down the multi-stage oil heater. At this time, the multi-stage oil heater maintains its current on / off state. Because This creates a temperature hysteresis between the two, preventing the multi-stage oil heater from frequently starting and stopping near the temperature critical point. The aforementioned on / off control means that the heater only has two states: full-power heating when powered on and heating stopped when powered off; continuous power adjustment is not performed.

[0046] The above-mentioned oil temperature control process during the shutdown phase is as follows: When the centrifugal heat pump unit is in a shutdown state, the control module 82 continuously obtains the temperature of the lubricating oil in the oil tank 1 from the oil tank temperature sensor 13 through the data acquisition module 81. .like Drop to below (For example, below 45℃) indicates that the oil temperature is too low, and the refrigerant may dissolve in large quantities in the lubricating oil at low temperatures. In this case, control module 82 simultaneously activates the primary oil heater 11 and the secondary oil heater 12 to rapidly increase the oil temperature with maximum heating power. As the oil temperature rises, when... Rise to more than When the temperature exceeds 55°C (for example), the control module 82 simultaneously shuts down both the primary oil heater 11 and the secondary oil heater 12. and Within the temperature hysteresis range (e.g., 45℃~55℃), the heater remains in its current state, thereby avoiding frequent start-ups and shutdowns near the temperature critical point, extending the service life of the heater, and ensuring that the lubricating oil temperature in oil tank 1 is maintained within a suitable range.

[0047] Specifically, when the centrifugal heat pump unit is in the start-up phase, the control module 82 determines the pressure of the oil tank vapor space based on the pressure of the vapor space. Query the saturated temperature-pressure relationship data corresponding to the refrigerant used in the centrifugal heat pump unit pre-stored in storage module 83 to obtain the saturated refrigerant temperature in oil tank 1. Calculate the oil temperature difference The saturation temperature-pressure relationship data is pre-stored in storage module 83. Different refrigerants have different saturation temperature-pressure relationships. by The input is obtained through interpolation or table lookup. A startup request-startup permission interaction mechanism is adopted. When no startup request is received, the control module 82 is in a standby monitoring state and does not actively trigger a startup action. Only when a startup request is received will the module initiate a startup action. At that time, the control module 82 sends a start permission signal to the compressor 53, wherein the lower limit setting value of the oil temperature difference is specified. A value greater than zero is used to characterize the minimum superheat margin that the lubricating oil needs to maintain relative to the refrigerant saturation temperature in oil sump 1 before startup, to prevent a large amount of refrigerant dissolved in the lubricating oil from flashing out due to pressure drop during startup. If If the start-up is blocked, the control module 82 continues to execute the oil heating control logic during the shutdown phase, continuously heating the lubricating oil to increase the oil temperature difference.

[0048] The above-mentioned oil temperature control process during the startup phase is as follows: When the control module 82 receives the startup request of the centrifugal heat pump unit, the control module 82 first obtains the pressure of the gas phase space of the oil tank 1 from the oil tank pressure sensor 14 through the data acquisition module 81. Then, it queries the pre-stored saturated temperature-pressure relationship data in storage module 83 and obtains the corresponding saturated refrigerant temperature through interpolation or table lookup. And calculate the oil temperature difference. .like (For example (>15℃), indicating that the lubricating oil temperature has sufficient superheat margin relative to the refrigerant saturation temperature, the amount of refrigerant dissolved in the lubricating oil is low, and the lubricating oil quality meets the start-up requirements. At this time, a start-up permission signal is sent to compressor 53, allowing the centrifugal heat pump unit to start. If If the lubricating oil temperature is insufficient, it indicates that the refrigerant dissolution rate may be too high. In this case, the compressor 53 is kept in the off-state, while the control module 82 continues to execute the oil heating control logic during the shutdown phase, controlling the oil heater to heat the lubricating oil until the oil temperature difference meets the requirements before issuing a start-up permit. This mechanism effectively avoids starting the compressor 53 when the lubricating oil quality does not meet the requirements, reducing the risk of bearing damage due to poor lubrication. Compared with the solution of directly measuring the refrigerant concentration in the lubricating oil, this solution does not require an additional refrigerant concentration sensor (such sensors are costly, complex to maintain, and have low reliability under high temperature and high pressure environments). It can indirectly determine the degree of refrigerant dissolution using only the existing oil tank temperature sensor and oil tank pressure sensor, which has the advantages of low cost and high reliability.

[0049] Please refer to Figure 1 and Figure 3 Specifically, when the centrifugal heat pump unit is in operation, the control module 82 continuously monitors... Query the saturation temperature-pressure relationship data in storage module 83. Real-time calculation And based on oil temperature difference The system uses a hierarchical control mechanism that compares the heating elements against multiple preset thresholds to control the start and stop of each heating unit. The multi-stage oil heater includes a primary oil heater 11 and a secondary oil heater 12, with the start-up oil temperature difference of the primary oil heater acting as the starting point. and step temperature difference (in The thresholds are defined as follows:

[0050]

[0051]

[0052]

[0053] satisfy This creates an ordered hierarchical logic where the first-stage heater starts first and then stops, while the second-stage heater starts last and stops first. Taking the above typical parameters as an example, =20℃, =5℃, then =20℃, =15℃, =25℃, =30℃. When the oil temperature difference... Descending to (Right now When the temperature is <20℃, start the first-stage oil heater 11; when the oil temperature difference... Continue to decline to (Right now When the temperature is below 15℃, the secondary oil heater 12 is activated, at which point the primary and secondary oil heaters operate simultaneously; when the oil temperature difference... Rise to (Right now When the oil temperature exceeds 25℃, the secondary oil heater 12 is shut down, and only the primary oil heater 11 continues to operate; when the oil temperature difference... Continue to rise to (Right now When the temperature exceeds 30℃, the first-stage oil heater 11 is shut down, and all heaters stop. The difference between the start-up threshold and the shutdown threshold of the first-stage oil heater 11 is... (i.e., 10℃), the difference between the start-up threshold and the stop-down threshold of the secondary oil heater 12 is the same. (i.e., 10℃) The start-up threshold of each heater is lower than its shut-off threshold, so that the start-up and shutdown actions of each heater form a hysteresis control with oil temperature difference as the variable, avoiding frequent start-up and shutdown near the critical point.

[0054] The above-mentioned operation phase of the oil heater staged control process is as follows: During the operation of the centrifugal heat pump unit, due to changes in operating conditions, the temperature of the lubricating oil and the refrigerant saturation temperature in oil tank 1 will change, resulting in oil temperature difference. Fluctuations. When the oil temperature difference... As the temperature gradually decreases, it indicates that the overheat margin of the lubricating oil temperature relative to the refrigerant saturation temperature is decreasing, and the amount of refrigerant dissolved in the lubricating oil may be increasing. At this point, control module 82 first activates the primary oil heater 11 for heating; if the oil temperature difference continues to decrease, it further activates the secondary oil heater 12 to raise the oil temperature with greater heating power. When the oil temperature difference... As the temperature gradually increases, it indicates that the overheat margin is increasing. The control module 82 first shuts down the secondary oil heater 12. If the oil temperature difference continues to rise, it then shuts down the primary oil heater 11. This graded control method allows the heating power to increase or decrease step by step with the change in oil temperature difference, reducing oil temperature fluctuations. At the same time, there is a hysteresis between the start and stop thresholds of each stage of the heater, avoiding frequent start and stop near the critical point and extending the service life of the heater.

[0055] Please refer to Figure 1 , Figure 4 and Figure 5 Meanwhile, when the centrifugal heat pump unit is in operation, the control module 82 controls the compressor bearing temperature. and motor bearing temperature As feedback, the opening degree of the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 is controlled by a PID algorithm. Both the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 are electrically adjustable valves, capable of continuously adjusting their opening degree within the range of 0% to 100% according to the control signal. In the PID algorithm, the bearing temperature deviation is the input, and the valve opening increment is the output. The proportional gain, integral time, and derivative time of the PID algorithm are tuned according to the system's response characteristics. Typical tuning methods include the Ziegler-Nichols method or trial and error. The typical range for the proportional gain is 2–10% / ℃, the typical range for the integral time is 60–300 seconds, and the typical range for the derivative time is 0–30 seconds. Taking the control of the compressor bearing oil cooling valve 41 as an example, after the compressor 53 starts, the control module 82 initializes the opening degree of the compressor bearing oil cooling valve 41 to the preset minimum opening degree. (For example, 10%), and use this as the lower limit of the valve opening output by the PID algorithm, that is, the valve opening output by the PID algorithm should not be lower than 10%. Real-time calculation of compressor shaft oil temperature difference. ,when (For example At 15℃, (For example, 65℃) is the set value, based on the real-time compressor bearing temperature. As the feedback value, the valve opening is output through a PID algorithm. When the bearing temperature is higher than the target, the valve opening is increased to enhance cooling; when the bearing temperature is lower than the target, the valve opening is decreased to weaken cooling. (For example When the temperature is 15℃, the setpoint will be lowered to... (For example, 65-5=60℃) to enhance cooling, where Correcting the temperature difference to the preset target temperature of the compressor side bearing and The decrease in target temperature increases the deviation of PID control, thus resulting in a larger valve opening command being output. Fall back to no more than Then restore the original settings. .in For independent parameter setting, the typical value range is 10–25℃. The logic for controlling the motor bearing oil cooling valve 42 is similar to that for controlling the compressor bearing oil cooling valve 41. After the compressor 53 starts, the control module 82 initializes the opening degree of the motor bearing oil cooling valve 42 to the preset minimum opening degree. (For example, 10%), and use this as the lower limit of the valve opening output by the PID algorithm, that is, the valve opening output by the PID algorithm should not be lower than 10%. Real-time calculation of motor shaft oil temperature difference ,when At that time, with (For example, 60℃) is the set value, based on the real-time motor bearing temperature. As the feedback value, the valve opening is output through a PID algorithm. When the bearing temperature is higher than the target, the valve opening is increased to enhance cooling; when the bearing temperature is lower than the target, the valve opening is decreased to weaken cooling. When that happens, the setting value will be lowered to To enhance cooling, in which Correcting the temperature difference to the preset target temperature of the motor-side bearing and .treat Restore original settings after falling back. . and They can be configured independently, with a typical value range of 10–25℃. With the compressor side The same value can be used to simplify parameter setting, or it can be configured independently according to different operating conditions of the motor bearing 52. When the centrifugal heat pump unit stops, both the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 are closed to their respective minimum openings to maintain basic oil circuit unobstructed during shutdown, and their control parameters are independent of each other. and They can be different. and They can be different. and They can be different, allowing the temperature control of the two bearings to be optimized independently without interfering with each other.

[0056] The working process of the compressor bearing oil cooling valve 41 is as follows: After the compressor 53 starts, the control module 82 initializes the opening degree of the compressor bearing oil cooling valve 41 to... This ensures a basic refrigerant flow through the compressor bearing oil cooler 31. During operation, the control module 82 obtains the compressor bearing temperature in real time from the compressor bearing temperature sensor 73 via the data acquisition module 81. The compressor oil supply temperature is obtained in real time from the compressor oil supply temperature sensor 71 through the data acquisition module 81. And calculate the compressor shaft oil temperature difference. Under normal operating conditions ( ), PID algorithm For target value, To provide feedback values ​​for closed-loop control, the opening of the compressor bearing oil cooling valve 41 is automatically adjusted to stabilize the compressor bearing temperature near the target value. When the bearing oil temperature difference... Exceeding the upper limit If the bearing temperature rises too much, meaning the difference between the bearing temperature and the oil supply temperature exceeds the normal range, it indicates increased heat generation or insufficient cooling of the bearing. In this case, the target temperature of the PID control will be automatically adjusted downwards. This allows the PID algorithm to output a larger valve opening, increasing refrigerant flow and enhancing cooling. Once the bearing oil temperature difference returns to normal, the original target temperature is restored. This mechanism can promptly enhance cooling when the bearing temperature rises abnormally, preventing overheating and damage.

[0057] The working process of the motor bearing oil cooling valve 42 is similar to that of the compressor bearing oil cooling valve 41: after the compressor 53 starts, the control module 82 initializes the opening degree of the motor bearing oil cooling valve 42 to... During operation, the control module 82 obtains the motor bearing temperature in real time from the motor bearing temperature sensor 74 through the data acquisition module 81. The motor oil supply temperature is obtained in real time from the motor oil supply temperature sensor 72 through the data acquisition module 81. And calculate the motor shaft oil temperature difference. Under normal operating conditions, the PID algorithm... For target value, Closed-loop control is performed based on the feedback value. When Exceeding the upper limit When the temperature difference decreases, the target temperature is automatically lowered to enhance cooling, and then the normal target temperature is restored after the temperature difference returns to normal. The control of the two oil cooling valves is independent and does not interfere with each other.

[0058] Please refer to Figure 1 and Figure 6In addition, the data acquisition module 81 performs validity checks on the output signals of each sensor in each sampling period. Validity checks include range exceedance detection and continuous failure timing. Range exceedance detection determines whether the sensor output value exceeds a preset reasonable range. For example, the reasonable range for a temperature sensor can be set to -40℃ to 200℃, and the reasonable range for a pressure sensor can be set to 0 to 5000 kPa. Continuous failure timing starts when the sensor output value is continuously outside its range or when the signal is abnormal (such as a fixed output value caused by a disconnection or short circuit). When the duration of continuous failure exceeds a preset failure determination time (e.g., 5 seconds), the sensor is determined to have failed. When any sensor data exceeds the preset range or the duration of continuous failure exceeds the preset failure determination time, the data acquisition module 81 sends a sensor failure alarm to the control module 82, triggering the degradation strategy of the corresponding control loop. When the compressor bearing temperature sensor 73 fails, the control module 82 terminates the PID closed-loop calculation of the compressor bearing temperature, and the compressor bearing oil cooling valve 41 remains at a preset safe fixed opening. (For example, 30%); When the motor bearing temperature sensor 74 fails, the control module 82 terminates the PID closed-loop calculation of the motor bearing temperature, and the motor bearing oil cooling valve 42 remains at a preset safe fixed opening. (For example, 30%); among which , The value of the fixed opening should ensure that the bearing can still be provided with basic cooling capacity under the worst operating conditions. The specific value is determined according to the heat exchange capacity of the oil cooler and the maximum heat generation of the bearing. The two degradation controls are independent of each other. If only one sensor fails, only the corresponding oil cooling valve will switch to the fixed opening, and the PID closed-loop control of the other channel will not be affected.

[0059] The above-mentioned sensor failure degradation control process is as follows: During the operation of the centrifugal heat pump unit, the data acquisition module 81 continuously checks the validity of the output signals of each sensor. Taking the compressor bearing temperature sensor 73 as an example, if the output data of this sensor exceeds the preset range (e.g., the output value deviates significantly from the normal temperature range), or if the duration of continuous output of invalid data by the sensor exceeds the preset failure judgment time (e.g., 5 seconds), the data acquisition module 81 determines that the sensor has failed and sends a failure alarm to the control module 82. After receiving the alarm, the control module 82 immediately terminates the PID closed-loop calculation of the compressor bearing temperature and locks the compressor bearing oil cooling valve 41 at a safe fixed opening. This ensures basic cooling capacity and prevents the bearings from overheating and being damaged due to complete loss of cooling. The failure handling logic for the motor bearing temperature sensor 74 is the same. The two degradation control paths are independent of each other; the failure of one sensor does not affect the normal PID closed-loop control of the other, thereby maximizing the safe operation of the centrifugal heat pump unit.

[0060] The complete working process of the entire high-pressure-ratio high-temperature centrifugal heat pump oil temperature control system is described below:

[0061] Please refer to Figures 1-6 When the centrifugal heat pump unit is in a shutdown state, the control module 82 executes the control logic for the shutdown phase. The data acquisition module 81 periodically collects the oil tank temperature through the oil tank temperature sensor 13. Control module 82 according to and and Based on the comparison results, the on / off state of the primary oil heater 11 and the secondary oil heater 12 is controlled by a switching quantity with hysteresis, so as to maintain the temperature of the lubricating oil in the oil tank 1 within the preset range and prevent the refrigerant from dissolving in the lubricating oil in large quantities at low temperature.

[0062] When control module 82 receives a start-up request from the centrifugal heat pump unit, it switches to the start-up control logic. Data acquisition module 81 collects the pressure of the vapor space in oil tank 1 via oil tank pressure sensor 14. Control module 82 according to The saturated refrigerant temperature can be obtained by querying the pre-stored saturated temperature-pressure relationship data in storage module 83. Calculate the oil temperature difference .like Then a start permission signal is sent to compressor 53, and the centrifugal heat pump unit enters the operating state; if If the start-prevention state is maintained, the control module 82 continues to execute the oil heating control logic during the shutdown phase, controlling the oil heater to heat the lubricating oil until the oil temperature difference meets the start-up conditions.

[0063] After the centrifugal heat pump unit enters the operating state, the control module 82 switches to the control logic of the operating phase. On the one hand, the control module 82 continuously adjusts the control logic according to the operating phase. Query saturation temperature-pressure relationship data Real-time calculation And according to the oil temperature difference Based on the comparison results with various threshold values, the start and stop of the primary oil heater 11 and the secondary oil heater 12 are controlled in stages to achieve step-by-step adjustment of the lubricating oil heating power. On the other hand, the control module 82 uses the compressor bearing temperature as a reference. and motor bearing temperature As feedback parameters, two independent PID control loops are used to control the opening of the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 respectively, achieving precise control of the oil supply temperature for the two lines. When the compressor bearing oil temperature difference... Or motor shaft oil temperature difference When the temperature exceeds its preset high limit, the PID control target temperature of the corresponding bearing is automatically lowered to enhance cooling. Once the temperature difference returns to normal, the target temperature is restored.

[0064] Throughout the operation, the data acquisition module 81 continuously verifies the effectiveness of each sensor. If the compressor bearing temperature sensor 73 or the motor bearing temperature sensor 74 fails, the control module 82 immediately terminates the corresponding PID closed-loop calculation and locks the corresponding oil cooling valve at a safe fixed opening. The two degraded controls are independent of each other.

[0065] When the centrifugal heat pump unit switches from the running state to the shutdown state, the control module 82 switches the control logic from the running stage to the shutdown stage, and the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 are closed to their respective minimum opening degrees. and To maintain basic oil circuit unobstructed during shutdown, PID calculations cease, and control switches to on / off control based on oil tank temperature. When a restart request is received again, control module 82 re-executes the control logic of the startup phase and performs pre-start condition checks.

[0066] Through the coordinated operation of the data acquisition module 81, control module 82, and storage module 83, this system achieves precise management of the lubricating oil temperature of the high-pressure-ratio high-temperature centrifugal heat pump unit under all operating conditions, including shutdown, startup, and operation. This effectively reduces the risk of bearing damage due to poor lubrication or overheating, and ensures the safe and stable operation of the centrifugal heat pump unit.

[0067] The implementation principle of this embodiment is as follows: This system, through the collaborative work of data acquisition module 81, control module 82, and storage module 83, comprehensively considers multiple operating parameters such as oil tank temperature, oil tank pressure, oil supply temperature, and bearing temperature, to achieve graded and precise control of the lubricating oil temperature of the high-pressure-ratio high-temperature centrifugal heat pump unit. Control module 82 executes different control logics according to different operating states of the centrifugal heat pump unit: During shutdown, it controls multi-stage oil heaters via on / off signals to prevent refrigerant from dissolving in large quantities in the lubricating oil at low temperatures; during startup, it uses the oil temperature difference as a prerequisite for startup permission to avoid starting the compressor 53 when the lubricating oil quality does not meet requirements, reducing the risk of bearing damage due to poor lubrication; during operation, it controls the start and stop of the heaters based on the oil temperature difference in stages to reduce oil temperature fluctuations, and simultaneously controls the opening of the oil cooling valve through a PID algorithm to adjust the cooling amount in real time according to the bearing temperature. When the bearing-oil temperature difference exceeds the limit, it automatically lowers the target temperature to enhance cooling. It also has sensor failure protection capabilities, ensuring the safe and stable operation of the centrifugal heat pump unit.

[0068] Example 2

[0069] Please refer to Figures 1-6The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control method provided in this application embodiment is used to control the lubricating oil system of a centrifugal heat pump unit. The lubricating oil system includes an oil tank 1, an oil pump 2, a compressor bearing oil cooler 31, a motor bearing oil cooler 32, a compressor bearing oil cooling valve 41, a motor bearing oil cooling valve 42, and a multi-stage oil heater disposed in the oil tank 1. The multi-stage oil heater includes at least two independently switched heating units, namely a primary oil heater 11 and a secondary oil heater 12. The inlet of the oil pump 2 is connected to the oil outlet of the oil tank 1, and the outlet of the oil pump 2 is divided into a first oil supply branch and a second oil supply branch via a diversion structure 21. The oil-side inlet of the compressor bearing oil cooler 31 is connected to the first oil supply branch, and its oil-side outlet is connected to the oil supply port of the compressor bearing 51; the oil-side inlet of the motor bearing oil cooler 32 is connected to the second oil supply branch, and its oil-side outlet is connected to the oil supply port of the motor bearing 52. The compressor bearing oil cooling valve 41 is installed on the refrigerant inlet pipe of the compressor bearing oil cooler 31 to regulate the refrigerant flow through the compressor bearing oil cooler 31; the motor bearing oil cooling valve 42 is installed on the refrigerant inlet pipe of the motor bearing oil cooler 32 to regulate the refrigerant flow through the motor bearing oil cooler 32. The oil return ports of both the compressor bearing 51 and the motor bearing 52 are connected to the oil sump 1, forming a lubricating oil circulation loop. The method includes the following steps:

[0070] S1, Data Acquisition Steps: Periodically collect oil tank temperature at a preset fixed sampling period. Pressure of the vapor space in the oil tank Compressor oil supply temperature Motor oil supply temperature Compressor bearing temperature and motor bearing temperature The system verifies the validity of the output signals of each sensor during each sampling period. The validity verification includes range exceedance detection and continuous failure timing. The sensors used include oil tank temperature sensor 13, oil tank pressure sensor 14, compressor oil supply temperature sensor 71, motor oil supply temperature sensor 72, compressor bearing temperature sensor 73, and motor bearing temperature sensor 74. These sensors are installed in their respective positions and transmit the collected data to the control module 82 for processing.

[0071] S2, Oil temperature control steps during shutdown: Based on on / off control... and , The comparison shows that the on / off state of the multi-stage oil heater is controlled with hysteresis. The multi-stage oil heater includes at least two independently on / off heating units. At the same time, all heating units are activated to raise the oil temperature as quickly as possible, preventing the refrigerant from dissolving in large quantities in the lubricating oil at low temperatures; when At the same time, all heating units are turned off; when At that time, the current on / off state remains unchanged.

[0072] S3, Start-up phase oil temperature control steps: Query the saturation temperature-pressure relationship data corresponding to the refrigerant used, which is pre-stored in storage module 83, and calculate the oil temperature difference. It adopts a startup request-startup license interaction mechanism, and only when... A startup permission is issued at that time. If If the start-prevention state is maintained, the oil temperature control steps during the shutdown phase will continue to heat the lubricating oil to increase the oil temperature difference until... Then issue the startup permission.

[0073] S4, Oil temperature control steps during operation: continuously according to... Query the saturation temperature-pressure relationship data in storage module 83. Real-time calculation Based on oil temperature difference The start-up and shutdown of each heating unit is controlled in stages according to thresholds, with the start-up oil temperature difference of the first-stage oil heater being the primary factor. and step temperature difference Calculate the start-stop thresholds for each stage of the heater. The thresholds are defined as follows: , , ,satisfy This achieves orderly, tiered control of the primary heater (start-then-stop) and the secondary heater (start-then-stop). Simultaneously, it uses compressor bearing temperature as a reference. Motor bearing temperature To provide feedback for controlling the opening of the two oil cooling valves using a PID algorithm, after startup, the opening of each valve is initialized to its respective preset minimum opening, which is then used as the lower limit of the PID output. The compressor shaft oil temperature difference is calculated in real time. and motor shaft oil temperature difference ,when or When the temperature exceeds its preset high limit, the target temperature of the corresponding bearing is lowered to enhance cooling. Once the temperature difference returns to normal, the target temperature is restored.

[0074] S5, Sensor Failure Degradation Control Steps: When the compressor bearing temperature sensor 73 fails, the PID closed-loop calculation of the compressor bearing temperature is terminated, and the compressor bearing oil cooling valve 41 is maintained at a preset safe fixed opening. When the motor bearing temperature sensor 74 fails, the PID closed-loop calculation of the motor bearing temperature is terminated, and the motor bearing oil cooling valve 42 is maintained at a preset safe fixed opening. The two degradation controls are independent of each other.

[0075] S6, State switching steps: When the centrifugal heat pump unit switches from the running state to the shutdown state, the control is switched from the oil temperature control step during the running phase to the oil temperature control step during the shutdown phase. The two oil cooling valves are closed to their minimum opening, the PID calculation is stopped, and the control is switched to on / off control based on the oil tank temperature. When a start request is received again, the oil temperature control step during the start phase is executed to determine the preconditions for start-up.

[0076] The complete working process of the above-mentioned high-pressure-ratio high-temperature centrifugal heat pump oil temperature control method is as follows:

[0077] First, after the centrifugal heat pump unit is powered on, the data acquisition step S1 continues to run, periodically collecting data from each sensor at a fixed sampling period and verifying its validity.

[0078] When the centrifugal heat pump unit is in a shutdown state, the shutdown phase oil temperature control step S2 is executed. The on / off state of the primary oil heater 11 and the secondary oil heater 12 is controlled via a hysteresis-controlled switching method to maintain the lubricating oil temperature in the oil tank 1 at a certain level. and Within the preset range.

[0079] When a start-up request for the centrifugal heat pump unit is received, the oil temperature control step S3 during the start-up phase is executed, based on the oil tank pressure. Calculate the oil temperature difference by querying the saturation temperature-pressure relationship data in storage module 83. Determine if the oil temperature difference meets the starting conditions. If a start-up permission signal is issued, the centrifugal heat pump unit will start and enter the operating state; if If the oil temperature control step S2 during the shutdown phase continues, the lubricating oil will be heated until the oil temperature difference meets the requirements.

[0080] After the centrifugal heat pump unit starts up and enters the operating state, it executes the oil temperature control step S4 during the operating phase. This step simultaneously performs two aspects of control: firstly, it continuously calculates the oil temperature difference. And according to the oil temperature difference The system controls the start and stop of the primary oil heater 11 and the secondary oil heater 12 in stages; secondly, it controls the opening of the compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 through two independent PID control loops, and automatically lowers the target temperature to enhance cooling when the shaft oil temperature difference exceeds the limit.

[0081] During operation, the sensor failure degradation control step S5 continuously monitors the sensor status. If the compressor bearing temperature sensor 73 or the motor bearing temperature sensor 74 fails, the corresponding PID closed-loop calculation is immediately terminated, and the corresponding oil cooling valve is locked at a safe fixed opening. The two degradation controls are independent of each other.

[0082] When the centrifugal heat pump unit switches from the running state to the shutdown state, state switching step S6 is executed, switching control from the oil temperature control step S4 during the running phase to the oil temperature control step S2 during the shutdown phase. The compressor bearing oil cooling valve 41 and the motor bearing oil cooling valve 42 are closed to their respective minimum openings, PID calculation is stopped, and control switches to on / off control based on oil bath temperature. When a start-up request is received again, the oil temperature control step S3 during the start-up phase is executed again to determine the pre-start conditions. This cycle repeats continuously, achieving full-condition management of lubricating oil temperature.

[0083] The implementation principle of this embodiment is as follows: This control method, through the coordinated operation of multiple steps and comprehensive consideration of multiple operating parameters, achieves graded and precise control of the lubricating oil temperature of a high-pressure-ratio, high-temperature centrifugal heat pump unit. Different control logics are employed under different operating conditions to ensure that the lubricating oil always operates within a suitable temperature range. It also possesses sensor failure protection capabilities. Compared to traditional control methods based solely on the absolute temperature of the oil tank, the introduction of an oil temperature difference index allows for the differentiation of refrigerant solubility differences in the lubricating oil even when the oil tank temperature is the same but the refrigerant saturation temperature varies due to different operating conditions. This enables a more accurate assessment of lubricating oil quality. Graded heating control allows for more precise adjustment of heating power, and the sensor failure degradation mechanism maintains basic protection capabilities even in the event of sensor failure.

[0084] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system, used to control the lubricating oil system of a centrifugal heat pump unit, the lubricating oil system comprising: The oil tank (1), oil pump (2), compressor bearing oil cooler (31), motor bearing oil cooler (32), compressor bearing oil cooling valve (41), motor bearing oil cooling valve (42), and a multi-stage oil heater installed in the oil tank, wherein the multi-stage oil heater includes at least two independently switched heating units; the inlet of the oil pump (2) is connected to the outlet of the oil tank (1), and the outlet of the oil pump (2) is divided into a first oil supply branch and a second oil supply branch through a diversion structure (21); the oil-side inlet of the compressor bearing oil cooler (31) is connected to the first oil supply branch, and its oil-side outlet... The oil inlet of the compressor bearing (51) is connected to the oil supply port of the compressor bearing (51); the oil side inlet of the motor bearing oil cooler (32) is connected to the second oil supply branch, and its oil side outlet is connected to the oil supply port of the motor bearing (52); the compressor bearing oil cooling valve (41) is set on the refrigerant inlet pipe of the compressor bearing oil cooler (31) to regulate the refrigerant flow through the compressor bearing oil cooler (31); the motor bearing oil cooling valve (42) is set on the refrigerant inlet pipe of the motor bearing oil cooler (32) to regulate the refrigerant flow through the motor bearing oil cooler (32); the oil return ports of the compressor bearing (51) and the motor bearing (52) are both connected to the oil sump to form a lubricating oil circulation loop; the high pressure ratio high temperature centrifugal heat pump oil temperature control system includes: The data acquisition module (81) is electrically connected to the oil tank temperature sensor (13), the oil tank pressure sensor (14), the compressor oil supply temperature sensor (71), the motor oil supply temperature sensor (72), the compressor bearing temperature sensor (73), and the motor bearing temperature sensor (74), respectively, and is used to periodically acquire the oil tank temperature at a preset fixed sampling period. Pressure of the vapor space in the oil tank Compressor oil supply temperature Motor oil supply temperature Compressor bearing temperature and motor bearing temperature ; The control module (82) is electrically connected to the primary oil heater (11), the secondary oil heater (12), the compressor bearing oil cooling valve (41), the motor bearing oil cooling valve (42), and the oil pump (2), respectively. The control module (82) is also communicatively connected to the main controller of the centrifugal heat pump unit, and is used to receive the operating status signal and start-up request signal of the centrifugal heat pump unit sent by the main controller. The control module (82) is used to execute different control logic according to the different operating states of the centrifugal heat pump unit, including: When the centrifugal heat pump unit is in operation, the control module (82) continuously adjusts according to... The saturated refrigerant temperature in the oil tank is obtained by querying the pre-stored saturated temperature-pressure relationship data corresponding to the refrigerant used in the centrifugal heat pump unit. Real-time calculation of oil temperature difference and based on The system uses a multi-level start-stop threshold calculated based on a reference oil temperature difference and a step temperature difference to control the start-stop of each heating unit in a graded manner; simultaneously, it uses... and As a feedback quantity, the opening degree of the compressor bearing oil cooling valve and the motor bearing oil cooling valve is controlled by a PID algorithm; and the compressor shaft oil temperature difference is calculated in real time. and motor shaft oil temperature difference ,when Exceeding the preset upper limit of compressor side shaft oil temperature difference At that time, the preset correction temperature difference of the PID control target temperature of the compressor bearing is adjusted to enhance cooling. Fall back to no more than Then restore the original target temperature; when Exceeding the preset upper limit of motor side shaft oil temperature difference At that time, the preset correction temperature difference of the PID control target temperature of the motor bearing is adjusted to enhance cooling. After the temperature drops, the original target temperature will be restored.

2. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 1, characterized in that, The control logic of the control module (82) when the centrifugal heat pump unit is in a shutdown state is as follows: The control module (82) is based on With heating start-up temperature limit and upper limit of heating stop temperature The on / off state of the multi-stage oil heater is controlled by a switching control method to maintain the oil tank temperature within a preset range. when At the same time, all heating units are activated, that is, the power supply circuits of each heating unit are connected simultaneously to raise the oil temperature as quickly as possible. when At the same time, all heating units are shut down, that is, the power supply circuit of each heating unit is disconnected simultaneously. when At this time, the current on / off state remains unchanged; in A temperature hysteresis is formed between the two to avoid frequent start-stop of the multi-stage oil heater near the temperature critical point; the switch control means that the heater only has two states: full power heating when powered on and heating stopped when powered off, without continuous power adjustment.

3. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 1, characterized in that, When the control module (82) is in the start-up phase of the centrifugal heat pump unit: according to Obtain the temperature of the saturated refrigerant in the oil tank And calculate the oil temperature difference. It employs a startup request-startup license interaction mechanism; upon receiving a startup request, it will only grant a license if... The start permission signal is sent to the compressor at the time; otherwise, the start-preventing state is maintained. At the same time, the control module (82) continues to run the oil heating control to continuously heat the lubricating oil to increase the oil temperature difference. The lower limit setting value of oil temperature difference The value is greater than zero, which is used to characterize the minimum overheat margin that the lubricating oil needs to maintain relative to the saturated temperature of the refrigerant in the oil tank before starting, so as to prevent the refrigerant dissolved in the lubricating oil from flashing out in large quantities due to the pressure drop during startup; when no startup request is received, the control module (82) is in standby monitoring state and does not actively trigger the startup action.

4. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 1, characterized in that, The multi-stage oil heater includes a primary oil heater (11) and a secondary oil heater (12), both of which are electric heaters and can be independently controlled on and off; in the hierarchical control logic of the control module (82) when the centrifugal heat pump unit is in operation, the reference oil temperature difference is the starting oil temperature difference of the primary oil heater. The step temperature difference is ,in The thresholds are defined as follows: , , satisfy This forms an ordered, hierarchical logic where the first-stage heater starts first and then stops, and the second-stage heater starts last and then stops first; the specific control process is as follows: when the oil temperature difference... Descending to When the oil temperature difference is reached, the first-stage oil heater (11) is started; when the oil temperature difference is reached... Continue to decline to At this time, the secondary oil heater (12) is further activated, and the primary and secondary oil heaters operate simultaneously; when the oil temperature difference... Rise to When the oil temperature difference is high, the secondary oil heater (12) is shut down, and only the primary oil heater (11) continues to operate; when the oil temperature difference is high... Continue to rise to When the first-stage oil heater (11) is turned off, all heaters will stop.

5. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 4, characterized in that, The difference between the start-up threshold and the stop-down threshold of the primary oil heater is: The difference between the start-up threshold and the stop-down threshold of the secondary oil heater is the same. The start-up threshold of each heater is lower than its shut-off threshold, so that the start-up and shutdown actions of each heater form a hysteresis control with oil temperature difference as the variable, avoiding frequent start-up and shutdown near the critical point.

6. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 1, characterized in that, When the centrifugal heat pump unit is in operation, the logic of the control module (82) controlling the compressor bearing oil cooling valve (41) includes: After the compressor starts, the opening degree of the compressor bearing oil cooling valve is initialized to the preset minimum opening degree. This is used as the lower limit of the valve opening output by the PID algorithm, meaning the valve opening output by the PID algorithm should not be lower than... Real-time calculation of compressor shaft oil temperature difference ;when At that time, with The set value is based on the real-time compressor bearing temperature. As feedback values, the valve opening is output through a PID algorithm. When the bearing temperature is higher than the target, the valve opening is increased to enhance cooling; when the bearing temperature is lower than the target, the valve opening is decreased to weaken cooling. When that happens, the setting value will be lowered to To enhance cooling, in Correcting the temperature difference to the preset target temperature of the compressor side bearing and The decrease in target temperature increases the deviation of PID control, thus outputting a larger valve opening command; Fall back to no more than Then restore the original settings. ;in Set parameters independently.

7. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 6, characterized in that, When the centrifugal heat pump unit is in operation, the logic of the control module (82) controlling the motor bearing oil cooling valve (42) includes: After the compressor starts, the opening degree of the motor bearing oil cooling valve is initialized to the preset minimum opening degree. This is used as the lower limit of the valve opening output by the PID algorithm, meaning the valve opening output by the PID algorithm should not be lower than... Real-time calculation of motor shaft oil temperature difference ;when At that time, with The set value is based on the real-time motor bearing temperature. As feedback values, the valve opening is output through a PID algorithm. When the bearing temperature is higher than the target, the valve opening is increased to enhance cooling; when the bearing temperature is lower than the target, the valve opening is decreased to weaken cooling. When that happens, the setting value will be lowered to To enhance cooling, in Correcting the temperature difference to the preset target temperature of the motor-side bearing and ;treat Restore original settings after falling back. ;in and They are independent and can be configured separately; the aforementioned With the compressor side Independent configuration.

8. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 7, characterized in that, The compressor bearing oil cooling valve (41) and the motor bearing oil cooling valve (42) are both electric regulating valves, which can continuously adjust their opening degree within the range of 0% to 100% according to the control signal; in the PID algorithm, the bearing temperature deviation is the input and the valve opening increment is the output; when the centrifugal heat pump unit stops, both valves are closed to the minimum opening degree to maintain the basic oil circuit unobstructed during the shutdown period; the control parameters of the compressor bearing oil cooling valve (41) and the motor bearing oil cooling valve (42) are independent of each other, wherein and Independent configuration, and Independent configuration, and Independent configuration allows for optimized temperature control of the two bearings without interference.

9. The high-pressure-ratio, high-temperature centrifugal heat pump oil temperature control system according to claim 1, characterized in that, The data acquisition module (81) periodically acquires each measurement quantity at a preset fixed sampling period, and performs validity checks on the output signals of each sensor in each sampling period. The validity checks include range overrun detection and continuous failure timing. When any sensor data exceeds the preset range or the duration of continuous failure exceeds the preset failure judgment time, the data acquisition module (81) sends a sensor failure alarm to the control module (82) and triggers the degradation strategy of the corresponding control loop: When the compressor bearing temperature sensor (73) fails, the control module (82) terminates the PID closed-loop calculation of the compressor bearing temperature, and the compressor bearing oil cooling valve (41) remains at a preset safe fixed opening. When the motor bearing temperature sensor (74) fails, the control module (82) terminates the PID closed-loop calculation of the motor bearing temperature, and the motor bearing oil cooling valve (42) remains at a preset safe fixed opening. The two degradation controls are independent of each other. If only one sensor fails, only the corresponding oil cooling valve switches to a fixed opening, and the PID closed-loop control of the other channel is unaffected.

10. A method for controlling the oil temperature of a high-pressure-ratio, high-temperature centrifugal heat pump, used to control the lubricating oil system of a centrifugal heat pump unit, the lubricating oil system comprising: The oil tank (1), oil pump (2), compressor bearing oil cooler (31), motor bearing oil cooler (32), compressor bearing oil cooling valve (41), motor bearing oil cooling valve (42), and a multi-stage oil heater installed in the oil tank, wherein the multi-stage oil heater includes at least two independently switched heating units; the inlet of the oil pump (2) is connected to the outlet of the oil tank (1), and the outlet of the oil pump (2) is divided into a first oil supply branch and a second oil supply branch through a diversion structure (21); the oil-side inlet of the compressor bearing oil cooler (31) is connected to the first oil supply branch, and its oil-side outlet... The oil inlet of the compressor bearing (51) is connected to the oil supply port of the compressor bearing (51); the oil side inlet of the motor bearing oil cooler (32) is connected to the second oil supply branch, and its oil side outlet is connected to the oil supply port of the motor bearing (52); the compressor bearing oil cooling valve (41) is set on the refrigerant inlet pipe of the compressor bearing oil cooler (31) to regulate the refrigerant flow through the compressor bearing oil cooler (31); the motor bearing oil cooling valve (42) is set on the refrigerant inlet pipe of the motor bearing oil cooler (32) to regulate the refrigerant flow through the motor bearing oil cooler (32); the oil return ports of the compressor bearing (51) and the motor bearing (52) are both connected to the oil sump to form a lubricating oil circulation loop, characterized in that the high pressure ratio high temperature centrifugal heat pump oil temperature control method includes: Data acquisition steps: Collect data periodically at a preset fixed sampling period. , , , , and The validity of the output signal of each sensor is checked in each sampling period, including range overrun detection and continuous failure timing. Oil temperature control steps during shutdown: Based on on / off control. and , The comparison, with hysteresis control of the multi-stage oil heater on / off; when At the same time, all heating units are activated to raise the oil temperature as quickly as possible; when At the same time, all heating units are turned off; when At this time, the current on / off state remains unchanged; Startup phase oil temperature control steps: Query pre-stored saturation temperature-pressure relationship data corresponding to the refrigerant used, and calculate... It employs a startup request-startup license interaction mechanism, only when... Issue startup permission at the appropriate time; if If the start-prevention state is maintained, the oil temperature control steps during the shutdown phase will continue to heat the lubricating oil to increase the oil temperature difference until... Then issue a startup license; Oil temperature control steps during operation: Based on The start-up and shutdown of each heating unit is controlled in stages according to thresholds, with the start-up oil temperature difference of the first-stage oil heater being the primary factor. and step temperature difference Calculate the start / stop thresholds for each stage of the heater to achieve orderly, hierarchical control of the first-stage heater (start first, then stop) and the second-stage heater (start last, then stop). And respectively... , To provide feedback for controlling the opening of the two oil cooling valves using a PID algorithm, after startup, the opening of each valve is initialized to its preset minimum opening, which is then used as the lower limit of the PID output opening. When the compressor shaft oil temperature difference... Or motor shaft oil temperature difference When the temperature exceeds the preset high limit, the target temperature of the corresponding bearing is lowered to enhance cooling. After the temperature difference returns to normal, the target temperature is restored. Sensor failure degradation control steps: When the compressor bearing temperature sensor fails, the PID closed-loop calculation of the compressor bearing temperature is terminated, and the compressor bearing oil cooling valve is kept at a preset safe fixed opening; when the motor bearing temperature sensor fails, the PID closed-loop calculation of the motor bearing temperature is terminated, and the motor bearing oil cooling valve is kept at a preset safe fixed opening; the two degradation controls are independent of each other. State switching steps: When the centrifugal heat pump unit switches from the running state to the shutdown state, the control is switched from the oil temperature control step during the running phase to the oil temperature control step during the shutdown phase. The two oil cooling valves are closed to their minimum opening, the PID calculation is stopped, and the control is switched to on / off control based on the oil tank temperature. When a start request is received again, the oil temperature control step during the start phase is executed to determine the preconditions for start-up.

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