A magnetic levitation compressor control method and control system

Abstract

A magnetic levitation compressor control method and control system, wherein the control method includes: dividing the compressor regulation into forced load reduction, anti-surge regulation and load regulation; the load regulation includes energy loading and energy load reduction regulation, the energy loading includes: increasing the inlet guide vane opening, and then increasing the compressor operating frequency when the inlet guide vane is opened to the maximum; or directly increasing the compressor operating frequency when the inlet guide vane actuator fails; the energy load reduction includes: first reducing the compressor operating frequency, and when the compressor operating frequency cannot be further reduced, then continuing to reduce the inlet guide vane opening. The present invention also includes a magnetic levitation compressor control system. The present invention enables the chiller control system to obtain the compressor surge line and compressor status in a timely manner, reduce communication delay time, reduce operation and maintenance costs, and greatly improve control accuracy; and solves the problems of the traditional control algorithm in which the frequency and the inlet guide vane opening are adjusted simultaneously, the unit has low energy efficiency, a small adjustment range, and is prone to surge shutdown.

Description

Technical Field

[0001] The present invention relates to the technical field of magnetic suspension compressor and chiller control, in particular to a magnetic suspension compressor control method and control system. Background Art

[0002] A magnetic levitation compressor uses magnetic levitation technology to achieve contactless operation. Its control methods primarily include magnetic bearing control, inverter control, temperature control, pressure control, and fault protection and diagnostics. For example, the core component of a magnetic levitation compressor is the magnetic bearing system, which supports and controls the movement of the rotor. Magnetic bearing control methods primarily include bearing force control and stability control to maintain rotor balance and stable operation. A magnetic levitation compressor typically uses an inverter to control the motor speed. Adjusting the motor's output frequency and voltage via the inverter allows for capacity adjustment. A magnetic levitation compressor requires real-time monitoring of internal compressor temperature (stator winding temperature), intake and exhaust temperatures, and intake and exhaust pressures to ensure proper operation. A controller allows for real-time adjustment of the compressor's operating status to meet system requirements.

[0003] Existing magnetic levitation compressors are typically combined with chillers as two independent systems. The magnetic levitation compressor is typically controlled by an autonomous control system, while the chiller is typically controlled by a centralized control system. The chiller controller controls the compressor's operating status (on / off) and adjusts its capacity (via variable frequency drive or a combination of multiple compressors) based on the chilled water outlet load demand to achieve chilled water outlet temperature control. The chilled water flow rate is controlled by controlling the operating status and speed of the chilled water pump to meet the unit's load requirements. The compressor controller then adjusts energy based on the chiller's calculated load demand.

[0004] However, the existing magnetic levitation compressor and chiller are set as two independent systems, which will cause the chiller to be unable to obtain the compressor surge line and compressor status in time. The chiller controller will make wrong judgments, causing the compressor to surge or even shut down. The communication delay during the data interaction between the chiller and the magnetic levitation compressor controller causes the data to be unable to be synchronized in time, making the chiller's control of the compressor not accurate enough; and the two control systems will make the unit's later operation and maintenance costs relatively high. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned deficiencies in the prior art and to provide a control method and control system for a magnetic levitation compressor with short communication delay time and precise control.

[0006] The technical solution of the present invention is:

[0007] A magnetic levitation compressor control method of the present invention comprises the following steps:

[0008] The compressor regulation is divided into forced load reduction, anti-surge regulation and load regulation;

[0009] The load regulation includes energy loading and energy unloading regulation. The energy loading includes: increasing the inlet guide vane opening, and then increasing the compressor operating frequency when the inlet guide vane is opened to the maximum; or directly increasing the compressor operating frequency when the inlet guide vane actuator fails; the energy unloading includes: first reducing the compressor operating frequency, and then further reducing the inlet guide vane opening when the compressor operating frequency cannot be further reduced;

[0010] The anti-surge regulation includes a frequency zone control step, namely: when it is detected that the actual operating frequency of the compressor is greater than the surge protection frequency, the load regulation is performed to control the inverter to normally increase or decrease the speed; when it is detected that the actual operating frequency of the compressor is less than the surge protection frequency and greater than the minimum surge operating frequency, energy load reduction is limited to prevent the compressor from entering the surge zone; when it is detected that the actual operating frequency of the compressor is less than the minimum surge operating frequency, the load regulation is exited and the anti-surge regulation mode is entered to control the frequency to be above the minimum surge frequency;

[0011] The triggering condition for the forced load reduction is: during the operation of the compressor, when it is detected that the operating current of the inverter is greater than the first current target value or the inverter temperature is greater than the first temperature target value, forced energy load reduction adjustment is performed; the exit condition for forced load reduction is: during the operation of the compressor, when it is detected that the operating current of the inverter is less than the second current target value or the inverter temperature is less than the second temperature target value, the forced load reduction mode is exited; when it is detected that the operating current of the inverter is greater than the third current target value or the inverter temperature is greater than the third temperature target value, the machine is shut down immediately.

[0012] Furthermore, the adjustment priority order of the compressor is: forced load reduction > anti-surge adjustment > load adjustment.

[0013] Further, the third current target value>the first current target value>the second current target value; the third temperature target value>the first temperature target value>the second temperature target value.

[0014] Furthermore, in the anti-surge regulation, the suction and exhaust temperatures, suction and exhaust pressure values, and inlet guide vane opening of the compressor are monitored and updated in real time, and the real-time operating compression ratio and guide vane opening percentage are calculated; the actual operating frequency of the compressor under the real-time operating compression ratio and guide vane opening is controlled to be not lower than the calculated minimum operating frequency, that is, the anti-surge frequency; and the surge minimum operating frequency is multiplied by the adjustment coefficient as the surge protection frequency.

[0015] Furthermore, in the anti-surge regulation, when the actual operating frequency of the compressor is greater than the calculated surge protection frequency, the anti-surge regulation is exited and the load regulation is entered, and the anti-surge regulation begins to be implemented after the compressor is started. When it is detected that the surge is severe and the axis trajectory of the compressor fluctuates seriously, the compressor enters a shutdown state.

[0016] Furthermore, the forced load reduction triggering condition is: during the operation of the compressor, when it is detected that the inverter operating current is greater than 370A or the inverter temperature is greater than 85°C, forced load reduction is performed; the exit condition of the forced load reduction is: during the operation of the compressor, when it is detected that the inverter operating current is less than 360A or the inverter temperature is less than 80°C; when it is detected that the inverter operating current exceeds 380A or the inverter temperature is greater than 90°C, the compressor is shut down immediately.

[0017] Furthermore, the compressor startup steps are also included:

[0018] When the compressor receives the start command from the controller, it turns on the start mode and the system performs self-check;

[0019] After the self-test is completed, it will be restarted after a certain delay;

[0020] After startup, control the magnetic bearing suspension;

[0021] The magnetic bearing is detected to be in suspension state within a certain period of time. Otherwise, a startup failure warning is issued and the startup ends.

[0022] After the magnetic shaft is normally suspended, the cooling solenoid valve of the compressor is started with a delay, the inlet guide vane actuator is opened, and the cut-in valve is opened;

[0023] After the inlet guide vane actuator is started, a start command is sent to the frequency converter through the controller;

[0024] The inverter is started and accelerated to 60% of the maximum frequency. When the surge frequency is detected to be less than 60% of the maximum frequency, it will run at this frequency for a certain period of time and then adjust the frequency to operate at normal load. When the surge frequency is detected to be greater than 60% of the maximum frequency, it will directly run at the surge protection frequency.

[0025] The compressor starts up and gradually closes the cut-in valve;

[0026] When the compressor operating frequency reaches the frequency calculated by the active optimization algorithm, the air supply valve is started;

[0027] The air supply valve is started up and enters the load regulation mode.

[0028] Furthermore, the compressor shutdown steps are also included:

[0029] When the compressor receives a stop command from the controller, it stops the optimized operation mode and enters the stop mode, and opens the cut-in valve;

[0030] During normal shutdown, if it is detected that the current operating frequency of the compressor is higher than the specified shutdown frequency, the inverter will be controlled to reduce the speed to the specified shutdown frequency. If it is detected that the current operating frequency is lower than or equal to the specified shutdown frequency, there is no need to adjust the speed of the compressor.

[0031] During normal shutdown, if the current frequency is less than or equal to the specified shutdown frequency, a free shutdown will be executed; during emergency shutdown, regardless of the current frequency, a free shutdown will be executed directly;

[0032] The inverter is shut down and the cooling solenoid valve of the compressor is closed;

[0033] Close the cut-in valve and close the inlet guide vane actuator;

[0034] After the inlet guide vane is closed, the shaft will drop after a certain delay or when the actual speed is lower than the target frequency. The shaft drop is completed and the shutdown is completed.

[0035] A magnetic levitation compressor control system of the present invention includes a controller and a temperature acquisition module, an analog quantity acquisition module, a valve control module and a communication module connected to the controller;

[0036] The temperature acquisition module is connected to the suction temperature sensor, the exhaust temperature sensor and the stator winding temperature sensor respectively, and is used to collect the suction temperature, exhaust temperature and motor stator winding temperature of the compressor;

[0037] The analog quantity acquisition module is respectively connected to the suction pressure sensor, the exhaust pressure sensor, the supply air pressure sensor and the IGV feedback opening sensor to respectively collect the suction pressure, exhaust pressure, supply air pressure and inlet guide vane opening size of the compressor;

[0038] The output end of the valve control module is respectively connected to the inlet guide vane actuator, the cooling solenoid valve, the cut-in valve and the air supply valve;

[0039] The controller is also connected to the magnetic bearing control panel, touch screen, motor cavity expansion valve and inverter control panel through the communication module; the cooling solenoid valve is arranged on the pipeline between the condenser outlet of the chiller and the compressor motor cavity expansion valve, and is used to control the on-off of this pipeline. The cooling solenoid valve and the motor cavity expansion valve form a dual redundant control of the pipeline from the condenser outlet to the motor cavity; the cut-in valve is arranged on the pipeline from the exhaust port of the compressor to the evaporator of the chiller;

[0040] The controller is a controller for the chiller, and the compressor control logic is integrated in the controller. It is used to calculate the real-time operating compression ratio and guide vane opening percentage after obtaining the compressor's suction and exhaust pressures and inlet guide vane opening, obtain the surge protection frequency, and perform load regulation and anti-surge regulation by comparing the actual operating frequency of the compressor with the surge protection frequency; it is also used to calculate the suction and exhaust superheat based on the compressor's suction and exhaust temperatures, and to determine whether the stator winding temperature exceeds the target temperature. Once exceeded, a fault alarm is issued and the compressor is controlled to shut down.

[0041] Specifically, intake and exhaust superheat = intake and exhaust temperature - saturation temperature corresponding to intake and exhaust pressure. This intake and exhaust superheat is obtained to protect the compressor. When the compressor is fully started and the exhaust superheat is detected to be ≤2°C, a fault alarm is triggered to shut down the compressor without further testing during the shutdown process. When the compressor is fully started and the intake superheat is detected to be ≤-2°C, a fault alarm is triggered to shut down the compressor without further testing during the shutdown process. Furthermore, when the stator winding temperature sensor detects a stator winding temperature ≥110°C, a fault alarm is triggered to shut down the compressor.

[0042] Furthermore, the controller is also used to: perform forced energy load reduction adjustment when it is detected that the inverter operating current is greater than the first current target value or the inverter temperature is greater than the first temperature target value; during the operation of the compressor, when it is detected that the inverter operating current is less than the second current target value or the inverter temperature is less than the second temperature target value, exit the forced load reduction mode; when it is detected that the inverter operating current is greater than the third current target value or the inverter temperature is greater than the third temperature target value, shut down immediately.

[0043] Beneficial effects of the present invention:

[0044] (1) By integrating the compressor control logic into the controller of the chiller and sharing the controller with the chiller, the chiller control system can obtain the compressor surge line and compressor status in a timely manner, avoiding data asynchrony caused by communication delay, reducing operation and maintenance costs, and greatly improving control accuracy. This solves the problem of long communication delay between the chiller and the compressor controller and delayed control output in the past;

[0045] (2) The controller establishes the data model of the magnetron, the data model of the compressor inverter, and the data model of the motor cavity expansion valve through the communication module, and performs automatic optimization calculations on this basis through the active optimization control algorithm loaded by the controller. The optimization control algorithm uses the chilled water outlet temperature of the chiller as the target value, controls the compressor energy output by changing the frequency during high load regulation, and controls the compressor energy output by the inlet guide vane opening during low load regulation. This solves the problems of the traditional control algorithm in which the frequency and the inlet guide vane opening are adjusted simultaneously, resulting in low unit energy efficiency, a small adjustment range, and easy surge shutdown. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the system structure of an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] like Figure 1 Shown: A magnetic levitation compressor control system includes a controller and a temperature acquisition module, an analog quantity acquisition module, a valve control module and a communication module connected to the controller.

[0049] Specifically, the temperature acquisition module is connected to an intake temperature sensor, an exhaust temperature sensor, and a stator winding temperature sensor. The intake temperature sensor is located on the compressor's intake line to detect the compressor's intake temperature; the exhaust temperature sensor is located on the compressor's exhaust line to detect the compressor's exhaust temperature; and the stator winding temperature sensor is located at a corresponding position on the stator to detect the motor's stator winding temperature. All three sensors are connected to the temperature acquisition module's input, where they process the data and send it to the controller.

[0050] The analog acquisition module is connected to the suction pressure sensor, exhaust pressure sensor, supply pressure sensor, and IGV feedback opening sensor. The suction pressure sensor is located on the compressor's suction line to detect the compressor's suction pressure; the exhaust pressure sensor is located on the compressor's exhaust line to detect the compressor's exhaust pressure; the supply pressure sensor is located on the compressor's supply line to detect the compressor's supply pressure; and the IGV feedback opening sensor is located at the compressor's inlet guide vane to detect the size of the inlet guide vane opening. The analog acquisition module converts the IGV opening size into an electrical signal and sends it to the controller to achieve automatic control of the guide vane opening. The controller controls the inlet guide vane actuator based on the received IGV feedback opening signal to adjust the IGV opening size, thereby achieving the purpose of controlling the compressor's intake volume, pressure, temperature, and other performance parameters.

[0051] In this embodiment, the output end of the valve control module is connected to the inlet guide vane actuator, cooling solenoid valve, cut-in valve, and air supply valve, respectively, to control the opening and closing of each valve. The inlet guide vane is located at the compressor's air inlet and regulates the airflow entering the compressor. The controller drives the inlet guide vane actuator to control the opening of the inlet guide vane, thereby adjusting the airflow rate and speed to improve the compressor's efficiency and performance. The cooling solenoid valve is located in the pipeline between the chiller's condenser outlet and the compressor's motor cavity expansion valve, controlling the opening and closing of this pipeline. The cooling solenoid valve and the motor cavity expansion valve provide dual redundant control of the pipeline from the condenser outlet to the motor cavity. Even if the motor cavity expansion valve fails to close tightly or the pipeline ruptures, the cooling solenoid valve can shut off the refrigerant flow in this pipeline to prevent energy waste or refrigerant leakage. The cut-in valve is located in the pipeline from the compressor's exhaust port to the evaporator and is used to balance the pressure ratio between the two vessels during compressor startup and shutdown, preventing excessive pressure ratio and compressor surge. The air supply valve is located in the compressor's air supply pipeline and controls the opening and closing of the air supply pipeline.

[0052] In this embodiment, the controller connects the magnetic bearing control board, touch screen, motor cavity expansion valve, and inverter control board via a communication module. The magnetic bearing control board is a circuit board that controls the operation of the magnetic bearing. Since magnetic bearings are contactless bearings that utilize electromagnetic force to enable the rotor to levitate and rotate, the magnetic bearing control board provides a stable power supply to the magnetic bearings and monitors parameters such as the magnetic bearing speed, temperature, and vibration to promptly detect and address any abnormalities. By adjusting the magnitude and direction of the electromagnetic force, the magnetic bearing control board can control the rotor's position and motion. The touch screen is used for human-computer interaction, allowing for the setting, detection, and display of relevant parameters. For example, the maximum and minimum operating frequencies of the compressor can be set via the touch screen. The motor cavity expansion valve precisely regulates the flow of refrigerant to the motor cavity. During the cooling cycle, refrigerant flows from the condenser, passes through the cooling solenoid valve, and enters the compressor motor cavity. Within the compressor motor cavity, the refrigerant evaporates, absorbing ambient heat, and then, as vapor, enters the compressor intake port. This cycle repeats, maintaining the motor cavity temperature within a reasonable range. The inverter control board precisely controls the motor speed, frequency, and voltage.

[0053] In this embodiment, the controller is a programmable logic controller, which is used to calculate the real-time operating pressure ratio and guide vane opening percentage after obtaining the suction and exhaust pressures and inlet guide vane opening of the compressor, obtain the surge protection frequency, and perform load regulation and anti-surge regulation by comparing the actual operating frequency of the compressor with the surge protection frequency.

[0054] The controller is also used to: perform forced energy load reduction adjustment when it is detected that the inverter operating current is greater than the first current target value or the inverter temperature is greater than the first temperature target value; during the operation of the compressor, when it is detected that the inverter operating current is less than the second current target value or the inverter temperature is less than the second temperature target value, exit the forced load reduction mode; when it is detected that the inverter operating current is greater than the third current target value or the inverter temperature is greater than the third temperature target value, shut down immediately.

[0055] The controller is also used to calculate the suction and exhaust superheat based on the suction and exhaust temperatures of the compressor detected by the suction temperature sensor and the exhaust temperature sensor, where the suction and exhaust superheat = suction and exhaust temperature - the saturation temperature corresponding to the suction and exhaust pressure; participate in compressor protection by obtaining the suction and exhaust superheat; when the compressor is started and the exhaust superheat is detected to be ≤2°C, a fault alarm is issued to stop the compressor, and the shutdown process is not detected; when the compressor is started and the suction superheat is detected to be ≤-2°C, a fault alarm is issued to stop the compressor, and the shutdown process is not detected.

[0056] The controller is also used to: when the suction pressure sensor detects that the suction pressure is less than <10kPa, a fault alarm will be issued to stop the compressor; when the exhaust pressure sensor detects that the exhaust pressure is ≥1550kpa, a fault alarm will be issued to stop the compressor.

[0057] The controller is also used to: when the stator winding temperature sensor detects that the stator winding temperature is ≥110℃, a fault alarm is issued to stop the compressor.

[0058] The controller is also used for: when the compressor's detection system detects that the inverter temperature is ≥85℃, the inverter control board transmits the information to the controller through the communication module, and the controller performs forced load reduction; when the inverter temperature is detected to be ≥90℃, a fault alarm is issued to stop the compressor; when the inverter operating current is detected to be >370A, an alarm is issued and the load is forced to be reduced; when the inverter operating current is detected to be >380A, a fault alarm is issued to stop the compressor.

[0059] The controller is also used for: when the compressor's detection system detects a large vibration peak (open circuit in suspended state), that is, the vibration peak is >5V, the magnetic bearing control board sends information to the controller via the communication module to issue an abnormal reminder; when the vibration peak is detected to be >6V, a fault alarm is issued to stop the compressor.

[0060] The controller is also used to issue a fault alarm and stop the compressor when the stator winding temperature sensor, motor cavity temperature sensor, or motor cavity pressure sensor is abnormal; for example, the stator winding temperature sensor is broken.

[0061] The controller is also used to, when it detects that the motor cavity temperature is ≥60℃, issue a fault alarm to stop the compressor; and when it detects that the exhaust temperature is ≥95℃, issue a fault alarm to stop the compressor.

[0062] In this embodiment, the compressor control logic is integrated into the chiller controller, so the controller is the controller of the chiller, which can completely integrate the originally scattered control authority and protection authority of the compressor into the chiller controller, so that the compressor and the water temperature of the chiller form a truly closed-loop control, greatly reducing the probability of surge in the magnetic levitation compressor, reducing the communication delay in the data interaction process, and making the compressor loading and unloading control more precise and the load adjustment range wider, thereby further reducing the unit shutdown caused by compressor fault alarm, achieving energy saving and high efficiency, and reducing the operation and maintenance costs of the magnetic levitation unit.

[0063] The control method of the magnetic levitation compressor in this embodiment mainly includes five control modes: compressor startup control, load (energy optimization) regulation, anti-surge regulation, forced load reduction, and compressor shutdown control, and the regulation priority order is: forced load reduction > anti-surge regulation > load regulation.

[0064] S101: Start the compressor. The specific steps are as follows:

[0065] (1) When the compressor receives the start command from the controller, it starts the start mode and the system self-checks to ensure that all components and the system are in normal condition;

[0066] (2) After the self-test is completed, it will start after a delay of 4 seconds to ensure system stability;

[0067] (3) After starting, control the magnetic bearing suspension;

[0068] (4) The magnetic bearing is detected to be in a suspended state within 3 seconds, otherwise a startup failure warning is issued and the startup ends;

[0069] (5) 3 seconds after the magnetic axis is normally suspended, start the cooling solenoid valve of the compressor (also known as the cooling electronic expansion valve), open the inlet guide vane actuator, and open the cut-in valve (the maximum opening is 100%);

[0070] (6) After the inlet guide vane actuator is started, a start command is sent to the inverter through the controller;

[0071] (7) The inverter accelerates to the starting frequency (60% of the maximum frequency). When the surge frequency is detected to be less than 60% of the maximum frequency, it will run at this frequency for 1 minute and then adjust the frequency to operate at normal load. When the surge frequency is detected to be greater than 60% of the maximum frequency, it will directly operate at the surge protection frequency.

[0072] (8) After the compressor starts, gradually close the cut-in valve to achieve a smooth start of the compressor and reduce the occurrence of current peaks;

[0073] (9) When the compressor operating frequency reaches the frequency calculated by the active optimization algorithm, the air supply valve is activated. The optimization algorithm is an algorithm used to optimize the performance of the compressor system. By online monitoring and analyzing the operating status of the system, the optimal operating parameters, including intake volume and exhaust volume, are calculated based on preset performance indicators and adjusted accordingly. In this embodiment, the air supply valve is activated to adjust the system's air supply. For example, when the system determines that the air supply needs to be increased, the air supply valve is activated to allow more air to enter the compressor.

[0074] (10) The air supply valve is started and enters the load regulation mode, which is also the energy optimization mode.

[0075] The present invention adopts a fuzzy control algorithm to perform active optimization calculations and water temperature trend predictions for chillers. The fuzzy control algorithm is an intelligent control algorithm that simulates human fuzzy reasoning and decision-making processes in terms of behavior. It first compiles the operator and expert experience into fuzzy rules, then fuzzifies the real-time signal from the sensor, uses the fuzzified signal as the input of the fuzzy rule, forms fuzzy reasoning, and adds the output obtained after reasoning to the execution compressor. The active optimization calculation and water temperature trend prediction of the fuzzy control algorithm can make up for the defect of traditional PID controllers that are broad but not specialized. It can allow the unit to achieve stepless adjustment within the range of 10% to 100% without surge shutdown. At the same time, the control system can meet the system adjustment needs of different users through simple parameter adjustment on the touch screen, greatly reducing the operation and maintenance time of the air-conditioning unit, fully realizing system automatic control and high efficiency and energy saving, and has high market promotion value. It can be said that this embodiment adopts an optimization algorithm to perform load regulation, anti-surge regulation and forced load reduction, and uses the chilled water outlet temperature of the chiller as the target value. During high-load regulation, the compressor energy output is controlled by changing the frequency, and during low-load regulation, the compressor energy output is controlled by the inlet guide vane opening. This solves the problems of the traditional control algorithm in which the frequency and the inlet guide vane opening are adjusted simultaneously, resulting in low unit energy efficiency, a small adjustment range, and easy surge shutdown.

[0076] S102: Load (energy optimization) regulation, including:

[0077] (1) Basic logic: During load increase, the principle is to increase the inlet guide vane opening first and then increase the compressor operating frequency (i.e., inverter frequency); during load reduction, the principle is to reduce the compressor operating frequency first and then reduce the inlet guide vane opening;

[0078] (2) Energy loading: During the loading process, the inlet guide vane opening is increased first. When the inlet guide vane is opened to the maximum, the compressor operating frequency is increased. If the inlet guide vane actuator fails, if loading is required, the guide vane will no longer be opened first, and the compressor operating frequency can be directly increased.

[0079] (3) Energy load reduction: During the load reduction process, the compressor operating frequency is reduced first. When the compressor operating frequency cannot be further reduced (limited by anti-surge regulation and minimum operating frequency), the inlet guide vane opening is further reduced.

[0080] The load regulation in this embodiment is performed after the compressor is combined with the chiller. The load refers to the cooling and heating load required by the chiller. The chiller controls the operating state of the compressor through the controller according to the cooling and heating load requirements.

[0081] S103: Anti-surge adjustment, including:

[0082] (1) The controller monitors and updates the suction and exhaust pressure values ​​and inlet guide vane opening of the compressor in real time, and calculates the real-time operating compression ratio and guide vane opening percentage; controls the real-time operating frequency of the compressor under the real-time operating compression ratio and guide vane opening to be no lower than the calculated minimum operating (anti-surge) frequency; and multiplies the minimum surge operating frequency by the adjustment coefficient (the default adjustment coefficient is 1.01, which can be modified through the touch screen) as the surge protection frequency.

[0083] (2) Regional control based on frequency.

[0084] a. When the actual operating frequency of the compressor is greater than the surge protection frequency, energy optimization adjustment (ie, load adjustment in step S102) is performed to control the normal speed increase or decrease of the inverter;

[0085] b. When the actual operating frequency of the compressor is lower than the surge protection frequency and higher than the minimum surge operating frequency, energy load reduction is limited to prevent the compressor from entering the surge zone, but energy loading is generally not limited.

[0086] c. When the actual operating frequency of the compressor is lower than the minimum surge operating frequency, the energy optimization adjustment is exited and the anti-surge adjustment is entered. At this time, the frequency will no longer be reduced but will be appropriately increased to ensure that the frequency is above the minimum surge frequency.

[0087] (3) When the actual operating frequency of the compressor is greater than the calculated surge protection frequency, the anti-surge adjustment is exited and normal energy optimization adjustment is entered. The anti-surge adjustment is implemented after the compressor is started. Under some unstable working conditions, the compressor may still experience surge. When the surge is severe and causes the axis trajectory to fluctuate severely, the surge protection of the compressor may be triggered, and the compressor will enter the shutdown state.

[0088] S104: Forced load reduction, including:

[0089] (1) Forced load reduction triggering condition: During the operation of the compressor, the inverter operating current is greater than 370A or the inverter temperature is greater than 85°C; at this time, forced load reduction is performed, and step S102 is entered to control according to energy load reduction;

[0090] (2) If the load reduction speed is slow or ineffective, and the operating current exceeds 380A or the inverter temperature is greater than 90°C, stop the machine immediately;

[0091] (3) Forced load reduction exit conditions: During the operation of the compressor, the operating current is less than 360A or the inverter temperature is less than 80℃.

[0092] S105: Compressor shutdown control, specifically including:

[0093] (1) When the compressor receives the shutdown command from the controller, it stops the optimization operation mode and enters the shutdown mode, and opens the cut-in valve;

[0094] (2) During normal shutdown, deceleration is performed first and then shutdown. If the current operating frequency is higher than the specified shutdown frequency (55% of the maximum frequency), the inverter is first decelerated to the specified shutdown frequency. If the current operating frequency is lower than or equal to the specified shutdown frequency, there is no need to adjust the compressor speed.

[0095] (3) The controller sends a shutdown command to the inverter. In normal shutdown, when it is detected that the current frequency is less than or equal to the specified shutdown frequency, a free shutdown is executed; in emergency shutdown, regardless of the current frequency, a free shutdown is executed directly;

[0096] (4) The inverter is shut down and the compressor cooling solenoid valve is closed;

[0097] (5) Close the cut-in valve and the inlet guide vane actuator;

[0098] (6) The shaft falls after the inlet guide vane is closed for 120 seconds or the actual speed is less than 10HZ;

[0099] (7) The shaft is dropped and the machine is shut down.

[0100] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A magnetic levitation compressor control system, characterized in that: It includes a controller and a temperature acquisition module, an analog quantity acquisition module, a valve control module and a communication module connected to the controller; The temperature acquisition module is connected to the suction temperature sensor, the exhaust temperature sensor and the stator winding temperature sensor respectively, and is used to collect the suction temperature, exhaust temperature and motor stator winding temperature of the compressor; The analog quantity acquisition module is respectively connected to the suction pressure sensor, the exhaust pressure sensor, the air supply pressure sensor and the IGV feedback opening sensor, and is used to collect the suction pressure, exhaust pressure, air supply pressure and inlet guide vane opening size of the compressor; The output end of the valve control module is respectively connected to the inlet guide vane actuator, the cooling solenoid valve, the cut-in valve and the air supply valve; the controller is also connected to the magnetic bearing control board, the touch screen, the motor cavity expansion valve and the inverter control board through the communication module; the cooling solenoid valve is arranged on the pipeline between the condenser outlet of the chiller and the compressor motor cavity expansion valve, and is used to control the on-off of this pipeline. The cooling solenoid valve and the motor cavity expansion valve form dual redundant control of the pipeline from the condenser outlet to the motor cavity; the cut-in valve is arranged on the pipeline from the exhaust port of the compressor to the evaporator of the chiller; The controller is a controller for the chiller, and the compressor control logic is integrated in the controller. It is used to calculate the real-time operating compression ratio and guide vane opening percentage after obtaining the compressor's suction and exhaust pressures and inlet guide vane opening, obtain the surge protection frequency, and perform load regulation and anti-surge regulation by comparing the actual operating frequency of the compressor with the surge protection frequency; it is also used to calculate the suction and exhaust superheat based on the compressor's suction and exhaust temperatures, and to determine whether the stator winding temperature exceeds the target temperature. Once exceeded, a fault alarm is issued and the compressor is controlled to shut down.

2. The magnetic levitation compressor control system according to claim 1, characterized in that: The controller is also used to: perform forced energy load reduction adjustment when it is detected that the inverter operating current is greater than the first current target value or the inverter temperature is greater than the first temperature target value; during the operation of the compressor, when it is detected that the inverter operating current is less than the second current target value or the inverter temperature is less than the second temperature target value, exit the forced load reduction mode; when it is detected that the inverter operating current is greater than the third current target value or the inverter temperature is greater than the third temperature target value, shut down immediately.

3. A magnetic levitation compressor control method, characterized in that: The magnetic levitation compressor control system according to claim 1 or 2 comprises the following steps: The compressor regulation is divided into forced load reduction, anti-surge regulation and load regulation; The load regulation includes energy loading and energy unloading regulation. The energy loading includes: increasing the inlet guide vane opening, and then increasing the compressor operating frequency when the inlet guide vane is opened to the maximum; or directly increasing the compressor operating frequency when the inlet guide vane actuator fails; the energy unloading includes: first reducing the compressor operating frequency, and then further reducing the inlet guide vane opening when the compressor operating frequency cannot be further reduced; The anti-surge regulation includes a frequency zone control step, namely: when it is detected that the actual operating frequency of the compressor is greater than the surge protection frequency, the load regulation is performed to control the inverter to normally increase or decrease the speed; when it is detected that the actual operating frequency of the compressor is less than the surge protection frequency and greater than the minimum surge operating frequency, energy load reduction is limited to prevent the compressor from entering the surge zone; when it is detected that the actual operating frequency of the compressor is less than the minimum surge operating frequency, the load regulation is exited and the anti-surge regulation mode is entered to control the frequency to be above the minimum surge frequency; The triggering condition for the forced load reduction is: during the operation of the compressor, when it is detected that the operating current of the inverter is greater than the first current target value or the inverter temperature is greater than the first temperature target value, forced energy load reduction adjustment is performed; the exit condition for forced load reduction is: during the operation of the compressor, when it is detected that the operating current of the inverter is less than the second current target value or the inverter temperature is less than the second temperature target value, the forced load reduction mode is exited; when it is detected that the operating current of the inverter is greater than the third current target value or the inverter temperature is greater than the third temperature target value, the machine is shut down immediately.

4. The magnetic levitation compressor control method according to claim 3, characterized in that: The adjustment priority order of the compressor is: forced load reduction > anti-surge adjustment > load adjustment.

5. The magnetic levitation compressor control method according to claim 3, characterized in that: The third current target value>the first current target value>the second current target value; the third temperature target value>the first temperature target value>the second temperature target value.

6. The magnetic levitation compressor control method according to claim 3, characterized in that: In the anti-surge regulation, the suction and exhaust temperatures, suction and exhaust pressure values, and inlet guide vane opening of the compressor are monitored and updated in real time, and the real-time operating compression ratio and guide vane opening percentage are calculated; the actual operating frequency of the compressor under the real-time operating compression ratio and guide vane opening is controlled to be no lower than the calculated minimum operating frequency, that is, the anti-surge frequency; the minimum surge operating frequency is multiplied by the adjustment coefficient to obtain the surge protection frequency.

7. The magnetic levitation compressor control method according to claim 3, characterized in that: In the anti-surge regulation, when the actual operating frequency of the compressor is greater than the calculated surge protection frequency, the anti-surge regulation is exited and the load regulation is entered. The anti-surge regulation begins to be implemented after the compressor is started. When it is detected that the surge is severe and the axis trajectory of the compressor fluctuates seriously, the compressor enters the shutdown state.

8. The magnetic levitation compressor control method according to claim 5, characterized in that: The forced load reduction triggering condition is: during the operation of the compressor, when it is detected that the inverter operating current is greater than 370A or the inverter temperature is greater than 85°C, forced load reduction is performed; the exit condition of the forced load reduction is: during the operation of the compressor, when it is detected that the inverter operating current is less than 360A or the inverter temperature is less than 80°C; when it is detected that the inverter operating current exceeds 380A or the inverter temperature is greater than 90°C, the compressor will be shut down immediately.

9. The magnetic levitation compressor control method according to claim 3, characterized in that: Also included are the compressor startup steps: When the compressor receives the start-up command from the controller, it starts the start-up mode and the system self-checks; after the self-check is completed, it delays for a certain time before starting again; after starting, the magnetic bearing is controlled to suspend; the magnetic bearing is detected to be in a suspended state within a certain period of time, otherwise a start-up failure warning is issued and the start-up is completed; after the magnetic shaft is normally suspended, the cooling solenoid valve of the compressor is delayed to start, the inlet guide vane actuator is opened, and the cut-in valve is opened; after the inlet guide vane actuator is started, a start-up command is sent to the inverter through the controller; the inverter is accelerated to 60% of the maximum frequency. When the surge frequency is detected to be less than 60% of the maximum frequency, it runs at this frequency for a certain period of time and then runs at the normal load adjustment frequency; when the surge frequency is detected to be greater than 60% of the maximum frequency, it runs directly at the surge protection frequency; the compressor is started and the cut-in valve is gradually closed; when the compressor operating frequency reaches the frequency calculated by the active optimization algorithm, the air supply valve is started; the air supply valve is started and the load adjustment mode is entered.

10. The magnetic levitation compressor control method according to claim 3, characterized in that: Also includes the compressor shutdown steps: When the compressor receives a shutdown command from the controller, it stops the optimized operation mode and enters the shutdown mode, and opens the cut-in valve; during normal shutdown, when it is detected that the current operating frequency of the compressor is higher than the specified shutdown frequency, the inverter is first controlled to reduce the speed to the specified shutdown frequency. When it is detected that the current operating frequency is lower than or equal to the specified shutdown frequency, there is no need to adjust the speed of the compressor; during normal shutdown, the current frequency is less than or equal to the specified shutdown frequency, and a free shutdown is executed; during emergency shutdown, regardless of the current frequency, a free shutdown is executed directly; after the inverter shutdown is completed, the cooling solenoid valve of the compressor is closed; the cut-in valve is closed, and the inlet guide vane actuator is closed; after a certain delay after the inlet guide vane is closed, the shaft is dropped or the actual speed is less than the target frequency, the shaft drop is completed, and the shutdown is completed.

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